# Repairing BOSCH B20CS30SNS/01 fridge



## jcdammeyer (Nov 6, 2022)

Alarm went off when temperature rose in freezer.  System test reports L 00 through L16 and does not result in an ERROR __ value.
Fan runs cooling the external coils.  Compressor does not come on.  Suspect either control board relay or some other board relay or else the compressor is toast.

Fridge is 12 years old.

Suggestions?  Control boards run over $500 and there are several not to mention cost of service call.  Equivalent fridge is in the $3500 range assuming inventory is available.


----------



## Janger (Nov 6, 2022)

ideas John....
1. bad crimp on connector? I had a bosch dishwasher fail due to a bad crimp on the heater coil. The wire melted off.
2. apply power manually to compressor to see if it still works? Sounds like lots of disassembly and work. 

Best - J


----------



## jcdammeyer (Nov 6, 2022)

This is what the motor control board looks like on the bottom:








						43.31C$ 52% OFF|Vcc3 1156 115-127v / 220-240v Hole Refrigerator Inverter Board For Embraco Wr49x10283 Inverters Converters Power Supplies Parts - Inverters & Converters - AliExpress
					

Smarter Shopping, Better Living!  Aliexpress.com




					www.aliexpress.com
				




Essentially 110VAC in 220VAC 3 phase out.  According to the bar code number the control signal is a frequency.  It measures about 2.5VAC.  The power into the board is 120VAC.  The fuse on the bottom left corner shows continuity.

The bottom of the plastic box is slightly discoloured in the area around the 6 driver transistors on the bottom of the board and the bridge drivers close to the motor connector.










So either the driver board is shot or the compressor itself is shot.

Used ones run up to $200 with no guarantee that it's the problem.  Compressor is 12 years old.  Methinks I'm better off to just replace the fridge.

Can't figure out how to get at the main control board from either inside or from the back.  The back panel is  held with a number of screws and a bunch of rivets.  Even with all of them removed it still appears glued into place.

What a shame.


----------



## Susquatch (Nov 6, 2022)

Amazing. A VFD run freezer. Who wuda thunk it! Wow! 

At the risk of repetition..... Connectors connectors connectors......  But you already know that so I assume you already checked them all. 

Easy to fall victim to the old blame it on whatever I can't see or understand trick. We've all been there, done that, no matter how much we should know better.... (Ask me how I know that......) 

Given that it's basically a VFD based 3phase system, you ought to be able to put a scope on it and walk the signals back one step at a time. Obviously you can't simply jump the motor, but maybe you have a spare low power VFD to do that with.


----------



## Janger (Nov 6, 2022)

It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ? 

Have you got another vfd you could use as a driver to test the compressor? You could borrow mine if you lived close? Maybe somebody else closer by could if you don’t have one?


----------



## Janger (Nov 6, 2022)

Janger said:


> It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ?
> 
> Have you got another vfd you could use as a driver to test the compressor? You could borrow mine if you lived close? Maybe somebody else closer by could if you don’t have one?


We need those right to repair laws. Products should be disassemble able. (Is that a word?) I mean repairable.


----------



## Janger (Nov 6, 2022)

I think the board is more suspect than the compressor given that heat discolouration you discovered. The substitute board is cheap enough. If it works buy a second? Add some cooling?


----------



## jcdammeyer (Nov 6, 2022)

Back after a run to the various appliance places to see what we can get for the interim or as a replacement.  Last year I promised my wife a wine fridge for Christmas but that never happened.  We decided we'd rather have an apartment size fridge for wine and other things.  And with that in mind that purchase never went further.  

So we're thinking for now we may get that 'wine' fridge for downstairs, but put it upstairs until we decide if we need to replace the big one or repair but have to wait for parts.  Seems most of the places around here don't have inventory.   Inventory is in Burnaby etc. and delivery for some time at the end of the week or next week. 

Now as far as testing.  


I have a 3 phase driver that I was testing a 1/3HP motor with.  I was thinking I could connect that to the compressor to see if it works but I  have no idea which way to spin it.  And I don't know if I'd toast the compressor by turning it backwards.

The alternative is to connect the fridge drive to the 1/3 HP motor.   But according to the web, that particular drive requires frequency in to spin the motor.  Bottom RHS of the drive photo shows a small bridge rectifier there so I'm guessing that it turns the frequency into a DC voltage level.  And yes, that's where right to repair should provide way more information on how to test and rebuild these drives.

I think I'll take stab at connecting the fridge compressor drive to the 1/3HP motor.  First though I'll put a scope on the control signal from the fridge to the drive to see what it's trying to tell the drive to do.  If I can duplicate that then I can at least see if it will turn an unloaded 3 phase motor.

Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements.  Apparently more efficient.  All the high end fridges we looked at today had that feature.


----------



## jcdammeyer (Nov 6, 2022)

Further tests show, relative to frame, each of the two control wires for the motor drive controller are 120VAC.  Difference between the two is 2.5VAC.  Frequency, measured with the scope relative to the frame is 60Hz.  The control signal in is buffered through an optical isolator triac driver.

Now it seems there is a repair for these if the bigger FETs or other parts aren't smoked:




and his tester:


----------



## Susquatch (Nov 6, 2022)

jcdammeyer said:


> Now as far as testing.  I have a 3 phase driver that I was testing a 1/3HP motor with.  I was thinking I could connect that to the compressor to see if it works but I  have no idea which way to spin it.  And I don't know if I'd toast the compressor by turning it backwards.



This was bothering me too as I thought about it. If the current VFD Works, you can use your scope to see which phase leads which. 



jcdammeyer said:


> The alternative is to connect the fridge drive to the 1/3 HP motor.   But according to the web, that particular drive requires frequency in to spin the motor.



What the heck does that mean? I no capiche. Of course it requires frequency. All AC motors require frequency. You totally completely lost me on that one. 



jcdammeyer said:


> Bottom RHS of the drive photo shows a small bridge rectifier there so I'm guessing that it turns the frequency into a DC voltage level.



Prolly just there to create a power supply for on board controls and smarts. 



jcdammeyer said:


> I think I'll take stab at connecting the fridge compressor drive to the 1/3HP motor.  First though I'll put a scope on the control signal from the fridge to the drive to see what it's trying to tell the drive to do.  If I can duplicate that then I can at least see if it will turn an unloaded 3 phase motor.



And also determine which way it is supposed to turn. 



jcdammeyer said:


> Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements.  Apparently more efficient.  All the high end fridges we looked at today had that feature.



Didn't know that. I would never have guessed. But it makes sense. Variable speed motors can save a lot of coin!


----------



## jcdammeyer (Nov 6, 2022)

Susquatch said:


> This was bothering me too as I thought about it. If the current VFD Works, you can use your scope to see which phase leads which.


I'm not so sure it works yet.


Susquatch said:


> What the heck does that mean? I no capiche. Of course it requires frequency. All AC motors require frequency. You totally completely lost me on that one.


Say you have a 3 phase drive like the one in the photo I posted earlier in this thread.   It takes a POT or 0-10V input to create the variable speed out to the motor.  The drive does that by varying the frequency while maintaining the 220VAC voltage to the windings

Now imagine you have my AC servo motor on my milling machine spindle.  Still a 3 phase motor this time along with an encoder on the back.  But the although the electronics can accept a 0-10V signal for velocity it can also take step/dir signals so you can even position the AC servo.

So I'm assuming that the fridge compressor accepts a frequency in of 53Hz to 150Hz which in turn results in the 3 phase driver electronics creating the 53Hz to 150Hz.  Again not a lot different from a VFD that has a pot or 0-10V and creates 20Hz to 120Hz for example.

But I don't really know.  The guys tester just couples the 60Hz line through the two resistors into the drive opto coupler input.    On my the part number ends up being this guy:








						SFH615A-3X008T Vishay - Datasheet PDF & Technical Specs
					

Download the SFH615A-3X008T datasheet from Vishay. Optocoupler Dc-in 1-CH Transistor Dc-out 4-PIN PDIP SMD T/r




					www.allaboutcircuits.com


----------



## Tecnico (Nov 6, 2022)

jcdammeyer said:


> Alarm went off when temperature rose in freezer.  SNIP!  Suspect either control board relay or some other board relay or else the compressor is toast.
> 
> Fridge is 12 years old.



First off, given your youtube links I presume you've Googled for posts in forums like appliance repair.  I never cease to be amazed at how often someone else has already had the same problem and posted a solution.  My recent experience with a heat pump is just the latest.  Looks like you're better equipped than me to understand the electrical side too.

My fridge story is the 4 year old Maytag that had a compressor fail, the sales guy laughed and said it was about right. Fridge before that I had the compressor replaced after about 15 years for a couple hundred bucks but nobody replaces compressors anymore.



Janger said:


> It’s run by a vfd. That’s amazing. Why or what engineering reason is there to do that? Fridges are usually on or off ?





jcdammeyer said:


> Oh and the higher end fridges run the compressors at different speeds depending on their cooling requirements. Apparently more efficient. All the high end fridges we looked at today had that feature.


The other reason for the VFD is it is probably used to minimize the noise emissions, partly because of controlling speed and partly by spreading out the (mechanical) power pulses over 3 phases compared to single phase.

IMO heat, showing witness discoloration is a marker (obviously the hotter they run, the shorter the life) but I'm inclined to suspect moving parts like the compressor.

Right to repair should also include having the product designed/manufactured to be worth repairing (blame marketing/bean counters not the engineers/designers) vs. throw away.  That also comes home to roost when you look at life cycle waste of scarce resources and things like appliances filling landfills.

Down off the soap box.  

Good luck with the diagnosis & repair!

D


----------



## DPittman (Nov 6, 2022)

Tecnico said:


> My fridge story is the 4 year old Maytag that had a compressor fail, the sales guy laughed and said it was about right. Fridge before that I had the compressor replaced after about 15 years for a couple hundred bucks but nobody replaces compressors anymore.


I've got a fridge in my basement that was my parents and is around 65-70 years old and I don't believe it has ever failed. The racks are and door handle are rough/missing but it runs like a charm.


----------



## jcdammeyer (Nov 6, 2022)

Oh and this is the processor on the board.


			https://www.nxp.com/docs/en/data-sheet/MC56F8013.pdf
		

The key element of the processor is:
_"One multi-function six-output Pulse Width Modulator (PWM) module"_
which provides the drives for the IR2304s





						Semiconductor & System Solutions - Infineon Technologies
					

Infineon semiconductor solutions - MCUs, sensors, automotive & power management ICs, memories, USB, Bluetooth, WiFi, LED drivers, radiation hardened devices.




					www.infineon.com
				



which drive the 6 FETs which provided the PWM based 3 phase AC waveform from the rectified/boosted 120VAC to create the 220VAC 3 phase.


DPittman said:


> I've got a fridge in my basement that was my parents and is around 65-70 years old and I don't believe it has ever failed. The racks are and door handle are rough/missing but it runs like a charm.


Our little fridge downstairs and the top load freezer are both older than than the Bosch.  But not nearly as sophisticated.  I'll report back once I get capacitors in stock and replace them.


----------



## Doggggboy (Nov 6, 2022)

This is too true


----------



## Janger (Nov 6, 2022)

The old iron does seem to go and go but the old iron also uses something like four or five times the electricity. Might be $200 a year to run those old fridges.

Frigidaire seems to make fridges that work. After owning some Maytag gear I’ll never buy them again. An asko brand dishwasher came with the house. The manual states we expect this appliance to last 20 years. I’ve owned it ten years now. One problem only so far the drain hose cracked easy fix.


----------



## jcdammeyer (Nov 6, 2022)

I worked it out but then deleted the posting as probably boring.  Essentially the cost of the fridge over 12 years works out, with our power costs, to using about 310W per hour 24/7.  That's not including the real power that it uses.     I don't think the old inefficient fridges used that much power.


----------



## Susquatch (Nov 7, 2022)

I still don't understand John. Perhaps there might be some fundamentals here driven by slightly different perspectives of how things work. Or maybe just your choice of words. English has to be the worst language in the world. 



jcdammeyer said:


> Say you have a 3 phase drive like the one in the photo I posted earlier in this thread. It takes a POT or 0-10V input to create the variable speed out to the motor. The drive does that by varying the frequency while maintaining the 220VAC voltage to the windings



I would have preferred to say that the VFD uses a 0 to 10 Volt signal to determine what frequency to output to the motor. The 0-10 itself doesn't create the output. The VFD creates the output using the 0-10 as a control signal. 



jcdammeyer said:


> Now imagine you have my AC servo motor on my milling machine spindle. Still a 3 phase motor this time along with an encoder on the back. But the although the electronics can accept a 0-10V signal for velocity it can also take step/dir signals so you can even position the AC servo.



Again, I'm confused. Does the Fridge motor have an encoder on it? If so, it isn't likely used for position control, just speed. 

Many VFDs have a Sensorless Vector mode to determine speed. An encoder on the motor is not required in this mode. However some can use a sensor (encoder) on the motor to determine speed. 

My VFDs are capable of being programmed to use both modes (and a few more). 

But none of my motors have an encoder. So I use SLV (sensor less vector) mode. Does yours have an encoder? 

Is there a chance that your source is confusing speed feedback with CNC position control? 



jcdammeyer said:


> So I'm assuming that the fridge compressor accepts a frequency in of 53Hz to 150Hz which in turn results in the 3 phase driver electronics creating the 53Hz to 150Hz. Again not a lot different from a VFD that has a pot or 0-10V and creates 20Hz to 120Hz for example.



Again, I think English is interfering with my understand and ability to follow you. 

The majority of 3phase motors cannot handle the full range of frequency outputs that VFDs can deliver. So VFDs are often programmed to output  minimum and maximum frequencies that are less extreme. 53hz is less extreme, but 150 is on the very high side. I presume this relates to the motors application bathed in refrigerant. 



jcdammeyer said:


> But I don't really know. The guys tester just couples the 60Hz line through the two resistors into the drive opto coupler input.



I confess I didn't watch the videos. I don't like YouTube and generally avoid it. So I can't really comment on this. 

Generally, my observation is that most VFDs are capable of generating their own 10V reference voltage internally. The user can either use this voltage or generate their own externally. I assume that yours uses an external 10V reference simply because it has another controller board that determines the speed it wants to run at instead of a human being controlling it via a potentiometer.


----------



## jcdammeyer (Nov 7, 2022)

Getting way too complicated.  I was trying to generalize.
According to the data sheets I've found for this 115VAC 1Phase input to 220VAC 3Phase output driver is that some of them use a simple ON/OFF control and others use frequency input.   As the photo of the label showed the output is 53Hz to 150Hz and the bar code # implies frequency input for control.  It's not your typical VFD of the sort we refer to

Given that they are using a very powerful Digital Signal Processor the ability to analyze an input signal for frequency and generate a corresponding 3 phase output control is rather trivial.

All electrolytic capacitors age over time and it's likely the ones on this board are no exception so I've ordered replacements. The board is at least 12 years old and the marking on the board is 2008 so it's perfectly reasonable that the age of the capacitors might well be an issue.

I used the most expensive, highest quality, widest temperature range capacitors for the control of the lights on the Lions Gate Bridge.  It's been running now since summer 2009 from dusk till dawn so not 24/7.  But even so I expect that they will start having failures in the next few years.  I hope not.  So far they've been great.


----------



## Susquatch (Nov 7, 2022)

jcdammeyer said:


> Getting way too complicated. I was trying to generalize.



This is absolutely hilarious. Usually you seem to love complicated! But I agree it is complicated! And prolly too complicated. Mostly, I am trying to understand what you are saying because I get the distinct feeling I can learn something. I love learning. Sometimes that requires challenging the sources. I do appreciate your patience. 



jcdammeyer said:


> According to the data sheets I've found for this 115VAC 1Phase input to 220VAC 3Phase output driver is that some of them use a simple ON/OFF control and others use frequency input. As the photo of the label showed the output is 53Hz to 150Hz and the bar code # implies frequency input for control. It's not your typical VFD of the sort we refer to



Yes, part of the learning I referred to above. What the heck is this frequency control input all about! 

And ya, it isn't typical. The mere fact that there is another controller controlling the VFD, indicates a significant step up in complexity and capability. Not that I need another project, but it also makes me think about doing similar things with the 3 VFDs I have in my shop. Not too likely to happen, but it gives my mind something to think about other than fixating on the other things going on in my life. 



jcdammeyer said:


> Given that they are using a very powerful Digital Signal Processor the ability to analyze an input signal for frequency and generate a corresponding 3 phase output control is rather trivial.



Exactly. But I'd love to know what it is that your fridge is doing that involves frequency input. My mind doesn't immediately embrace the need for such an input or analysis. Which implies that there is a chance to learn something cool!



jcdammeyer said:


> All electrolytic capacitors age over time and it's likely the ones on this board are no exception so I've ordered replacements. The board is at least 12 years old and the marking on the board is 2008 so it's perfectly reasonable that the age of the capacitors might well be an issue.



Yup! Prolly a good call. 



jcdammeyer said:


> I used the most expensive, highest quality, widest temperature range capacitors for the control of the lights on the Lions Gate Bridge. It's been running now since summer 2009 from dusk till dawn so not 24/7. But even so I expect that they will start having failures in the next few years. I hope not. So far they've been great.



I hope not too.

But Awesome Lighting System! Does your contract include maintenance? Hopefully that doesn't mean crawling around up there......... I would die just thinking about it! 

John - please don't let me try your patience. It's not my intent to challenge you. I'm really only insanely curious because the information doesn't fit my current knowledge base. 

Feel free to bluntly tell me to pound salt or better yet provide a few links to explore on my own.


----------



## Janger (Nov 7, 2022)

“By way of example, if you have a fridge with a top freezer from the 1980s with a capacity of 19.0-21.4 cubic feet, it's likely to use around 2,000 kWH per year. If you pay $.10 for electricity per kWh, that means the aging refrigerator is costing you about $.55 per day, $16.67 per month, and $200 per year.”

Reference: https://www.directenergy.com/learning-center/how-much-electricity-does-my-refrigerator-use 

And we don’t pay $0.10 a kWh it’s more like $0.18 due to all the extra fees etc. an old fridge is expensive to run. Using $0.18 kWh it’s $360 a year!


----------



## Janger (Nov 7, 2022)

The discussion on vfd’s and your fridge John is interesting.


----------



## DPittman (Nov 7, 2022)

Janger said:


> “By way of example, if you have a fridge with a top freezer from the 1980s with a capacity of 19.0-21.4 cubic feet, it's likely to use around 2,000 kWH per year. If you pay $.10 for electricity per kWh, that means the aging refrigerator is costing you about $.55 per day, $16.67 per month, and $200 per year.”
> 
> Reference: https://www.directenergy.com/learning-center/how-much-electricity-does-my-refrigerator-use
> 
> And we don’t pay $0.10 a kWh it’s more like $0.18 due to all the extra fees etc. an old fridge is expensive to run. Using $0.18 kWh it’s $360 a year!


Yes I need to check again the electricity consumption of my old fridge but from what I remember it was not nearly as bad as I thought.

Old fridges may be more expensive to run in the short term but buying a new $1000-$2000 new fridges and throwing them in the junk every 5 years isn't economical or environmentally friendly either.  

I started thinking about my old fridge and that there must be a date on it somewhere....sure enough 1951.  71 years old!


----------



## Susquatch (Nov 7, 2022)

DPittman said:


> Yes I need to check again the electricity consumption of my old fridge but from what I remember it was not nearly as bad as I thought.
> 
> Old fridges may be more expensive to run in the short term but buying a new $1000-$2000 new fridges and throwing them in the junk every 5 years isn't economical or environmentally friendly either.
> 
> I started thinking about my old fridge and that there must be a date on it somewhere....sure enough 1951.  71 years old!



The only two fridges in my life that never had to be replaced or repaired are also the first two I ever got. Prolly similar vintage to yours cuz they were already well used when I got them. One was a hand-me-down fridge we got when we got married.


----------



## jcdammeyer (Nov 7, 2022)

Susquatch said:


> Exactly. But I'd love to know what it is that your fridge is doing that involves frequency input. My mind doesn't immediately embrace the need for such an input or analysis. Which implies that there is a chance to learn something cool!
> 
> I hope not too.
> 
> But Awesome Lighting System! Does your contract include maintenance? Hopefully that doesn't mean crawling around up there......... I would die just thinking about it!


Nope.  Haven't even had to provide spare or replacement parts.


Susquatch said:


> John - please don't let me try your patience. It's not my intent to challenge you. I'm really only insanely curious because the information doesn't fit my current knowledge base.


No problem.  There's no such thing as a dumb question.  Only dumb and rude answers.


Susquatch said:


> Feel free to bluntly tell me to pound salt or better yet provide a few links to explore on my own.


This fridge has what they call a "super cool" function.  For both the fridge and freezer.  Switches back to normal after max 6 hours.  Designed to run the fridge harder to quickly cool down a large amount of stuff put into the freezer or fridge.  We've never actually used it.

Anyway, I'm going to guess they increase the speed of the compressor motor to do this.  Hence the need for a frequency controlled input rather than ON/OFF.

Now none of this is new in the general appliance world.
This is a piece of the data sheet for the IRAM module also used in my STMBL 3phase harmonic AC servo drive.  Unfortunately this part was discontinued which caused real headaches for the STMBL designers.
The original purpose for the device was washing machine motors which run slowly up to very high spin speeds.




I bought a harmonic drive off EBAY and then these kits from Andy Pugh in the UK who had done a batch based on attending a machine tool show in the UK attended by the German designers.  Luckily I was able to get the ICs before they went away and I have 3 of these modules as I was going to try them on my brushed servos too.





What's cool about these is they are quite small and can handle step/dir or the smart serial used by the MESA boards for LinuxCNC or even 0-10V signals although I don't know how well that's been tested.

What I'm trying to say is that 3 phase motors even without encoders are all over the place although obviously they work better with encoders and then are usually called AC Servo motors.

I'll see if I can find a general description of how these systems work.


----------



## jcdammeyer (Nov 7, 2022)

Janger said:


> “By way of example, if you have a fridge with a top freezer from the 1980s with a capacity of 19.0-21.4 cubic feet, it's likely to use around 2,000 kWH per year. If you pay $.10 for electricity per kWh, that means the aging refrigerator is costing you about $.55 per day, $16.67 per month, and $200 per year.”
> 
> Reference: https://www.directenergy.com/learning-center/how-much-electricity-does-my-refrigerator-use
> 
> And we don’t pay $0.10 a kWh it’s more like $0.18 due to all the extra fees etc. an old fridge is expensive to run. Using $0.18 kWh it’s $360 a year!


Exactly.  So amortize that $4400 fridge over 12 years and add $30 per month.  

Interesting day so far.  Stopped in at Reliance Appliance repair and asked about a new compressor driver.  The orginal part number was useless to them.  As they put it:  They need the fridge part # and can then look up the compressor driver.  Although sometimes it's not sold separately so then you need the certified freon guy to install the new compressor and driver.  

He says they order from Bosch and Bosch orders from Embraco but they can't order direct from Embraco.  Oh how I wish for the right to repair legislation.  But then I took Electronics  10,20 and 30 in High School and we learned how to repair things so it's in my blood.

Now I have to call Reliance with the fridge model number and apparently they don't normally stock that sort of thing anyway so it might be quite some time before I can get a repair part.


----------



## jcdammeyer (Nov 7, 2022)

BTW, here's a short 18 second video of my ELS running the STMBL drive connected to my Harmonic Drive Motor.  The beeps you hear are the SLEW and MOVE buttons being pressed to send stepping pulses to the STMBL

One day I really will cast the housing for this and add the face place so I can mount the collet chuck.


----------



## Susquatch (Nov 7, 2022)

jcdammeyer said:


> I'll see if I can find a general description of how these systems work.



Any chance this is what they are talking about?









						FAQ: What is V/Hz control mode for AC drives?
					

AC motors are commonly paired with variable frequency drives (VFDs), which control motor speed by regulating the frequency of the supplied voltage. Depending on the application and level of... Motion Control Tips




					www.designworldonline.com
				




Still not really a frequency input but yet fits reasonably well with what you were describing and certainly fits with the need to adjust torque.


----------



## jcdammeyer (Nov 7, 2022)

Susquatch said:


> Any chance this is what they are talking about?
> 
> 
> 
> ...


This is likely way too complicated but uses the series processor that is in my fridge compressor controller.


			https://www.nxp.com/docs/en/application-note/AN1911.pdf
		


Although hard to find in the document the basic idea is that the AC from the line is turned into higher voltage DC.  This is then switched on and off using what they call pulse width modulation out six pins to 3 pairs of drivers in such a way that you simulate 3 sine waves 120 degrees apart.  

After that it's just a matter of what voltage and frequency are created.  The natural inductance and capacitance of the motor is enough of a filter to make that ON/OFF high voltage be smoothed into something like a sine wave.  Change the frequency and you get a different speed.


----------



## Susquatch (Nov 7, 2022)

jcdammeyer said:


> the basic idea is that the AC from the line is turned into higher voltage DC. This is then switched on and off using what they call pulse width modulation out six pins to 3 pairs of drivers in such a way that you simulate 3 sine waves 120 degrees apart.
> 
> After that it's just a matter of what voltage and frequency are created. The natural inductance and capacitance of the motor is enough of a filter to make that ON/OFF high voltage be smoothed into something like a sine wave. Change the frequency and you get a different speed.



No wonder we are having trouble communicating. You have assumed I don't know what a VFD is.....LOL!  What you have just described is the basic operating principal of a VFD. If I were describing it, I'd add that VFD's are basically fancy inverters. Most are even called inverters.

Sometimes the process starts with a DC voltage like a battery. Sometimes with AC at various voltage levels. Regardless of which it is, they then create a high voltage DC which is subsequently chopped to create single or triple phase AC outputs. As you have said previously, the actual process is quite a bit more complex.

My interest is not in how a VFD works. No wonder you got leery about it. I don't think I'd want to describe how it works to most people either - especially not on a forum. But maybe over liquid refreshments or in a meeting. I only describe it generally above to give you some confidence in my knowledge level.

My interest is this case is not about how a VFD works, it is only about this weird frequency control "INPUT" that you described at the beginning of your thread. I am familiar with sensor control, sensorless vector control, direct control, etc. I'm also familiar with the way most VFD's use a 10V divider potentiometer to provide user control of output frequency. 

However, I'm not familiar with any frequency input control other than feedback from the output to fine tune the control system.

The article I linked to used some terminology in it that I thought might be what you referred to from your sources. In my view, the article provides a rather confusing description because it isn't an input in the normal sense, it's more of an output.

Nonetheless, I was not aware than any of my VFD's varied their output voltage as output frequency changed. That is clearly new info to me. So I plan to do some testing to see what mine are actually doing in that respect. 

I confess that it's odd that I didn't notice anything when I was assessing the output noise levels on my oscilloscope. I would have thought that would have jumped out at me as I ran up and down the frequency range watching the noise spikes.

Given that a refrigerator compressor is basically a refrigerant pump (constant high load), the required VFD output is significantly different from what is required for a lathe or a mill that usually sees very low loads - unless the operator likes 80 thou cuts like some members on here! So I can certainly see why an output voltage adjustment is appropriate as output frequency changes. But again, other than for feedback purposes, I see these as outputs not inputs.

Does that help?


----------



## jcdammeyer (Nov 7, 2022)

I'm just going by what I've been reading on line.  There is also conflicting information about how the control is done.    Hard to guess who really is an expert and who was just lucky.

Here's what I've found from the manufacturer.  Some controllers say they have frequency in.  Mine is one of those.

I found the main control board but without a schematic I can't tell exactly which set of wires run down to the motor driver.  

One source says control should be 4V to 6V which would enable the drive at a set speed.  Another one has a that test cable made by taking 120VAC through a diode and a 100K resistor into the opto-isolator.  I'm about to make up that setup and then I'll scope the output side of the opto-isolator.  It should be pulses at 60Hz based on how the opto-coupler works.  

More when I have tried it.  I will also report if I create magic smoke.


----------



## PaulL (Nov 7, 2022)

Tecnico said:


> The other reason for the VFD is it is probably used to minimize the noise emissions, partly because of controlling speed and partly by spreading out the (mechanical) power pulses over 3 phases compared to single phase.


I'm guessing it's to avoid having a starter capacitor on a motor that's always cycling on and off.  I'd be willing to believe a lot of fridge reliability problems are the starter caps.


----------



## jcdammeyer (Nov 7, 2022)

Did the older type fridges have starting caps?


----------



## jcdammeyer (Nov 7, 2022)

jcdammeyer said:


> More when I have tried it.  I will also report if I create magic smoke.


And there was smoke.  I had intended to insert a small isolation transformer so I could measure with the scope.  Forgot to do that.  

Touched the ground lead of the scope to what I incorrectly thought was the emitter pin of the opto isolator and zap.  A flash of light from what turned out to be a 0603 size 100 Ohm resistor.  I've replaced that but it no longer behaves the way it did before.

What it did when I first plugged it in with this setup:





was the motor locked for a moment.  Then released.  Locked and released and then that was it.  Cycle power it would lock at least one for a few seconds and then release.  Even tried to turn but only a half a turn before it just released.

Now this 1/3HP motor has 12 ohm windings while the fridge compressor has 6 ohm windings.   They are both 220VAC motors.  That's only DC so doesn't say much for number of turns and inductance.  But clearly it tried to turn but maybe one of the driver channels for one phase is shot.  Maybe it's the capacitors like the youtube video alluded to.   The caps should be here tomorrow.  But at this point...

Back at square one other than having ordered $8 worth of caps and a meter to read ESR which will come in handy for other projects.

Not sure where this saga will go next.


----------



## Susquatch (Nov 7, 2022)

jcdammeyer said:


> I'm just going by what I've been reading on line. There is also conflicting information about how the control is done. Hard to guess who really is an expert and who was just lucky.
> 
> Here's what I've found from the manufacturer. Some controllers say they have frequency in. Mine is one of those.



All I've been able to find is what I provided earlier plus a few other references to VF (voltage frequency) mode. All of them imply that the frequency portion is a feedback mechanism that the VFD can use to determine slip and correct for it. Nothing I find suggests that it is used for control - just feedback. But that difference could be as simple as the definitions that different people have for the terms feedback and control. 

To me, control means "go to 1500 rpm". Feedback means "I'm a bit slow at 1450rpm"


----------



## Susquatch (Nov 7, 2022)

jcdammeyer said:


> the motor locked for a moment. Then released. Locked and released and then that was it.



My experience with that is limited. I had a similar experience when I accidentally locked a motor (hi/low clutch engaged at same time as back gear. The VFD simply detected the lock and then released till I hit the e-stop. It was one of those terrifying holy crap moments. But no harm was done - that I know of.


----------



## VicHobbyGuy (Nov 7, 2022)

jcdammeyer said:


> Not sure where this saga will go next.


I have a 2.5 y.o. Bosch fridge - expensive ($4200) and a lovely thing when it works which is does..mostly. A couple of times, it has 'lost its mind' and stopped cooling ... it seemed to recover with a power down a.k.a. 'reboot'. but how can we be confident about a refrigerator like that? Delays in service calls are in the weeks nowadays. I tried getting the 'Extended Warranty' to service the machine - it took over a month before they sent somebody, and when he ran the self-test and like me got no reply from the machine brains, concluded that a new controller board was required. "I'll see about getting a board and we will contact you." 3 months later, they contacted me. Fridge has been working OK all that time so I declined. I figured the odds were 50-50 that 'service' would make things worse. Consequently, I now share my single garage shop space with a full-size 'backup fridge', which I did manage to get delivered in a couple of days after the first 'incident'.. 
My advice: If the saga goes toward 'new refrigerator', pick a different brand. But you probably concluded to do that a few days ago.
BTW, we have a 30+ y.o. small chest freezer in the basement which keeps stuff rock solid frozen, still. We store the expensive (isn't it all these days?) frozen food down there.


----------



## jcdammeyer (Nov 7, 2022)

Susquatch said:


> All I've been able to find is what I provided earlier plus a few other references to VF (voltage frequency) mode. All of them imply that the frequency portion is a feedback mechanism that the VFD can use to determine slip and correct for it. Nothing I find suggests that it is used for control - just feedback. But that difference could be as simple as the definitions that different people have for the terms feedback and control.
> 
> To me, control means "go to 1500 rpm". Feedback means "I'm a bit slow at 1450rpm"


Control is where I think you are making it too complex.   

For the VFDs we use with our mills or lathes it's most often a 0-10V signal.  Often created with a Pulse Width Modulation bit stream of 0V and 5V and then amplified to be 0-10V.

If I have a motor controlled with CANopen or MODBUS I can send the controller a message to tell it to run 1500 RPM.  I can even tell it how fast I want it to accelerate to that.   My GS-1 VFD running my lathe has both MODBUS and 0-10V or the pot on the front panel to set speed.

But it's just as reasonable that a controller receives a frequency on it's control input that tells it to turn at a specific speed.  So it might get 60Hz to turn 1800 RPM which is equivalent to no speed controller at all for our line frequency.  It might get 120Hz to tell it to turn 3600 RPM.  or 30Hz to tell it to turn 900 RPM.

I don't know what sort of speed control is on this module when it says Frequency.


----------



## jcdammeyer (Nov 7, 2022)

VicHobbyGuy said:


> I have a 2.5 y.o. Bosch fridge - expensive ($4200) and a lovely thing when it works which is does..mostly. A couple of times, it has 'lost its mind' and stopped cooling ... it seemed to recover with a power down a.k.a. 'reboot'. but how can we be confident about a refrigerator like that? Delays in service calls are in the weeks nowadays. I tried getting the 'Extended Warranty' to service the machine - it took over a month before they sent somebody, and when he ran the self-test and like me got no reply from the machine brains, concluded that a new controller board was required. "I'll see about getting a board and we will contact you." 3 months later, they contacted me. Fridge has been working OK all that time so I declined. I figured the odds were 50-50 that 'service' would make things worse. Consequently, I now share my single garage shop space with a full-size 'backup fridge', which I did manage to get delivered in a couple of days after the first 'incident'..
> My advice: If the saga goes toward 'new refrigerator', pick a different brand. But you probably concluded to do that a few days ago.
> BTW, we have a 30+ y.o. small chest freezer in the basement which keeps stuff rock solid frozen, still. We store the expensive (isn't it all these days?) frozen food down there.


Yes.  Rock and a Hard Place.  This fridge has been good except for the defrost drain plugging up with dog hairs.  Solution for a while is to just wait until the ice builds up and then break it out.  Quite possible the buildup internally behind the plastic wall caused the compressor to run to often or too long and that overheated and blew the drive.

We've decided to expand our horizons a bit.  We want something quiet and not all of them are.


----------



## Susquatch (Nov 8, 2022)

jcdammeyer said:


> If I have a motor controlled with CANopen or MODBUS I can send the controller a message to tell it to run 1500 RPM. I can even tell it how fast I want it to accelerate to that. My GS-1 VFD running my lathe has both MODBUS and 0-10V or the pot on the front panel to set speed.



You can set the accel and decel rates on the TECO vfds too and they will also accept external commands.




jcdammeyer said:


> We've decided to expand our horizons a bit. We want something quiet and not all of them are.



This reads like you are giving up on it......



jcdammeyer said:


> But it's just as reasonable that a controller receives a frequency on it's control input that tells it to turn at a specific speed. So it might get 60Hz to turn 1800 RPM which is equivalent to no speed controller at all for our line frequency. It might get 120Hz to tell it to turn 3600 RPM. or 30Hz to tell it to turn 900 RPM.
> 
> I don't know what sort of speed control is on this module when it says Frequency.



Yes, it is just as reasonable. But it's my turn to suggest that this might be making it too complicated. 

The more I think about this and the more I read, the more I think the reference to frequency as a control input is incorrect (by my definition but ok by someone else's definition). I think it is simply feedback of the real speed from the motor back to the VFD so the VFD can adjust the output frequency to compensate for slip.

Compressors are basically pumps. Pumps are continuous load devices. Variable speed pumps can provide significant energy savings but being able to perform well at different speeds requires slip compensation. This is very commonly done with an encoder on the motor so the VFD can know the motors exact speed. The encoder feedback is a frequency by anyone's definition. Whether you call it an input or a control is just an arbitrary choice. 

I come to this opinion because:

1. Encoder feedback is a frequency. 
2. Most VFDs can be set to use motor feedback from an encoder. 
3. VFDs that drive Pumps commonly use encoder feedback to adjust for slip. 

It just seems too coincidental to conclude otherwise. 

Unless you disagree with this assessment, my curiosity is sufficiently satisfied. 

Back to your fridge..... I doubt encoder feedback (or control) is the cause of your problem. So prolly no need to think further about that possibility. 

I'm sorry John, I can't think of anything to try beyond what you have done. Unless you can get better service info it may well be that your only option is part swapping (which I hate). I'd guess that swapping out the compressor is impractical though - certainly beyond what I would tackle. So that leaves you with the other boards and components. Almost like Russian roulette.


----------



## jcdammeyer (Nov 8, 2022)

Susquatch said:


> The more I think about this and the more I read, the more I think the reference to frequency as a control input is incorrect (by my definition but ok by someone else's definition). I think it is simply feedback of the real speed from the motor back to the VFD so the VFD can adjust the output frequency to compensate for slip.


The two pin connector is an input from the controller and is not in any way connected to the motor.   The only connection to the motor is via 3 pins and frame.


Susquatch said:


> 1. Encoder feedback is a frequency.
> 2. Most VFDs can be set to use motor feedback from an encoder.


This should not be thought of as "Most VFDs" and there is no encoder feedback.


Susquatch said:


> 3. VFDs that drive Pumps commonly use encoder feedback to adjust for slip.


In the commercial world maybe but the two I have (in an earlier photo) do not have encoder feedback.  They might well detect back EMF from the driven current to detect slipping.  I doubt this compressor Single Phase to Three phase driver is that sophisticated.


Susquatch said:


> It just seems too coincidental to conclude otherwise.
> 
> Unless you disagree with this assessment, my curiosity is sufficiently satisfied.


This is as far as I have gone with the reverse engineering.  I can't easily remove the board from the plastic box as the heat conductive glue under the driver transistors and input diodes used for the voltage step up circuit are encased in this glue and stuck onto a metal plate which in turn is clipped onto the plastic box.  So I can't trace from the bottom of the board.  

Contrast that again with the full metal heatsink on the red Baldor VFDs or even the STMBL in the earlier photos.

Note here that the control input could conceivably be simple ON/OFF optically isolated or a frequency request in or even PWM in.  

It's when I put the scope ground onto the ground side of the 100R resistor that it went up in smoke. After replacing that resistor the system no longer behaves as before so I broke something else too.

When the module was still in the fridge I measured the AC voltage across CN05B at 2.5VAC (RMS).  

The power input terminals are marked N and P.  There is infinite resistance between the N and the Ground pin.  There is 10 MegOhm between the P and the ground pin.   But the AC coupling may be a lot lower and I should have either isolated the scope ground or used an isolation transformer to so the scope would float and not conduct current through the ground pin.  A rookie mistake.  Or an old fart mistake in this case.






Susquatch said:


> I'm sorry John, I can't think of anything to try beyond what you have done. Unless you can get better service info it may well be that your only option is part swapping (which I hate). I'd guess that swapping out the compressor is impractical though - certainly beyond what I would tackle. So that leaves you with the other boards and components. Almost like Russian roulette.


The single phase to 3 phase motor control modules are known to fail.  Bosch part diagram #D608.  I have one in a shopping cart at $492.86 at PartSelect.ca and can ship today if I order in the next 4 hours.  Don't know what shipping would cost.  

Not sure if I will do this or just get a new fridge.


----------



## Susquatch (Nov 8, 2022)

jcdammeyer said:


> The two pin connector is an input from the controller and is not in any way connected to the motor. The only connection to the motor is via 3 pins and frame.



Well that settles that! LOL!

Don't be so hard on yourself. You do WAAAAY better than most. 

Ya, $500 plus shipping is a LOT to gamble. If it was under 200 I'd be a player but prolly not at 500 plus. Any chance it could it be returned? 

I vote to cut your losses at this point too. You gave it a great shot.


----------



## jcdammeyer (Nov 8, 2022)

The new replacement single phase to three phase compressor driver now has a Purolator tracking number.  Appears to be coming from Calgary so will be here on Thursday. 

This was the easiest decision assuming it fixes things.  Why?  Because any other fridge we want has at least a two week delivery.  

I tested the opto isolator and sure enough it still works.  Using my IR temperature probe the two power supply chips sit about 6C above ambient.  However the processor also rises to 8C above ambient.  I'm pretty sure that flash of burning resistor due to the high AC voltage coupled through the scope ground also fried a part or all of the processor.  No holes.  But still dead I suspect.

For my own stuff when I get a unit back with fried processor I just remove it, solder in a new one and install new firmware.   Probably not that hard to get a replacement processor but firmware not so much.

Now fingers crossed that it was only the compressor driver that was defective.


----------



## Susquatch (Nov 8, 2022)

jcdammeyer said:


> The new replacement single phase to three phase compressor driver now has a Purolator tracking number.  Appears to be coming from Calgary so will be here on Thursday.
> 
> This was the easiest decision assuming it fixes things.  Why?  Because any other fridge we want has at least a two week delivery.
> 
> ...



Now we all wait. I'm praying with you.


----------



## jcdammeyer (Nov 10, 2022)

Purolator arrived just after 2:30PM.  Took a few hours after replacement and powering up the fridge in Super Cold mode to reach this temperature.  But the fridge has been repaired.


----------



## PaulL (Nov 10, 2022)

Most chillingly excellent!


----------



## jcdammeyer (Nov 11, 2022)

PaulL said:


> Most chillingly excellent!


Thanks.  Just sad that I toasted the original board which I think I could have repaired.
The replaced board was made in 2017.  The original in 2008.  The fuse is different but for the model and version number is the same.   Made in China.  With COTS type drivers and ICs.  A perfect candidate for "Right to Repair".

If I step back a few years (OK, more than a few) I've run into this sort of thing before.  I took Electronics 10..30 in High School.  We learned basic electronics and these new things called semiconductors.  Since I was in the Radio Broadcasting club doing both announcing and the electronics maintenance it wasn't surprising that my career after high school was a disk jockey job at a very small radio station; CJOI 1440 AM.

They had an automation system.  Tapes, cartridges (like 8 tracks but pinch roller was in the machine, not the cart) and two big long tapes with even and odd time of day announcements.  The reel to reel held the music, the carts the commercials.  The selection of items was done with... get this... punch cards.

The IGM system (International Good Music) would read the first 3 columns of the card and preselect the device.  Rotate the cartridge carousel to the right spot and load the cart read to play.  Read the proper reel to reel. 

Now if it was a Time Card with T00 in the first 3 columns it knew that a time announcement (even or odd) was next and once per minute the system incremented the cart with the time announcements to the next minute.  But these were short.  Often shorter than the time to sequence a carousel to the correct position and load a cart.

The system would read the card, eject it and read the next card's 3 columns and queue up that device.  Then when the current song or commercial was done, the time would play and then the queued cartridge.  No delay.

The system was broken.  It would read the time card.  Kick it out as expected.  And then kick out the entire deck.  All the commercials and music.  Once the reader was empty it would default to the reel to reel player and just do music.  Until the tape ran out...

Long story shortened is the system came with schematics and standard RTL logic devices.    My education and hobby experience helped to solve the problem.  During the evenings for the first 2.25 hours of my shift I had to play religious tapes.  So I spent some time trouble shooting the machine that might cost me my job.  

After finding a temperature sensitive RTL chip in the card reader logic section and replacing it the card reader went from reading the first 3 columns with a tick tick tick sequence to burp sequence easily 10x as fast.  When the tick tick tick took too long the timer expired and ejected the cards to the end of the deck.

Fixed!  But I didn't lose my job.  They no longer wanted the automation system.  The secretary claimed the Model 735 computer driven IBM Selectric Typewriter as her own typewriter and the Automation system was abandoned.

Without schematics and standard RTL devices it would have been very expensive to repair if at all.


----------



## Susquatch (Nov 11, 2022)

jcdammeyer said:


> Purolator arrived just after 2:30PM. Took a few hours after replacement and powering up the fridge in Super Cold mode to reach this temperature. But the fridge has been repaired.



Absolutely awesome news John! I have been holding my breath on this end hoping for that outcome! I feared the worst so this is a great outcome if you ask me!


----------



## jcdammeyer (Nov 11, 2022)

The sad thing is this motor driver module is made in China.  Other than where the fuse sits it's pretty well identical to the first one with even the same barcode ID for control type.  Made in 2017 instead of 2008.  There is no way it should cost $500.  Lots of people along the way getting their cut.

Especially when it was possible to build up something like this which has two boards, two processors, fan, heatsink and more connectors for about $120.  This is the STMBL and runs a 3 phase servo motor with encoder and either step/dir or serial protocol etc.  The key to it was the transistor driver array which is now discontinued.  I don't know if a replacement was found.

More on this in a CNC thread I'll start soon.


----------



## jcdammeyer (Nov 12, 2022)

The STMBL motor driver in the photo presented in the previous post was developed and the code etc. is available in this new thread.








						STMBL motor driver -- Electronics and Software.
					

This thread will be about the STMBL drive which is open source for both hardware and software.  However it's poorly documented and now 6 years or so old.   https://github.com/rene-dev/stmbl A link for getting started is here...




					canadianhobbymetalworkers.com


----------



## Tecnico (Nov 14, 2022)

Susquatch said:


> Absolutely awesome news John! I have been holding my breath on this end hoping for that outcome! I feared the worst so this is a great outcome if you ask me!


+1

Been crossing my fingers for a good outcome, congratulations!

D


----------



## jcdammeyer (Nov 25, 2022)

My Capacitor ESR tester arrived today.   Checked a bunch of random caps in my junk box.  They all appear to be good.  Next step.  Dig out the original 3 phase motor controller and check the caps and compare them with the new ones that came from Mouser.  If any are off I'll replace them, power up the board and see if that 4.9V supply jumps up to what I read somewhere is supposed to be more like 6.8V.  
Not that this will fix the board since I likely blew up the processor but it will create some closure.


----------



## Susquatch (Nov 25, 2022)

jcdammeyer said:


> My Capacitor ESR tester arrived today.



Which one did you get? Do you like it so far? Would you buy it again?


----------



## jcdammeyer (Nov 25, 2022)

Susquatch said:


> Which one did you get? Do you like it so far? Would you buy it again?


I didn't get mine from Amazon.  My label isn't covered up like the amazon one and I got two sets of probes with mine.  Price with shipping was about the same.


			https://www.amazon.ca/Capacitance-MESR-100-Ranging-Circuit-Tester/dp/B07X3SDWYX
		






To be honest I have no experience with ESR testers.  The chart was crooked on the front but then I don't always get the sticky's down square either.  Zeroing with the leads shorted does not result in 0 but in 0.002 or so.  Not sure that's a real issue.  The auto range and manual range appear to work.

I measured a brand new 220uF 35V which worst case, the label says is 0.170 Ohms.  I measured it at half that.  The data sheet for the device states 0.16 Ohm impedance.  So I'd say this brand new one is pretty good.    I'll measure the one in the power supply and report back.


----------



## Susquatch (Nov 25, 2022)

jcdammeyer said:


> I didn't get mine from Amazon.  My label isn't covered up like the amazon one and I got two sets of probes with mine.  Price with shipping was about the same.
> 
> 
> https://www.amazon.ca/Capacitance-MESR-100-Ranging-Circuit-Tester/dp/B07X3SDWYX
> ...



Thanks John.


----------



## jcdammeyer (Nov 25, 2022)

So I pulled out the big one.   It's within spec.  Then a couple of the smaller 33uF 25V.  Holy S%$t.
New one has an ESR of about 0.65 Ohms.  The two I pulled are 16 and 18 Ohms.    Since low ESR is important in switching power supplies it's not a surprise that these two (which are for the two low voltage supplies) resulted in what was probably a low voltage reading..
Had I waited one day and then just arbitrarily  replaced the caps it's likely the compressor drive would have worked.  As long as I didn't put the scope ground on the wrong pin.

Now I'd love to get one of the installed Lions Gate Bridge Lights back into my shop so I can measure the cap in that one and compare it to one that has maybe 10 hours.


----------



## jcdammeyer (Dec 2, 2022)

Here's my last posting on this subject.  Finally got around to installing the new capacitors in the defunct 3 phase driver.  Connected it to the motor and of course it still doesn't work since I toasted the processor.

But.  Now instead of seeing about 6.5 V across one of the 33 uF 25V caps I now measured 16V which is more in keeping with the drive requirements of the transistors used to make the 3 phase power for the fridge compressor.  

So had I waited and installed the replacements that arrived the next day and not pulled out the scope I'd have had a successful repair.

Up side?  There's always an up side.  I now own a Capacitor ESR meter.


----------

