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Adding an emergency stop button on 3 phase motor, yes or no

R

RickyD

Member
Hi Guys,
I was wondering after modding my mill and also my lathe to VFD and 3 phase motor, if I should add an emergency STOP button, in case something goes wrong.
I guess, a big red button that would cut the 3 phase current going to the motor. I saw that removing current to the VFD, leave it ON for a couple seconds before it shut down so it's not quick enough. Also, finding and pressing the small STOP button on the VFD is not practical in case of real emergency.
So my question is: Can it damage the motor to suddenly cut the 3 phase power going to it ?
Do you have better solutions for achieving that?
Thanks !!
 
Your VFD should support a low voltage ESD function. Use that. Killing the 3phase between the VFD and motor is not recommended.

ESDNew.JPG


In this picture the LV ESD is on the left. LV FWD/REV/STOP is on the right and the metal ON/OFF sw is for power to the the VFD.
 
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Ok, I understand, and thanks for you comments... I believe my VFD does not have a low voltage control built-in. It requires an optional IO board.
I have the KBDA-27D
I will try to find a way, or get the IO board.
 
General question - does the VFD stop the motor abruptly when this LV eStop is used?

If not, would the addition of an active shaft brake make sense ?

Asking for a friend
 
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Arbutus said:
General question - does the VFD stop the motor abruptly when this LV eStop is used?

If not, would the addition of an active shaft brake make sense ?

Asking for a friend
Click to expand...

No, mine just free wheels to a stop, but I don't have a braking resistor either.
 
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Looking at the KBDA manual, table 12 on page 26, it appears to have a 28 position terminal block with various ways to initiate a STOP.
Page 19 references injection braking.
 
RickyD said:
Ok, I understand, and thanks for you comments... I believe my VFD does not have a low voltage control built-in. It requires an optional IO board.
I have the KBDA-27D
I will try to find a way, or get the IO board.
Click to expand...
wow that is insane, over $600 bucks for the VDF and if doesn't support I/O without an aux board that costs another $150.

In your case though, I'd buy it, because if you wire the motor or the VFD into the e-stop you lose all possible braking. You paid a lot for the feature, so why eliminate it in case of emergency
 
I just purchased another used 2HP Altivar with Sensorless Flux Vector control and external braking, this one was $70 on eBay. I have three used Altivar's now. All work perfectly. The only bad VFD I have experienced was purchased new and failed IIRC with < 10 hours of actual use but beyond the return period from the big river store. I'm sticking to name brands with: certifications, SLV and external braking.

A little FYI about certified vs. non-certified products. Beyond the obvious safety aspect, there are a number of EMC tests performed to verify that the device:
1) Does not radiate excessive electrical noise that will disturb adjacent electronics
2) Can withstand electrical transients that typically occur during electrical storms and switching on/off of motors etc.

These tests require expensive test equipment and some expertise however they quickly demonstrate the failure modes of poorly designed equipment. We fixed products that were being sold for years that would for the most part make it past the warranty period, but where by no means "reliable". We could blow them up 100% of the time with one simple fast transient or combo wave test within seconds. The lucky end users were simply using them in a more benign environment. With just a little bit of additional filtering in just the right location, we could run these tests over and over with no failures. So often that name brand product with the extra $10 worth of components is better value even if it cost $200 more.
 
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In the case of normally open fwd/rev switches, ie non momentary (drum switch, apron switch), the e stop can be wired in series and will initiate braking just as if the regular switch was turned off. Even momentary switches can be wired in a similar fashion but the e stop would become its own input and braking would be programmed separately.
 
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