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Tips/Techniques 3 Phase motor

Tips/Techniques
Dabbler said:
@Tomc938 @justin1

Welcome to the wonderful world of NEMA motor sizing... Especially with offshore equipment!!!

I use this chart, and it hasn't let me down, yet. This way you can be sure the motor diameter, the mounting base and bolt holes, and shaft diameter will work, and tells you what to measure..e Saves a lot of trouble.
Click to expand...
Thanks John! I’ll do some measuring and checking tomorrow. Thankfully I have a hole mover in my shop just in case.
 
Dabbler said:
@Tomc938 @justin1

Welcome to the wonderful world of NEMA motor sizing... Especially with offshore equipment!!!

I use this chart, and it hasn't let me down, yet. This way you can be sure the motor diameter, the mounting base and bolt holes, and shaft diameter will work, and tells you what to measure..e Saves a lot of trouble.
Click to expand...
That motor seems to be IEC-European motor sizing.
 

Attachments

Tomc938 said:
Thanks John! I’ll do some measuring and checking tomorrow. Thankfully I have a hole mover in my shop just in case.
Click to expand...

Looking good. I like Baldor Motors.

It isn't VFD Rated but that won't be an issue if you keep the frequency between 50Hz and 75Hz. You can prolly safely push that to 40 and 80 (which is a sweet 2:1) if you keep the loads low. Just watch the motor temp at low frequency and the bearing temp at high speed.
 
Susquatch said:
Looking good. I like Baldor Motors.

It isn't VFD Rated but that won't be an issue if you keep the frequency between 50Hz and 75Hz. You can prolly safely push that to 40 and 80 (which is a sweet 2:1) if you keep the loads low. Just watch the motor temp at low frequency and the bearing temp at high speed.
Click to expand...
Agreed, FWIW I have a non VFD rated motor on my drill press, when I'm drilling large holes, say 1" I turn the speed down really low, not sure how low but I'm guessing < 20Hz and if I put my hand on the motor case after drilling a few holes like that it's basically at very most slightly warm perhaps 30-35 deg C. I don't have any extra cooling, I'm going to worry about that old motor the day it gives trouble, but my hunch is I will be long gone by then. Not sure how old that motor is, it was an eBay special from a commercial dryer. Probably would be different if I was drilling all day, but for intermittent use at slow speed it works like a champ. I think that Baldor is going to do a great job and might surprise to the good side at lower speeds, please let us know.
 
The 3hp motor on my Emco lathe is non vfd rated, and it also barely gets warm doing fairly heavy work at 25hz. I am aware of the potential issues though, and will usually go to a lower gear on the lathe if I anticipate prolonged low speed use.
 
I have found plastic fans on some motors, this is/appears to be part of the problem with cooling at low Hz operating of some motors. The motor starts to get warm, the fan being plastic expanses more then ment for and slips on the shaft lowering cooling/raising temps of motor more. I have found a few cooling fans not doing anything but rattleing around on the shaft. Needless to say the motor may soon let the smoke out.
Older motors and high end motors generally have a metal fan and a keyed shaft and are a bit more robust then a lot of present motors. So maybe a old barn with little heating maybe a good thing.
Keeping cooling screens/ vents clean and unblocked can make a big difference and maybe an extra cooling fan too. A vfd rated motor is sometimes the way to go --- if you can find one and the money to get it.
 
Does anyone remember the movie Apollo 13? Specifically that character who was the manufacturing rep for the LEM. As I recall, he has only two scenes - the first to tell the flight director that his company couldn't guarantee performance of the craft when used out of spec; and the second to fist pump the performance of the craft his company produced

Out of spec operations on AC motors are much the same. It might melt, but if it doesn't it can do a lot.

More seriously, AC induction motors are very simple machines. Not so simple as the inclined plane, but they are chunks of iron and copper. Like the other thread about cutting threads, know the math before you experiment too broadly, but unless your duty cycle is continuous, there is quite a lot of leeway

Is it Friday yet?
 
Clough42 has a good series of videos on installing a new motor and VFD. Very thorough. I would consider adding additional cooling if I plan to run it slow for long periods of time.

So far I works with things 4" or smaller with only the occasional work on something larger.
 
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