3 Phase motor getting hot.

[eceg]

I just replaced same type of motor, same serial #, RPM, HP, everything the same. I got this motor from the manufacture.Before I diconnect the wires, I even wrote down the connections as low voltage connections.I connected the same wire connections on this new motor. It runs for about 15-20 min and it's getting hot. Nothing tripping, no blown fuses. I checked the voltages, all 3 wires has the about the same 205vac. This is very unsual to me.

I called the manufacture and asked them about this, and they said as long as the motor is not over amprage the motor is fine. I even asked the technical, why it didn't get that hot with the old motor with the same connections. They said these motors suposely will get warm. Again, as long as they don't get over amprage is okay.

Any experts here can help me about this issue. The motor runs about 12 hrs a day. I don't want it to be burnt. I was thinking to re-connect the wires to high voltage connections, but the input voltage is 208 @ the control panel. I'm afraid it will blow something if I connect high voltage. Is it okay for me just to test the high voltage to see if the hot goes away? Please help. Thanks in advance.

Regards,

ECEG

 

[dpc]

First step is to check the current into the motor with a clamp-on ammeter. If the current exceeds the nameplate rating, there is a problem.

If you can hold your hand on it, it's probably OK. Motors can get pretty hot if fully loaded.

It would be helpful to know the motor horsepower, nameplate current, and rpm.






David Castor

http://www.cvoes.com

 

[electricpete]

How hot is hot? May not be a problem. It may be that you have a high efficiency motor that is designed to run hotter than the old because they improved efficiency by cutting back on mechanical power diverted to the cooling fan.

There could possibly be other reasons for motor to run hot related to changeout process.... perhaps misalignment, miswiring. Perhaps if you give more details we can guess (hot hot is it, how much current, is it balanced, vibration, etc). But my gut is you are overreacting to the temperature.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[davidbeach]

How do you replace a motor with one of the same serial number?

 

[edison123]

May be he means the same model/frame number.

eceg - Post the nameplate details of both the motors and the motor current now.



Muthu

http://www.edison.co.in

 

[electricpete]

fwiw, we have late 70’s vintage Westinghouse NEMA frame motors where several of them have the exact same thing written into the “Serial Number” block on the nameplate. From what I gather in this case it is actually a date code listed in the block on the nameplate labeled "serial number". That certainly is not what most people would think of as a s/n (unique identifier).

My comments are not very relevant.... Just thought I would rant a little. I wouldn’t presume to speculate explanations for the OP’s s/n.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[DickDV]

As long as the motor amps are within nameplate specs, I wouldn't worry about the temp. Even an Insulation Class B motor is good for 90 degrees C rise over 40 degrees C ambient so that's 130 degrees C--30 degrees hotter than boiling water! I don't think the "hold your hand on it" rule works very good at those temps.

A Class F motor is 15 degrees C hotter than Class B and the Class H is hotter yet.

My guess is the motor's OK. Check the amps to be sure.

 

[dpc]

I don't think the "hold your hand on it" rule works very good at those temps

You have to be able to count to 10 really fast!

An electrician once told me that if you can't count to 10, try 5!!



David Castor

http://www.cvoes.com

 

[rbulsara]

I have operated motors at temperatures too hot to touch. 50 deg. C over ambient rated, outdoors in tropics.


Rafiq Bulsara

http://www.srengineersct.com

 

[eceg]

I'm so sorry all. I was bit busy and didn't have the chance to post the name plate of the 2 motors.

It's GUSHER pump.
Model : 11201-XLONG
Serial : 1203-260
Volts: 230-460
AMP: 1.6 - 8
HP: 1/2
RPM: 3450
CY: 60
Ref: 34G61 - 3229S2
IMP 2281 - B


I just checked the amprage of the wires using clamp on. They are about 0.8 to 1.4 amps. Are they too low? The motor is locked tight, no vibrations. I can feel it's running smooth.



I may have to rebuild the the old pump and put it back, but it looks very rusty & nasty. If I have no other choice, I would have to sandblast, rebuild, and repaint ...Sigh.
All these might properly cost more than a new pump. Not to mention the time spent. I hate to get another new pump...and I end up having the same problem.

Anymore ideas guys. Thanks

 

[LionelHutz]

My idea. Leave it alone and let it work.

There is a problem if either of these are true. You have measured the current with some type of accurate current measuring device and have found the current is above the motor rated current. You have measured the temperature of the motor with some type of accurate temperature measuring device and have found the motor is running above it's rated temperature.

 

[dpc]

I agree with Mr. Lionel Hutz. It's only a 1/2 hp motor to begin with and if the motor is not overloaded, it may outlive all of us.

David Castor

http://www.cvoes.com