Motor Connections

[jmcinty2]

I recently had a discussion with an engineer, about motors that are frequently failing on one of our lines. Some background on the motors;
Bodine Motor; Volts 208-240/360-415AC, Amps 1.3-1.6/0.7-0.9, Rev/Min 1700, KW .210, 50 cycle. Rated for continuous duty. Motors are used on conveyor system carrying minimal load. Feed to motors are 480 volt Ungrounded Delta.

Motors are continually failing, but no one can come up with the reason why. The bearings on the motor seem to be failing due to excessive heat. There is much speculation on why, but no one can come up with the answer.

The engineer said that the problem may be with the service. He said that the (main service) if connected Delt and not Y connection may have an effect on these motors. Did anyone run into a problem like this before????? Also, voltage drop for a motor 5% or 10%????

Other lines using the same motors are not having a problem.

 

[infinity]

Re: Motor Connections

Are the motors operating at 50 Hz or 60 Hz?

 

[petersonra]

Re: Motor Connections

Originally posted by jmcinty2:
Bodine Motor; Volts 208-240/360-415AC, Amps 1.3-1.6/0.7-0.9, Rev/Min 1700, KW .210, 50 cycle. Rated for continuous duty. Motors are used on conveyor system carrying minimal load. Feed to motors are 480 volt Ungrounded Delta.


Other lines using the same motors are not having a problem.

We really do not have adequate information here. If the following assumptions are true, there may be a couple things you can look at.

Assumption 1: Your plant is fed with 480V/60Hz, and this is what is feeding your motors.
Assumption 2: The nameplate ratings on the motor are as described (which seems odd).

I would suggest you are running the motors at a faster speed than they are designed for. This may be what is causing the bearing failure regardless of actual load.

You may also find that the load is more than you think, at least for some periods of time.

I am curious why you would use motors rated for 50 Hz on a 60Hz power supply.

You may find that you can put a VFD on the whole line and supply 50 Hz power to these motors.

[ July 01, 2005, 03:13 PM: Message edited by: petersonra ]

 

[jim dungar]

Re: Motor Connections

Motors do not care if the service is wye or delta. All they care about is voltage and frequency.

What frequency do you have?
Is the load smaller than the motor rating?

 

[benaround]

Re: Motor Connections

jmcinty2,

Why would you get these motors and wire them with 480vac?

What is the problem ?

(A) You have the wrong motors. That extra 65 volts will get you a little extra heat.

There are plenty of times you'll need a buck/boost transfomer on a motor rated 230vac and all you've got is 208vac.


frank

 

[Ken9876]

Re: Motor Connections

Motors are continually failing, but no one can come up with the reason why. The bearings on the motor seem to be failing due to excessive heat. There is much speculation on why, but no one can come up with the answer.

Are the shafts & couplings lined up correctly?
Is there to much tension on the belts or chains?
How Fast are they failing?

 

[tom baker]

Re: Motor Connections

Are these motors fed from VFD?
VFD's can cause circulating currents in the bearings and the bearings will pit. There is a simple solution its a type of grounding device for the bearing, but I don't have the details on it.
For a 480 v system, motors are rated 460 volts, designed to be operated at +/- 10% volts from 460.

 

[jmcinty2]

Re: Motor Connections

Further investigation showed the feeds to the motors are 208volt 3 phase. Feed from a step down transformer 480 delta /208/120Y. No VFD involved. Motors are running on 60hz. The motors are also rated to run at 50hz or 60hz. Also the motors are European (German).

 

[1madison]

Re: Motor Connections

Are these motors the original motors, and if so did this problem just start happening.Are these replacement motors , and if so what was the reason for replacing the motors what were the previous motors rated .It sounds as if someone purchased the wrong motors as 460 volt motors are standard ratings.

 

[physis]

Re: Motor Connections

I'm still curious what the actual voltage at the motors is. Hasn't it been measured?

 

[dave0317]

Re: Motor Connections

Bodine Motor; Volts 208-240/360-415AC, Amps 1.3-1.6/0.7-0.9, Rev/Min 1700, KW .210, 50 cycle. Rated for continuous duty. Motors are used on conveyor system carrying minimal load. Feed to motors are 480 volt Ungrounded Delta.

Further investigation showed the feeds to the motors are 208volt 3 phase. Feed from a step down transformer 480 delta /208/120Y. No VFD involved. Motors are running on 60hz. The motors are also rated to run at 50hz or 60hz. Also the motors are European (German).

not a unusual motor. ive seen hundreds used in a plant with european equipment. u say in first post that the motors are feed with 480v, yet upon investigation, its really fed by 208v. most all motors are recieved from motor shops if dual voltage are wired for the higher voltage. maybe unpon replacement the motor leads has not been changed for the voltage used? if connected for high voltage, yet fed low, the motor will still operate, but will build excessive heat. the speed will be slower, yet may not be detectable without using a hand tach to verify.

 

[jmcinty2]

Re: Motor Connections

We had the vendor come in and check out the motors. Turns out the bearings are bad (Made in china). We are in the process of changing out 20 motors on the line. Engineer still thinks its a voltage problem. Thanks for the input and suggestions. Very Informative site!!!