460 V motor on 495V

[TDike]

We have a customer running one of our 460V 3-ph 60hz systems on 495V. It's within the +/- 10% tolerance of the motor, but this voltage is sustained and not intermittent. The motor is overheating and tripping the overload. Short of building a custom motor for this application, what can the customer do to reduce his voltage?

 

[DickDV]

Why is this motor judged to be overloaded when the Service Factor Amps is 1.9 and the measured amps is 1.5-1.7?

 

[rbulsara]

Is service factor amperage for continuous duty? This has always baffled me. I only understand full load or rated amps.

Beside, the motor is overheating and tripping so whatever amps it is drawing the cooling is not enough. (may be bad t'stat but I doubt it)

Rafiq Bulsara

http://www.srengineersct.com

 

[electricpete]

with the flow control valve turned down the motor still overheats and trips out.

What is the current when flow control valve is turned down?

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[electricpete]

... my point being if you are tripping at lo current it would be obvious thermostat problem. As it is at 1.7A it's a tougher call whether it is an overload or thermostat problem.

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[jraef]

Kilxon protection for a 480V 3 phase pump motor? Hopefully that is not the only protection you are using. If so, most likely the fluid heat is getting transferred to the motor case, however indirectly, and causing them to open. I would disable those thermal devices and use a solid state overload relay in the motor starter. You should have 2 brown wires in the peckerhead that are going to a relay somewhere or up to the controller. those wires are the thermal devices (there are probably two in series). Just disconnect them and jumper out whatever they were going to, then add back in a proper overload protection device.



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[waross]

"Water is 90-100 deg," F or C ?
Could the other motor have failed because the heat of the water cooked the grease out?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TDike]

Water is 90-100 deg F. Pump head is somewhat isolated (except for shaft) with a 1" airgap so water temp plays only a small part on the overheating. Ambient temp is low 80's. Overload is hard wired and not easily accessible without taking the motor apart.

Motor is considered overloaded since amperage is within .2 of the full load amps and the voltage is on the high side.

Other than the high voltage, this setup is no different than hundreds of other installations.

We are going to recommend that the customer talk to their power company about the high voltage.

 

[waross]

If your pumps have a history of burnout when run at full load, either change brands or use a larger pump. You are only 3% over nominal voltage. (There is no standard 460V systems. 460V motors run on 480V systems.
As long as you are fixated on the voltage you will never find the true problem. You probably need to reduce the flow of the pump. Also, check the calibration of your meters.

Bill
--------------------
"Why not the best?"
Jimmy Carter