460 V motor on 495V
460 V motor on 495V
(OP)
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?





RE: 460 V motor on 495V
Muthu
www.edison.co.in
RE: 460 V motor on 495V
RE: 460 V motor on 495V
That could be a function of:
1 – the mechanical load
2 – the overload setting
3 – malfunction of overload or high ambient temperature at overload
It is not immediately obvious that high voltage is the problem to address. If anything, high voltage (within reasonable limits) tends to reduce current for motors under load.
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RE: 460 V motor on 495V
The power company is usually able to drop the voltage in 21/2 steps. Failing that if youcan find a couple of 480:12V dry type transformers that are buck boost rated they may be connected in auto-transformer wye configuration to drop the voltage about 12 Volts. I am skeptical that the voltage is causing the heating. How is the no load current?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 460 V motor on 495V
Rafiq Bulsara
http://www.srengineersct.com
RE: 460 V motor on 495V
David Castor
www.cvoes.com
RE: 460 V motor on 495V
380 V - (Corresponding to 460 V, 60 Hz) - 9.9 Amps
415 V - 12.8 amps
A 9% rise in voltage increased the no-load current by nearly 30%.
I would suggest reducing the voltage at the source.
Muthu
www.edison.co.in
RE: 460 V motor on 495V
Near full load, it should act differently.
Here foe one motor you'll see below 100% voltage, current is decreasing as voltage increases. From 100 – 105% voltage the current is roughly flat. Above 105% it starts increasing.
http:
I suppose there is a remote possibility if your way into saturation higher voltage with other factors kicks you over the edge. But in that case I believe the motor is overloaded (or overload set incorrectly) anyway. Properly loaded motor at 10% overvoltage should not trip.
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RE: 460 V motor on 495V
RE: 460 V motor on 495V
I think maybe there are other issues at play here. Can you post the make and model of the overload relay, along with heater elements or trip dial settings, motor nameplate data and if possible, measured current? There is more here than meets the eyes, especially of those of us thousands of miles away.
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RE: 460 V motor on 495V
How about you post the motor nameplate details and the load currents you're measuring ?
Muthu
www.edison.co.in
RE: 460 V motor on 495V
Voltage measured at the site is 495/494/493 with 1.5/1.6/1.7 amps measured. Motor is coupled to a pump moving about 30 GPM and even with the flow control valve turned down the motor still overheats and trips out. The overload is an internal style snap switch similar to those made by Klixon.
RE: 460 V motor on 495V
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 460 V motor on 495V
Try the following or a combination there of:
1. Lower tap settings, if possible and see if it helps.( If shut down is a big issue, buy a small transformer just for the motor)
2. Find a way to reduce the load, if possible.
3. Improve cooling.
Failing that up size the motor. Btw, what type of pump is it? Centrifugal pump will see reduced load by restricting the discharge. Positive displacement pump might see an increase.
Rafiq Bulsara
http://www.srengineersct.com
RE: 460 V motor on 495V
RE: 460 V motor on 495V
How is no-load (uncoupled/open shaft) current ?
Muthu
www.edison.co.in
RE: 460 V motor on 495V
Is this a good quality motor or a no-name out of China?
The water temperature may be pushing the motor temp up. That takes up a lot of your thermal rise overhead.
If you can come up with a pair of dry type transformers rated 480V:12V you can drop the voltage by about 12 volts. With a motor current of 1.7A the 12 Volt winding must be rated for 1.7A or more.
That works out to 20 VA.
A pair of 50 VA transformers should do the job.
I suspect a mechanical load problem rather than an electrical problem but if you are sure the issue is the voltage,start looking for a pair of transformers.
The transformers should be Buck-Boost rated.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 460 V motor on 495V
Not getting a lot of help form the technician onsite. They just did a complete remodel of their facility and claim this is the only motor they are having problems with. Of course the other motors may be wound for 480 instead of 460 making them more tolerant of the high voltage.
RE: 460 V motor on 495V
A complete remodel and now having problems with one motor. Stop agonizing and replace it with the next larger size. Tell them that the new motor is rated for 460V or 480V. No other motors having problems is the answer to your voltage problem. There isn't any. The remodeling has apparently lowered the dynamic head and the pump is now overloading.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 460 V motor on 495V
RE: 460 V motor on 495V
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
RE: 460 V motor on 495V
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: 460 V motor on 495V
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: 460 V motor on 495V
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: 460 V motor on 495V
Could the other motor have failed because the heat of the water cooked the grease out?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 460 V motor on 495V
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.
RE: 460 V motor on 495V
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