25hp Electric motor heats up
25hp Electric motor heats up
(OP)
I have a 25hp 415v delta 2pole motor driving a pump. It is connected to a 415v (as before) on same supply. When running off load it takes only 3.8 Amps per phase, balanced. On load it takes 25amps per phase,balanced, exactly as an adjacent similar pump and motor. Off load it can run for 1.5hrs with the temperature staying as ambient. On load it heats up in an hour, enough to trip a thermal overload in the windings of 120degs. The other motor runs for long time and does not heat up. When running off load the rpm are 3000 and on load it drops by 100 rpm to 2900rpm. I have never met a similar problem. Can any one help please? Thanks in anticipation.





RE: 25hp Electric motor heats up
I.e. not occluded with debris or paint (if open frame)?
I.e. is the internal fan present, rotating, and properly sized (if TEFC)?
I.e. is the external fan present, rotating, and properly sized (if TEFC)?
Are the windings clean, or covered with ... well, crud?
Is the motor properly sized for the hydraulic horsepower that the pump is producing? (Flow and deltaP and viscosity)
Exactly how similar are the adjacent pump and motor that you are using as a standard?
Mike Halloran
Pembroke Pines, FL, USA
RE: 25hp Electric motor heats up
Keith Cress
kcress - http://www.flaminsystems.com
RE: 25hp Electric motor heats up
Pump or fluid system differenceswould shore in current .
By the way....120 deg C ? Measured where/how?
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(2B)+(2B)' ?
RE: 25hp Electric motor heats up
Bill
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"Why not the best?"
Jimmy Carter
RE: 25hp Electric motor heats up
This is to low.
Do you have any other information: rated current, frequency, efficiency, PF?
RE: 25hp Electric motor heats up
The motor has been working in place for a decade or so according to the owner. I assume that if the motor was overloaded the current would rise more than the other sister pump;s current which is working perfectly well.
Regards and thanks once again
RE: 25hp Electric motor heats up
"Will work for salami"
RE: 25hp Electric motor heats up
Is this a client that you know well? Or is it one of those that knows everything so well and tells you what the problem is and what it is not?
"Identical" is seldom identical.
No nameplate. Also a problem. And that low idling current, I had expected 30 - 40 % of FLA not 3.8 A. Sounds like the motor is running at too low a voltage. Then slip increases and motor heats without necessarily drawing excessive current from grid.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: 25hp Electric motor heats up
RE: 25hp Electric motor heats up
Thanks.I will get to you with the results. Have a pleasant weekend.
RE: 25hp Electric motor heats up
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 25hp Electric motor heats up
One was when a Schorch motor with a warning "DO NOT CONNECT TO A VFD!" on it had been run from a VFD and the other one was a suspect rotor bar problem, but never verified. Motor replaced and no one cared too take it apart. It was just scrapped.
In my world, rotor bar problems are an interesting theory - but very seldom the problem. Bring a clamp with analogue display to see if there are slow motor current variations. There should be if you have a rotor bar problem. But there are others causes for slow current variations.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: 25hp Electric motor heats up
Having given this explanation, my belief is that the motor is improperly connected. This is due to the low current reading for no load operation.
RE: 25hp Electric motor heats up
RE: 25hp Electric motor heats up