Service factor for electric motors
Service factor for electric motors
(OP)
A quick question regarding the service factor on the nameplate of electric motors. This is the percentage above rated HP the motor can operate safely. My question is whether this means the motor can run at this elevated HP for extended periods? Or is it simply intended for short intervals. What effect would running it for long intervals have on the life of the motor?
Steamguy2
www.SteamPlantEngineering.com - Discussion & resources for professionals in the Power Generation Industry





RE: Service factor for electric motors
Most likely the actual temperature rise will increase by more than 10C going from FLA to SFA.
The halving is an empirical relationship and there are a lot of assumptions built into it.
Most people would consider SF loading is intended for temporary overloads not continuous operation.
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RE: Service factor for electric motors
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: Service factor for electric motors
RE: Service factor for electric motors
RE: Service factor for electric motors
Using the motor continuously into its service factor as in the pump industry is not a recommended practice.
Pump industry providers, having a fierce competition for initial cost, offer a motor-pump sets operating into marginal limits that will result in a problem for the final user.
Since the voltage fluctuations, phase unbalance and harmonic content of the electric power supplied to the motor will increase the motor losses; working on the service factor will result in shortened life expectancies for the motor.
RE: Service factor for electric motors
3300V 1195HP 50Hz
%Load Pf% Eff%
115 91.2 93.7
100 91.6 94.6
75 91.8 95.8
That loss of eficiency translates to more heat losses, which will result in higher winding temperatures and earlier insulation breakdown. Maybe if a pump application is not really using all of the available HP anyway, the net result would be negligible, but no matter what, heat x time = failure.
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: Service factor for electric motors
Steamguy2
www.SteamPlantEngineering.com - Discussion & resources for professionals in the Power Generation Industry