ac induction motor

[jacktheripper]

Curiously what are the implications of operating these motors in their service factor and at 50%,100% loads and in overload.

 

[buzzp]

Well, anytime you operate in the service factor you are reducing the life of the motor (See many other threads). Also, operating at reduced load will cause the efficiency to go down, as well as decreasing the power factor. The motor may or may not run cooler at reduced load.

 

[electricpete]

good discussion by buzz.

except I didn't know what you meant by "The motor may or may not run cooler at reduced load". To my knowledge decreasing load always decreases temperature. No-load losses are at most approx 60% of total losses. The remaining losses (load losses) vary approx with the square of load.

 

[buzzp]

electricpete, that comment was for submersible motors. Should of made that clear.

 

[jbartos]

Suggestion to jacktheripper (Electrical) Jul 1, 2002 marked by ///\\\.
Curiously what are the implications of operating these motors in their service factor
///If you follow NEMA MG-1 statement, the motor will have shorter lifecycle. However, the motor can be built to operate within overload condition corresponding service factor and it can outlast its identically rated motor with the same service factor, e.g. SF=1.15, continuously operating at SF=1.0 or lower. This is may be difficult to understand; however, the motor life-cycle in continuous operation depends how the manufacturer builds it. This is somewhat similar to the inverter duty motors.\\ and at 50%,
///Efficiency low, power factor may be somewhat higher or lower (it just depends on the motor design), lifecycle higher, slip small, etc.\\100% loads
///The motor rated parameters should prevail, depending on the motor manufacturing tolerances.\\ and in overload.
///It just depends on how big overload. It can potentially burn.\\

 

[jacktheripper]

Thanks gentlemen, for your reponses it has really cleared some doubts up.