Two speed two winding induction motor

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panthripu

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Hi Friends
I would like your expert opinion on one of my finding. An induction motor with two speed two windings and conical rotor , is being used for wire rope winch application.
The slow speed windings when checked with no load takes almost 90% of full load current. This is something surprising for me.
Have someone have similar findings in such types of applications or crane applications ? The motor nameplate indicates 0.9kW,8.3A, cos phi-.45.
 
Smart $

Smart $

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Could be low-speed is wound for high torque, while high-speed not so much. Saves having to have a two-speed transfer case with a single speed motor.
 
Jraef

Jraef

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With a .45 power factor, most of the current you measured with no load would have been because of that poor power factor, which is always bad when a motor us unloaded. For a typical motor with a .7 pf, I've seen the unloaded pf be as low as .2. On a motor with a LOADED pf of only .45, I can imagine the unloaded being less than .1.

Also, a conical motor always draws significant current just on magnetizing it because the magnetizing is part of the work in order to unlock it. You can't make comparisons to a standard motor. Conical motors are for specialized applications, they are not good at using energy efficiently.
 
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Jraef

Jraef

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Sahib said:
There is no relationship between motor efficiency and power factor..........
Click to expand...

Always with the irrelevant side tracks...

I didn't say that. We KNOW the motor already has a poor of, it's on the nameplate. I'm ALSO saying that the current used by a conical motor is not comparable to a standard motor because there is an extra magnetic component to the current draw that is not related to loading. Those TWO factors will contribute to what APPEARS to be unusually high current measurements when the motor is unloaded.
 
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panthripu

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two speed two winding induction motor

two speed two winding induction motor

Great!!!
I appriciate all of you for valuable information.
Jraef,your explanation is quite logical and thanks for such information. By the way , if you or any other have loading/current curves for such low p.f. motor to understand it in better way.
Regarding the dust in the rotor, it is very clean and infact we tried to minimize the air-gap to reduce the current , and it helped but little.
 
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