Rotational Losses of Asynchronous Machines

[okivrak]

As known; rotational losses in an asynchronous machine includes;

* Core Losses
* Friction & Windage Losses
* Stray Losses (Miscellaneous Loses)

For an asynchronous MW size generator; are all the rotational losses constant for all operating conditions? In other words; can we say " Rotational losses of an asynchronous machine are constant at rated load and 20% load"?

Or must we say " Rotational losses should vary as a percent ratio of the input power"?

Thank you.

 

[dpc]

I believe that rotational losses are strictly a function of speed of rotation.

 

[electricpete]

I will tell you the answer for induction motor. I don't know if terms are different for sync generator.

The "stray-load loss" is that portion of total loss not accounted for by the other losses: rotor I^2R, stator I^2R, core, friction/windage. (Ref IEEE112-1996 paragraph 5.4).

The stray-load loss varies in proportion to load-squared (Ref IEEE739-1995 paragraph 3.7.4).

 

[jbartos]

Suggestion: " Rotational losses should vary as a percent ratio of the input power" is more appropriate.

 

[okivrak]

Thank you all for considerations.