DC Motor Efficiency???

[swwee]

Dear Friends,

Can someone enlighten me why there is "NO" efficiency requirement for DC motor ?

Thanks.

 

[Lewish]

What kind of "requirement" are you referring to. Most DC motors I am familiar with have an efficiency rating on the decal of the motor. But, I have rather limited exposure to DC motors.

 

[swwee]

Thanks for the response. The requirements that I am referring to the efficiency levels defined by EPAct in US, NRC in Canada, and CEMEP eff 1 in Europe.

 

[Lewish]

Ah, yes, those. I thought of EPac, but not the others. Consider this thought: AC induction motors have been running at efficiencies of way under 80% for many years. Only in the last few years have we seen increasing availability of good to very good efficiency in an AC motor. Even today, I know of some vendors who manufacture a very quality motor, in terms of life expectancy, resistance to environment, etc., but which still only has a 75% efficiency rating.
DC motors on the other hand have been in the high 80% range for years and typically you find they are in the low 90% range. So, I guess no one considered it necessary to put out a requirement on them.

Hope this helps.

 

[jbartos]

Suggestion: DC motors have lower efficiency in comparison with induction motors since they use resistors for starting, speed control, and commutators for the current switching to appropriate windings or turns. Although, some improvements, e.g. dc motor drives, improve DC motor control efficiency in comparison to the resistor speed control of a DC motor. Also, the DC motors come in a smaller number from production lines in comparison to AC motors.