DC Motor Voltage Effects
DC Motor Voltage Effects
(OP)
What are the effects of decreasing the terminal voltage on a DC motor (with brushes). I cannot find the manufacturer's data sheet on this specific motor. Is there a certain voltage the motor will no longer work at (assuming it is higher than the back EMF)? Can I say that for every volt it is dropped, the life of the motor will be decreased by x% ?
Thanks,
JT.
Thanks,
JT.





RE: DC Motor Voltage Effects
All of the above is true if the excitation is kept constant or if it is a PM motor.
If there is a separate parallel field winding, there are several other things to take into account. Or if it has a series field winding. None of which has been stated.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor Voltage Effects
Other effects you will have to consider is "brush drop" and environmental conditions such as temperature and humidity.
Brush drop is a non-linear voltage drop which is similar to a silicon diode drop in an electronic circuit. The appearance of brush drop is a consequence of the thin layer of cuprous oxide, an insulator that develops on the surface of the commutator. This is a result of a reaction between atmospheric oxygen and the commutator material facilitated by the heat generated by motor operation and arcing. Note conduction through the cuprous oxide layer occurs due to localized dielectric breakdown when current is passed through the brushes. The pros of this cuprous oxide film are that the voltage drop tends to reduce arcing effects, and serves to extend brush life. The con is that the voltage drop reduces the efficiency of lower voltage motors. Moreover the structural integrity of the film can change in very low humidity environments; consequently brush wear may be accelerated under these conditions.
Hope this helps...