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Motors with capacitors

Motors with capacitors

Motors with capacitors

(OP)
Can somebody please explain to me, what the reason for installing a capacitor to the terminals of a DC motor.??

Is it somthing to do with suppression or modification of terminal resistance.??

Thanks and best regards,
Russell......

RE: Motors with capacitors

If the capacitors are small the reason fo installing them might be EMI-reduction.

RE: Motors with capacitors

electricuwe - would that be reduction of voltage spikes during switching?

RE: Motors with capacitors

I've most often heard of capacitors being installed on motors for power factor correction.

RE: Motors with capacitors

power factor correction for dc?  I can't buy that one.

What about a universal motor intended for either ac and dc.... would it possibly have  a starting capacitor? (I'm not too familiar with them).

still wondering whether electricuwe was talking about emi during starting or running.

RE: Motors with capacitors

Oops, missed the dc part.  

RE: Motors with capacitors

Mechanical commuation by the commutator causes spikes similar to electronic switching. At least for small DC-motors it is common to add some small capacitors to avoid RFI.

RE: Motors with capacitors

Pete... A universal (drill, vacuum)motor needs no cap for starting. You could put a cap across the line with the motor for the spikes as Electricuwe points out.

RE: Motors with capacitors


As a kid, it was virtually impossible to find a mil-surplus DC motor that did not have a <1ìfd "bathtub" capacitor strapped across its power terminals.  
  

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