Gents,

I request your help in order to clarify me which electrical failure modes is possible to detect with ultrasound measurements in DC Motors? Mechanical failure modes seems clearer.

Regards,

Allen

Hola Allen,
what are you expecting to be different?
I have used ultrasound on bearings and I have had some success listening to brushes - particularly for excessive arcing.
best regards,
Tom Murphy

Allen,

The DC Motor that failed on me, initially generated a very low "Humm" and this I believe was due to SCR component defect; 6th LF harmonic.
As this harmonic increased in amplitude over a 4 week period, the "Humm" was audible a couple of hundred feet away; without the need for any gadget.
The failure resulted in Rotor/Stator/Commutator damage.
As Tom indicates, excessive arcing could also be detected to monitor brush wear condition; if there is no inspection window.

Regards...Rajan