[Dale(294engr]]

Metal chips entering Victor result from not so careful drilling & filing i.e. lack of prior adequate protective covering over electronics+motors to catch metal flakes (usually aluminium) as the typical culprit leading to sparks, smoke & destruction from highly conductive metal slivers which easily enter under the fan ....into the big unprotected air hole in Victors... over & cooling the H-bridge FETs (high current electronic switches) Fan helps to maintain lowest temp = lowest possible "ON" resistance from positive temp coefficient of FET (=loss = heat via P=I^2R watts when FET turns ON)

A second cause of failure albeit less frequent is "high voltage spike punch through" source to drain =high current path of the Victors FETs shorts +12v to ground withing thes 9 parrallel devices, resulting in sparks, smoke and sometimes fire depending on how fast the circuit breaker trips.

Such high voltage spikes are unavoidable in PWM switchers, as physics demands when energy is stored in an inductor via magnetic field (motor armature) then abruptly removed, the voltage increases as the field cuts quickly the through multiple windings, Voltage approaches infinity!!

V=L/time short transition time in PWM result in very high voltage spikes

(or until something breaks down like the enamel insulation on magnet wire)

so the design must consider this and protect the FETs

.. occassionally built-in protections fail and sparks fly.

It is amazing it doesnt happen more frequently.. but it does happen! in this case it is not your fault nor one you have control.

Merely replace the Victor... and assure NO metal filings enter in the future (instruct team to cover all electronics prior to filing drilling and be careful removal of cover not let any fdebris fall into electrical areas. (also the vents holes of motors are vulnerable to such contamination shorts)

Good Luck this year...