Reply to post: Reverse polarity is rapid death but electrolytic caps always need care

ASUS recalls motherboards that flame out thanks to backwards capacitors

Anonymous Coward
Anonymous Coward

Reverse polarity is rapid death but electrolytic caps always need care

I sometimes use integrated stepper motor drivers that come with the control PCB attached to the back of the motor in a metal case and they started failing. I opened some up and looked inside to find the smoking remains of a 50V capacitor on the 48V circuit which due to the sealed box always runs hot. I am amazed that any of them survived normal use. Pushing the machine along the axis by hand I could easily generate a back EMF of >60V.

I complained to the manufacturer but they said that the 50V capacitor was fine to use at 48V and don't worry about the heat.

Moral of the story is pick electrolytics with 50% over voltage rating and go for 5000h at 105C as the absolute minimum if they will run warm.

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