I have a AC motor that uses a non-polar capacitor and at steady state it is around 50[Vpp]. When the motor is switched off it somtimes has large transients of about 140[V] over the capacitor but they are about 50[Mhz] and very short in duration (about 50ns!). If the cap is only rated for 100[V] is this miniscule transient going to have any real effect on the lifespan of the capacitor?

Thanks for your input.

 

The best answer at the moment is that it might degrade the capacitor over time. What can you tell us about the capacitor?

 

I'd be more worried about the switch. I'd suggest a contact suppressor across it. Then you won't get a click on the radio when you switch it off.