Caution - Burned out CIM blows Victor

[Ether]

Originally Posted by Al Skierkiewicz

Guys,
The fact that 40 amp breakers are in the circuit means nothing. These circuit breakers can withstand up to 600% overload for a few seconds and 200% for several seconds without trip. Even if they trip, they reset themselves within a second or two. The CIM motor is designed to be intermittent duty. Remember they are designed for trailer hitch lifts so at most they run a minute or two under load and then aren't used for days. They have no holes in the motor to let in cooling air or let out heat. The heat is transferred from the internal structures through the bearing end plates and through the magnet structure via convection and radiation. None of these are very efficient.
As such, when you run practice matches even with normal driving and loads, they eventually build up internal heat. We have toasted CIM motors in demos and long practice sessions. As Sanddrag has pointed out, they were run for quite a while. When the internal temperature runs hot on any motor, the varnish that covers the wire starts to melt. A few shorted windings, lower the power output or speed and lowers the series resistance. So this is a domino effect as the current rises which translates to more heat. At some point the Victor is trying to feed a very low resistance or a short. As great as they are, Victors are not miracle workers. Permanent failure is the result. (sometimes fire and smoke)

Nice summary Al, thanks. Minor point: I think you meant "conduction" not "convection".


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