@gunrunnerjohn posted:I've had less stellar results than Roy with running four motors. I have several sets where it worked pretty well, but then a couple of others the cruise behavior was almost nonexistent.
I have to disagree about the drive FET's. While in a perfect world they'd not dissipate much power, I've replaced FET's due to stalled motors on a number of Cruise Commanders and Cruise Commander M boards. I've yet to have to replace the bridge rectifier on any of them. I can't comment about exactly what in the design makes the FET's vulnerable to overload, they certainly seem to be the weak link in the chain.
IF you overload a MOSFET driver, it has such low on resistance, it is gonna burn...
That being stated, the Cruise Commander will handle 4 motors. If within the operating currents of the MOSFETs and running 4 motors with a consist, the Bridge Rectifier is the one to reach the highest temperatures. Over the long term the Bridge will "leak" from running hot and then the diodes in the bridge won't block reverse current flow well. While the bridge may survive, the MOSFTs will fail in this case. which probably explains why you see the MOSFETs fail.
Roy is correct, that the Bridge needs to stay cool, and thus the MOSFET drivers will not degrade and fail over time.
jon
