Been there, done that, got the T-shirt and the hat. Those Vacon drives (that's what the CH drive actually is) are notorious for fan problems. They do something funky inside like using 3phase motors by running them from single phase with a capacitor phase adder and de-rating the capacity of the motor in order to avoid having single phase motors, but the capacitor phase adder BS fails just as much (more?) than a single phase motor would. Then when you replace the motor, it still doesn't work because that wasn't the problem. There is an entire fan control assembly that must be replaced. It may end up costing you almost as much as a new drive. I just did this on 250HP Vacon drive, the repair was going to cost almost $10k, new (not Vacon) drive was $14k. Guess which way we went...
Ah, just noticed you said 10HP, that may not be the same. Still, Vacon are notorious for fan failures at any size, so there is likely still some sort of fan control assembly inside that is defunct and needs replacement. My theory is that because they are made for the 50Hz world and the fans are AC powered, the system fails over time when connected to 60Hz. Most other mfrs power the fans with DC do it doesn't matter, but that requires a DC-DC power supply inside. It seems Vacon tried to avoid that by powering the fans with AC but failed to account for the 60Hz issue properly. I experienced this with the first generation of Sq. D drives that came out after Schneider bought them and began using the Telemecanique products instead of the old Sq. D Omegapack drives here in the U.S. Lots of fan failures until they changed the entire drive design. Just a theory though.
