3 phase AC motor wont start after overloading
A typical AC motor is a bunch of (very) cleverly-wound coils to create magnetic fields in the right sequence to make it spin. If there's humming, there's current flow. If the shaft isn't turning, either there's a substantial mechanical load (check if you can turn the shaft manually) or the magnetic fields aren't being set up properly. The latter means either your supply is incorrect in some fashion, or the motor is damaged. I'd check the resistance of the windings, and the resistance from each winding to the chassis. You could also hi-pot test from winding to chassis, but only if you have the spec of what it's supposed to be.