I have a centrifugal blower, which probably use a permanent-split capacitor motor(it has 3 wires, and 1 10uF capacitor). Not long after I turn on the motor, its humming sound increases, as if it's speeding up. For fear it's going to explode, I turn it off at this stage. Both the motor and capacitor feels hot. What can be wrong with the blower?
An AC induction motor runs at one speed only. Three wires is a curious claim, since most PSC uses two. If three terminals are present on a PSC, a small Cap is used on the winding of higher resistance. Split phase motors use start, run, and common with a start relay to disengage start promptly. Overheating is a sign of a start windings failure to disengage. Check the manufacturer's website for a wiring diagram and instructions.