Motor temperature rise too high or smoking, which may be caused by what reason?

1)overload: make the stator current is rotor balancing machinetoo large.(2)single phase operation, power supply or touch switch point contact undesirable phase.(3)the power supply voltage is too low or connection errors wholesalemotor.blogspot.com (such as Δ misconnection into Y).(4)the stator winding grounding or alternate with, turn-to-turn short circuit.motor fan (5)wound rotor coil

terminal loose or cage rotor broken bar.(6)the rotor chamber.(7)ventilation.