I have a 3-phase wound rotor motor on a cable reel for a bulk material ship-loader. Looking through the prints I see the rotor winding configuration is swapped from wye to delta via a relay at a transition point on the pier. Would this cause the motor to reverse direction as I have not found anything in the line to swap the phases. Please advise and thank you.
Electrical – wound rotor winding swap
motor
Best Answer
The the rotor winding is normally internally wye connected with the three windings connected to slip-rings, the external resistors could be either wye or delta connected. A wye to delta change would, in effect, reduce the external portion of the rotor resistance. That would change the speed, but not reverse the motor. No change in the rotor circuit would reverse the motor.
The added diagram in the question indicates a wound rotor induction motors with slip-rings and external rotor resistors. The contactors in the rotor circuits short the resistor taps together to reduce the resistance. That reduces the slip and increases the speed for any given load torque. Higher rotor resistance can also be used to provide higher starting torque. See the illustration below.
There is no indication that the motor can be reversed.
Wound Rotor Induction Motor Torque vs. Speed Curves With Load Line
Image from Fitzgerald Kingsley Umans, Electric Machinery 4th ed. R2 is the total rotor resistance, internal plus external.