The speed-torque characteristic of a repulsion induction motor is similar to that of a D.C
Right Answer is:
Compound Motor
SOLUTION
A repulsion motor operates on the principle that magnetic poles repel each other, not on the principle of a rotating magnetic field. The stator of a repulsion motor contains only a run winding very similar to that used in the split-phase motor. The speed-torque characteristic of a repulsion induction motor is similar to that of a D.C Compound Motor.
Repulsion Induction Motor
It works on the combined principle of repulsion and induction. The construction of the stator of this type of motor is similar to that of a repulsion motor, i.e., the main stator winding of a single-phase induction motor. In the rotor, there are two separate windings. One winding is similar to the rotor winding of a repulsion motor i.e usual d.c winding connected to the commutator. The other winding is of squirrel-cage type, placed below the repulsion-motor type winding. The behavior of the repulsion induction motor is, therefore, the combination of the behavior of the repulsion motor and an induction motor.
Under starting conditions, very little current will flow through the inner squirrel-cage winding since the reactance of the squirrel-cage winding which is placed deep into the rotor slot is very high. As the rotor picks up speed, the frequency of the rotor induced emf and hence the rotor reactance will decrease. More current will flow in the rotor squirrel-cage winding. The motor will work as a combination of repulsion and induction motor.
Speed-torque characteristic of a repulsion induction motor
The starting torque repulsion induction motor is 2.25 to 3 times the full-load torque and the starting current will be 3 to 4 times the full-load current. The single-phase repulsion-induction motor has the advantages of high starting torque and good speed regulation. It has the ability to continue to develop torque under sudden heavy applied loads.
The starting torque of the repulsion induction motor is high and it provides fairly constant speed regulation, therefore, its torque-speed characteristics closely resemble DC compound motor.
