The correct answer is: A. shunt motor.
A repulsion induction motor is a type of electric motor that uses both repulsion and induction principles to produce torque. The stator of a repulsion induction motor is similar to that of a standard induction motor, with a three-phase winding that is energized by an alternating current source. The rotor of a repulsion induction motor, however, has two windings: a primary winding and a secondary winding. The primary winding is connected to the stator winding, and the secondary winding is short-circuited.
When the motor is turned on, the alternating current in the stator winding creates a rotating magnetic field. This magnetic field induces a current in the rotor winding, which in turn creates its own magnetic field. The interaction of these two magnetic fields produces torque, which causes the rotor to turn.
The speed of a repulsion induction motor is determined by the frequency of the alternating current source and the number of poles on the stator. The torque of a repulsion induction motor is determined by the current in the rotor winding.
The speed-torque characteristic of a repulsion induction motor is similar to that of a DC shunt motor. In both cases, the speed increases as the load torque decreases. However, the speed-torque characteristic of a repulsion induction motor is not as linear as that of a DC shunt motor. This is because the secondary winding of a repulsion induction motor has a small amount of resistance, which causes the speed to drop slightly as the load torque increases.
The other options are incorrect because they do not describe the speed-torque characteristic of a repulsion induction motor. A series motor has a speed-torque characteristic that is the opposite of that of a repulsion induction motor. The speed of a series motor decreases as the load torque increases. A compound motor has a speed-torque characteristic that is somewhere in between the speed-torque characteristics of a shunt motor and a series motor. The speed of a compound motor decreases as the load torque increases, but the decrease is not as pronounced as it is for a series motor. A separately excited motor has a speed-torque characteristic that is independent of the load torque. The speed of a separately excited motor is determined by the voltage applied to the stator winding.