The correct answer is: D. Both shunt and compound motor.
A three-point starter is a type of electric motor starter that uses three terminals to control the motor. The three terminals are the line voltage, the motor winding, and the starting resistor. The starting resistor is used to limit the current to the motor when it is first started. This prevents the motor from overheating.
Three-point starters can be used for both shunt and compound motors. Shunt motors have a field winding that is connected in parallel with the armature winding. Compound motors have a field winding that is connected in parallel with the armature winding and also in series with the armature winding.
When a three-point starter is used for a shunt motor, the starting resistor is connected in series with the motor winding. This limits the current to the motor when it is first started. The starting resistor is then gradually removed from the circuit as the motor accelerates.
When a three-point starter is used for a compound motor, the starting resistor is connected in series with the armature winding. This limits the current to the motor when it is first started. The starting resistor is then gradually removed from the circuit as the motor accelerates. The starting resistor is also connected in series with the field winding. This helps to reduce the starting current to the motor.
Three-point starters are a safe and efficient way to start electric motors. They are commonly used in industrial applications where large motors are used.