The correct answer is: A. synchronous condenser.
A synchronous condenser is an overexcited synchronous motor that is operated on no load. It is used to improve power factor and to regulate voltage.
A synchronous motor is an AC motor that has a rotating magnetic field. The magnetic field is created by a stator winding that is energized with AC current. The rotor of a synchronous motor is a permanent magnet or an electromagnet. When the stator winding is energized, the magnetic field rotates at a constant speed. The rotor aligns itself with the stator field and turns at the same speed.
An overexcited synchronous motor is a synchronous motor that is operated with more field current than is required to produce rated torque. This causes the motor to operate at a leading power factor. A leading power factor means that the motor is consuming reactive power from the power system. This reactive power can be used to improve the power factor of other loads on the system.
A synchronous condenser is an overexcited synchronous motor that is operated on no load. It is used to improve power factor and to regulate voltage. When a synchronous condenser is operated on no load, it draws reactive power from the power system. This reactive power can be used to improve the power factor of other loads on the system. The synchronous condenser can also be used to regulate voltage by absorbing or injecting reactive power into the system.
The other options are incorrect because:
- A generator is a machine that converts mechanical energy into electrical energy.
- An induction motor is an AC motor that has a rotating magnetic field that is created by the stator winding. The rotor of an induction motor is a squirrel cage rotor that is not connected to the stator winding. The rotor of an induction motor turns at a speed that is slightly less than the speed of the stator field.
- An alternator is a machine that converts mechanical energy into electrical energy. An alternator is similar to a generator, but it produces AC current instead of DC current.