Week 11. To perform No load test of the alternator to observe the change in its output parameters.

To understand and observe the behavior of an alternator at No load and obtain it’s no load characteristics curve.

Theory:

The efficiency of large motors can be determined by directly loading them and by measuring their input and output powers. For large motors, it may be difficult to arrange loads for them. Moreover, power loss will be large with direct loading tests. Thus, no load and blocked rotor tests are performed on the motors. As the name suggest no load test is performed when rotor rotates with synchronous speed and there is no load torque. This test is similar to the open circuit test on transformer. Actually, to achieve synchronous speed in an induction motor is impossible. The speed is assumed to be synchronized. The synchronous speed can be achieved by taking slip = 0 which creates infinite impedance in the rotor branch. This test gives the information regarding no-load losses such as core loss, friction loss and windage loss. Rotor copper loss at no load is very less that its value is negligible. Small current is required to produce adequate torque. This test is also well-known as running light test. This test is used to evaluate the resistance and impedance of the magnetizing path of induction motor.