Retardation test on DC shunt motor is used for finding Stray Losses.

Retardation test is a type of load test conducted on DC shunt motor to determine its performance characteristics. This test is performed by applying a braking torque to the motor shaft and measuring the corresponding armature current, voltage, and speed. The motor is run in the reverse direction to create a braking effect.

The purpose of conducting the retardation test is to calculate the total losses in the motor, which includes copper losses, iron losses, and friction losses. The test is also used to determine the stray losses in the motor.

Stray losses are losses that occur in the motor due to eddy currents and hysteresis losses in the iron core, as well as due to the leakage of magnetic flux from the rotor and stator. These losses are not related to any specific component of the motor but are rather due to the interaction of the components with each other.

During a retardation test, the motor is run in the reverse direction, which causes a magnetic field to be produced in the opposite direction. This field interacts with the stray magnetic fields in the motor, causing eddy currents to flow in the iron core and resulting in stray losses. By measuring the armature current and voltage during the test, the stray losses can be calculated.

In conclusion, the retardation test on DC shunt motor is used for finding stray losses, which are losses that occur in the motor due to eddy currents and hysteresis losses in the iron core, as well as due to the leakage of magnetic flux from the rotor and stator.