Which test is used to determine the efficiency of a traction motor?

Explanation:-

• A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives (trains).
• DC series motor is used as traction motor.

Field test for series motor:

• This test is applicable to two similar series motor.
• One of the machines is run as a generator while the other as a motor.
• Therefore input power is only losses in the machines.
• Gives efficiency of DC series machine.

Hopkinson’s or Regenerative or Back To Back Test:

• Two identical DC shunt machines are coupled mechanically and tested.
• One of the machines is run as a generator while the other as a motor.
• Therefore input power is only losses in the machines.
• Performed at rated speed.
• Temperature rise and commutation qualities can be observed.

Retardation or running down test:

• Applicable to shunt motors and generators.
• Used for finding the stray losses.
• Machine is speeded up slightly beyond its rated speed and then supply is cut off from the armature while keeping the field excited.
• Armature will slow down and its kinetic energy is needed to meet rotational losses. i.e., friction and windage losses.

Swinburne’s Test:

• This test is performed no load.
• The rated speed is adjusted by the shunt field resistance.
• As it is a no load test, it cannot be done on a dc series motor.
• Give efficiency of DC machine.