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How much is the torque developed if a 400 V DC shunt motor gave the following readings during the brake test: Length of brake arm = 200 cm Reading of spring balance at the end of brake arm = 40 kg­-wt Supply voltage = 400 V

How much is the torque developed if a 400 V DC shunt motor gave the following readings during the brake test: Length of brake arm = 200 cm Reading of spring balance at the end of brake arm = 40 kg­-wt Supply voltage = 400 V Correct Answer <span style="">784.8 N-­m </span>

Brake test of the DC motor:

  • It is a direct method to determine the efficiency of a DC motor.
  • It consists of applying a brake to a water-cooled pulley mounted on the motor shaft.
     

The torque produced in a DC shunt motor during a brake test is given by:

T = 9.81 × W × L

Where, T = Developed torque

W = Reading of spring balance in kg­-wt

L = Length of the brake arm

Calculation:

Given:

W = 40 kg­-wt

L = 200 cm = 2 m

T = 9.81 × 40 × 2

T = 784.8 N-­m

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