Question

A shunt-wound DC motor with the field coils and rotor connected in parallel (see the figure) (Figure 1)operates from a 130 VV DC power line. The resistance of the field windings, RfRfR_f, is 201 ΩΩ . The resistance of the rotor, RrRrR_r, is 4.10 ΩΩ . When the motor is running, the rotor develops an emf EEEMF. The motor draws a current of 4.88 AA from the line. Friction losses amount to 47.0 WW .

a)

Compute the field current IfIfI_f.

Express your answer in amperes.

b)Compute the rotor current IrIrI_r.

c)Compute the emf EEEMF.

d)Compute the rate of development of thermal energy in the field windings

e)Compute the rate Pth,rotorPth,rotorP_th,rotor of development of thermal energy in the rotor.

f)Compute the power input to the motor PinPinP_in.

g)Compute the efficiency of the motor.

Answer 1