Question

The armature windings of a dc motor have a resistance of 8.0 Ω . The motor is connected to a 120-V line, and when the motor reaches full speed against its normal load, the back emf is 108 V. The load is increased so it causes the motor to run at half speed.

What will be the current in the motor in this case? (Express your answer to two significant figures and include the appropriate units.)

Answer 1

R=82 Conf E= 120v Emf induced Endurad = 108v. As the load is increase to reduce the speed to half bed Eind & Speed. reduces to half Einduced also € =108v €=545, V = 6 + Para PaRa = V-Gb Pa = V- EG Ro-54 82SA Ra 8

This method be used in all case as one cannot say back emf reduces to half when speed reduces to half. When speed reduces Emf also reduces but it also depends on change in the Load. So in general we can solve this if load or Initial Armature current are specified. It also depends on the flux in the armature.