Exam 44: Use of Reduced Voltage for Starting

The resistance in series with the armature reduces the starting armature current to approximately ________________times the full-load current value.

The counter emf equals the applied voltage __________the armature (IR) drop.

The current taken by the armature will be abnormally high unless the DC supply is increased gradually.

The total starting current is equal to the armature current plus the field current of 1 ampere.

Two factors that limit the current taken by a motor armature from a given line are the counter emf and the _________resistance.

Excessive torque and heat may cause the insulation to overheat on starting and the________ of the armature.

The proper resistor can be selected by knowing the required resistance and the power value in______________ .

The starting of fairly large DC motors requires that current be increased gradually and at the same time resistance must be inserted in series with the armature of the motor.

Resistors may be rated in watts.

The counter emf developed by a motor is proportional to the speed of the motor unless the field is constant.