Deck 23: Across-The-Line Starting

Question 1

In a grounded system, the current sensing device must be in the ____________________ conductor.

Answer 1

ungrounded

Question 2

In-rush current is referred to a(n) ____________________ current.

Answer 2

locked rotor

Question 3

In direct current motors, by what is the initial in-rush current limited?

Answer 3

Initial in-rush current is limited by the resistance of the windings. When the armature begins to turn, counter EMF is developed in the armature. Counter EMF is the main current limiting force in a direct current motor.

Question 4

Direct current motors depend on inductive reactance to limit current flow.

Question 5

Contactors intended to connect direct current motors to the line often have arc suppression and magnetic blowout coils.

Question 6

What do direct current starters and contactors that do not utilize arc suppressors or magnetic blowout coils use to break the circuit?

Question 7

In a DC contactor with two coils, the ____________________ coil is intended for momentary duty and not continuous operation.

Question 8

Some DC contactors contain two separate coils. Describe the two coils.

Question 9

The type of bars used to construct the rotor has a great effect on the operating characteristics of the motor.

Question 10

Across-the-line starting is the simplest of all starting methods.

Question 11

Why is it that small DC motors can be started across-the-line?

Question 12

Direct current motors require only one ____________________ contact to connect or disconnect them to the power line and one overload sensing device.

Question 13

Across-the-line starting is only used for alternating current.

Question 14

How is across-the-line starting accomplished?

Question 15

The type of rotor is identified by a code letter on the ____________________ of a motor.