Deck 24: Resistor and Reactor Starting for Ac Motors

Question 1

Name two conditions where it is not possible to start a motor across-the-line.

Answer 1

The two conditions are excessive starting current and excessive torque.

Question 2

Why is time delay one of the most popular methods of determining when to connect the motor directly to the power line?

Answer 2

Time delay is one of the most popular methods of determining when to connect the motor directly to the power line because it is simple and inexpensive.

Question 3

Some control circuits sense ____________________ speed to determine when to shunt the resistors out of the power line.

Answer 3

motor

Question 4

Some resistor and reactor starters use multiple steps of starting. How is this accomplished?

Question 5

Figure 24-1


The accompanying diagram uses ____________________ to shunt the resistors out of the circuit after some period of time.

Question 6

In an inductive circuit, the current must rise at an exponential rate.

Question 7

One way of determining when to shunt the resistors out of the circuit is by sensing motor current.

Question 8

In a resistive circuit, the current will take some time to reach its full Ohm's law value.

Question 9

Figure 24-4


In the circuit shown in the accompanying figure, the current sensor contacts are normally open.

Question 10

What are two of the most common methods of reducing the amount of starting current?

Question 11

Current ____________________ are used to sense the amount of motor current.

Question 12

Figure 24-1


In the accompanying figure, what happens right after the START button is pressed?

Question 13

Resistors connected in series with the motor limit the amount of in-rush current.

Question 14

____________________ is accomplished by connecting resistors in series with the motor during the starting period.

Question 15

Reactors limit in-rush current with ____________________ instead of resistance.