Motors and Starters

Question 1

The starting current using a DOL starter is the same as the running current, True or False?

Answer 1

False, it can be several times greater.

Question 2

According to the WA Distribution Connection Manual, a 4KW three phase squirrel cage motor has what maximum inrush current per KW?

Answer 2

8.6A per KW

Question 3

The contactor of a DOL starter energizes when the start button is pressed but drops out when the start button is opened. Why might this happen?

Answer 3

A non-latching contactor has been installed, or the holding contacts are faulty.

Question 4

What is the purpose of a Wye-Delta starter?

Answer 4

To limit the inrush current

Question 5

Describe the operation of a Wye-Delta starter?

Answer 5

When energized, the three phase motor is started while connected in Wye connection. Then after a set period of time, changes to run in a Delta connection.

Question 6

What is torque proportional to the square of?

Answer 6

Voltage

Question 7

Torque in a Wye connection is what percentage compared to a Delta connection?

Answer 7

33%

Question 8

Voltage in a Wye connection is what percentage compared to a Delta connection?

Answer 8

57.5%