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Flashcards in Motor Starters Deck (70)
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1

Motor starters can be of two main types what are they

Across the line {FVS}
Reduced voltage starters
(Reduces V at start, full V for run)

2

What is the most common starting method?

Full voltage/ across the line start

3

What are the terminal marking for a part winding starter

T1-T3 and T7-T9

4

List the terminal marking on a wye-delta starter.

T1-T6

5

What is the purpose of a reduced voltage starter

To reduce the inrush current at start

6

List two starting modes that are common on electric soft starters

Ramp start
And current limiting start

7

True or false
the load to a rotary converter must not be connected until the converter reaches its rated speed and is supplying 3 phase power

True

8

True or false
Static phase converter can supply more than one load

False
Can only supply one load at a time

9

True or false
A rotary phase converter can supply more than one load

True

10

Can a static phase converter supply power to a single three phase motor?

Yes it can

11

True or false
Static phase converts are more balanced than Rotary phase converters

False
Rotary phase converters are the balanced of the two types

12

True or false
Single phase motors are available above 15 hp are often found above 5hp

False
Not available above 15 hp and rarely found above 5hp

13

By how much does a wye/delta starter reduce the starting line current, compared to a full voltage start?

Starting line current would 1/3 smaller

14

True or false
Starting torque is reduced by 1/3 of what it would be if the motor was started at full voltage.

True

15

The overloads of a wye delta starter are based on the line current.
True or false?

False they are based on the phase current (57.7% of the line current)

16

A continuity test on a dual voltage delta motor would show how many groups of leads?

3 groups of 3 leads

17

True or false
Dual voltage motors reduce stocking costs for manufacturers and wholesalers

True

18

True or false
A continuity test on a dual voltage wye motor would reveal 1 group of three leads and 3 groups of two leads.

True

19

A single voltage wye start delta run motor is required for wye/delta starting
True or false

True

20

A continuity test on a single voltage six lead motor would reveal what?

3 groups of two leads

21

What are the three basic functions of a vfd?

Rectifier
Filter
Inverter

22

What does the rectifier do?

Turns ac supply into dc and supplies the dc voltage to the dc link

23

What does the filter do?

Provides a clean and smooth DC source for the inverter

24

What does an inverter do?

Converts the DC to an AC voltage which is voltage a frequency controlled

25

True or false
Changing the timing of pulse cycles will change the output frequency when using pulse width modulation.

True

26

Will changing the width of the pulses in PWM change the output voltage?

Yes

27

What is the Igbt?

It’s is a high current fast switching voltage controlled device. In charge of the on/off switching of the pulse.

28

True or false
I order to not exceed the fla rating of the motor, the motor voltage (E) must be lowered as frequency is lowered

True
V/Hz ratio

29

What must a nameplate state to indicate a motor is compatible with a vfd

Inverter duty

30

What is open loop feedback

It means the vfd runs according to preset values set within the programming