Motor Starters

Question 1

IEC motor labels instead of T1,T2,T3

Answer 1

T1, T2, T3, T4, T5, T6
U1, V1, W1, U2, V2, W2

Question 2

Rotary phase converter

Answer 2

Looks like induction motor without shaft. Does not drive a mechanical load
High capacitance electrolytic capacitor applies leading current to start motor generator

Question 3

Rotary phase convert can supply multiple motors?

Answer 3

Yes, the largest should be started first

Question 4

An across the line magnetic motor starter requires a disconnect or not?

Answer 4

Separate disconnect means on line side of starter

Question 5

Wye-delta starter requirements and stats

Answer 5

•6 leads
•33.3% starting compared to same motor in delta
•Inrush current 1/3 compared to delta

Question 6

Single voltage / dual voltage number of leads

Answer 6

6 single
9 dual

Question 7

Clockwise at the shift of motor is Nema or IEC?

Answer 7

Clockwise is Nema
Counter clockwise IEC

Question 8

Full voltage manual and magnetic initial starting current % and starting torque %?

Answer 8

Starting current 500-600%
Starting torque 150%

Question 9

Reduced voltage starters cons?

Answer 9

They can reduce inrush current but also reduce starting torque

Question 10

Full voltage starting (across line starters) pros

Answer 10

•Produce high starting torque
•produce high rush current

Question 11

Part winding starters and motors … what does it do? And what good for ?

Answer 11

2 or more sets of windings
•only one energized at full voltage to start motor
•then energizes both windings in parallel
• good for small loads to no loads

Question 12

Part winding starter
When first started ?

Answer 12

Impedance is higher and inrush current lower
•inrush current reduced to 60-65%

Question 13

Auto transformers starter need to know ?

Answer 13

•Current is proportional to starting voltage
•line current proportional to square start voltage
•start torque proportional to square start voltage

Question 14

Part winding Taps

Answer 14

Starting torque 80, 65, 50%
Starting voltage 64, 42, 25%

Question 15

Auto transformer starter transition .. closed and open

Answer 15

•Closed transition offer better performance
•maintain current through windings during transition from reduced to full voltage

Question 16

Rotary phase converters are same basic construction as ?

Answer 16

Three phase motor

Question 17

Wye delta starter reduce start voltage and start current to?

Answer 17

Start voltage 58%
Start current 33%

Question 18

WRIM compared to SCIM with equal hp rating will have a reduced or increased starting current ?

Answer 18

Reduced starting current

Question 19

Which phase converter is best for variable loads ?

Answer 19

Rotary phase converter

Question 20

Starting current of a motor is reduced proportional to?

Answer 20

Reduced starting voltage