electrical

Question 1

In a capacitor-start Induction run motor, which set of windings have a lower resistance, the run winding or start windings?

Answer 1

Run winding.

Question 2

What are the minimal number of terminal leads required for a single-phase motor?

Answer 2

2 leads

Question 3

Which single phase motor has a commutator and brushes?

Answer 3

Universal motor

Question 4

which single phase motor is the cheapest?

Answer 4

shaded coil motor

Question 5

Calculate the synchronous speed of a 10-pole motor operating at 60 hertz.

Answer 5

Synchronous speed = F x 120/P

= 60 x 120/10

=720 rpm

Question 6

Calculate slip% of an 8-pole motor rotating(rotor) at 860rpm operating at 60 hertz?

Answer 6

Slip % = Sync speed – rotor speed /Sync speed x 100

= (900 – 860/900) x 100

= 4.44%

Question 7

What is the minimum number of stator leads for a dual voltage, reversible split phase motor?

Answer 7

6 leads

Question 8

A single phase, 4 pole split phase motor has a 3% slip at 60 hertz. Calculate the rotor speed.

Answer 8

Synchronous speed = F x 120/Poles

= 60 x 120/ 4 = 1800rpm

Rotor speed = 1800 x 3% = 54 RPM

Rotor speed = 1800 – 54 = 1746 RPM

Question 9

Are the starting torque characteristics of a Capacitor-Start Induction-Run motor greater or less than a resistive start motor?

Answer 9

greater

Question 10

When current flows through a conductor a magnetic field is produced around the conductor, what is this principle called?

Answer 10

magnetic induction

Question 11

Anytime a conductor cuts through a magnetic field a voltage is induced into that conductor. What is this principle called?

Answer 11

electromagnetic induction

Question 12

What is the rotational force produced by a motor called?

Answer 12

interaction of 2 magnetic fields

Question 13

A single voltage, reversible split phase motor has 4 terminal conductors at a junction box. Which two terminals are interchanged to reverse the motor?

Answer 13

Leads T5 and T8.

Question 14

What type of disconnecting means for a split phase motor functions as both a starting relay and overload relay?

Answer 14

hot wire relay

Question 15

Which split phase motor has their windings energized all the time?

Answer 15

Capacitor-Stat Capacitor Run.

Permanent split motor.

Question 16

What type of single-phase motor does not have a squirrel cage assembly?

Answer 16

Universal Motor.

Question 17

Why are pole pieces laminated?

Answer 17

to prevent eddy currents

Question 18

When creating a magnetic field are the lines of flux in the direction of north to south across an air gap?

Answer 18

YES.

Question 19

What is the typical phase displacement in a shaded pole motor?

Answer 19

10 degrees

Question 20

What is the typical phase displacement between currents in the run and start windings in a resistive start induction motor?

Answer 20

90 degrees

Question 21

The nameplate of a 4-pole motor has a Full load rotational speed of 1705rpm. Under no load its speed increases to 1750 rpm.

Answer 21

Speed regulation = no load – full load / full load x 100

= (1750 – 1705)/1705 x 100

= 2.63%

Question 22

What approximate percentage of rotor speed does a centrifugal switch open it?

Answer 22

75 to 80%

Question 23

what is the resistance to magnetism?

Answer 23

reluctance

Question 24

If a Centrifugal switch fails to open what can happen to the start windings?

Answer 24

overload and over heat

Question 25

Which single pole motor is non-reversible?

Answer 25

shaded pole

Question 26

What type of AC machine converts electrical input into mechanical input?

Answer 26

motors

Question 27

Does an increase in current through a single conductor result in a increase of magnetic field around the conductor?

Answer 27

YES

Question 28

What is the amount of magnetism left in a material after the magnetizing force has stopped called?

Answer 28

Residual magnetism

Question 29

How are hysteresis currents reduced in core materials?

Answer 29

sillicon steel alloys

Question 30

hat components support the shaft and allow the rotor to rotate freely?

Answer 30

Bearings

Question 31

What happens to a load in a universal motor when a load is increased?

Answer 31

Rpm decreases

Question 32

In a universal motor, are the armature windings and field windings connected in parallel or series, or a combination of both?

Answer 32

Dc series

Question 33

Does a shaded coil motor rotate towards the shaded coil or away from the shaded coil?

Answer 33

towards

Question 34

A motor has a full load nameplate speed of 3450 rpm at 60 hertz. Calculate the number of poles and slip percent.

Answer 34

Number of poles Sync speed = F x 120 / P = 3450 rpm = 60 x 120 / p P = (60 x 120) / 3450rpm P = 2 Slip percent Slip % = sync speed – rotor speed / sync speed x 100 = (3600 – 3450) / 3600 x 100 4.17%

Question 35

what is the rotational force profuced by a motor?

Answer 35

torque

Question 36

what compoonent forms the axis for rotation of the rotor assembly in a ac machine?

Answer 36

shaft

Question 37

2 types of capacitors

Answer 37

electrolytic capicitor oilfilled capacitor

Question 38

what are the minimum number of stator leads required for a single voltage reversible split phase induction motor

Answer 38

4 lead

Question 39

in a capacitance start induction run split phase motor, start field windings are wound with more turns of smaller wire

Answer 39

more and small

Question 40

does a current relay use N/O or N/C contacts

Answer 40

N/O

Question 41

whih relay is the cheapest?

Answer 41

Centrifugal switch

Question 42

which switch is used externally to disconnect the start capacitor in a capstart cap runmotor?

Answer 42

potential relay