AC Motors

Question 1

AC motor operation

Answer 1

Rotating magnetic field from 3 phase AC fed into the stator

Magnetic field turns with each AC phase - spins a rotor

Question 2

Squirrel cage

Answer 2

Aluminium with steel on the outside

Electromagnet when rotated - reinforced by the steel

Question 3

Why will the rotor move slower than the stator

Answer 3

One has to move faster than the other to induce relative movement to produce an electro magnetic field

Asynchronous motor

Diff in speed = slip speed

Question 4

If a loss of phase occurs on a AC motor

Answer 4

When
Running - motor will continue to run at a reduced speed but may overheat

Not running - machine will not start and fuses/CBs will blow in the other 2 phases

Question 5

Spilt phase motor

Answer 5

Capacitor in an AC circuit delays the voltage by 90*

Capacitor spilts the relationship between voltage and current

Rotates at a less smoother rate

Question 6

3 phase synchronous motor and what is required

Answer 6

Rotor moves at the speed of the induced AC stator

Pony motor is required to speed it up to the correct speed and then it locks on