Test Flashcards
The windings of a 3 phase motor are physically positioned in the stator so they
Oppose each other creating a magnetic field causing it to rotate
2 maths
Check
3 maths
Check
What is the principle of induction in a 3 phase motor
The magnetic flux caused by the stator current interacts with the magnetic flux caused by the rotor current in such a way they the rotor moves in the direction of the rotating magnetic field
Where are the windings of a 3 phase squirrel cage motor found
In the inner lining of the stator
What type of rotor has slip rings
Permanent capacitor motor
When testing the insulation resistance to earth of a 415v 3 phase induction motor, the minimum acceptable reading is
<200M ohm
The centrifugal switch should disconnect the start winding when it reaches
75% Synchronous speed
Split phase induction motors are best used to power
Multi speed air-conditioner fans
How can rotational directions of a split phase motor be reversed
Switch the winding configurations around on either run or start
A cap start motor has the in series with which 2 parts
Centrifugal switch and start winding
Cap start motors are best suited to power
Washing machines
Mechanical to electrical
Electrical to mechanical
Alternator
Motor
A 3 phase induction motor can be used as a synchronous generator providing the prime mover drives the rotor
At the rated name plate speed of the motor
Name 4 of the main parts of a synchronous alternator/motor
Stator, windings, rotor, frame
Alternators that obtain their dc field supply from an external source are said to be
Separately excited
23
Voltage regulator - Alternator - exciter
If a self excited single phase alternator fails to produce at its output terminals with the prime mover running what. will happen
Windings will burn out and it will get damaged
Large 3 phase synchronous motors may have their rotor dc windings short circuited to become an induction motor and then have the short removed and dc applied to the rotor because
Leading powerfactor loads require this
