There are three main parts to a motor, the stator, the rotor, what else ?
- bearings
- slip rings
- end shields
- terminal housing
What is the most common type of motor used in industry today for low starting torque applications?
- synchronous
- induction
- DC wound type
- commutator type
Squirrel cage and Double cage are examples of which type of motor ?
- synchronous
- induction
- DC wound type
- commutator type
Identify the correct construction of a Squirrel Cage rotor from the descriptions below.
- multiple copper windings slotted into a steel cylindrical core
- multiple copper windings slotted into a soft iron cylindrical core
- short-circuited copper or aluminium bars clad in laminated Iron
- a cylindrical steel core with short-circuited copper bars
What is determined from the formula (N - n)/N
- frequency
- slip
- synchronous speed
- number of poles
By what term is the 'difference between synchronous speed of the stators rotating magnetic field and rotor speed' known?
- torque
- flux
- slip
- frequency
By what term is the 'stators rotating magnetic field' better known?
- n
- slip speed
- N
- frequency
What is the average 'slip' of an induction motor at normal load?
- 0.5 - 2.5%
- 2.5 - 5.5%
- 5.5 - 10.5%
- 10.5 - 20.5%
What type of rotor is shown here?
- squirrel cage
- double cage
- faraday cage
- multi-cage
What is indicated by the term 'p' in the equation N=f/p
- power
- percentage slip
- poles
- pole-pairs
What is connected to the slip-rings on the shaft of a 3-phase wound ROTOR induction motor?
- 3 phase electric supply
- DC supply to energise the stator windings
- 3 interlocked variable external resistances
- reduced 3-phase electric supply
What type of motor has multiple sets of rotor bars to enable higher starting torques with lower starting current ?
- standard induction motor
- wound rotor induction motor
- double cage induction motor
- slip-ring induction motor
What type of motor is best suited for a large industrial AC motor required to start-up under moderate load?
- synchronous motor
- double cage induction motor
- DC motor
- squirrel cage induction motor
What is a major disadvantage of a squirrel cage induction motor?
- size
- cost
- requirement for expensive 'special' starting equipments (Inverter drive etc)
- high current draw when starting up
What is a major disadvantage of a squirrel cage induction motor?
- size
- cost
- requirement for expensive 'special' starting equipments (Inverter drive etc)
- low starting torque
What type of AC motor is best suited for an industrial application required to start-up under low load conditions?
- synchronous motor
- double cage induction motor
- series-wound 'universal' motor
- squirrel cage induction motor
Which one of the following is not an advantage of a wound rotor induction motor?
- can be started under load
- high starting torque
- initial starting current is limited
- easy to repair
What items are fitted to 3-phase induction motors in the positions indicated by the arrows?
- bearings
- fans
- shaft couplings
- electrical connections
What is the missing axis on the squirrel cage induction motor characteristics graph shown here?
- voltage
- torque
- pole-pairs
- slip
What is meant by the term 'DOL'?
- Direct Over Load
- Direct On Line
- Direct Over Limit
- Direct Off Load
In a DOL starter, identify the characteristic of the 'START' switch?
- momentary, normally-open
- momentary, normally-closed
- latching, normally-open
- latching, normally-closed
In a DOL starter, identify the ITEM the disconnects the supply to the control circuit in the event of an excess current-draw from the motor?
- adjustable overload
- contactor
- latch
- stop button
In a DOL starter, how is the momentary 'Start' switch bypassed to allow the motor to remain energised?
- use of a latch circuit
- use of a coil
- manually holding the start button in
- use a contactor
In a DOL starter, identify the part that acts as an electromagnetic switch arrangement to provide power to the motor?
- contactor block
- coil
- start switch
- 3-phase mains switch
What speed does the Rotor turn in relation to the speed of the Stators rotating magnetic field?
- slightly behind
- slightly ahead
- same speed
- the two are largely unrelated
Identify the characteristic of a 'wound rotor' induction motor
- high start torque
- low start torque
- stable speed
- quiet running
In a DOL starter, how are remote 'start buttons' connected into the control circuit?
- in parallel with the main start button
- in series with the main start button
- in parallel with the main stop button
- in series with the main stop button
How can a WOUND ROTOR Induction motor be made to run at SYNCHRONOUS speed?
- once the external resistances have been switched out, connect a DC supply to the rotor
- reduce the value of the external resistances as the motor builds up speed
- increase the value of the external resistances when the rotor is up to full speed
- Vary the frequency of the supply to the motor so it matches the speed of the rotor
In a DOL starter, identify the characteristic of the 'STOP' switch?
- momentary, normally-closed
- momentary, normally-open
- latching, normally-open
- latching, normally-closed