Three-phase Wound rotor motors
Three-phase Wound rotor motors, design, operation, uses - 10 questions from a bank of questions
Answer ALL questions. Look for any feedback given if you get an answer incorrect. Keep choosing an answer until you get it correct. CORRECT or INCORRECT answers are indicated at the TOP of the page. A score is given at the TOP of the page when the exercise has been completed. © K.Brown 2015
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There are three main parts to a motor, the stator, the rotor, what else ?
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bearings
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slip rings
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end shields
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terminal housing
What is the most common type of motor used in industry today, as shown here?
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synchronous
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induction
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DC wound type
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commutator type
Squirrel cage and Double cage are examples of which type of motor ?
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synchronous
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induction
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DC wound type
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commutator type
Identify the correct construction of a Squirrel Cage rotor from the descriptions below.
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multiple copper windings slotted into a steel cylindrical core
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multiple copper windings slotted into a soft iron cylindrical core
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a cylindrical soft iron core with short-circuited copper or aluminium bars
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a cylindrical steel core with short-circuited copper bars
What is determined from the formula shown here?
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frequency
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slip
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synchronous speed
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number of pole pairs
By what term is the 'difference between synchronous speed of the stators rotating magnetic field and rotor speed' known?
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torque
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flux
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slip
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frequency
By what term is the 'stators rotating magnetic field' better known?
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magnetic speed
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slip speed
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synchronous speed
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frequency
What is the average 'slip' of an induction motor at normal load?
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0.5 - 2.5%
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2.5 - 5.5%
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5.5 - 10.5%
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10.5 - 20.5%
What type of rotor is shown here?
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squirrel cage
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double cage
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faraday cage
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multi-cage
What type of rotor is shown here?
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squirrel cage
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double cage
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faraday cage
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multi-cage
What is indicated by the term 'P' in the equation shown here?
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power
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percentage slip
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position
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poles
What is indicated by the term 'N' in the equation shown here?
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synchronous speed
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percentage slip
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frequency
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poles
What is connected to the slip-rings on this wound rotor 3-phase induction motor?
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3 phase electric supply
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DC supply to energise the stator windings
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3 interlocked variable resistances
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reduced 3-phase electric supply
What type of motor has multiple rotor bars to enable high starting torques with low starting current ?
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standard induction motor
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wound rotor induction motor
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double cage induction motor
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slip-ring induction motor
What type of motor is best suited for a large industrial conveyor belt in a quarry, like the one shown here?
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synchronous motor
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double cage induction motor
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DC motor
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squirrel cage induction motor
What is a major disadvantage of a double cage induction motor?
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size
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cost
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low starting torque
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high current draw when starting up
What is a major disadvantage of a squirrel cage induction motor?
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size
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cost
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requirement for expensive 'special' starting equipments (Inverter drive etc)
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high current draw when starting up
What is a major disadvantage of a squirrel cage induction motor?
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size
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cost
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requirement for expensive 'special' starting equipments (Inverter drive etc)
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low starting torque
What type of motor is best suited for an industrial extraction fans, like the ones shown here?
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synchronous motor
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double cage induction motor
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DC motor
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squirrel cage induction motor
Which one of the following is not an advantage of a wound rotor type induction motor?
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can be started under load
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high starting torque
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initial starting current is limited
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easy to repair
What items are fitted to 3-phase induction motors in the positions indicated by the arrows?
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bearings
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fans
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shaft couplings
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electrical connections
What is the missing axis on the squirrel cage induction motor characteristics graph shown here?
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voltage
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torque
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pole-pairs
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slip
OK