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15 Cards in this Set
- Front
- Back
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List two factors that determine the cross-sectional area of a cable used to supply a three phase induction motor |
Distance / length of cable Draw / load of motor |
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State two reasons for using reduced voltage starting for a three phase induction motor |
Reduced current Reduce output torque Reduce amount of work done by motor 4 reasons why universal motors are more suitable than single phase induction motors for use in portable tools |
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4 reasons why universal motors are more suitable than single phase induction motors for use in portable power tools |
Size Cost Ac/dc High speeds on light loads Ease of speed control |
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How is the direction of rotation change in a universal motor |
To change field windings or armature not both |
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State the purpose of a phase failure relay |
Overload relay in each line detects any increase in current |
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Define the term slip speed |
The drag or losses of the motor |
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How many capacitors are there in the circuit of a permanently split capacitor motor |
One |
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What device is used to provide starting torque in a shaded pole motor |
Shading coil / ring fitted to each pole |
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State one advantage that a single phase capacitor start induction run motor has over other single phase induction motors |
It has a higher starting torque |
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What happens to the speed of a 3 phase induction motor when the load is increased |
Speed will remain the same |
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What happens to the speed of a 3 phase induction motor when the load is increased |
Speed will remain the same |
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Pull out torque |
Maximum torque that your motor will sustain without damaging your motor |
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State two reasons why induction motor rotor bars normally skewed |
To increase starting torque To prevent electromagnetic cogging |
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Starting torque |
The amount of torque at starting in order to overcome the inertia of starting from rest |
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Full load torque |
The value of torque that your motor is designed to run at full capacity |
