Refer to FIGURE 6.1 below and answer the questions that follow - NSC Electrical Technology Power Systems - Question 6 - 2021 - Paper 1
Question 6
Refer to FIGURE 6.1 below and answer the questions that follow.
6.1.1 Name parts A, B and C. (3)
6.1.2 Explain how a rotating magnetic field is created in the stat... show full transcript
Worked Solution & Example Answer:Refer to FIGURE 6.1 below and answer the questions that follow - NSC Electrical Technology Power Systems - Question 6 - 2021 - Paper 1
Step 1
6.1.1 Name parts A, B and C.
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6.1.2 Explain how a rotating magnetic field is created in the stator windings.
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Answer
Each of the stator windings is connected to a line of the three-phase supply in the terminal box. Each coil creates a magnetic field at alternate intervals (120°). The coils are spaced around the stator in such a way that it creates the impression of a rotating magnetic field. This is achieved by the three phases reaching maximum strength 120° out of phase with each other.
Step 3
6.1.3 State TWO applications of squirrel-cage induction motors.
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Answer
Cranes
Conveyor belt systems
Lathes
Drill presses
Bench grinders
Step 4
6.1.4 State TWO contributing factors that determine the speed of rotation in a three-phase induction motor.
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Answer
Number of pole pairs
Frequency of the supply
Step 5
6.2.1 Is this motor connected in star or in delta?
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Answer
This motor is connected in delta.
Step 6
6.2.2 State how the direction of rotation of this motor can be reversed.
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Answer
Swap any TWO of the supply lines.
Step 7
6.2.3 Name TWO important procedures to follow before testing the insulation resistance of the motor in FIGURE 6.2.
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