6.1 Name TWO parts of a stator with reference to induction motors - NSC Electrical Technology Power Systems - Question 6 - 2023 - Paper 1
Question 6
6.1 Name TWO parts of a stator with reference to induction motors.
6.2 FIGURE 6.2 below shows the name plate of an induction motor. Answer the questions that follow... show full transcript
Worked Solution & Example Answer:6.1 Name TWO parts of a stator with reference to induction motors - NSC Electrical Technology Power Systems - Question 6 - 2023 - Paper 1
Step 1
Name TWO parts of a stator with reference to induction motors.
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Answer
Stator windings: These are the coils that create the rotating magnetic field necessary for motor operation.
Terminal box: This component houses the electrical connection points for external circuits.
Step 2
Motivate why this nameplate belongs to a three-phase motor.
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Answer
The nameplate indicates a three-phase voltage supply of 400 V. A three-phase motor typically uses three coils spaced 120 degrees apart to create a rotating magnetic field, which is essential for efficient operation.
Step 3
Identify the efficiency of the motor.
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The efficiency of the motor is given as 85%. This indicates the ratio of the useful output power to the input power, reflecting the motor's performance.
Step 4
Calculate the synchronous speed of the motor.
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Answer
To calculate the synchronous speed (
n_s = rac{120 imes f}{p}
where:
f is the frequency (50 Hz)
p is the number of poles (2).
Substituting the values:
n_s = rac{120 imes 50}{2} = 1500 ext{ r/min}
Step 5
Calculate the slip in r/min.
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Slip is calculated using the formula:
extslip=ns−nfullextload
where:
ns=1500extr/min
nfullextload=1250extr/min.
Thus:
extslip=1500−1250=250extr/min
Step 6
Explain how power in a three-phase induction motor is transferred from the stator to the rotor.
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In a three-phase induction motor, the stator creates a rotating magnetic field by supplying three-phase currents through the stator windings. This rotating field cuts the rotor conductors, inducing an electromotive force (EMF) in them due to electromagnetic induction. The interaction between the magnetic field and the current flowing through the rotor generates torque, transferring power from the stator to the rotor.
