18 Questions
What is the ratio of increase in phase voltage when connected to a delta configuration?
√3
What is the main difference between single-phase and polyphase induction motors?
The rotation of the stator field
What is the principle behind the rotation of the rotor in a single-phase induction motor?
Electromagnetic induction
What would happen to the magnetic field if the rotor is rotated by an outside force?
The magnetic field would change direction
What is the relationship between the rotor field and the stator field in a single-phase induction motor?
They are in the opposite direction
What is the main advantage of single-phase induction motors?
They are the least expensive and require the least maintenance
What is the angular spacing between individual phase windings around the stator?
120°
What is the direction of the resultant magnetic field rotation during a three-phase cycle?
Clockwise
At point 1, what is the characteristic of the magnetic fields in coils 2-2A and 3-3A?
Weaker magnetic fields
What is the purpose of the left-hand rule in determining the electromagnetic polarity of the poles?
To determine the polarity of the poles at a given instant
What is the assumption made in explaining rotor movement using the diagram?
A bar magnet is mounted in the centre of the stator and is free to rotate
What is the total angular displacement of the magnetic field after completing one full three-phase cycle?
360°
What is the purpose of the capacitor in the starting circuit of a capacitor start split-phase motor?
To create a 90° electrical phase difference between the two windings
What is the effect of the currents in the main and auxiliary windings being 90° out of phase?
The motor produces a rotating magnetic field
What happens to the starting winding when the motor reaches nearly full speed?
It is cut out by a centrifugal device
What is the purpose of the centrifugal device in the capacitor start split-phase motor?
To disconnect the starting winding at nearly full speed
What is the effect of the inductive reactance (XL) of the main winding?
It causes the current to lag the line voltage by 45°
What is the phase shift between the currents in the main and auxiliary windings?
90°
This quiz covers the electrical fundamentals of delta configuration and single-phase induction motors, including the increase in phase voltage and current, and the characteristics of single-phase AC induction motors.
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