Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
With an increase in the number of poles - dispersion coefficient and power factor of three-phase induction motor will __________ & ___________ respectively.
increases, increase
decreases, decrease
decrease, increases
increases, decrease
increases, decrease
Increasing the number of poles in an induction motor decreases the synchronous speed, which increases the magnetizing current and leakage reactance relative to the output, leading to a higher dispersion coefficient and a lower power factor.
Increasing the number of poles in an induction motor decreases the synchronous speed, which increases the magnetizing current and leakage reactance relative to the output, leading to a higher dispersion coefficient and a lower power factor.
╧ГтЙИIsтАЛImтАЛтАЛ тАФ dispersion coefficient depends on magnetizing current
PтИЭNsтАЛ1тАЛ тАФ poles are inversely proportional to synchronous speed
As the number of poles (P) increases, the air-gap length relative to pole pitch increases, and the leakage flux increases. This causes the magnetizing current to rise to maintain the required flux, which directly reduces the power factor and increases the dispersion (leakage) factor ╧Г.
Higher pole counts lead to larger leakage flux paths.
The power factor of an induction motor is generally poor and worsens as the magnetizing component increases.
Dispersion coefficient represents the ratio of leakage flux to useful air-gap flux.
Lower synchronous speed is useful for high-torque, low-speed applications.
Increased weight and volume of the machine.
Lower efficiency and power factor compared to 2-pole or 4-pole designs.
Industrial fans, blowers, and low-speed conveyor systems.
For a given frame size, increasing poles reduces output power capacity.
Option B is incorrect because dispersion increases, not decreases, with higher pole counts.
D is correct тАФ As the number of poles increases, the magnetizing reactance decreases and leakage reactance increases, resulting in an increased dispersion coefficient and a lower power factor.
Remember that in induction motors, any factor that increases the magnetizing current (like high pole counts or large air gaps) will always degrade the power factor.