The main thing to understand is that increasing the number of poles reduces the motor's synchronous speed. A 2 pole motor on 60 hz power has a synchronous speed of 3,600 rpm. For an induction motor, that will typically drop by a “slip” percentage, typically about 4% to 3,450 rpm.

Answer:

In an induction motor, the number of poles plays a significant role in determining the motor's speed. The speed of an induction motor is inversely proportional to the number of poles. Therefore, as the number of poles increases, the speed of the motor decreases.

Explanation:

1. Introduction to Induction Motor:
An induction motor is a type of AC motor that is widely used in various industrial and commercial applications. It operates on the principle of electromagnetic induction, where the rotating magnetic field induces current in the rotor, causing it to rotate.

2. Synchronous Speed:
The synchronous speed (Ns) of an induction motor is the theoretical speed at which the rotating magnetic field would rotate if the motor had no slip. It is given by the formula:

Ns = 120 * f / P

where Ns is the synchronous speed in revolutions per minute (RPM), f is the frequency of the power supply, and P is the number of poles.

3. Relationship between Speed and Number of Poles:
From the synchronous speed formula, it is evident that the speed of the motor is directly proportional to the frequency of the power supply and inversely proportional to the number of poles.

4. Effect of Increasing Number of Poles:
As the number of poles increases, the synchronous speed decreases. This means that for a given frequency of the power supply, a motor with a higher number of poles will have a lower speed compared to a motor with fewer poles.

5. Induction Motor's Speed:
The actual speed of an induction motor is always less than its synchronous speed due to the slip. The slip is the difference between the synchronous speed and the actual speed.

6. Conclusion:
In conclusion, the statement "Greater the number of poles, lesser the speed" is correct for an induction motor. As the number of poles increases, the speed of the motor decreases. This relationship is essential to consider while selecting an induction motor for a specific application where the desired speed is a crucial factor.

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