In countries with a 50Hz line frequency, if the machine turns at just under 300 RPM, is it classified as a two-pole or four-pole motor?

To determine whether a motor is classified as a two-pole or four-pole motor based on its RPM and the line frequency, it's essential to understand how synchronous speed relates to the number of poles in an AC motor.

The synchronous speed of an AC motor can be calculated using the formula:

[ \text{Synchronous Speed (RPM)} = \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}}. ]

In countries with a line frequency of 50 Hz, if the machine is running at just under 300 RPM, we can use the formula to find out how many poles the motor has.

1. For a two-pole motor:

[ \text{Synchronous Speed} = \frac{120 \times 50}{2} = 3000 \text{ RPM}. ]

This speed is significantly higher than 300 RPM, indicating it is not a two-pole motor.

2. For a four-pole motor:

[ \text{Synchronous Speed} = \frac{120 \times 50}{4} = 1500 \text{ RPM}. ]

This is also too high for a speed of just under