What would be the rpm of a four-pole motor rated at 150 hp, 120 volts, and 60 cycles?

To determine the RPM (revolutions per minute) of a four-pole motor, we can use the formula for calculating synchronous speed, which is given by:

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

In this case, the motor operates at a frequency of 60 cycles per second (which is equivalent to 60 Hertz) and has four poles. Substituting the known values into the formula:

[ \text{Synchronous Speed (RPM)} = \frac{120 \times 60}{4} ]

Calculating this gives:

[ \text{Synchronous Speed (RPM)} = \frac{7200}{4} = 1800 \text{ RPM} ]

This synchronous speed of 1,800 RPM is significant because it represents the speed at which the magnetic field in the motor rotates. The actual operating speed of an induction motor is usually slightly lower than the synchronous speed due to slip, but for the purposes of calculating the RPM based on the synchronous formula, 1,800 RPM is the correct value.

Therefore, the given answer correctly identifies the RPM of a four-pole