What is the calculated RPM of a four-pole motor rated at 150hp, 120 volts, and 60 cycles?

To determine the calculated RPM of a four-pole motor, you can use the formula for synchronous speed, which is given by:

[

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

]

In this scenario, the motor operates at a frequency of 60 cycles per second (or 60 Hz) and has four poles. Plugging in these values results in:

[

Synchronous\ Speed\ = \frac{120 \times 60}{4}

]

Calculating that gives:

[

Synchronous\ Speed\ = \frac{7200}{4} = 1800\ RPM

]

The synchronous speed is the theoretical maximum speed at which the magnetic field rotates in the motor. An induction motor would typically run slightly slower than this synchronous speed due to slip, but the question focuses on the calculated value based on the number of poles and the frequency.

Thus, the calculated RPM of the four-pole motor is indeed 1800 RPM, making this the correct answer. This value is commonly found in motors designed for standard applications in North America.