What primarily determines the speed of a three-phase squirrel cage motor?

The speed of a three-phase squirrel cage motor is primarily determined by the system frequency and the number of poles. In alternating current (AC) motors, the synchronous speed can be calculated using the formula:

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

This formula illustrates the direct relationship between the frequency of the supply voltage and the number of magnetic poles in the motor. Increasing the frequency will result in a higher synchronous speed, while more poles will decrease the speed.

Torque and RPM do relate to the operational dynamics of the motor, and while voltage and load affect performance, they do not directly influence the fundamental speed characteristics as defined by frequency and pole count. Similarly, wire gauge and length are important for electrical resistance and efficiency but do not impact the motor's rotational speed fundamentals. Thus, the speed of a three-phase squirrel cage motor is ultimately governed by these two primary factors: system frequency and the number of poles in the design.