To determine the synchronous speed of an electric motor, two primary factors must be considered:
1. Number of Poles per Phase:
- The motor consists of poles that create the magnetic field. The number of poles is typically referred to as the number of magnetic poles that exist in each phase of the motor. This is a critical factor as it directly influences how fast the magnetic field rotates.
2. Frequency of the Applied Voltage:
- The frequency of the applied voltage (usually measured in Hertz, Hz) is another crucial aspect. Frequency denotes how many cycles per second the voltage completes. This determines how frequently the magnetic poles in the motor are energized and de-energized, thus affecting the rotational speed of the magnetic field.
When combined, these two factors determine the synchronous speed of the motor, which is the speed at which the magnetic field rotates and, ideally, it's the speed the rotor would match if there were no slip. The actual relationship is given by the formula:
[tex]\[ \text{Synchronous Speed (NS)} = \left( \frac{120 \times \text{Frequency (F)}}{\text{Number of Poles (P)}} \right) \][/tex]
Therefore, the correct choice from the given options is:
number of poles per phase, frequency of the applied voltage
