How does the speed of an induction motor changes when mains frequency increases?Question 1Select one:a.decreasesb.increasesc.does not change

Analysis of the Question

1. Understanding Induction Motors: Induction motors operate based on the principle of electromagnetic induction, where the speed of the motor is closely related to the frequency of the electrical supply.

2. Key Concept - Synchronous Speed: The synchronous speed ($N_s$) of an induction motor is calculated using the formula: $N_s = \frac{120 \times f}{P}$ where $N_s$ is the synchronous speed in revolutions per minute (RPM), $f$ is the supply frequency in hertz (Hz), and $P$ is the number of poles in the motor.

3. Effect of Frequency on Speed: From the synchronous speed formula, it can be observed that as the frequency ($f$) increases, the synchronous speed ($N_s$) also increases, assuming that the number of poles ($P$) remains constant.

Conclusion

Given the relationship between frequency and the synchronous speed of an induction motor, we can state that an increase in mains frequency results in an increase in the motor speed.

Final Answer

b. increases