The speed of a synchronous motor depends on:
Supply frequency
The speed of a synchronous motor is determined by the frequency of the power supply it is connected to. This relationship is derived from the formula for the synchronous speed (in revolutions per minute) of a synchronous motor, which is given by:
N_s = \frac{120 \times f}{P}
- N_s is the synchronous speed in RPM (revolutions per minute).
- f is the frequency of the supply in Hertz (Hz).
- P is the number of poles of the motor.
Let's analyze the options given in the question to see why "Supply frequency" is the correct answer:
- Supply frequency: As shown in the formula, the synchronous speed is directly proportional to the supply frequency. Hence, a change in the frequency will directly affect the motor speed, confirming that the correct answer is supply frequency.
- Field resistance: Field resistance does not affect the speed of a synchronous motor. It primarily affects the field current and, consequently, the excitation but not the speed.
- Load only: The load applied to the motor affects the torque and power delivered by the motor but does not affect the synchronous speed. The speed of a synchronous motor is independent of the load.
- Armature current: Similar to the field resistance, the armature current affects the torque and efficiency but not the speed of the motor.
Therefore, the speed of a synchronous motor depends on the supply frequency.
Similar Questions
Why does a squirrel cage induction motor not develop maximum starting torque?
Which point or region represents the Pull-out Torque in the shown torque-speed characteristic of a 3-phase induction motor?
Which set of statements correctly describes the steady state speed-torque characteristics of a three-phase synchronous motor?
i) Runs at constant synchronous speed
ii) Starting torque is zero
iii) Torque increases significantly with slip
iv) Not suitable for variable speed drives
v) Maintains speed under varying loads
When an alternator operates at unity power factor, the armature current:
Field failure protection in an alternator is provided to detect:
Important Questions from Alternator and Synchronous Motors
Consider the table given:
Constructional feature
Machine type
Mitigation
(P) Damper bars
(S) Induction motor
(X) Hunting
(Q) Skewed rotor slots
(T) Transformer
(Y) Magnetic locking
(R) Compensation winding
(U)Synchronous machine
(Z) Armature reaction
(V) DC machine
The correct combination that relates the constructional feature, machine type and mitigation isTorques are associated with synchronous motor; which of the following torques is also known as breakaway torque?
A generating voltmeter uses ___________.
In a synchronous motor hunting takes place
Which of the following statements about the armature reaction of an alternator with unity power factor is NOT true?
