Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
Direction of three phase induction motor can be changed by
Reducing load
Changing two phases
Reducing frequency
Reducing voltage
Changing two phases
Quick Trick: To reverse the direction of rotation (RMF) in any 3-phase motor, simply swap any two supply phase terminals (e.g., interchange R and Y, keeping B fixed).
To reverse the direction of rotation (RMF) in any 3-phase motor, simply swap any two supply phase terminals (e.g., interchange R and Y, keeping B fixed).
Understand the Rotating Magnetic Field (RMF)
The direction of rotation of a 3-phase induction motor depends directly on the phase sequence of the supply (e.g., R-Y-B), which determines the direction of the rotating magnetic field created in the stator.
Reversing the Phase Sequence
Interchanging any two line connections alters the phase sequence (e.g., from R-Y-B to R-B-Y). This reverses the direction of the rotating magnetic field, which in turn causes the rotor to spin in the opposite direction.
A: Reducing load only increases speed closer to synchronous speed but does not reverse direction. C: Reducing frequency decreases synchronous speed without changing rotational direction. D: Reducing voltage decreases developed torque but keeps rotation direction unchanged.
B is correct because interchanging any two phase connections reverses the supply phase sequence and the direction of the stator's rotating magnetic field.
Questions on reversing rotation apply identically to 3-phase synchronous motors and 3-phase induction motors: swapping two supply lines is always the key.