The parameter of an equivalent circuit of a three-phase induction moto...
Magnetic reactance (Xm) is depends on airgap flux and the flux is depends on V/f.
Xm ∝ ϕ ∝ V/f
Hence, magnetizing reactance gets affected by reducing the rms value of the supply at the rated frequency.
Additional Information
The total resistance at rotor is represented as

where s is slip. Now, if we create an equivalent transformer circuit for induction motor, the secondary resistance will be r
2. Thus the load resistance will be

.
Induction motor modelled as a transformer
When all the rotor parameters are shifted to stator side induction motor circuit is given by
So

is the resistance which shows the power which is converted to mechanical power output or useful power.
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The parameter of an equivalent circuit of a three-phase induction moto...
Effect of Reducing RMS Value of Supply Voltage on Equivalent Circuit Parameters of a Three-Phase Induction Motor
The equivalent circuit parameters of a three-phase induction motor represent the electrical characteristics of the motor. When the rms value of the supply voltage at the rated frequency is reduced, it affects certain parameters of the equivalent circuit. One of the parameters that is affected in this situation is the magnetizing reactance.
Explanation:
When the rms value of the supply voltage is reduced, the flux produced by the stator winding also reduces. This reduction in flux affects the magnetizing reactance of the motor. Let's understand why:
1. Stator Resistance: The stator resistance remains unaffected by the reduction in the supply voltage. The stator resistance represents the resistance of the stator winding and is mainly responsible for the copper losses in the motor.
2. Rotor Resistance: The rotor resistance also remains unaffected by the reduction in the supply voltage. The rotor resistance represents the resistance of the rotor winding and is responsible for the rotor copper losses.
3. Rotor Leakage Reactance: The rotor leakage reactance is mainly influenced by the rotor winding design and is not significantly affected by the reduction in the supply voltage.
4. Magnetizing Reactance: The magnetizing reactance is primarily dependent on the magnetic flux produced by the stator winding. When the rms value of the supply voltage is reduced, the flux produced decreases. As a result, the magnetizing reactance also decreases. This is because the magnetizing reactance is inversely proportional to the flux.
Therefore, the correct answer is option 'C' - magnetizing reactance. Reducing the rms value of the supply voltage at the rated frequency affects the magnetizing reactance of the three-phase induction motor.