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Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In the design of single-phase induction motor · The value of the stator induced voltage = __________ the supply voltage.
0.75
0.80
0.85
0.95
0.95
In the design of a single-phase induction motor, the stator induced electromotive force (EMF) is approximately 0.95 times the supply voltage · This difference accounts for the voltage drop across the stator winding resistance (Rs) and leakage reactance (Xs).
In the design of a single-phase induction motor, the stator induced electromotive force (EMF) is approximately 0.95 times the supply voltage · This difference accounts for the voltage drop across the stator winding resistance (Rs) and leakage reactance (Xs).
V=Es+Is(Rs+jXs) — Phasor equation for the stator winding
Es=4.44fNϕm — EMF equation of the stator winding
The applied supply voltage V is balanced by the back EMF Es and the voltage drop due to stator impedance Zs. The relationship is given by the Kirchhoff's Voltage Law: V=Es+Is⋅Zs. Since the winding resistance and leakage reactance are kept minimal to maintain high efficiency, the induced back EMF remains very close to the supply voltage magnitude.
The induced EMF (Es) is slightly less than the applied voltage due to stator winding impedance.
Higher efficiency is achieved by minimizing the Is2Rs losses, keeping Es close to V.
In small motors, the voltage drop is often 5% of the rated voltage.
Ensures high electromagnetic torque production
Minimizes copper losses within the stator structure
Higher induced voltage leads to higher insulation stress requirements
Requires precise winding geometry to maintain this ratio
Fractional horsepower motors
Household appliances like fans and washing machines
The 0.95 factor is a design standard to ensure the motor operates near its rated magnetic flux levels.
Options 0.75, 0.80, and 0.85 represent poorly designed machines with excessive voltage drops.
D is correct — The stator induced voltage is kept at approximately 0.95 of the supply voltage to account for stator winding impedance drops while maintaining optimal flux density.
Always remember that in electrical machines, the relationship between EMF and terminal voltage determines the efficiency and internal power factor of the machine.