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
What is the Important of Circle Diagram in three-phase induction motor?
Performance of the induction motor at various load condition can be easily found by performing NoLoad Test once.
Performance of the induction motor at various load conditions can be easily found with one circle diagram.
Both
none of these
Both
The Circle Diagram of a three-phase induction motor is a graphical method derived from the Heyland or Ossanna equivalent circuit. It allows for the determination of the motor's performance characteristics, such as slip, torque, efficiency, and power factor, under various load conditions using data obtained solely from the No-Load and Blocked-Rotor tests.
The Circle Diagram of a three-phase induction motor is a graphical method derived from the Heyland or Ossanna equivalent circuit. It allows for the determination of the motor's performance characteristics, such as slip, torque, efficiency, and power factor, under various load conditions using data obtained solely from the No-Load and Blocked-Rotor tests.
IsтАЛ=I0тАЛ+I2тА▓тАЛ тАФ Total stator current as sum of no-load current and reflected rotor current
TemтАЛ=╧ЙsтАЛs3V12тАЛR2тА▓тАЛтАЛ тАФ Electromechanical torque produced by the induction motor
The principle relies on the fact that the locus of the stator current phasor, as the load varies, is a circle. By performing a No-Load test (to find shunt branch parameters) and a Blocked-Rotor test (to find leakage impedance), one can construct this circle. Once drawn, any operating point on the circle corresponds to a specific load, enabling graphical calculation of motor parameters without repeated full-load testing.
Requires only two simple tests: No-load and Blocked-rotor.
Provides a visual representation of the current phasor movement.
Useful for calculating pull-out torque and starting torque.
Assumes constant supply voltage and frequency.
Simple graphical visualization of machine performance.
Avoids complex analytical calculations for variable load conditions.
Approximation based on constant parameters, ignoring saturation effects.
Less accurate than modern numerical simulation methods.
Predicting induction motor torque-speed curves.
Estimating power factor at different loads in industrial plant design.
The Circle Diagram is essentially a geometric manifestation of the Th├йvenin equivalent circuit of the induction motor.
Option A is partially correct as it highlights the input data required (No-Load/Blocked-Rotor), while Option B emphasizes the utility of the resulting diagram.
C is correct тАФ The Circle Diagram serves as a powerful graphical tool that synthesizes data from standard tests to predict motor performance metrics across all loading states.
Always remember that the Circle Diagram assumes the stator resistance is negligible; if high accuracy is needed, the Ossanna diagram should be used instead of the simpler Heyland circle.