Theory: No load Test of Three-phase Induction Motor The no load test is similar to the open circuit test on a transformer. It is performed to obtain the magnetizingbranch parameters (shunt parameters Rc and Xm) in the induction machine equivalent circuit. In this test, the motor is allowed to run with no-load at the rated voltage of rated frequency across its terminals. Machine will rotate at almost synchronous speed, which makes slip nearly equal to zero. This causes the equivalent rotor impedance to be very large (theoretically infinite neglecting the frictional and rotational losses). Therefore, the rotor equivalent impedance can be considered to be an open circuit which reduces the equivalent circuit diagram of the induction machine Fig. 1 (a) to the circuit as shown in Fig. 1 (d). www. R1 jx R2' jx 2' wm lo Ic Im Vph R2"((1-s)/s). Rc jxm > R1 jX 1 (a) lo R1+R2' (X1+X2') wm www Ic Vph Rc R2' jX2' wm yo lo Im jXm www Ic Vph Rc Vph jXm Im (b) lo 07 www Rc BR lo jXm EX Im (c) (d) Fig.1. Development of equivalent circuit of induction motor in open circuit test Experimental Procedure: 1. Connect the circuit as shown in the connection diagram in Figure 2. 127v U 11 U₁ A IM > 127v VLL1 V V No ° Shaft 127v VLL2 W 12 W A Fig. 2. Induction motor open circuit test 2. Start the motor by ensuring the shaft is at no load condition. 3. For starting, increase the voltage to reach rated voltage. 4. Note the readings of voltmeter, ammeter and wattmeter by carefully and fill them in table 1 5. Reduce the voltage to zero and turn the main switch off. Table 1: The measured parameters during open circuit test of the induction motor Parameter Measurement Value VLL 240 IL P1 P2 Pinput Report 1. Draw the circuit diagram of open circuit test. Give some explanations 2. Calculate the machine parameters that is can be obtained from No-Load test (Rc and Xm). 3. What is the power factor of the machine? Comment on its value. 4. Comment on the slip of the machine in this case. 5. What are the different losses that are present in an induction machine in this case?

Theory: No load Test of Three-phase Induction Motor The no load test is similar to the open circuit test on a transformer. It is performed to obtain the magnetizingbranch parameters (shunt parameters Rc and Xm) in the induction machine equivalent circuit. In this test, the motor is allowed to run with no-load at the rated voltage of rated frequency across its terminals. Machine will rotate at almost synchronous speed, which makes slip nearly equal to zero. This causes the equivalent rotor impedance to be very large (theoretically infinite neglecting the frictional and rotational losses). Therefore, the rotor equivalent impedance can be considered to be an open circuit which reduces the equivalent circuit diagram of the induction machine Fig. 1 (a) to the circuit as shown in Fig. 1 (d). www. R1 jx R2' jx 2' wm lo Ic Im Vph R2"((1-s)/s). Rc jxm > R1 jX 1 (a) lo R1+R2' (X1+X2') wm www Ic Vph Rc R2' jX2' wm yo lo Im jXm www Ic Vph Rc Vph jXm Im (b) lo 07 www Rc BR lo jXm EX Im (c) (d) Fig.1. Development of equivalent circuit of induction motor in open circuit test Experimental Procedure: 1. Connect the circuit as shown in the connection diagram in Figure 2. 127v U 11 U₁ A IM > 127v VLL1 V V No ° Shaft 127v VLL2 W 12 W A Fig. 2. Induction motor open circuit test 2. Start the motor by ensuring the shaft is at no load condition. 3. For starting, increase the voltage to reach rated voltage. 4. Note the readings of voltmeter, ammeter and wattmeter by carefully and fill them in table 1 5. Reduce the voltage to zero and turn the main switch off. Table 1: The measured parameters during open circuit test of the induction motor Parameter Measurement Value VLL 240 IL P1 P2 Pinput Report 1. Draw the circuit diagram of open circuit test. Give some explanations 2. Calculate the machine parameters that is can be obtained from No-Load test (Rc and Xm). 3. What is the power factor of the machine? Comment on its value. 4. Comment on the slip of the machine in this case. 5. What are the different losses that are present in an induction machine in this case?

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.28MCQ

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