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). Vph R1 jX lo > Ic Rc Ic Vph Rc ник чик lo R2' jx 2' Im R2" ((1-s)/s). jXm (a) lo R1+R2' j(X1+X2') www. Vph R1 R2' jX2' jX 1 lo ပ Ic Rc www (b) /lo Im jXm lo Im Ic Vph jXm Rc www Im E jXm (c) (d) Fig.1. Development of equivalent circuit of induction motor in open circuit test 1. Connect the circuit as shown in the connection diagram in Figure 2. 127v U 11 U 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?

Any chooses is correct?

(Q1f, Draw and compare the per-phase electrical equivalent circuits of a transformer and of an induction motor. Using simple magnetic circuits, explain how the values of the magnetising (shunt) impedances compare in the two devices and what is the cause of the difference between the two? Figure 2. A transformer and an induction motor. Among other differences, one is typically rectangular, and the other one is round :D

Full solutions for the question with explanation

Draw the per-phase equivalent circuit of a three-phase squirrel-cage induction machine. List all of the elements in the equivalent circuit and briefly state their function

9. How does the concept of magnetic saturation impact the performance of transformers and inductors?

Design a winding diagram given the following specifications. • Simplex Wave Progressive Winding • No. of Poles = 4 • Turn/coil = 1 • Conductor/Slot = 2 • No. of Commutator Segments = 27 • No. of Slots = 27 %3D

A 10-kVA, 1-phase transformer has a turn ratio of 300/23. The primary is connected to a 1500-V,               60 Hz supply. Find the secondary volts on open-circuit and the approximate values of the currents in the two windings on full-load. Find also the maximum value of the flux.

A 6 pole wave wound d.c. shunt generator has 500 conductors. A generator delivers 50 kW of power at 250 voltage at full load. The resistance of the field circuit is 125 2. Actual brush shift is 10°. Then find the demagnetizing and cross magnetizing ampere turns per pole and how many additional turns must be wound on each pole to eliminate the demagnetizing effect.

What conclusions we come up with after doing open circuit test on single phase transformer.