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?

Do you think that a three – phase induction motor could be used to establish the phase sequence of a three – phase line? Explain in 2-5 sentences

Full solutions for the question with explanation

1. The operation of Commutator in DC Motor is * O a) to convert dc to ac O b) to convert ac to dc O c) to convert fixed dc to variable dc O reverse the current direction in the rotating windings each half turn

A synchronous generator runs at 250 rpm and generates at 50-Hz. There are 216 slots, each containing 5 conductors arranged in a full-pitched winding for 3-phase star connection. All the conductors of each phase are in series and the flux per pole at no-load sinusoidally distributed over the pole pitch is 30 mWb. Find the emf induced in each phase winding and the terminal voltage.

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.

Can you please answer Problem 49 to 51.

6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor

Describe the figures below and how each of figure below are working

A DC series generator is supplying a current of 5A to a series lighting system through a feeder ofto total resistance, 1.0 ohm. The terminal voltage is 2500 V. The armature and series fieldresistances are respectively 18 and 15 ohms respectively. A 30-ohm diverter resistance isshunted across the series field. Determine the power developed in the armature of thegenerator?