A device which taps electrical energy from the electric power system is called a load on the system. The load may be resistive (e.g., electric lamp), inductive (e.g., induction motor), capacitive or some combination of them. The various types of loads on the power system are : Continue reading

# Important Terms in variable load problems

(i) Connected load. It is the sum of continuous ratings of all the equipments connected to supply system.

# Assignment Three Phase Induction motor

Assignment 3: Three phase induction motor

1. Explain the equivalent circuit and Phasor diagram of three phase induction motor.
2. Discuss the procedure of no-load and blocked rotor test with test setup arrangement.
3. List out the basic steps of drawing the circle diagram with any one example.
4. Explain the unbalanced operation of the induction motor. Also discuss the case of single phasing.
5. Explain in brief about the cogging and crawling phenomena.
6. What are the desirable starting conditions for a three phase IM? Discuss all the starting methods with the circuit diagram.
7. Explain the construction, operation and equivalent circuit of double cage induction motor.
8. Discuss the methods of speed control of three phase induction motor.

Using circle diagram method, solve the followings:

1. Motor data: 3 phase, 20 HP, 440 Volt, 50Hz, 4 pole
2. No load test: 440 V, 10 A, 1.5 kW
3. Blocked rotor test: 120 V, 30 A, 2.25 kW
4. Determine   Full load current and PF & Maximum possible output power

1.  Motor data: 3 phase, 10 HP, 200 Volt, 50Hz, Slip ring IM, Rs = 0.38Ω and Rr = 0.24Ω  per phase, winding turns ratio unity
2. No load test: 200 V, 7.7 A, 0.195 pf
3. Blocked rotor test: 100 V, 47.6 A, 0.454 pf
4. Determine,   Starting & Maximum torque, Slip at maximum output and maximum output

1. Motor data: 3 phase, 40 HP, 440 Volt, 50Hz, 4 pole
2. No load test: 440 V, 16 A, 0.15 pf
3. Blocked rotor test: 100 V, 55 A, 0.225 pf
4. Ratio of rotor to stator copper losses is 0.9
5. Determine,   Full load current and PF & Maximum possible output power

1. Motor data: 3 phase, 15 HP, 230 Volt, 50Hz,Slip ring, Rs = 0.42 Ω and Rr = 0.3 Ω  per phase, winding turns ratio unity
2. No load test: 230 V, 9 A, 0.2143 pf
3. Blocked rotor test: 115 V, 45 A, 0.454 pf
4. Determine   Starting & Maximum torque & maximum output.

# Sub Station And Classification

The assembly of apparatus used to change some characteristic (e.g. voltage, a.c. to d.c., frequency, p.f. etc.) of electric supply is called a sub-station.