What are the various methods of there phase transformer

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Reference no: EM132399122

ASSIGNMENT - Three phase systems

Question - 1

An unbalanced star-connected load shown in Figure-1 has branch impedances of Z_R = 10∠30°Ω, Z_y = 20 ∠ 45°Ω, and Z_B = 20 ∠ 60°Ω and is connected across a balanced 3- phase, 3-wire supply of 440V. Find the following parameters:

(i) Line currents, and

(ii) Voltage across each impedance.

Question - 2

a) Calculate the readings of the two wattmeter's with current coil in line R and B Connected to measure the total power for a balanced delta-connected load, fed from a three phase, 200 V balanced supply with phase sequence as R-Y-B. The load impedance per phase is (14-j14) Ω. Also draw the circuit.

b) The readings of the two wattmeter's connected to measure a 3-Phase power is 8KW, each when the power factor is factor is unity. What will be the reading of the wattmeter's if the power factor falls to (i) 0.7 lagging (ii) 0.5 lagging and (iii) 0.4 lagging, the total 3 Phase power remaining unaltered.

Question - 3

a) In a 3-phase 4-wire system, the currents in R, Y and B lines under abnormal conditions of loading are as under :I_R = 150∠ 30° A, I_Y = 250∠150° A, and I_B =150∠30° A. Calculate the zero, positive and negative phase sequence currents in the R line and return current in the neutral connection.

b) A 50 MVA, 11KV, 3-phase alternator was subjected to different types of faults. The fault currents were: 3-Phase fault = 2000A, Line -to-Line fault 2600 A and Line-toground fault 4200A. The generator neutral is solidly grounded. Find the values of three sequence reactances of the alternator. Ignore resistances.

Question - 4

a) Describe the constructional details of the three phase core and shell type transformers.

b) What are the various methods of there phase transformer connections? Describe any three types of connections in detail with diagrams, and state their advantages, disadvantages and applications.

Question - 5

Sketch and explain the typical torque-slip characteristics of a there phase induction motor and explain the effect of change in the rotor resistance on the torque-slip characteristics.

Question - 6

Explain the process of crawling in three phase induction motor.

Reference no: EM132399122

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