Given V1 480 VaC T1 15 T2 51 Z1 3 j4 Z2 30 j40 a Wh

Given: V₁ = 480 V_aC; T₁ = 1:5 ; T₂ = 5:1 ; Z₁ = 3 + j4?; Z₂ = 30 + j40?.

(a) What is the purpose of the transformers in this circuit?

(b) Which of the two transformers is a step up transformer, and which is the step down transformer?

(c) What happens if we switch the two transformers? Is it something we would want to do in a practical system? Why?

(d) How would the efficiency change if we were to increase/decrease the turn\'s ratio of the transformers?

1) Consider the circuit diagram below and answer questions a-d. Z1 represents the line impedance and Z2 represents the load impedance. Do not solve the circuit. - T1 OO 34 I 30 as 1:5 5:1

Solution

(A)

THE PURPOSE OF TRANSFORMERS IN THIS CIRCUIT IS TO STEP UP THE VOLTAGE AT CERTAIN LEVEL AND TRANSMIT THAT STEP UP VOLTAGE AND AGAIN STEP DOWN THE VOLTAGE AT THE LOAD END.

(B)

The first transformer T1 is a step up transformer and the second transformer T2 is a step down transformer.

(C)

If we switch the two transformers nothing will happen just the voltage which is produced by the fist transformer is supplied to second transformer and then to load. Generally we can see this type of case in distribution systems in practical. Where the voltage generated in power plant is stepped up and transmitted to a long distance and then it is stepped down near substations and this voltage is supplied to load centres.

(d)

The efficiency of transformers depends on the power loss. So if turns are increased or decreased also the will depends on the how much power is lost.Generally an ideal transformer is 100% efficient where as in practical case the effiency of a transformer is above 95%.