Question Details

In a single phase transformer, the total iron loss is 2500 W at nominal voltage of 440 V and frequency 50 Hz. The total iron loss is 850 W at 220 V and 25 Hz. Then, at nominal voltage and frequency, the hysteresis loss and eddy current loss respectively are

Options

A

1600 W and 900 W

B

900 W and 1600 W

C

250 W and 600 W

D

600 W and 250 W

Correct Answer :

900 W and 1600 W

Solution :

The correct option is 900 W and 1600 W.

Step-by-step explanation:

The total iron loss (Wi) in a transformer is the sum of hysteresis loss (Wh) and eddy current loss (We):

Wi=Wh+We

The relationships of these losses with voltage (V) and frequency (f) depend on the ratio Vf, which is proportional to the maximum flux density (Bm):

BmVf

Let us check the ratio of voltage to frequency for both given conditions:
Case 1: Nominal voltage V1=440 V and frequency f1=50 Hz.
Ratio: V1f1=44050=8.8

Case 2: Voltage V2=220 V and frequency f2=25 Hz.
Ratio: V2f2=22025=8.8

Since the ratio Vf is constant in both cases, the maximum flux density Bm remains constant. Under this condition, the hysteresis loss is directly proportional to frequency, and the eddy current loss is proportional to the square of the frequency:
Hysteresis Loss: Wh=A·f
Eddy Current Loss: We=B·f2
where A and B are constants.

Therefore, the total iron loss can be written as:

Wi=Af+Bf2

Dividing both sides by f yields:

Wif=A+Bf

Now, we substitute the values of both cases into this equation to solve for the constants A and B:

For Case 1 (Wi1=2500 W and f1=50 Hz):
250050=A+50B
50=A+50B (Equation 1)

For Case 2 (Wi2=850 W and f2=25 Hz):
85025=A+25B
34=A+25B (Equation 2)

Subtracting Equation 2 from Equation 1:

(A+50B)-(A+25B)=50-34

25B=16

B=1625=0.64

Substituting B=0.64 back into Equation 2:

34=A+25(0.64)

34=A+16

A=34-16=18

Finally, we calculate the individual losses at the nominal voltage and frequency (f=50 Hz):

Hysteresis loss (Wh):
Wh=A·f=18·50=900 W

Eddy current loss (We):
We=B·f2=0.64·502=0.64·2500=1600 W

Therefore, the hysteresis loss and eddy current loss are 900 W and 1600 W respectively.

Note: The attached image displays an AC circuit with a source frequency parameter of ω = 1 k rad/sec, a 4 mH inductor, a 0.5 mF capacitor, a 2 Ω resistor, and a load resistor RL. This diagram is unrelated to the single-phase transformer losses problem, which has been solved directly using the parameters specified in the question text.

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