How Do You Calculate Transformer Losses and Resistances from Test Data?

[alnywk]

urgent : single phase transformer

Homework Statement

A 2200/220 V, 500kVA, 50Hz distribytion transformer has been tested by means of the open circuit. the test data obtained is as follow:
open circuit test: V(l)= 220V, I(l)= 85A, P(oc)= 1800W
short circuit test V(h)=95V, I(h)=227.3A P(sc)= 8.2kW



2. Relevant question

1.equivalent resistance referred to the low voltage side (state all assumption)

2. resistance of the low side winding only

3.transformer copper loss of the secondary winding during the open circuit test

4. transformer core loss when rated voltage is applied

5. explain if it justified to use the power input during the open circuit test as core loss?

The Attempt at a Solution

 

[unplebeian]

It is so clear that you want us to do your homework. Here is a hint. OC tests are used to find parameters on the primary side, and SC tests are for the secondary side. Once you find out your core loss, you can assume it to be a constant and not varying with load. Only the Cu losses will change with load.

 

[piercas]

1. The equivalent resistance referred to the low voltage side can be calculated using the open circuit test data, as follows:
R_eq = (V_oc^2 / P_oc) - R_l
Where V_oc is the open circuit voltage, P_oc is the open circuit power, and R_l is the resistance of the low voltage winding. Assuming that the transformer is ideal and has no leakage inductance, the equivalent resistance is equal to the resistance of the low voltage winding.

2. The resistance of the low side winding only can be calculated using the open circuit test data and the equivalent resistance, as follows:
R_l = R_eq - (V_oc^2 / P_oc)

3. The transformer copper loss of the secondary winding during the open circuit test can be calculated using the open circuit test data and the equivalent resistance, as follows:
P_cu = I_l^2 * R_l
Where I_l is the current in the low voltage winding.

4. The transformer core loss when rated voltage is applied can be calculated using the short circuit test data, as follows:
P_core = P_sc - P_cu
Where P_sc is the short circuit power and P_cu is the transformer copper loss calculated in question 3.

5. It is not justified to use the power input during the open circuit test as core loss. The open circuit test measures the core loss and the transformer copper loss together, so using the power input as core loss would not accurately reflect the actual core loss. It is important to use the short circuit test data to calculate the core loss separately from the copper loss.