Regulation & Efficiency Test of Single-phase Transformer by Direct Loading Method

Experiment No.: 5

Experiment Name:

Determine the regulation & efficiency of single-phase transformer by direct loading method.


To determine

  1. Regulation of single-phase transformer by direct loading method
  2. Efficiency of single-phase transformer by direct loading method


Although two chief difficulties which do not warrant the testing of large transformer by direct load test are:

  1. Large amount of energy has to be wasted in such a test.
  2. It is stupendous (impossible for large transformer) task to arrange a load large enough for direct loading. Yet this test can be performed to find out the efficiency & voltage regulation of small rating transformers.

Efficiency, η = Output Power / Input Power

% η =((P2) / (P1)) × 100

% Voltage regulation up= ((No load voltage – Full load voltage)/Full load voltage)×100

% Voltage regulation down= ((No load voltage – Full load voltage)/No load voltage)×100

Circuit Diagram:

Observation Table:


Apparatus Used:

Sl. No.Name of ApparatusQuantitySpecificationMakers name
 1. Single phase wattmeter 2 0-750-1500-3000 W
150-300-600 V
5-10 A
2.Single Phase Transformer1230/115 V 
3.Ammeter10-5 A, MI typeKEW
4.Ammeter10-10 A, MI typeSushama
5.Voltmeter10-300 V, MI typeSushama
6.Digital Multimeter10-750 V AC, 0-1000 V DC,
0-10 A
7.Rheostat10-100 W, 1kW

Remarks: This method is not applicable for large rated transformer as a large amount of energy has to be wasted in such a test. During this test we should cautious about the heat radiated by the resistive load.

Leave a Comment

Your email address will not be published. Required fields are marked *

Free Mock Test Series on SSC JE Electrical. Test yourself Now!


You cannot copy content of this page


Enjoy this blog? Please spread the word :)