LOAD TEST ON TRANSFORMER

NEED FOR LOAD TEST

Load Test helps to determine the total loss that

takes place, when the transformer

is loaded .Load test is used mainly

1. to determine the rated load of the

machine and the temperature rise

2. to determine the voltage regulation and

efficiency of the transformer.

CONTD.. The losses that are generated inside the

Transformer

on load appear as heat. This heats the

transformer and the temperature of the

Transformer

increases. The insulation of the transformer is the one to get affected by this rise in the

temperature

CONTD.. This aspect of temperature rise cannot be

guessed from the electrical equivalent

circuit. Further, the losses like dielectric

losses and stray load losses are not modeled in

the equivalent circuit and the actual loss under

load condition will be in error to that extent.

LOAD TEST ASCERTAINED Hence the only sure way of ascertaining

the rating is by conducting a load test.

WHAT U DO IN A LOAD TEST

EFFICIENCY

EFFICIENCY VS X

REGULATION: 1.Voltage regulation(V.R) is the change

in the

magnitude of secondary voltage from no

load to desired load.

2.This change is expressed as a percentage of

the load voltage.

USE OF V.R. To get the best performance out of your

transformer, you need the lowest possible

voltage regulation

EXPRESSION FOR VOLTAGE REGULATION:

APPROX. EQUIVALENT CIRCUIT

Since, the change in secondary

voltage depends only on the load current, the

equivalent circuit is further simplified

VECTOR DIAGRAM FOR LAGGING PF

FINAL EXPRESSION:

CAUSE OF V.R Thus voltage regulation is because of

resistance and leakage reactance of the

transformer

DISADVANTAGE Large amounts of energy are wasted

It is a stupendous task to arrange a load large

enough for direct loading