we are not having anyother work, so only we are testing that.
The residual magnetisation present in the current transformer coils may cause the errors during measurement of high currents. So that it is necessary to check that.
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
The no load losses are the losses caused by energizing the transformer. These are constant losses, regardless of loading. This in effect tells you the efficiency of the transformer. (Power in) - (no load losses) = (Power out)
Open Circuit test is done to find out core losses of the transformers.which include Eddy Current Losses and Hysteresis Losses only, if during open circuit test secondary will have some load then I2R losses due to load current in secondary as well primary will be included in test results which is not desired while performing Open circuit test.
Transformer short circuit tests are used to determine the impedances (positive and zero sequence) of the transformer. A simple explanation: to do this one winding is shorted, and voltage is applied to another winding to circulate the normal full load current of the transformer. The impedance of the transformer is the applied voltage divided by the induced current. If one winding was not shorted, the voltage divided by induced current would not give the impedance of the transformer - the induced current would be much lower, giving a much higher impedance measurement that would be essentially meaningless.
How do you zero phase current transformer test
I am sure there is more than one way of doing this but what I am currently implementing in my own study of I_mag is the following: At no load perform an over excitation test where you vary the input voltage from 0 V and monitor the current flowing through the primary windings of the transformer. Over-excite the transformer until the rate at which current, I_in increases in the primary windings is relatively larger than the change in Vout , across the secondary windings (this is the point of saturation). Plot your results of voltage Vout (y- axis) against current I_in (x-axis) and you should come up with a characteristic B-H curve. (Remember that the B field is proportional to voltage and the H field is proportional to current from magnetic circuits theory) You are then to decide which point on your curve you will regard as the 'knee' point or the point at which the curve starts to deviate from the linear region. This 'knee' point will correspond to your I_mag. While I_in is not necessarily equal to I_mag at no load, at the knee point on your curve these two currents will be approximately equal.
You don't.
The residual magnetisation present in the current transformer coils may cause the errors during measurement of high currents. So that it is necessary to check that.
eddy current loss in the transformer core is reduced by
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
RATIO ERROR The secondary current is less than the expected value. The secondary is less in magnitude. This diffence is known as ratio error. PHASE ERROR The angle between the expected and actual secondary current is known as phase error.
To identify transformer winding shortage. If there is shortage between winding turns magnetic current test is the best to identify. Shaukt from Abudhabi.UAE
see http://ezinearticles.com/?Testing-a-Transformer--How-To-Accurately-Test-A-Transformer&id=56803 Normally to test a CT we go on with two tests 1. the primary injection test 2. the polarity test 1. primary injection test: a particular amount of current is made to flow through the primary and the amount of current we get from secondary is measured. 2. the name itself describes the test...
why need dielectric test for transformer
The short-circuit test runs the rated current through the windings of the transformer to measure the copper-loss, or power lost in the winding resistances. Because the transformer is run at low voltage for this test, there is very little additional power loss in the iron core of the transformer.
A no-load test is done with the normal supply connected in the way the transformer is intended to be used. It is also known as an open-circuit test to distinguish it from a short-circuit test, and its purpose is to measure the power loss in the iron core of the transformer and the no-load current drawn from the supply.