Where Used
The AT3600 offers two basic alternative ways to confirm that the transformer has been assembled properly, with the appropriate number of primary and secondary turns.
Turns ratio is the preferred test for signal, pulse and switched mode power transformers, where the normal operating conditions require only small excursions of the B-H curve, never extending beyond the linear regions.
Where the magnetic coupling between the primary and secondary is poor, it is preferable to measure the turns ratio by inductance. This test measures the inductance of both the primary and secondary and calculates the turns ratio from these measured values.
(For line frequency transformers, designed to operate over the full extent of the B-H curve, including the non-linear regions, the preferred method is to use an open - circuit voltage test to check for the correct number of turns on each winding.)
Clearly a turns ratio test cannot tell you the actual number of turns on a winding, only the ratio between one winding and the next. You should therefore have at least one inductance test in your program to give confidence that the absolute number of turns is correct as well as the ratio.
Measurement Conditions
The inductance of a winding can often depend upon the flux density in the core/windings. Since during measurement, the flux density will depend upon the signal energising the winding, it is important that both windings are energized at the same level. This will ensure that both inductances are measured along the same region of the B/H curve of the core, to give a true ratio.
Setting the Test Parameters
The simplest method of setting the test parameters is to use the ‘Measure’ button, to do this you have to program the test from a computer that is connected to the Auxiliary port of the tester. There are two other methods of inputting the test parameters, one is to set the primary voltage and frequency and let the editor set the secondary voltage, and the second is to set both voltages manually.
Using the Measure Button to Set Test Parameters
To do this you must be programming the test from a computer that is connected to the tester’s auxiliary port. Select the integration period you require, enter the primary and secondary terminals, then click on the measure button. The editor will then enter the test signal and show the measured turns ratio. Set percentage limits on this ratio and click ‘OK’ (you may select a polarity test before clicking ‘OK’).
Setting the Primary and Secondary Parameters Manually
To do this you will need to know the inductance of the primary and secondary windings.
The optimum test conditions are chosen for an inductance value that is between the primary and secondary (Lm).
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