7.1.7 QL - Quality Factor
The Q factor measurement would normally follow a measurement of the inductance of the primary winding in the test program.
As with an inductance measurement, the Q factor test would normally be used 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.
A Q factor test is one way of highlighting shorted turns within the transformer.
To measure Q factor, the tester performs exactly the same steps that would be used to measure inductance. The only difference is in the calculation at the end of the test: the measured voltage is divided by the current to obtain a complex impedance from which the Q factor is calculated.
The test signal can have a frequency in the range 20Hz to 1MHz, and an amplitude from 1mV to 5V.
Normally when following an inductance test, you would choose the same test conditions for the QL test. If the QL test does not have an associated inductance test, then choose the test conditions as detailed in the Table on page 7.1.8, base on the value of the inductance of the winding under test.