7.1.4 RLS or RLP - Equivalent Series or Parallel Resistance
The equivalent series or parallel resistance measurements are alternatives to a Q factor measurement to follow the inductance test in the program.
As with the Q factor measurement, an equivalent series or parallel resistance 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.
An equivalent resistance test is also one way of highlighting shorted turns within the transformer.
As with measuring inductance and Q factor, to measure an equivalent series or parallel resistance, the tester applies an ac voltage across the selected winding. It then measures the voltage across and current through the winding using harmonic analysis. The measured voltage is divided by the current to obtain a complex impedance and the equivalent series or parallel resistance calculated.
If, in the program, the RLS or RLP test follows either an LS or LP test which has the same test conditions (voltage and frequency), and is applied to the same winding, then the measurement results from the previous inductance test can be re-used, saving program execution time.
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 RLS or RLP test. If the RLS or RLP 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.