2.3 RLS or RLP - Equivalent Series or Parallel R
The equivalent series or parallel resistance measurements are
alternatives to a Q factor measurement to follow the inductance test in
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
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
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 3 MHz, and an
amplitude from 1 mV to 5 V.
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 under section 1.11, based
on the value of the inductance of the winding under test.