Applicable laminate tests
The AT Series-testers currently has the ability to perform the following
applicable laminate transformer tests: -
CTY is a continuity test designed to ensure that the transformer is
correctly seated in its fixture and that all the winding termination
integrity is good. The minimum resistance is 10KOhms up to 10MOhms
R is the direct current, (DC) resistance offered by an inductor due to the
resistance of the winding. The lower the resistance the more current an
inductor will handle. Resistance is presented in mOhms to MOhms
Voltage open circuit, this test applies a voltage to the primary and reads
the voltage induced in the secondary winding the results are presented as a
secondary voltage from 100mV to 500V with a test voltage from 1V to 270V @
20Hz to 1.5KHz. Phase is also measured as a polarity i.e. positive (in
phase), negative (anti-phase).
Insulation resistance tests are designed to check for poor shielding and
insulation between windings. Voltage and current is measured and by dividing
the voltage by the current insulation resistance measurements are presented
in MW to GW with a test voltage from 100V to 7KV @ DC.
Magnetizingcurrent is the combination of the current required to magnetize
the core and the current required to supply the losses in the core. Results
are presented as a current from 1mA to 2A (3A peak) with a test voltage from
1V to 270V @ 20Hz to 1.5KHz.
At no load and with the secondary open circuit a transformer will still draw
current this current is proportional to the core losses (eddy currents and
hysteresis). Faraday's law suggests that providing the voltage and frequency
is increased proportionally core loss should remain the same. Therefore if a
dramatic power increase is detected it would indicate a winding fault.
Results are presented in watts from 1 mW to 40 watts with a test voltage
from 1V to 270V @ 20Hz to 1.5KHz.
Hi-pot AC tests are isolation safety tests, which tests the isolation
between windings and between winding and core and winding to shield. Current
flow is measured between each test point and is presented in mA to mA with a
test voltage from 100V to 5.5KV @ 50Hz to 1KHz.
A typical laminate test sequence might be:
- CTY Continuity.
- R Resistance.
- VOC Voltage open circuit.
- MAGI Magnetizing current.
- STRW Stress watts.
- IR Insulation resistance.
- HPAC High potential AC. Safety-test.