C H A P T E R 7 – T E S T S A N D T E S T C O N D I T I O N S
AT5600 User Manual 98-119 issue 14 Page 148
7.34. STRX – Stress Watts (External Source)
Where Used
The Stress Watts (External Source) test tests the transformer for breakdown of
winding insulation by measurement of the energizing power of a winding, usually
the primary, with the remaining windings open circuit. This test applies the voltage
from an external AC source (usually at twice the normal operating voltage and
frequency), and measures the power drawn.
This test uses an external source to provide the test signal which must be coupled
to the tester via a Voltech AC Source Interface (contact your supplier for details).
See the AC Source Interface user manual or the Editor Help system for details of
how to configure external AC sources for use with an AT5600. This test is suitable
for large line frequency bobbin wound and some HF transformers. It checks the
integrity of inter-turn insulation, the magnetic material and joints at higher than the
normal operating voltage.
Measurements Conditions
A constant voltage (supplied by an external source) is applied to the winding
under test. Both the RMS voltage and the power are measured. If necessary (and
depending on the source type used), the voltage can be trimmed to the user
specified value, and the measurement repeated. The measurement is repeated
many times until the dwell time has elapsed. The result given is the measured
power.
The test can detect winding insulation defects in the following way:
• The winding insulation is stressed using the increased voltage
(increased volts per turn).
• Increasing the frequency in proportion to the voltage increase ensures
that the magnetic core of the transformer is exercised over the same
area as it would be at the normal operating voltage and frequency. - The
core losses remain the same.
• A significant increase in the power drawn when tested at increased
voltage and frequency indicates a failure of the winding insulation that
would not be detected at normal operating conditions.
The test signal can have a frequency in the range 20Hz to 5KHz, and an
amplitude from 5V to 600V depending on the type of external source used. The
current rating of a single AC Source Interface is 10A RMS. See also the STRW
test which uses the AT5600s internal generator which can provide up to 270V AC
at 25W.
To Next Page
Loading...
Need help?
General
