2.32 WATX - Wattage (External Source)
The Wattage test measures the power needed to energise a particular
winding, usually the primary, with the remaining windings open circuit.
It is usual to configure the test signal to the normal operating
conditions of the transformer to determine the power needed to energise
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 AT.
This test is suitable for line frequency transformers (25-400Hz) and
checks the no load losses in the transformer.
During the Wattage (External Source) test, a constant, user specified ac
voltage from an external source is applied across the winding in question.
All other windings are held open circuit during this test.
The AT measures the voltage across and current through the winding.
The Wattage is the product of the in phase components of the current and
If, in the program, the WATX test follows either a VOCX or MAGX test
which has the same test conditions (voltage and frequency), and is applied
to the same winding, then the measurement results from the previous tests
can be re-used, saving program execution time.
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 WATT test which uses the ATs internal generator, which can
provide up to 270V ac at 40W.