M
AVTMMTO3xx Rev 3 Sept 2013
14
TEST FUNCTION
1. Entering the test report information.
2. Entering the transformer nameplate information.
3. Starting the test.
4. Data Display.
5. Stopping the test
6. Populating the PowerDB table
7. Saving the data
AUTOMATIC DISCHARGE FUNCTION
Discharge of a transformer after testing is critical to prevent excessive voltage
buildup across the transformer bushings upon removal of leads. When any
current source is disconnected from a transformer, the energy in a transformer
will continue to flow. If there is high impedance (air) in the nature current loop,
the voltage across the inductor will increase until there is a current path found
for the energy. The MTO3XX has discharge circuitry built-in. It will
automatically initiate when the current source is disconnected from the
transformer. It will also provide visual indication of discharging on the front
panel and the PC screen.
DEMAGNETIZATION FUNCTION
The demagnetization of a transformer after DC winding resistance testing
is recommended. This will ensure smooth startup and consistent diagnostic
results. If not performed, there may be a residual flux present in the transformer
at startup. Inrush currents on the primary side of the transformer may exceed
relay settings for shutdown. Demagnetization is also recommended before
performing SFRA and excitation current measurements.
MTO demagnetizes the transformer by automatically magnetizing the core of the
transformer in the positive and negative direction with multiple cycles of reduced
current. During demagnetization, the system will display what cycle the unit is
processing.
Primary H leads need to be the only leads attached for effective
demagnetization.
NOTE: The demagnetization cycle will take some time for completion. It is
equivalent to taking multiple tests in sequence.
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