M
AVTMTTR310 Rev 8 May 2016
24
Three-Phase, Three-Winding Transformers
This type of transformers has primary, secondary and tertiary windings. Primary
and secondary windings are tested as a regular three-phase, two-winding
transformer. To test tertiary winding, perform the following setup procedure:
1. Connect the wing-nut ground terminal of the test set to a low-impedance
earth ground using the 15 ft (4.6 m) ground lead supplied.
2. Connect the three-phase test cables to the respective H and X receptacles of
the test set. Make sure that the connectors are screwed tight to the
receptacles.
3. Connect the heavy-duty clips marked H0, H1, H2, and H3 of the test lead to
the corresponding (high-voltage winding) terminals of the transformer under
test.
4. Connect the heavy-duty clips marked X0, X1, X2 , and X3 of the test lead to
the corresponding tertiary (low-voltage winding) terminals (Y0, Y1, Y2, and
Y3) of the transformer under test.
WARNING
Never interchange connections between the high- and low-
voltage transformer terminals. Failure to observe proper
connections will result in a safety hazard and may result in
damage to the test set or transformer.
The unused H0 and X0 terminals should be kept clear of ground and personnel
because they could become energized during the test. Refer to Table 5-2 for test
lead markings.
With delta connected windings, H0 or X0 is not used. With wye connected
windings, a neutral connection is normally available.
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