3.4.21 PHAS - Interwinding Phase Test
The interwinding phase may be tested between one winding and another. A test source voltage is applied to one winding, and the voltages across two other windings (one of which may be the driven winding) are measured. The interwinding phase is measured by finding the phase difference between the voltages measured on the primary and secondary windings.
This test is suitable for most types of transformers although unusual with line frequency transformers, it tests the windings for the correct phasing. It is most useful for determining the effect of audio and telecommunications transformers when placed in a transmission line.
On selecting "PHAS Interwinding Phase" from the 'available tests' window, the following dialog box is displayed:
To program the test:
- Enter the value of voltage for the signal and the required frequency of the test. (If in doubt, refer to Chapter 7 - ‘Test Conditions’, which lists recommended test conditions.)
Note also that the Measure button may be used here as outlined in section 3.9.
- Select the integration time required. 'Medium' is the default setting. 'Long' will give more stable readings (for tighter limits) at the expense of an increased test time, and 'Short' will test at the maximum speed, but may give a slightly noisier reading.
- Enter the terminal names of the winding to be energized. Enter the terminal names of the primary and secondary windings on which the PHAS test is to be performed. Note: either of these windings can be the energized winding.
- Set the phase limits:
For phase tests, the convention of the result returned by the AT depends on the minimum limit requested. If this limit is >0 the result returned is between 0° and 360°. If the minimum limit is >-180°, the result returned is between –180° and 180°, otherwise the result returned is between –360° and 0°. This is done to ensure continuity of results and ease of setting limits irrespective of where the phasor diagram is being checked.
- Select ‘OK’. The test specification will then be displayed in the program window.