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| Figure 7-6 Connection for determining core loss. |

| comparatively simple tests, and the total losses of the transformer found by adding them together. |

| Core Loss |

| These may be determined by a connection similar to that for the impedance test (Fig. 7-6). Care should be taken with the primary terminal leads as they are left open-circuited and a high voltage may be produced across them. The rated low voltage is applied across the secondary winding and the wattmeter reading will represent the core loss. |

| Copper Loss.. |

| The transformer under test is connected again as for the impedance test (Fig. 7-5). The low voltage winding is short-circuited, and the voltage applied to the primary or high voltage winding is adjusted so that full-load (primary) current is indicated by the ammeter. The wattmeter reading will represent the full load copper loss. |

| Continuity Test for TCUL Transformers |

| This test is to ascertain that the circuit remains closed throughout the whole range of tap changes in a Tap Changing Under Load transformer. The connections for this test are similar to those for impedance tests; in fact, this test is often made just before the impedance test is run. |

| With the low-voltage winding short-circuited, and full-load current in both windings, the tap changing mechanism is operated through its full range and the ammeter observed throughout to make sure the current is not interrupted, which would be an indication of an open circuit at the tap position where such interruption is noted. The current is recorded for each tap position. |

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