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Page 110

| Resistance and Polarity Tests |

| These two tests may be made at the same time using the same dc source for the polarity test. Referring to Fig. 7-1, the dc battery is connected in place of the ac source across one winding (normally the high-voltage one) and the voltmeter placed across its terminals to obtain a positive deflection. The two voltmeter leads are then transferred directly across the transformer to the low-voltage terminals, without crossing the leads. The current in the first winding is interrupted, inducing a momentary voltage in the second. If a negative kick is observed on the voltmeter, the polarity of the transformer is subtractive; if a positive kick, the polarity is additive. |

| Phase Displacement Test.. |

| As mentioned earlier for three-phase transformers, it is necessary to know the polarity of each set of phase windings, as well as the angular displacement that |

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