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Transformer nameplate and treatment method

Transformer nameplate is the name transformers performance, technical specifications and use of occasions, as used to meet the user selection and operation of the transformer. When faced with the transformer nameplate signs unclear or old transformer, what test to judge? Transformer engineers suggest that there are two ways to test:
(1) DC method.
When measuring a single-phase transformer, pull a 1.5-volt dry cell into the primary side of the primary coil and pull in a DC millivolt meter in the secondary coil. When close the switch K moment, the needle swing toward the positive direction (or open the switch when the needle needle to the negative direction), then connect the positive end of the battery is the same polarity, or the same name end. Test the polarity and level of three-phase transformers, and more use of DC method. Test method: the primary coil connected to the side of the battery and switch K, first in the A termination of the battery positive, B termination battery negative, and then in the secondary coil a, b, c into the three millivolts table, then Table should pay attention to the order of access, for example, in the secondary coil a, b, a termination in the meter positive, b termination in the meter negative: b, c, b connected to the positive, c then negative: a, c , A then positive, c then negative. After connected, the switch K closed, measured between the ab, bc, ac between the meter instructions. Then the battery connected in the primary coil between the BC and AC were measured, the measured results were tabulated, you can determine the level of the transformer under test.
(2) exchange method.
Connect a pair of the same name ends of the primary and secondary coils, such as Aa, with wires and then pull in AC (lower for easy measurement) between the primary AX coils. Use the voltmeter to measure the voltage V1 between the AX value, the voltage V2 between the voltage value and the voltage V3 between the ax value. If V2 is the difference between V1 and V3, then Aa is the same polarity. If V2 is the sum of V1 and V3, AX is the same polarity.
The nameplate of the transformer is usually  and noted The main technical data are:
(1) KVA rated capacity. That is, the rated output capacity of the transformer. Such as single-phase transformer rated capacity = U line × I line; three-phase transformer capacity = U line × I line.
(2) the rated voltage. Indicate the primary coil terminal voltage and the secondary coil terminal voltage (without load) value. Note the three-phase voltage transformer terminal voltage U line value.
(3) rated current amperage. Refers to the rated capacity and allowable temperature rise conditions, the primary coil and secondary coil allows long-term through the line current I line value.
(4) voltage ratio. Refers to the primary coil rated voltage and secondary coil rated voltage ratio.
(5) Wiring method. Single-phase transformers have only one set of high and low voltage coils, only for single-phase use, three-phase transformers have Y / type.
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 In addition to the above technical data, there are rated frequency, phase, temperature rise, the transformer impedance percentage.