Several methods of measuring polarity of current transformer

- Feb 19, 2020-

1 DC method
Connect the positive pole of 1.5-3V dry battery to the primary coil L1 and L2 of the transformer, connect the negative pole to the positive pole of the milliammeter at the secondary side K1 of the transformer, and connect the negative pole to K2. After connecting the wire, close the positive deviation of the pointer of the milliammeter and pull it apart, the negative deviation of the pointer of the milliammeter indicates that the terminal of the transformer connected to the positive pole of the battery is the same polarity as the terminal connected to the positive end of the milliammeter, that is, L1 and K1 are the same polarity, that is, the transformer To reduce polarity. If the pointer swings contrary to the above, it is polarity.
2 exchange method
Connect the L2 of the primary and secondary coils of the current transformer with the K2 of the secondary side by wires, apply the AC voltage of 1-5V (small range) at the secondary side, and use the voltmeter below 10V to measure the value of U2 and U3, if U3 = u1-u2, it is depolarization. U3 = U1 U2 is additive polarity.
Note: during the test, make the incoming voltage as low as possible to prevent the coil from being damaged by too much current. In order to make the reading clear, the voltmeter should be selected as small as possible. When the converter ratio is less than 5, the AC method is relatively simple and accurate. Do not use this method to measure the transformer whose converter ratio is more than 10, because the value of U2 is smaller, the value of U3 is close to that of U1, and the reading of voltmeter is not It is easy to distinguish the size, so it is not easy to distinguish when measuring, so it is generally not suitable to use this method to measure polarity.
3 meter method
Generally, the instrument transformer calibrator has polarity indicator. Before measuring the current transformer error, the instrument can check the polarity in advance. If the indicator does not indicate, the polarity of the tested current transformer is correct (polarity reduction).