If the control box high voltage indicates that the meter is not normal (ie, the voltage data raised during the test cannot be detected). Preliminary inspection of the appearance, the secondary output of the auto-regulator is normal, the voltmeter is not abnormal, and the line connection is correct. What is the reason for this situation?

Instrument inspection and fault cause analysis: The control loop in the control box is normal, the input and output are normal; the connecting wire is tested with the multimeter ohmmeter, and it is also normal; therefore, it may be that the high voltage test transformer is faulty. It can be seen from the schematic diagram that the high-voltage test transformer has three concentric coils-the primary coil, the high-voltage output coil, and the instrument-specific coil. During operation, after the voltage loop in the control box is turned on, the ratio of the primary coil of the high-voltage test transformer to the high-voltage output coil is unchanged by the adjustment of the auto-regulator, and the number of turns is much smaller than that of the high-voltage output coil. 

Therefore, the boost value can be read from the meter. After the test transformer was disassembled, it was found that there was no abnormality in the primary coil and high-voltage output coil of the transformer, and the special coil of the instrument had obvious overheating traces. Therefore, it was judged that the dedicated coil of the

instrument was burnt.