Application of clamp ammeter in electrical installation inspection
1. Identify the polarity of the current transformer circuit
When using a standard watt-hour meter to check the running high-voltage side watt-hour meter on site, if you need to check the correctness of the polarity of the current transformer circuit, you can use a clamp-on AC ammeter to judge
2. For the three-phase three-wire watt-hour meter, first clamp and measure the A and C phase currents connected to the standard meter respectively, and the values should be equal or similar. Then clamp the vector sum of phase A and C, if its value is equal to or close to the value of phase A and C, it means that the two phases to be clamped are of the same polarity, if it is equal to or close to that of phase A and C, ten thousand times , then the two phases measured by the clamp are of opposite polarity.
For the three-phase four-wire watt-hour meter, the A, B, C, and phase currents must be clamped first, and their values should be equal or similar. Then measure the vector sum of the three phases A, B, and C. The value is zero, indicating that the polarity of the three phases to be clamped is the same. One or two of the three phases are measured in reverse polarity.
In the same way, if other checks are made on the running equipment on site, as long as the secondary side of the current transformer involved is , or △ connection and the △ connection is correct, the above method is also applicable.
Check thyristor and silicon rectifier components
During the operation of thyristor or silicon rectifier element, a pulsating DC current flows, and its magnitude changes with time, so it can be detected by an AC clamp ammeter.
When checking, just clamp the positive or negative main wiring of each thyristor or silicon rectifier element, and judge whether the element is normal according to the presence or absence and magnitude of the current reading. If the reading of the clamp meter is zero, it means that the component is not working, either the thyristor trigger circuit is faulty, or the component is damaged, or the fuse core may be blown. Conversely, if the current values of the three-phase components are basically balanced, it indicates that the main circuit and the thyristor trigger circuit are working normally. If the three-phase current is seriously unbalanced, it may be that the trigger circuit of the thyristor has not been debugged well, or there may be a fault in the AC part of the rectifier device, for example, one phase of the rectifier transformer is disconnected, etc.
