When installing the motor, is it necessary to use a clamp ammeter?
The clamp ammeter is used to measure the actual current of a phase line, because the clamp ammeter is equivalent to the CT of the open circuit of the primary winding, and the current detected once will be displayed in the second reflection, regardless of the connection of the three-phase motor.
The first step is to measure the phase separately, which can directly measure the phase voltage of the secondary side of the voltage transformer (the method is the same as above) or directly measure the phase voltage (the input end of the clamp meter). However, it is necessary to insert a probe and select an appropriate measurement range. Its "bayonet" can only be a special clamp meter for measuring AC current. Make the pointer stay on the right side, and use the same method as the common multimeter to gradually change from high-grade to low-grade when the voltage level is unknown;
The second step is to measure the voltage in parallel with the probe. The clamp meter cannot directly "clamp" the voltage with its attached multimeter and adjust the transfer switch to the appropriate range.
Use of digital clamp meter
1. Mechanical zero adjustment is required before measurement.
2. Choose a suitable range, first choose a large range, then choose a small range or look at the nameplate value estimation.
3. When using the minimum range measurement, when the reading is not obvious, the measured wire can be wound several times, and the number of turns should be based on the number of turns in the center of the jaw, so the reading = indicated value × range/total deviation × number of turns.
4. After measurement, put the transfer switch in the maximum range.
5. When measuring, the measured wire should be in the center of the jaw, and the jaw should be closed to reduce the error.
Matters needing attention of digital clip-on watch
1. The voltage of the tested line should be lower than the rated voltage of the clamp meter.
2. When measuring the high-voltage line current, wear insulating gloves, shoes and stand on the insulating mat.
3. The jaws should be closed tightly, and the range cannot be changed by electricity.
Measuring the current of a single winding of a motor with a clamp ammeter is a phase current, but it will bring trouble to the actual measurement, or all three pairs of winding wires will be externally connected. The current on the power line is always the line current; It is difficult and impractical to calculate the power of the motor. The power factor is an uncertain factor. Unless you connect the power factor table, you should know that the power factor will change with the load.
