Why measure the current with a clamp ammeter every time a motor is installed?
What is measured with a clamp ammeter is the actual current of one phase line, because the clamp ammeter is equivalent to a CT with an open primary winding. The current detected in one test will be reflected and displayed in the second test, which is not related to the connection method of the three-phase motor.
The first step is to measure the phase voltage separately. The phase voltage on the secondary side of the voltage transformer can be directly measured (using the same method as above), and the phase voltage can be directly measured at the input end of the clamp meter. However, the probe needs to be inserted and the appropriate range needs to be selected. Its "clamp" can only measure AC current and is a specialized clamp meter. Keep the pointer to the right and use it the same way as a regular multimeter, gradually shifting from high to low in the case of unknown voltage levels;
The second step is to measure the voltage in parallel with the probe. The clamp meter measures the voltage through its accompanying multimeter. The clamp meter cannot directly clamp the voltage, so the conversion switch is modulated to an appropriate range.
Instructions for using digital clamp watches
1. Mechanical zeroing is required before measurement.
2. Choose the appropriate range, first select the large range, then select the small range, or estimate the nameplate value.
3. When using the minimum range measurement and the reading is not yet clear, the measured wire can be wound a few turns, and the number of turns should be based on the number of turns in the center of the clamp. The reading is=indicated value x range/full deviation x number of turns.
4. After the measurement is completed, the conversion switch should be placed at the maximum range. Diangongwugwu.com Electrical Engineering Learning Network All rights reserved.
When measuring, the measured wire should be placed in the center of the clamp and the clamp should be tightly closed to reduce errors.
Notes on digital clamp watches
1. The voltage of the tested circuit should be lower than the rated voltage of the clamp meter.
When measuring the current of high-voltage lines, it is necessary to wear insulated gloves, insulated shoes, and stand on an insulated mat.
3. The jaws must be tightly closed and cannot be changed range with electricity.
Using a clamp ammeter to measure the current of a single winding of an electric motor is phase current, but it may cause trouble in actual measurement. Either connect all three pairs of winding wires to the outside; The current on the power line is always the line current; It is difficult and impractical to calculate the power of a certain motor. The power factor is an uncertain factor, unless you also connect a power factor meter. However, you should know that due to the load, the power factor is changing.
