Measuring Three-Phase Current with a Clamp Meter: Step-by-Step Guide
1. Firstly, select the voltage level of the clamp type ammeter correctly, check whether its external insulation is good, whether there is any damage, whether the pointer swings flexibly, and whether the clamp is corroded. Estimate the rated current based on the motor power to select the range of the meter.
2. Before using a clamp ammeter, carefully read the instruction manual to determine whether it is an AC or AC/DC dual-purpose clamp ammeter.
3. Due to the low accuracy of the clamp ammeter itself, the following method can be used to measure small currents: first, wrap the wire of the circuit being tested a few times, and then place it into the clamp of the clamp ammeter for measurement. At this time, the current value indicated by the clamp gauge is not the actual value being measured. The actual current should be the reading of the clamp gauge divided by the number of turns the wire is wound.
4. The jaws of the clamp type meter should be tightly closed during measurement. If there is any noise after closure, the jaws can be opened and reset once. If the noise still cannot be eliminated, the joint surfaces on the magnetic circuit should be checked for smoothness. If there is dust, they should be wiped clean.
5. The clamp meter can only measure the current of one phase of the wire at a time, and the measured wire should be placed in the center of the clamp window. It is not allowed to clamp multiple phase wires into the window for measurement.
6. The voltage of the tested circuit cannot exceed the value indicated on the clamp meter, otherwise it may cause grounding accidents or electric shock hazards.
7. Measure the working current of a cage type asynchronous motor during operation. According to the magnitude of the current, it is possible to check and determine whether the motor is working properly to ensure safe operation and extend its service life.
8. When measuring, it can be done once for each phase or once for all three phases. At this time, the number on the meter should be zero (because the sum of three-phase current phasors is zero). When there are two phase lines in the clamp, the displayed value on the meter is the current value of the third phase. By measuring the current of each phase, it can be determined whether the motor is overloaded (the measured current exceeds the rated current value), whether there is a problem with the power supply voltage inside the motor or (the device that converts other forms of energy into electrical energy is called the power supply), that is, whether the three-phase current imbalance exceeds the limit of 10%.
9. Before measuring with a clamp meter, it is necessary to estimate the magnitude of the measured current before deciding which range to use. If it is impossible to estimate, you can first use the maximum range gear and then switch to a smaller one to obtain accurate readings. Cannot use low current range to measure high current. To prevent damage to the instrument.
