Advantages of clamp-on ammeter-Clamp-on ammeter to measure three-phase current
The biggest advantage of clamp ammeter is that it can measure current without interruption. Clamp ammeters are mainly divided into two categories: pointer and digital. According to the different results and uses, clamp ammeter can be divided into clamp ammeter for measuring AC and clamp ammeter for electromagnetic system for AC and DC.
Usually, when measuring current, it is necessary to disconnect the circuit to be measured before connecting the ammeter or the primary winding of the ammeter to the circuit to be measured. With the clamp ammeter, the measured current can be measured without disconnecting the measured circuit. Although the accuracy level of clamp ammeter is not high, usually 2.5 or 5.0, it is widely used because of its convenient use. Clamp ammeter is generally used to measure load current with voltage not exceeding 500v V. The commonly used clamp ammeter can be divided into transformer type and electromagnetic type according to its different structural forms. Among them are t301 clamp ammeter which only measures AC current, t302 clamp ammeter which measures both AC current and AC voltage, and mg series AC/DC clamp ammeter.
Measuring three-phase current with clamp ammeter
Three-phase current needs to be detected one phase at a time, after all, there is a phenomenon of unbalanced three-phase current.
Measurement method:
1. First, correctly select the voltage level of the clamp ammeter, and check whether its external insulation is good, whether it is damaged, whether the pointer swings flexibly, and whether the jaws are corroded. According to the motor power, the rated current is estimated to select the measuring range of the meter.
2. Read the instructions carefully before using the clamp ammeter to find out whether it is an AC or AC/DC clamp ammeter.
3. Because the accuracy of the clamp ammeter itself is low, the following methods can be adopted when measuring small current: firstly, the wire of the circuit to be measured is wound several times, and then it is placed in the jaw of the clamp ammeter for measurement. At this time, the current value indicated by the clamp meter is not the actual value to be measured, and the actual current should be the reading of the clamp meter divided by the number of windings of the wire.
4. The jaws of the clamp meter should be closed tightly when measuring. If there is noise after closing, the jaws can be opened again. If the noise still cannot be eliminated, check whether the joint surfaces on the magnetic circuit are smooth and clean, and wipe them clean when there is dust.
5. The clamp meter can only measure the current of one phase conductor at a time. The conductor to be measured should be placed in the center of the clamp window, and it is not allowed to clamp all the multiphase conductors into the window for measurement.
6. The voltage of the circuit to be measured should not exceed the value indicated on the clamp meter, otherwise it will easily lead to a grounding accident or the risk of electric shock.
7. Measure the working current of the cage asynchronous motor in operation. According to the current, whether the motor works normally can be checked to ensure the safe operation of the motor and prolong its service life.
8. When measuring, you can measure every phase or three phases. At this time, the number on the table should be zero (because the phasor sum of three-phase currents is zero). When there are two phase wires in the jaw, the value displayed on the table is the current value of the third phase. By measuring each phase current, you can judge whether the motor is overloaded (the measured current exceeds the rated current value), and whether there is a power supply voltage inside the motor or (other forms of devices that can be converted into electric energy are called power supplies).
9. Before the clamp meter is measured, the measured current should be estimated before deciding which range to use. If it is impossible to estimate, you can use the maximum range first and then change it to a smaller one to get an accurate reading. You can't use a small current scale to measure a large current. To prevent damage to the instrument.
