Clamp ampermetras susideda išreiškia srovę transformatorių ir ampermetrą.
Geležis šerdis iš transformatorius yra padaryta į a kilnojamas atidarymas ir in the shape of a clamp. The movable part is connected to the handle 6. When the handle is sandariai sugriebtas, the iron core of the current transformer opens, and the measured cutoff wire 4 can be placed in the clamp, making the cutoff wire the primary coil of the current transformer. Uždaryti the clamp, and alternating magnetic flux passes through the iron core of the current transformer, generuojant indukuota current in the secondary winding 5 of the transformer. The Ammeter is connected to both ends of the secondary winding. The current value indicated by its pointer is in direct proportion to the working current of the clamped cut-off wire, and the measured current value can be read directly from the dial.
Use of clamp ampermetras
Prieš matavimas
Pirma, the clamp ampermeter should be correct selected retaring to the type and voltage level of the current to be measured. The voltage of the line to be measured should be lower than the rated voltage of the clamp. When measurement the current of high-voltage lines, the high-voltage clamp ampermeter corresponding to its voltage level shall be selected. Clamp on ampermeter of low voltage level can only measure the current in low-voltage system, but cannot measure the current in high-voltage system.
Antra, the appearance of the clamp Ammeter should be checked correct before use. The insulation of the ampmeter must be check to see if it is in good condition. The shell should be free of damage and the handle should be clean and dry. If the pointer is not in the zero position, mechanical zero adjustment should be performed. The jaw of the clamp type ampmeter should be sandariai connected. If the pointer dreba, the jaw can be open and closed again. If the shakeking still exist, it should be carefully check, attention should be paid to removing debris and dirt from the jaw, and then measurement should be carry out.
The clamp Ammeter cannot measure the current of bare conductor because the clamp Ammeter must contact the measured line. When using a high-voltage clamp meter for measurement, it should be operated by two people. During measurement, insulated gloves should be worn, standing on an insulated pad, and other equipment should not be touched to prevent short circuits or grounding.
When measuring currents below 5 amperes, in order to make the reading more accurate, if conditions permit, the measured current carrying wire can be wound several times and placed in a clamp for measurement. At this point, the actual current value of the measured wire should be equal to the reading value of the instrument divided by the number of wire turns placed in the clamp.
When measuring, attention should be paid to maintaining a safe distance between all parts of the body and the charged body. The safe distance for low-voltage systems is 0.1-0.3 meters. When measuring the current of each phase of high-voltage cables, the distance between the cable heads should be at least 300 millimeters, and the insulation should be good. Only when the measurement is considered convenient can it be carried out. When observing the timing of the watch, special attention should be paid to maintaining a safe distance between the head and the charged part. The distance between any part of the human body and the charged part should not be less than the entire length of the clamp watch.
When measuring the current of low-voltage fusible fuses or horizontally arranged low-voltage busbars, each phase of fusible fuses or busbars should be protected and isolated with insulation materials before measurement to avoid causing phase to phase short circuits. When one phase of the cable is grounded, it is strictly prohibited to measure to prevent ground breakdown and explosion caused by low insulation level of the cable head, which may endanger personal safety.
After the measurement, if the clamp Ammeter of the clamp Ammeter is used for measurement, the indicated value will be greatly different from the measured actual value, or even there will be no indication. The reason is that the head of the clamp Ammeter of the magnetoelectric system is connected to the secondary coil of the transformer, and the head voltage is obtained from the secondary coil. According to the principle of electromagnetic induction, the mutual inductance electromotive force is E2=4.44fW Ф m. It is not difficult to see from the public notice that the magnitude of the mutual inductance electromotive force is directly proportional to the frequency. When using this type of clamp meter to measure rotor current, due to the low frequency on the rotor, the voltage obtained on the meter head will be much smaller than when measuring the same power frequency current (because this type of meter head is designed for AC 50Hz power frequency). Sometimes the current is very small and cannot even make the rectifier element in the meter head conductive, so the clamp meter does not indicate or the indicated value differs significantly from the actual value.
