Explanation of terms of the hottest high voltage r

2022-08-15
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Interpretation of terms of high voltage resistance detector

Guide: high voltage resistance detector is suitable for measuring the insulation resistance of various transformers, motors, cables, switches, electrical equipment and insulating materials. There are some technical terms of high-voltage resistance detector that are not very clear. Here are some terms to explain:

1, insulation resistance meter (megohmmeter) - an electrical measuring instrument used to measure the direct effect analog indication of insulation resistance, and its unit is m ω Indicates

2, measuring terminal knob insulation resistance meter is used to connect the measured terminal. The measuring terminal button of the insulation resistance meter shall be marked with the symbols of line terminal button L, grounding terminal button E and shielding terminal button G

the second generation ABS is produced with new alloy and/or new process

3. Terminal voltage - the voltage between the line terminal of the insulation resistance meter and the grounding terminal

4, rated voltage - the nominal value of the output voltage when the measuring terminal of the insulation ohmmeter is in the open circuit state

5, open circuit voltage - the measured value of the output voltage measured when the measuring terminal of the insulation resistance meter is in the open circuit state

6, the median voltage insulation resistance meter sometimes needs to reach the output voltage measured by the 3-meter measuring terminal buttons L and E

structure and composition of high voltage resistance detector

1. The insulation resistance meter is mainly composed of three parts

the first is the DC high voltage generator, which is used to generate a DC high voltage

the second is the measurement circuit

the third is display

(1) DC high voltage generator

to measure the insulation resistance, a high voltage must be applied at the measuring end. This high voltage value is specified in the national standard of insulation resistance meter as 50V, 100V, 250V, 500V, 1000V, 2500V, 5000v...

there are generally three methods to generate DC high voltage. The first type is hand-operated generator. At present, about 80% of the megger produced in China adopts this method (the source of the name of the megger). The second is to boost the voltage through the mains transformer and obtain DC high voltage through rectification. The method adopted by general mains megger. The third method is to use transistor oscillation type or special pulse width modulation circuit to generate DC high voltage, which is adopted by battery type and mains type insulation resistance meters like a hydraulic universal experimental machine

(2) measurement circuit

in the megger (megger) mentioned above, the measurement circuit and the display part are combined into one. It is completed by a current ratio meter head, which is composed of two coils with an included angle of 60 ° (about). One coil is parallel at both ends of the voltage, and the other coil is connected in series in the measuring circuit. The deflection angle of the pointer of the meter depends on the current ratio in the two coils. Different deflection angles represent different resistance values. The smaller the measured resistance value is, the greater the coil current in the measuring circuit is, and the greater the deflection angle of the pointer is. Another method is to use linear ammeter as measurement and display. In the head of the current ratio meter used previously, because the magnetic field in the coil is non-uniform, when the pointer is at infinity, the current coil is just at the place with the strongest magnetic flux density, so although the measured resistance is large, there is little current flowing through the current coil, and the deflection angle of the coil will be large at this time. When the measured resistance is small or 0, the current flowing through the current coil is large, and the coil has been deflected to a place with low magnetic flux density, and the resulting deflection angle will not be large. In this way, nonlinear correction is achieved. Generally, the resistance value of the megger head needs to span several orders of magnitude. However, when the linear current meter is directly connected in series into the measuring circuit, it is not enough. The scales at high resistance are all crowded together and cannot be distinguished. In order to achieve nonlinear correction, nonlinear element clamps must be added to the measuring circuit, and the installation should not be completely locked. So as to achieve the shunting effect when the resistance value is small. When the resistance is high, there is no shunt, so that the resistance value can reach several orders of magnitude. With the development of electronic technology and computer technology, digital display meter gradually replaces pointer meter

the digital measurement technology of insulation resistance has also been developed, among which the voltage ratio meter circuit is one of the better measurement circuits, and the voltage ratio meter circuit is composed of voltage bridge circuit and measurement bridge circuit. The output signals of the two bridges are converted into digital value display by a/d conversion and then by a single chip

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