-Yangzhou Darui -

HV Insulation Resistance Tester - Yangzhou Darui

Published: 2020-07-29 20:08:56

产品价格：0.00

Category: Insulation Resistance Tester

Product Description

High-Voltage Insulation Resistance Tester

高压绝缘电阻测试仪，英文名称：High Voltage Insulation Resistance Tester。该仪器适用于测量各种变压器、电机、电缆、开关、电器设备及绝缘材料的绝缘电阻。

高压绝缘电阻测试仪俗称，或称摇麦、高阻计、绝缘电阻测试仪等。绝缘电阻表是大量使用于电力网站和用电设备绝缘电阻的检测仪表，对保证产品质量和运行中的人身及设备安全具有重要意义，电器产品的绝缘性能是评价其绝缘好坏的重要标志之一，它通过绝缘电阻反映出来。

Product Structure

1，高压绝缘电阻测试仪主要由三部分组成。

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

Second is the measurement circuit.

Third is the display.

(1) DC High Voltage Generator

Measuring insulation resistance requires applying a high voltage at the measurement terminals. The high voltage values specified in the national standard for insulation resistance meters are 50V, 100V, 250V, 500V, 1000V, 2500V, 5000V...

There are generally three methods for generating DC high voltage. The first is the hand-cranked generator type. Approximately 80% of those produced in China use this method (the origin of the name "megger"). The second method is through mains transformer step-up and rectification to obtain DC high voltage. This is generally the method used by mains-powered megohmmeters. The third method uses transistor oscillators or dedicated PWM circuits to generate DC high voltage, which is generally used by battery-powered and mains-powered insulation resistance meters.

(2) Measurement Circuit

In the megger (megohmmeter) described above, the measurement circuit and display section are combined into one. It is accomplished through a ratio meter movement, which consists of two coils with an angle of approximately 60° between them. One coil is connected in parallel across the voltage terminals, and the other coil is connected in series within the measurement circuit. The deflection angle of the meter pointer is determined by the current ratio between the two coils, with different deflection angles representing different resistance values. The smaller the measured resistance, the greater the current flowing through the coil in the measurement circuit, and thus the greater the pointer deflection angle. Another method uses a linear ammeter for measurement and display. In the ratio meter movement described above, since the magnetic field within the coils is non-uniform, when the pointer is at the infinity position, the current coil is exactly at the location of maximum magnetic flux density. Therefore, even when the measured resistance is very large and the current flowing through the current coil is very small, the coil deflection angle will still be relatively large. When the measured resistance is small or zero, the current flowing through the current coil is larger, and the coil has already deflected to an area of lower magnetic flux density, resulting in a deflection angle that is not very large. This achieves nonlinear correction. Generally, the resistance display of a megohmmeter movement needs to span several orders of magnitude. However, when a linear ammeter movement is directly connected in series in the measurement circuit, this does not work — the scale marks at high resistance values would all be crowded together and indistinguishable. To achieve nonlinear correction, nonlinear elements must be added to the measurement circuit, thereby producing a shunting effect at low resistance values and no shunting at high resistance values, enabling the resistance display to span several orders of magnitude. With the development of electronic and computer technology, digital display meters have gradually replaced pointer-type instruments.

Digital measurement technology for insulation resistance has also been developed, among which the voltage ratio meter circuit is one of the better measurement circuits. The voltage ratio meter circuit consists of a voltage bridge and a measurement bridge. The signals output from these two bridge circuits are respectively converted through A/D conversion and then processed by a microcontroller for digital display.

Tester

测定产品的绝缘电阻，是指带电部分与外露非带电金属部分（外壳）之间的绝缘电阻，按不同的产品，施加一直流高压，如100V、250V、500V、1000V等，规定一个最低的绝缘电阻值。有的标准规定每kV电压，绝缘电阻不小于1MΩ等。在家用电器产品标准中，通常只规定热态绝缘电阻，而不规定常态条件下的绝缘电阻值，常态条件下的绝缘电阻值由企业标准中自行制定。如果常态绝缘电阻值低，说明绝缘结构中可能存在某种隐患或受损。如电机绕组对外壳的绝缘电阻低，可能是在嵌线时绕组的均线槽绝缘受到损伤所致。在使用电器时，由于突然上电或切断电源或其它缘故，电路产生过电压，在绝缘受损处产生击穿，造成对人身的安全或威胁。

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HV Insulation Resistance Tester - Yangzhou Darui

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