| Insulation resistance needs to be inspected carefully in all the electrical safety testing projects which are ruled by the metrological law in our country. In the process of testing and maintaining the electric equipments and electric devices, checking up insulation resistance is a very important step, especially for the non-standard and special purpose equipment. We can find the damage situation of insulators in time by measuring insulation resistance, such as moisture, aging and penetrating defects and so on, which is used extensively in many aspects. Most of the original insulation testers are half mechanization type, this type of insulation testers has kinds of shortcomings of small range and low accuracy, which are not multi-usage and don’t display all datum. So, we had designed a novel insulation tester which has the characters of big range of measurement(1M～1T),high accuracy and strong anti-jamming, at the same time,testing the resistance value of capacitance and showing the ratio of absorption and polarization of the insulation. This equipment meets the need of market.This paper was developed based on referring to the abundant relevant papers domestic and international(at home and abroad), the intelligent insulation tester designed in this paper should has the following functions:firstly, Instrument voltage setting must has four regular voltage gears:500V,1000V,2500V and5000V; secondly, the samples’insulation resistance, the absorption and polarization ratio can be measured(texted) at the same time, and tests have prompts in15seconds,60seconds and10minutes, meanwhile, it must show out the absorption and polarization ratio; thirdly, Battery was asked to have low-voltage, over-voltage and over current protection, and was able to automatically cut off power supply; lastly, it must be discharged rapidly, that in general can put the storage of the charge in a few seconds, which will effectively guarantee the instrument and personal security.According to the requirements, the hardware circuit and software design were designed for the system. This paper briefly introduces the background and basis of the subject firstly, and then briefly expounds the domestic and overseas current situation and development trend, at last, selecting testing method, determining the total design project of the system. The design is divided into:the power supply part; High voltage dc power part (inverter circuits, times voltage circuit, PWM waveform control, over-voltage, low-voltage and over current protection circuits); Sampling circuit part; The man-machine interactive circuit and the software design, among this, the software design is divided into A/D conversion parts, voltage comparison part, the computation part, display section, etc. In the system in order to measure convenience, the power supply part is divided into the utility power supply and battery power supply, Among them, the utility power supply was used for power supply and charging the battery; In the design of the high-voltage dc power part, the PWM waves generated by the TL494, and4feet,15feet and16feet of the TL494were responsible for the over-voltage, low-voltage and over current protection of the equipment, the inverter circuits choose push-pull inverter circuit, raising the voltage through a transformer, times voltage circuit obtained respectively voltage:500V and1000V and2500V and5000V; The sampling circuit sent the sampling voltage to the single chip microcomputer; Sampling voltage through the A/D conversion, proceeding voltage comparison, selecting the sampling resistance automatically, computing the resistance, absorption and polarization ratio, finally displaying out the results through the liquid crystal.According to the request of the device, we conducted the Resistance range measurement, Precision measurement, detection of anti-jamming ability, all of these meeting the requirements, Finally a intelligent insulation tester was successfully developed. |
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