CN201926710U - Programmable power supply insulation resistance and grounding resistance comprehensive test instrument - Google Patents

Abstract

The utility model discloses a program-controlled power supply insulation resistance and grounding resistance comprehensive tester, which comprises an insulation resistance testing loop, a grounding resistance testing loop, an A/D converter, a micro-controller, a keyboard and a display, an insulation resistance testing loop and a grounding The signal output ends of the resistance test circuit are all connected to the A/D converter, the A/D converter is connected to the microcontroller through the signal transmission line, and the keyboard and display are connected to the microcontroller through the interface. The comprehensive tester can better Realize the comprehensive test of electrical equipment power supply insulation resistance and grounding resistance, with small size, easy to carry and use, stable work, large measurement range, high test accuracy, reliable performance, easy operation, and can realize the integration of measurement, control and display, etc. advantage.

Description

A comprehensive tester for program-controlled power supply insulation resistance and grounding resistance

technical field

The utility model belongs to the technical field of electrical detection, in particular to a program-controlled power supply insulation resistance and grounding resistance comprehensive tester.

Background technique

Electrical safety is the basic performance requirement for the normal operation of electrical equipment, and its basic indicators include: insulation resistance, grounding resistance, leakage current and withstand voltage strength. Among them, insulation resistance refers to the resistance value between two parts of conductors separated by insulating materials, and its value reflects the insulation strength between two parts of conductors; grounding resistance refers to the contact between the accessible metal body of electrical equipment and the lead-out of the equipment. It is a parameter that has a direct impact on human safety, and it is generally tens of milliohms. At present, most of the domestic electrical safety performance testers are single-index testers, and due to the requirement to generate large current and high voltage, the signal power supply system often uses traditional analog circuits for power supply, so it is bulky and inconvenient to operate, and the test accuracy is relatively poor.

Utility model content

The purpose of this utility model is to provide a program-controlled power supply insulation resistance and grounding resistance comprehensive tester which can realize the comprehensive test of insulation resistance and grounding resistance, has stable operation, high test accuracy, and can realize the integration of measurement, control and display. .

The technical solution adopted to realize the purpose of this utility model is: the comprehensive tester includes an insulation resistance test circuit, a ground resistance test circuit, an A/D converter, a microcontroller, a keyboard and a display, an insulation resistance test circuit and a ground resistance test circuit. The signal output terminals of the loop are all connected to the A/D converter, the A/D converter is connected to the microcontroller through the signal transmission line, and the keyboard and display are connected to the microcontroller through the interface;

The insulation resistance test circuit is composed of a program-controlled DC high-voltage power supply, an insulation resistance test circuit, a power supply voltage acquisition circuit and a voltage divider circuit. and the signal output end of the power supply voltage acquisition line are respectively connected with the A/D converter, the power supply voltage acquisition line is provided with a fixed resistance, one end of the voltage dividing line is connected with the power supply voltage acquisition line through the fixed resistance, and the other end is connected in parallel with A plurality of sampling resistors, the sampling resistors are connected to the insulation resistance testing circuit through switching relays, and the program-controlled DC high-voltage power supply is connected to the microcontroller through a signal transmission line;

The ground resistance test loop has a program-controlled AC current power supply, which is connected to a voltage signal acquisition circuit and a ground resistance test circuit through a voltage limiting resistor, and a voltage signal collector and a voltage signal collector are arranged on the voltage signal acquisition circuit. True-RMS converter, its signal output end is connected with the A/D converter, a current sensor is arranged on the ground resistance test circuit, its signal output end is connected with the A/D converter, and the current sensor passes through The wire is connected with the program-controlled alternating current power supply, and the programmed alternating current power supply is connected with the microcontroller through the signal transmission line.

The voltage true-effective value converter adopts AD536 converter.

The current sensor adopts Hall current sensor LEM module.

The microcontroller adopts 16-bit single-chip microcomputer 87C196.

The program-controlled power supply insulation resistance and grounding resistance comprehensive tester made according to the above scheme can better realize the power supply insulation resistance and grounding resistance of electrical equipment through the setting of the insulation resistance test circuit and the grounding resistance test circuit, and the switching control by a microcontroller. The comprehensive test of grounding resistance has the advantages of small size, easy to carry and use, stable work, large measurement range, high test accuracy, reliable performance, easy operation, and can realize the integration of measurement, control and display.

Description of drawings

Fig. 1 is a structural representation of the utility model.

Detailed ways

Referring to Fig. 1, the program-controlled power supply insulation resistance and grounding resistance comprehensive tester of the present utility model has an insulation resistance test circuit, is used for the test of insulation resistance; A ground resistance test circuit, is used for the test of ground resistance; A device 2 is used to convert the voltage signal and current signal of the insulation resistance test loop and the ground resistance test loop into digital signals respectively; a microcontroller 1 is used for the switching control of the insulation resistance test or the ground resistance test state and the control of the test signal Processing, access; a keyboard 15 for inputting operation instructions and a display 16 for displaying test information. The signal output ends of the insulation resistance test loop and the ground resistance test loop are all connected to the A/D converter 2, the A/D converter 2 is connected to the microcontroller 1 through a transmission line, and the keyboard 15 and the display 16 are connected to the microcontroller 1 through an interface. 1 on. The insulation resistance test circuit is composed of a program-controlled DC high-voltage power supply 7, an insulation resistance test circuit, a power supply voltage acquisition circuit and a voltage division circuit. The power supply voltage acquisition circuit is connected in parallel with the insulation resistance test circuit, and is connected with the program-controlled DC high-voltage power supply 7 . The signal output terminals of the power supply voltage acquisition circuit are respectively connected to the A/D converter 2 . There is a fixed resistor 6 on the power supply voltage acquisition line, and one end of the voltage dividing line is connected to the power supply voltage acquisition line through a fixed resistor 8; the other end is connected in parallel with several sampling resistors 3, and the sampling resistor 3 is tested by switching the relay 4 and the insulation resistance. The line connection is used to automatically switch the range under the control of the microcontroller 1, so as to ensure the measurement accuracy and realize the whole measurement of the insulation resistance. The programmable DC high-voltage power supply 7 is connected to the microcontroller 1 through a signal transmission line, and is used for switching the test state. The ground resistance test circuit has a program-controlled AC current power supply 9, the program-controlled AC current power supply 9 passes through a voltage limiting resistor 10 and is connected with a voltage signal acquisition circuit and a ground resistance test circuit, and the voltage signal acquisition circuit is provided with a voltage signal acquisition circuit. device 13 and a voltage true-to-rms converter 14, the signal output terminal of which is connected to the A/D converter 2. The voltage true-to-rms converter 14 can be an AD536 converter. The AD536 has the advantages of simple use, less peripheral circuits, single and double power supply modes can be selected, and is widely used in test instruments. The ground resistance testing circuit is provided with a current sensor 12, whose signal output terminal is connected to the A/D converter 2, and the current sensor 12 is connected to the program-controlled AC current power supply 9 through wires. The current sensor 12 can be a Hall current sensor LEM module, which can measure current signals of arbitrary waveforms, and has high precision, good linearity, fast response, strong overload capability, and the primary circuit and secondary circuit are completely isolated. The programmable alternating current power supply 9 is connected with the microcontroller 1 through a signal transmission line, and is used for switching the test state. Described microcontroller 1 can adopt 16 single-chip microcomputers 87C196, and there are 8 or 10 A/D converters, 16KB ROM and 488Byte RAM with sampling and holding functions of 13 channels inside it, and the main frequency can reach 20MHz. The A/D conversion time is 22μS, which has a strong signal processing capability, and can control the PWM signal with a variable duty cycle and a maximum resolution of 1/65536 (16 bits); using a keyboard 15 and a display chip 8279, it can Preset and display the current, voltage, resistance and detection time, making the operation easier.

Working principle: When the comprehensive tester is in use, it can switch the working state (insulation resistance test state or grounding resistance test state) by operating the microcontroller 1 according to the type of resistance to be tested, and select the program-controlled DC high-voltage power supply 7 according to the working state Or the program-controlled AC current power supply 9 is used as the test power supply of the resistance to be measured 5 or the resistance to be measured 7, and the resistance to be measured 7 or the resistance to be measured 9 is connected to the insulation resistance test line or the ground resistance test line, through the A/D converter 2 Input microcontroller 1 for closed-loop control and measurement.

When testing the insulation resistance, the programmable DC high voltage power supply 7 generates three DC voltage signals (250VDC, 500VDC, 1000VDC) required by the IEC61010 standard under the control of the microcontroller 1 and applies them to the resistance 5 to be tested. The insulation resistance test range of this comprehensive tester can be set to 0.01MΩ-1000MΩ. Since the A/D conversion system can only collect DC voltage signals of 0V-5V, in order to ensure the measurement accuracy of the system and realize the whole measurement of insulation resistance, The sampling resistor 3 is used for automatic range switching, and the microcontroller controls the switch 4 through the relay to select among 4 sampling resistors of different sizes (0.1KΩ, 1KΩ, 10KΩ, 100KΩ). Automatically adjust to the appropriate range. During the test, when the resistance value of the measured resistance 5 is small, due to the voltage dividing effect of the sampling resistor 3, the voltage applied to both ends of the measured resistance 5 is obviously lower than the required voltage value. In order to solve this problem, this comprehensive tester adds a voltage sampling link before the measured resistance 5, that is, connects the resistance 6 in parallel at the input end, and the high voltage is attenuated by the resistance in series to obtain the sampling voltage U1. The potential difference between U1 and the voltage sampling value U2 on the sampling resistor 3 is the actual voltage across the resistor 5 to be measured. In this way, the microcontroller 1 can output a voltage control signal after comparison to control the voltage range of the program-controlled DC high-voltage power supply 7, so that the voltage applied to the resistance 55 to be tested can be accurately controlled and the test accuracy can be improved. Then, by measuring the voltage U2 on the sampling resistor 3 and the resistance value of the sampling resistor 3, the current flowing through the resistance to be measured 5 is detected, and then the voltage of the resistance to be measured 5 is calculated according to the set voltage applied to the resistance to be measured 5 Resistance.

When carrying out the grounding resistance test, according to the IEC61010 standard, the program-controlled AC current power supply 9 generates an alternating current of 1.5 times the rated current of the electrical appliance or 25A (the larger of the two is selected), and the no-load voltage does not exceed 12V. Make it flow between the grounding post (or grounding electrode) and each easily accessible metal part, by measuring the voltage drop, calculate the grounding resistance value according to the applied current value (the grounding resistance should not exceed 0.1Ω).

Claims (4)

1. a program-controlled power supply insulation resistance and grounding resistance comprehensive tester, is characterized in that: it comprises insulation resistance test circuit, ground resistance test circuit, A/D converter, microcontroller, keyboard and display, insulation resistance test circuit and The signal output ends of the grounding resistance test loop are all connected to the A/D converter, the A/D converter is connected to the microcontroller through the signal transmission line, and the keyboard and display are connected to the microcontroller through the interface; The insulation resistance test circuit is composed of a program-controlled DC high-voltage power supply, an insulation resistance test circuit, a power supply voltage acquisition circuit and a voltage divider circuit. and the signal output end of the power supply voltage acquisition line are respectively connected with the A/D converter, the power supply voltage acquisition line is provided with a fixed resistance, one end of the voltage dividing line is connected with the power supply voltage acquisition line through the fixed resistance, and the other end is connected in parallel with A plurality of sampling resistors, the sampling resistors are connected to the insulation resistance testing circuit through switching relays, and the program-controlled DC high-voltage power supply is connected to the microcontroller through a signal transmission line; The ground resistance test loop has a program-controlled AC current power supply, which is connected to a voltage signal acquisition circuit and a ground resistance test circuit through a voltage limiting resistor, and a voltage signal collector and a voltage signal collector are arranged on the voltage signal acquisition circuit. True-RMS converter, its signal output end is connected with the A/D converter, a current sensor is arranged on the ground resistance test circuit, its signal output end is connected with the A/D converter, and the current sensor passes through The wire is connected with the program-controlled alternating current power supply, and the programmed alternating current power supply is connected with the microcontroller through the signal transmission line. 2. The program-controlled power supply insulation resistance and grounding resistance comprehensive tester as claimed in claim 1, characterized in that: said voltage true-rms converter adopts AD536 converter. 3. The program-controlled power supply insulation resistance and grounding resistance comprehensive tester as claimed in claim 1, characterized in that: said current sensor adopts a Hall current sensor LEM module. 4. The program-controlled power supply insulation resistance and grounding resistance comprehensive tester as claimed in claim 1, characterized in that: the microcontroller adopts a 16-bit single-chip microcomputer 87C196.

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