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  There are four common testing methods for the output voltage of a withstand voltage tester, including the electrostatic voltmeter method, voltage transformer method, voltage divider with voltmeter method, and high resistance box with milliammeter method. The DBNY-S withstand voltage tester developed by Dingsheng Electric is mainly used to test the withstand voltage capability of various electrical equipment, insulating materials, and insulating structures. This withstand voltage tester can adjust the magnitude of the test voltage and set the breakdown current. Based on the technical requirements of the verification regulation, this article recommends several testing methods for the output voltage.
  
  Four testing methods for the output voltage of a withstand voltage tester
  
  1. Electrostatic voltmeter method
  
  2. Voltage transformer method
  
  3. Voltage divider with voltmeter method
  
  4. High resistance box with milliammeter method
  
  According to the above four methods and ideas, the testing system composed of selected standard instruments and self-made voltage dividers should have their errors comprehensively evaluated to meet the requirements of the verification regulation. In addition, there are many specifications of withstand voltage testers (equipment), and the measurement methods for their high-voltage output are not limited to the above four. Based only on the applicable scope and technical indicators of the current verification regulation, this article introduces useful methods and basic principles for output voltage testing for reference by relevant personnel.
  
  1. Withstand voltage tester
  
  
  
      A withstand voltage tester is also called an electrical insulation strength tester or a dielectric strength tester. It applies a specified AC or DC high voltage between the live parts and non-live parts (usually the shell) of electrical equipment to test the withstand voltage capability of the insulating material. During long-term operation, electrical equipment not only withstands the effect of rated working voltage but also short-term overvoltage effects higher than the rated working voltage caused by operation (the overvoltage value may be several times higher than the rated working voltage). Under the effect of these voltages, the internal structure of electrical insulating materials will change. When the overvoltage intensity reaches a certain value, it will cause insulation breakdown of the material, the equipment will not operate normally, and the operator may get an electric shock, endangering personal safety.
  
  
  
      1. Structure and composition of the withstand voltage tester
  
  
  
      (1) Voltage boosting part
  
  
  
      It consists of a regulating transformer, a step-up transformer, and switches for connecting and disconnecting the power supply of the voltage boosting part.
  
  
  
      The 220V voltage is applied to the regulating transformer through the connecting and disconnecting switches, and the output of the regulating transformer is connected to the step-up transformer. Users only need to adjust the regulator to control the output voltage of the step-up transformer.
  
  
  
      (2) Control part
  
  
  
      It consists of current sampling, timing circuit, and alarm circuit. When the control part receives a start signal, the instrument immediately connects the power supply of the voltage boosting part. When it receives a signal that the current in the tested circuit exceeds the set value and issues an audible and visual alarm, it immediately disconnects the power supply of the voltage boosting circuit. When it receives a reset or time-out signal, it disconnects the power supply of the voltage boosting circuit.
  
  
  
      (3) Display circuit
  
  
  
      The display shows the output voltage value of the step-up transformer. It also displays the current value from the current sampling part and the time value from the timing circuit, usually in countdown mode.
  
  
  
      (4) The above is the structure of a traditional withstand voltage tester. With the rapid development of electronic technology and single-chip microcomputer and computer technology, programmable withstand voltage testers have also developed rapidly in recent years. The main difference between a programmable withstand voltage tester and a traditional one is the voltage boosting part. The high voltage boosting of a programmable withstand voltage tester is not adjusted by a regulator through the mains, but is generated by a single-chip microcomputer controlling a 50Hz or 60Hz sine wave signal, which is then amplified by a power amplification circuit for boosting. The output voltage value is also controlled by the single-chip microcomputer. The principles of other parts are not much different from traditional withstand voltage testers.
  
  
  
      2. Selection of withstand voltage tester
  
  
  
      The most important two indicators when selecting a withstand voltage tester are that the maximum output voltage value and the maximum alarm current value must be greater than the voltage value and alarm current value you need. Generally, the product standard under test specifies the applied high voltage value and the alarm determination current value. If the applied voltage is higher and the alarm determination current is larger, then the power of the step-up transformer of the withstand voltage tester needs to be larger. Generally, the power of the step-up transformer of a withstand voltage tester is 0.2kVA, 0.5kVA, 1kVA, 2kVA, 3kVA, etc. The maximum voltage can reach tens of thousands of volts. The maximum alarm current is 500mA-1000mA, etc. So when selecting a withstand voltage tester, you must pay attention to these two indicators. If the power is selected too large, it will cause waste; if selected too small, the withstand voltage test cannot correctly judge whether it is qualified or not. According to the method for selecting the power of a withstand voltage tester specified in IEC414 or (GB6738-86), we think it is relatively scientific. "First adjust the output voltage of the withstand voltage tester to 50% of the specified value, then connect the tested product. When the observed voltage drop is less than 10% of that voltage value, the power of the withstand voltage tester is considered sufficient." That is, if the withstand voltage test voltage value of a certain product is 3000 volts, first adjust the output voltage of the withstand voltage tester to 1500 volts and then connect the tested product. If the output voltage drop of the withstand voltage tester is not greater than 150 volts at this time, then the power of the withstand voltage tester is sufficient. There is a distributed capacitance between the live parts and the shell of the tested product. There is a capacitive reactance CX in the capacitor. When an AC voltage is applied across this CX capacitor, a current will be generated.
  
  Medical withstand voltage tester

  
  

Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.