Discussion on the Required Conditions for Programmable Leakage Current Tester

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Although both the withstand voltage test and the leakage current test can be used to test the insulation strength of the object under test, there are some key differences in the test process and results. The withstand voltage test is conducted under high voltage after short-circuiting the insulation system of all current-carrying components of the object under test, while the leakage current (touch current) test is conducted under electrical conditions using test equipment to simulate human body impedance.

Although these two tests are different, they are very useful in ensuring product safety. The withstand voltage test is a 100% routine test, while the leakage current test is generally considered a type test.

With the widespread adoption of today's Low Voltage Directive (LVD), the withstand voltage test and leakage current test will become standard production line tests, and more tests such as insulation resistance test and ground impedance test will be added.

High-quality electrical products undergo safety specification tests in many aspects, including withstand voltage test, insulation resistance test, ground impedance test, leakage current (touch current) test, etc. Among these safety specification test items, the troublesome part is the leakage current test (touch current test). The product can measure abnormal leakage current through the leakage current test, and the leakage current tester is a common test instrument for leakage current testing.

Operating the leakage current (touch current) test

In recent years, many product safety specifications have required products to undergo leakage current testing, whether in product design testing or production line testing, especially during the design stage. Through these tests, product design engineers can obtain important information about product integrity, making products more compliant with safety standards. When the object under test is tested at rated voltage or 1.1 times the specified output rated voltage, that is, when the product is tested under actual use and fault conditions, in the ground leakage current test, the ground wire of the object under test is measured to determine the current flowing back to the system neutral line. In the cabinet leakage current test, the current magnitude from different points on the cabinet to the system neutral point is measured.

The withstand voltage (insulation) test simulates that the insulation system of the object under test must be able to withstand higher voltage for a certain period under conditions far exceeding normal use. Passing the withstand voltage test means that the product can operate safely in normal use and can withstand normal switching transients. This is a universally effective test, and product manufacturers can also use it to determine the basic quality mark of the product for users.

In a simple test combination, the connection between the withstand voltage tester and the object under test can be through a socket box or test leads, and then the withstand voltage tester applies voltage to the object under test. If the leakage current passing through is too large, the withstand voltage tester will display a fault, indicating that the object under test has not passed the test. If no excessive leakage current passes through the test, the withstand voltage tester will display that it has passed, indicating that the object under test has passed the test. The value of excessive leakage current is determined by the set value of the maximum allowable current level, which can be adjusted on the withstand voltage tester to determine whether the test passes. The withstand voltage tester actually emphasizes the degree of insulation between current-carrying conductors and non-current-carrying conductors, such as exposed non-current-carrying metal, which is a good way to find product design problems, such as conductors placed too close together.

Conditions for operating the withstand voltage test with a programmable leakage current tester

For a programmable leakage current tester, generally speaking, the specifications of safety and regulatory agencies do not specify the measured value of the withstand voltage test, but it is determined by the manufacturer of the product under test. If the maximum withstand voltage leakage current value is not specified, the best test method is to set the withstand voltage leakage current value that reaches the trip level, which is slightly higher than the value when the test object normally cuts off power under this test.

For the withstand voltage leakage current, the most common safety standards and specifications can refer to several UL standards, generally using "120 kilohms" as a reference. This specification sets a fixed resistor, which will definitely cause a fault indication in the withstand voltage test. In the early days, it was 1000 volts plus twice the rated voltage of the device on one side of the cover. This is a common setting for the withstand voltage test. Because most test objects used in the United States have a rated voltage of 120

In the leakage current test, the measured current can be used to calculate an approximate value for the trip setting of the withstand voltage test current. This is only an approximation because deviations in equipment components may cause slight differences in leakage current readings for different test objects. When calculating the relevant leakage current setting, it is very important to understand the basic differences between the withstand voltage test and the leakage current test. Although most leakage current testers provide switching tests for output lines (L/N), they only measure the leakage current from one current-carrying component to the enclosure of the device under test at a time. The withstand voltage test measures the leakage current of two current-carrying components simultaneously, thus showing a higher leakage current reading. An effective rule of thumb is to set the withstand voltage test trip current to about 20% to 25% of the result calculated by the following formula:

(Withstand voltage test voltage / Leakage current test voltage) * Leakage current test current = approximate value of withstand voltage test current.

Programmable leakage current tester







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