AC/DC Test Transformer
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The AC/DC test transformer, utilizing advanced production equipment, adopts new processes of coil winding epoxy vacuum casting and CD-type iron core, compared with similar oil-immersed transformers, it significantly reduces weight and volume, improves insulation strength and moisture resistance in quality, and effectively weakens magnetic flux leakage while greatly enhancing the transformer's ability to withstand test short-circuit current impacts.
The AC/DC test transformer is input into the operation box (or console) with power frequency power supply, and the voltage is adjusted by the auto-transformer to be input to the primary winding of the test transformer. According to the principle of electromagnetic induction, power frequency high voltage can be obtained in the secondary (high voltage) winding. This power frequency high voltage can be rectified by high-voltage silicon stack and filtered by capacitors to obtain DC high voltage, whose amplitude is 1.4 times the effective value of the power frequency high voltage. However, when using DC, the short-circuit rod should be pulled out, and when using AC, the short-circuit rod should be inserted.
The high-voltage test transformer is the basic test equipment used by power plants, power supply bureaus, and scientific research units for AC withstand voltage tests. It has passed the standards of the National Quality Supervision Bureau and is used for insulation strength tests under specified voltages on various electrical products, electrical components, insulating materials, etc., to assess the insulation level of products, discover insulation defects of tested objects, and measure the ability to withstand overvoltage.
Principle and Features
Series high-voltage test transformers are single-phase transformers with connection group label ⅠⅠ. The working process of a single high-voltage test transformer is to connect AC 220V (380V for above 10kVA) voltage to the power control box (console), adjust it to 0~200V (0~400V for above 10kVA) output to the primary winding of the test transformer through the auto-transformer inside the power control box (console) (for above 50kVA, the auto-transformer is external). According to the principle of electromagnetic induction, the required high voltage for testing can be obtained in the high-voltage winding of the test transformer.
The AC/DC high-voltage test transformer is a new product produced after improvement based on the similar product YDJ(G) type high-voltage test transformer, according to the national standard for test transformers DL/T848.2—2004. This series of products has the characteristics of small size, light weight, compact structure, complete functions, and convenient use. It is applicable to electric power, industrial and mining, scientific research. It is widely used in lighting, machine tool electrical appliances, mechanical and electronic equipment, medical equipment, rectifier devices, etc. The product performance can meet various special requirements of users. It is an indispensable instrument for power frequency withstand voltage tests and DC leakage tests on various high-voltage electrical equipment, electrical components, and insulating materials in high-voltage tests.
◇ Ambient temperature not higher than +40℃, not lower than —20℃;
◇ Relative air humidity not greater than 90%;
◇ Altitude not exceeding 3500 meters;
2. Working voltage
◇ The input voltage of the power control box (console) is power frequency 220V or 380V, with relative error not exceeding ±10%; (the specific voltage used is selected according to the user's specified test transformer specification)
3. Rated parameters of series test transformers
2. The main parts of the tested object should be cleaned thoroughly and kept absolutely dry to avoid damaging the tested object and causing errors in test values.
3. For tests on large equipment, generally a no-load test of the test transformer should be conducted first, that is, raising the voltage to the test voltage without connecting the test object, in order to calibrate the indication accuracy of the instruments and adjust the gap distance of the discharge ball gap.
4. During the withstand voltage test, the voltage increase speed should not be too fast, and sudden pressurization should be prevented, such as sudden closing when the voltage regulator is not at zero position, and sudden power off should also be avoided. Generally, the switch should be opened after the voltage regulator is reduced to zero position.
5. During the voltage increase or withstand voltage test, if the following abnormal conditions are found: (1) the pointers of voltage and current meters swing greatly, (2) the tested object emits abnormal sounds, (3) insulation is found to be burnt or smoking, the voltage should be immediately reduced, the power cut off, the test stopped, and the cause investigated.
6. When using this product for high-voltage tests, in addition to being familiar with this manual, the relevant national standards and operating procedures must be strictly implemented. Reference can be made to GB311—83 "Regulations for Preventive Tests of Electrical Equipment" and others.
