The Working Principle Of Triple Frequency Withstand Voltage Generator

Thetriple frequency withstand voltage generatoris designed to meet the triple frequency induction withstand voltage test and partial discharge test in the preventive test code for electrical equipment. This paper introduces the working principle of frequency tripling voltage withstand generator.

It is an important test to check whether the product meets the national standard during the induction voltage withstand test of transformer and mutual inductor. The longitudinal insulation induction test of inter layer, inter turn, section and inter phase insulation of winding is an important item to test whether the winding meets the requirements. In order to improve the test voltage of winding and make the core of transformer or mutual inductor not be over saturated, the excitation current is too large, so the test frequency should be increased, generally 100Hz ~ 400Hz.

There are many ways to obtain 100Hz ~ 400Hz power supply, among which the more used ones are:

1. Combination of three variable frequency generators (100Hz ~ 400Hz);

2. The combination of three single-phase transformers (150Hz), the second is more convenient.

Combination mode of three single-phase transformers: the primary side is star connection, and the secondary side is open triangle. When the core is not saturated, the main magnetic flux produced by it must be flat top wave. Because the main flux of flat top waveform contains a large component of the third harmonic energy φ 3, and the third harmonic flux frequency F3 = 3f1, the main flux induces the third harmonic phase potential. As the core of this connection method works in a saturated state, the no-load current I presents a sharp crest wave, in addition to the fundamental wave, which also contains high-order harmonics. Because of the opening of the secondary side, the three-phase fundamental components cancel each other and only the third harmonic output is left.

The third harmonic generator uses the saturation characteristic of the magnetic circuit to take out the third harmonic voltage with larger harmonic component, which is used as the power supply of the generator, and conducts the turn to turn, section to section, layer to layer frequency multiplication and voltage test for the induction coil electrical products such as transformer, mutual inductor, etc.; the insulation strength and voltage withstand level of the opening and closing coils are used.

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