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Basic Principles of Triple Frequency Generator

time:2021/4/10   source:华天电力  reading:500 time

The triple frequency power generator is designed to meet the triple frequency induction withstand voltage test and partial discharge test in the <<Electrical Equipment Preventive Test Regulations>>.

Transformer and transformer induction withstand voltage test is an important test to check whether the product meets the national standard. The longitudinal insulation induction test of the interlayer, turn, segment and phase insulation of the winding is an important item to test whether the winding meets the requirements. In order to increase the winding test voltage, so that the core of the transformer or transformer will not be oversaturated and cause the excitation current to be too large, so the test frequency should be increased, generally 100Hz-400Hz.

Triple Frequency Induced Withstand Voltage Test Set.png

There are many ways to obtain a 100Hz-400Hz power source. Among them, the more suitable ones are: ① combination of three variable frequency generators (100Hz-400Hz); ② combination of three single-phase transformers (150Hz), and the convenient method is the second method.

The combination of three single-phase transformers: the primary side is a star connection, and the secondary side is an open triangle. When the iron core is not saturated, the main magnetic flux generated by it must be a flat-top wave. Since the main magnetic flux of the flat-top waveform contains a large component of the third harmonic magnetic energy Φ3, and the third harmonic magnetic flux frequency f3=3f1, the main magnetic flux induces a third harmonic phase potential.

Since the primary side is a star connection and the secondary side is an open delta connection, the iron core is in a saturated state, and the no-load current I presents a peak wave. In addition to the fundamental wave, it also contains high-order harmonics. The amplitude of I in the higher harmonics is relatively large. Due to the opening of the secondary side, the three-phase fundamental components cancel each other out, leaving only the third harmonic output.

The SFQ triple frequency power generator uses the saturation characteristics of the magnetic circuit to extract the third harmonic voltage with a large harmonic component, as the power supply of the generator, for the inter-turn and section of the induction coil type electrical products such as transformers and transformers. Frequency doubling and voltage doubling test between layers and layers; to assess the insulation strength and withstand voltage level of the coil.

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