The product is designed to meet the triple frequency induced withstand voltage test and partial discharge test in GB1094.3 - 85, GB1207 and Preventive Test Code for Electric Power Equipment-1995.

The transformer induced withstand voltage test is one of the most important test to inspect if the products meet the national standards. The longitudinal insulation induced test of the insulation between layers, between turns, between sections and between phases of windings is one of important item for testing if windings meet the requirements. In order to improve the winding test voltage, and not make the core oversaturated resulting in excessive exciting current, the test frequency shall be improved to generally 100Hz-400Hz.

There are many ways to obtain the 100Hz-400Hz power supply, wherein, the suitable ways are: ①. Combination of three frequency conversion generators (100Hz-400Hz).② Combination of three single-phase transformers (150Hz). Way ② is the most convenient.

Way of combination of three single-phase transformers: The primary side is star connection and the secondary side is open-delta connection, therefore, when the iron core is not saturated, it will necessarily generate the main flux of flat-topped wave. The main flux in flat-topped waveform contains a large component of third harmonic magnetic energy Φ3 and the third harmonic flux frequency f3=3f1, therefore the main flux induces third harmonic phase voltage.

As the primary side is star connection and the secondary side is open-delta connection, when the iron core work reaches saturation, the no-load current I will take on peaked wave, containing higher harmonic besides the fundamental wave. Wherein, the I amplitude in the higher harmonic is larger, as the secondary side is open and the fundamental components of the three phases offset each other, there is only third harmonic output left.

Under the situation that the complete machine voltage output is 150Hz power supply, tuning is conducted to generate resonance for the realization. There will be certain squeal of the resonance when the voltage increases, which is normal.

Output voltage: Three-phase 380V, 50Hz

Output voltage: 0-800V (maximum 1,500V), 150Hz

Input current: 44 A

Output current: 22 A

Waveform: Sine wave, distortion degree less than 1%

Capacity: 1－30kVA

Load characteristic: Resistive, inductive or capacitive