The modulated variable frequency series resonant withstand voltage device is a withstand voltage test equipment specially designed for high-voltage electrical equipment, especially suitable for the AC withstand voltage test of 11kV 30MW hydro generator. The core of this device is to adjust the inductance to achieve resonance with the device under test, so as to generate high voltage and high current on the device and perform withstand voltage tests.
The device is mainly composed of four parts: frequency conversion control power supply, excitation transformer, reactor and capacitor voltage divider. Among them, the reactor adopts a unique two-piece separate design, which makes the device more flexible and adapts to different test needs.
Inductive variable frequency conversion series resonant withstand voltage device has many advantages in the power system:
Small power supply capacity requirement: Because the device uses the resonance principle to generate high voltage and large current, the power supply only needs to provide the active consumption part of the system, so the power supply required for the test is only 1 q of the test capacity, which greatly reduces the requirement for power supply capacity.
Reduced size and weight: The whole device becomes lighter and easier to handle and install due to the elimination of the bulky high-power voltage regulating device and the ordinary high-power power frequency test transformer. Generally speaking, its volume and weight are only 1 10 to 1 30 of ordinary test equipment.
Output waveform optimization: The resonant circuit in the device can effectively improve the waveform distortion of the output voltage and obtain a purer sine waveform, thus avoiding the false breakdown caused by the harmonic peak to the sample.
Prevent excessive short-circuit current: In the state of series resonance, once the insulation breakdown occurs in the test piece, the circuit will be detuned immediately, and the loop current will quickly drop to 1 q of the normal test current. Compared with the parallel resonant or test transformer method, the short-circuit current and the breakdown current are hundreds of times different, which effectively protects the test product and test equipment.
No recovery overvoltage: When the breakdown occurs in the specimen, the high voltage will disappear immediately and the arc will be extinguished immediately due to the loss of resonance conditions. The recovery voltage establishment process is an intermittent oscillation process of energy accumulation, which is a long process and does not have any recovery overvoltage, thus ensuring the safety and reliability of the test.
To sum up, with its characteristics of high efficiency, lightness, safety and reliability, modulated variable frequency conversion series resonant withstand voltage device is widely used in the AC withstand voltage test of various high-voltage electrical equipment in the power system, especially for large equipment such as hydro generators. It is an indispensable and important equipment in the testing and maintenance of power systems.