Variable Frequency AC Resonance Test System| Detailed introduction of technical principles

The testing principle of a resonant AC withstand voltage test device (usually referring to a variable frequency series resonant device) is based on the voltage amplification effect of series resonance.

Its core principle is: adjusting the output frequency of the variable frequency power supply so that the inductive reactance of the fixed reactor in the circuit is equal to the capacitive reactance of the test object (equivalent to a capacitor), i.e., X_L = X_C. At this time, the system achieves series resonance, the total impedance of the circuit is minimized, and the current reaches its maximum.

In the resonant state, the voltage U_L across the reactor is equal in magnitude but opposite in phase to the voltage U_C across the test object's capacitance. Therefore, the high voltage U_C obtained on the test object is Q times the excitation voltage U (Q is the system quality factor), i.e., U_C = Q × U. This high voltage is a standard sine wave, meeting the withstand voltage requirements. This principle allows the device to efficiently complete power frequency AC withstand voltage tests on large-capacitance test objects such as cables and GIS with only a small amount of active power to compensate for circuit losses, using a smaller power supply capacity and lighter equipment. Variable frequency AC resonant test system, variable frequency series resonant AC withstand voltage test device, variable inductance AC resonant test system 540kVA 270kV 30-300Hz. This resonant AC withstand voltage test device is mainly used for AC withstand voltage testing of 10kV, 35kV, and 110kV cables, 110kV main transformers, GIS, and circuit breakers.

It has a wide range of applications and is an ideal withstand voltage test equipment for municipal, county-level high-voltage testing departments and power installation and maintenance engineering units.

The resonant AC withstand voltage test device mainly consists of a variable frequency power supply, excitation transformer, reactor, capacitive voltage divider, and compensation capacitors.

1. 110kV circuit breaker, GIS, test frequency 30-300Hz, test voltage 265kV, test time 1min

2. 110kV/400mm² cable 0.7km, capacitance ≤0.115uF, test frequency 30-300Hz, test voltage 128kV, test time 60min

3. 110kVA/80000kVA main transformer fully insulated, capacitance ≤0.02uF, test frequency 45-65Hz, test voltage 160kV V, Test time 1min

4. 10kV/300mm² cable 8km, capacitance ≤3.004uF, test frequency 30-300Hz, test voltage 17.4kV, test time 60min

5. 35kV/300mm² cable 4km, capacitance ≤0.778uF, test frequency 30-300Hz, test voltage 52kV, test time 60min

1. Features overvoltage, overcurrent, zero-start, and system detuning (flashover) protection functions.

2. Equipment weight and volume are 1/10-1/30 of ordinary testing equipment. The power required for testing is only 1 Q of the test capacity.

3. The device has three operating modes: fully automatic mode, manual mode, and automatic tuning and manual boost mode.

4. Data storage and printing; stored data numbers are numerical, conveniently helping users identify and search.

5. The frequency starting point can be arbitrarily set within the specified range during automatic frequency sweep.

6. DSP platform technology: Functions can be added, removed, and upgraded according to user needs; the human-machine interface is more user-friendly.

7. Improved output voltage waveform.

8. Prevents large short-circuit currents from burning out fault points.

9. No recovery overvoltage will occur.

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