Complete Set of Variable Frequency Series Resonance Test Equipment

This device is primarily designed for AC withstand voltage testing of electrical main equipment at 10 kV, 35 kV, 110 kV, 220 kV, substations, and transmission lines. The impedance tester is designed with multiple separate components, capable of meeting the test conditions for high-voltage, low-current equipment while also satisfying the AC withstand voltage testing requirements at low voltage. It has a wide range of applications and serves as an ideal withstand voltage device for high-pressure test departments at provincial, municipal, and county levels, as well as power installation and maintenance engineering units.

This device mainly consists of a variable frequency control power supply, an excitation transformer, an inductor, and a capacitor voltage divider.

• The required power capacity is greatly reduced. A cascaded resonant power supply utilizes a resonant inductor and the test item’s capacitor resonance to generate high voltage and large current. Within the system, the power supply only needs to provide the portion of power that consumes real power; therefore, the required power for testing is 1/Q of the test capacity.
• The weight and volume of the device have been greatly reduced. In a cascaded resonance power supply, it eliminates bulky high‑power voltage regulators and ordinary high‑power industrial‑frequency test transformers, while a resonance induction power supply requires only 1/Q of the test capacity, significantly reducing system weight and volume—typically 1/10–1/30 compared to a conventional test device.
• Improve the waveform of the output voltage. A resonant power supply is a resonant filter circuit that improves the distortion of the output voltage waveform to achieve a good sinusoidal shape and effectively prevents harmonic peaks from causing accidental breakdown of samples.
• Prevent large short-circuit currents from damaging fault points. In resonance mode, when the sample’s insulation weakness is breached, the circuit immediately loses resonance, and the loop current quickly drops to 1/Q of the normal test current. In parallel resonance or experimental transformer methods for voltage tests, the breakdown current immediately increases by tens of times. Compared between the two, the short-circuit current differs from the breakdown current by hundreds of times. Therefore, series resonance can effectively identify weak points in insulation and eliminates concerns about large short-circuit currents damaging fault points.
• There will be no overvoltage recovery. During arcing events, when the resonant conditions are lost, the high voltage immediately disappears, the arc extinguishes instantly, and restoring the voltage takes a long time. It is easy for the power supply to disconnect before reaching the spark voltage again. The restoration process of this voltage involves intermittent oscillation and energy accumulation; it’s a lengthy process, and there will not be any overshoot of voltage.

• The device features overvoltage, overcurrent, zero-position startup protection, system phase imbalance (hunting), and other protective functions. Overvoltage and overcurrent protection levels can be set according to user needs. During hunting, the device activates the hunting protection function and records the hunting voltage value for testing analysis.
• The entire device is very lightweight—single unit weight does not exceed 65 kg—making it convenient for on-site use.
• The device has three operating modes, allowing users to flexibly choose according to the site conditions and increasing testing speed. Operating mode is:Fully automatic mode, manual mode, auto-tune manual voltage increase mode.
• It can store and print data remotely, and the numbers assigned to stored data make it easier for users to identify and find them.
• When the device automatically scans frequencies, the starting frequency can be set freely within a defined range. The scanning direction can be selected as up or down. Simultaneously, a large LCD screen displays the scan curve, allowing users to intuitively understand whether the resonance point has been found.
• It utilizes DSP platform technology, allowing convenient addition or removal of features and upgrades according to user needs, which also makes the human–machine interaction interface more user-friendly.

• Output voltage waveform distortion rate: <1.0%
• Continuous working time allowed: Under rated conditions, works continuously for 15 minutes at a time.
• Device quality factor: Q > 50
• Under full load during cable and generator testing, quality factor Q > 30 (dependent on load).
• Power transformer and line test quality factor at full load: Q > 30 (dependent on the load).
• Input power: three-phase 380V or single-phase 220V. When the power supply is 380V, a rated load test can be performed; when the power supply is 220V, only a 1/2 load test can be conducted.
• Frequency adjustment range: 20 Hz–300 Hz
• System measurement accuracy: 1.5%
• The device features overvoltage protection, overcurrent protection, zero-position startup protection, surge protection, and other protective functions.

Variable Frequency Power Supply

Rated power: 5.5–500 kW; input: 380 V/220 V; output: 0–400 V, 20–300 Hz

High Voltage Reactor

0–1000 kV, 1–10 A, inductance 30–600 H, continuous operation for 15 min

Excitation Transformer

Capacity: 3.5–500 kVA, adaptable 200 V/400 V input

Capacitive Voltage Divider

Voltage range: 10–1000 kV; capacitance: 300–5000 pF; accuracy: ±1.0%.

Frequency Control

20–300 Hz, 0.1 Hz step, instability ≤0.02%

Loading condition

Full load at 380V, half load at 220V

Temperature Performance

Temperature increase < 60°C, long-term test stability

Current Output

13–1250 A, meets various high-voltage testing requirements