The principle of resonant transformer is mainly based on the principle of series resonance or parallel resonance, which is used to generate high current and high voltage, and is usually applied to large capacitive or inductive loads.

Basic principles

The basic formula for a resonant transformer is ω=1/√ (LC), where ω is the angular frequency of the power source, and L and C are the inductance and capacitance of the load or equipment, respectively. To satisfy this equation, at least one parameter in ω, L, and C needs to be adjustable. In order to meet the requirements of output voltage or current, one of L and C must be adjustable, and in order to accurately find the resonance point, the parameters also need to be able to be infinitely fine tuned. Therefore, modern resonant transformers generally use a variable frequency power supply as the power source to adjust ω, with a tapped reactor as L, and when combined with C, the resonant point can be easily found.

Working principle

Series resonance:

In a series circuit, when the capacitance reactance XC is equal to the inductance reactance XL, i.e. XC=XL, the phase of the voltage U and current I in the circuit are the same, and the circuit exhibits pure resistance. This phenomenon is called series resonance (also known as voltage resonance).

When a series resonance occurs in the circuit, the impedance Z=√ R ² (XC-XL) ²=R, the total impedance in the circuit is minimized, and the current will reach its maximum value.

Parallel resonance:

The principle of parallel resonance is different from series resonance, but it also utilizes the natural frequency of circuit components to match the frequency of the external signal, thereby achieving a resonant state.

In a parallel circuit, when the imaginary part of the total admittance of the circuit is zero, that is, the circuit is purely resistive, and parallel resonance occurs.

Application and Characteristics

Application:

Resonant transformers are widely used in AC testing of power equipment with large capacitance, such as cables, capacitors, and generators.

By adjusting the air gap length of the iron core magnetic circuit, a continuously changing inductance L is obtained, which resonates with the ground capacitance C of the test sample, thereby achieving a larger load current or voltage with a smaller excitation current or voltage.

characteristic:

The required power capacity is greatly reduced. Series resonant power supply generates high voltage and high current through the resonance of resonant reactor and tested capacitor. In the entire system, the power supply only needs to provide the active consumption part of the system.

The weight and volume of the equipment have been greatly reduced. The series resonant power supply eliminates the need for bulky high-power voltage regulating devices and ordinary high-power power frequency test transformers. The resonant excitation power supply only requires 1/Q of the test capacity (Q is the system quality factor, i.e. the voltage resonance multiple), greatly reducing the weight and volume of the system.

Improve the waveform of the output voltage. A resonant power supply is a resonant filtering circuit that can improve the waveform distortion of the output voltage, obtain a good sine waveform, and effectively prevent harmonic peaks from causing false breakdown of the test sample.

In summary, a resonant transformer is a type of transformer that operates based on the principles of series resonance or parallel resonance, and has a wide range of applications and unique performance characteristics.