CN-121985466-A - Excitation circuit, system and control method of electronic induction accelerator based on square wave excitation

CN121985466ACN 121985466 ACN121985466 ACN 121985466ACN-121985466-A

Abstract

The invention discloses an excitation circuit, an excitation system and an excitation control method of an electronic induction accelerator based on square wave excitation, which are used for a small electronic induction accelerator. The system comprises a rectifying and filtering power supply, an IGBT driving circuit, an LC resonant circuit and a computer control system. The rectification power supply provides direct current, the direct current is converted into square wave excitation signals through the IGBT driving circuit, a resonance loop connected with the resonance capacitor in parallel is driven by the electromagnet coil, and high-voltage sine wave excitation current is generated at the near resonance frequency. The computer control system controls the square wave phase to move forward after resonance is established, so that the rising edge of the square wave phase is positioned at the left side of the zero crossing point of the sinusoidal current, and oscillation is maintained efficiently. The permanent magnet can be used for providing direct current bias, and an asymmetric sine magnetic field is formed by superposition of the direct current bias and alternating current excitation, so that the effective acceleration time is prolonged to a near half period. The invention reduces the design difficulty of the magnet and the power supply loop and has the advantages of adjustable frequency and controllable resonance.

Inventors

CHEN HAISHENG
GONG JUN
LI BO
LI CHUAN

Assignees

泛华检测技术有限公司

Dates

Publication Date: 20260505
Application Date: 20260313

Claims (10)

1. The excitation circuit of the electronic induction accelerator based on square wave excitation is characterized by comprising an IGBT driving circuit, a resonant circuit, an LC parallel resonant circuit and a high-voltage sine wave excitation current, wherein the IGBT driving circuit is used for converting a direct current power supply into a square wave excitation signal, the resonant circuit is formed by connecting an electromagnet coil and a resonant capacitor in parallel, and the square wave excitation signal is applied to two ends of the LC parallel resonant circuit and used for excitation at a place close to the natural resonant frequency of the resonant circuit.
2. The excitation circuit of the electronic induction accelerator based on square wave excitation of claim 1, wherein the IGBT driving circuit comprises an IGBT, and a control chip is connected between a grid electrode and an emitter electrode of the IGBT and used for receiving an adjustable duty cycle PWM control signal generated by the control chip so as to adjust the frequency and the duty cycle of the square wave excitation signal.
3. The excitation circuit of the electronic induction accelerator based on square wave excitation of claim 2, further comprising a permanent magnet arranged in the structure of the magnet of the electronic induction accelerator, wherein an electromagnetic field generated by the resonant circuit is overlapped with a permanent magnetic field generated by the permanent magnet to jointly form the excitation magnetic field.
4. The excitation circuit of the electronic induction accelerator based on square wave excitation of claim 3, wherein the waveform of the superimposed excitation magnetic field is an asymmetric sine wave.
5. The excitation circuit of claim 4, further comprising a computer control system for controlling the phase of the square wave excitation signal to move forward after the resonant tank completes excitation, and for causing the rising edge of the square wave excitation signal to be located to the left of the zero crossing point of the high voltage sine wave excitation current and the falling edge to be located to the right of the zero crossing point of the high voltage sine wave excitation current.
6. An excitation system of an electronic induction accelerator based on square wave excitation, comprising: The rectification and filtering system is used for rectifying and filtering alternating current into a direct current power supply; The input end of the IGBT driving circuit is connected with the direct current power supply and is used for converting the direct current power supply into square wave excitation signals; The input end of the resonant circuit is used for receiving the square wave excitation signal and forming stable voltage and current oscillation at a position close to the resonance frequency so as to generate high-voltage sine wave excitation current; and the computer control system is used for controlling the phase of the square wave excitation signal to move forwards after the resonance circuit is excited, and enabling the rising edge of the square wave excitation signal to be positioned at the left side of the zero crossing point of the high-voltage sine wave excitation current and the falling edge to be positioned at the right side of the zero crossing point of the high-voltage sine wave excitation current.
7. An excitation control method of an electronic induction accelerator based on square wave excitation is applied to the excitation system of the electronic induction accelerator based on square wave excitation as claimed in claim 6, and is characterized by comprising the following steps: converting alternating current into direct current power supply through a rectifying and filtering system; Converting the direct current power supply into a square wave excitation signal through an IGBT driving circuit, and applying the square wave excitation signal to a resonant circuit formed by parallel connection of an electromagnet coil and a resonance capacitor; Controlling the fundamental frequency of the square wave excitation signal to be close to the natural resonant frequency of the resonant circuit so as to excite and generate high-voltage sine wave excitation current; after the resonance circuit is excited and established, the phase of the square wave excitation signal is controlled to move forwards through a computer control system, so that the rising edge of the square wave is positioned at the left side of the zero crossing point of the high-voltage sine wave excitation current, and the falling edge is positioned at the right side of the zero crossing point, thereby compensating the energy loss of the circuit and maintaining stable resonance; and superposing an alternating current excitation magnetic field generated by the resonance circuit and a direct current bias magnetic field generated by a permanent magnet arranged in the electromagnetic induction accelerator magnet to form an excitation magnetic field of an asymmetric sine wave so as to prolong the effective acceleration time of electrons.
8. The method of excitation control of an electronic induction accelerator according to claim 7, wherein the square wave excitation signal is used for supplying excitation current to the resonant tank and compensating for resonant energy loss, and the stable resonant state of the resonant tank is maintained by supplementing energy at a time corresponding to the time before and after zero crossing of the voltage of the electromagnet coil.
9. The method for excitation control of an electronic induction accelerator based on square wave excitation according to claim 8, wherein the current amplitude of the square wave excitation signal is smaller than the amplitude of the high-voltage sine wave excitation current.
10. The method for excitation control of an electronic induction accelerator based on square wave excitation of claim 9, wherein the computer control system controls the forward phase of the square wave excitation signal to be 30 degrees.

Description

Excitation circuit, system and control method of electronic induction accelerator based on square wave excitation Technical Field The invention relates to the technical field of electron accelerators, in particular to an excitation circuit, an excitation system and a control method of an electron induction accelerator based on square wave excitation. Background The electron induction accelerator is widely applied in various fields including the fields of radiology, radiodiagnosis, baggage-parcel detection, nondestructive detection, customs container detection and the like. The working principle of the cyclotron is to accelerate electrons by using a vortex electric field generated by a variable magnetic field. To obtain a swirling electric field, the field current and field waveforms of the magnet are typically sinusoidal waveforms as shown in fig. 1. In order to meet the direction of electron cyclotron motion, the direction of the magnetic field or exciting current cannot be changed, i.e. electrons can normally move only in the upper half period of the sine waveform. Furthermore, electron acceleration can only be used to accelerate electrons in the rising segment of the waveform, i.e., the entire sinusoidal waveform, only a quarter of a period. To increase the electron mean current intensity, one changes the waveform of the useless negative half period in the sine waveform to a positive waveform, i.e. to form a dc ripple waveform similar to that shown in fig. 2. The problem is that the complexity of the circuit is greatly increased, and a power switch with withstand voltage of more than 1000V and current of more than 200A is required to control the generation of current waveform. The high-voltage high-current has four adverse effects, namely high cost and easy damage of the power switch device, thick high-current transmission cable, difficult length and bending of the high-current transmission cable, difficult design of leading out the cable by radiation protection self-shielding, and easy interference of the high-current on other control and monitoring signals. In addition, the waveform slope at the electron injection timing is the largest regardless of the sinusoidal waveform or the dc ripple waveform, and the waveform shape at the injection timing is difficult to adjust as shown in fig. 1 and 2. This results in a shorter electron capture time, typically no more than 3 mus, making it difficult to increase the electron beam current. For this reason, patent (CN 202111230266.1) proposes a method of generating a dc pulsating current by superimposing a static magnetic field with a sine wave magnetic field. The method needs to adopt an LC resonance method to generate high-voltage high-current, and the traditional method adopts a white circuit to excite LC resonance. The white circuit excites LC resonance by adopting a sine waveform of a small signal, and the method has the problems of complex waveform generation, difficult frequency and phase change and the like. Disclosure of Invention Aiming at the defects of the prior art, the invention provides an excitation circuit, an excitation system and an excitation control method of an electronic induction accelerator based on square wave excitation, and aims to solve the problems in the background art. The technical scheme is that the electronic induction accelerator excitation circuit based on square wave excitation comprises an IGBT driving circuit, a resonant circuit, an LC parallel resonant circuit and a square wave excitation signal, wherein the IGBT driving circuit is used for converting a direct current power supply into a square wave excitation signal, the resonant circuit is formed by connecting an electromagnet coil and a resonant capacitor in parallel, and the square wave excitation signal is applied to two ends of the LC parallel resonant circuit and used for exciting and generating high-voltage sine wave excitation current at a position close to the natural resonant frequency of the resonant circuit. Further, the IGBT driving circuit comprises an IGBT, and a control chip is connected between a grid electrode and an emitter electrode of the IGBT and used for receiving an adjustable duty ratio PWM control signal generated by the control chip so as to adjust the frequency and the duty ratio of the square wave excitation signal. Further, the structure of the electron induction accelerator magnet is provided with a permanent magnet, and an electromagnetic field generated by the resonant circuit is overlapped with a permanent magnetic field generated by the permanent magnet to jointly form the excitation magnetic field. Further, the waveform of the superimposed excitation magnetic field is an asymmetric sine wave. Further, the system also comprises a computer control system, wherein the computer control system is used for controlling the phase of the square wave excitation signal to move forward after the excitation of the resonant circuit is completed, and e