Jiangtao Shi

Precise Measurement of the Inductance and Resistance of a Pulsed Field Magnet Based on Digital Lock-in Technique

In order to guarantee the safe operating conditions of pulsed field magnets and anticipate impending catastrophic failure, the precise measurement of inductance and resistance of the magnet is most useful. A measurement system based on the Digital Lock-In (DLI) technique has been developed. A non-inductive reference resistor with high thermal stability is connected with the magnet in series. Two reference signals are generated virtually. The voltages across the reference resistor and the magnet are used as measurement signals which are sampled synchronously by the Analog-to-Digital Converter (ADC) and processed with a DLI amplifier algorithm. The inductance and resistance of the magnet can then be derived by computation. The Infinite Impulse Response (IIR) filter design, measurement system implementation and error analysis are described. The accuracy of the inductance measurement is better than 0.01% in practice. The measurement system has been implemented at the Wuhan National High Magnetic Field Center (WHMFC) with excellent performance.

Design of a Program-Controlled Precise Synchronous Triggering System Applied to Pulsed High Magnetic Field Facility

Recently, a Program-controlled Synchronous Triggering System (PSTS) is developed at Wuhan National High Magnetic Field Center. The designed system could generate triggering signal for thirteen power modules and eight magnets distributed in different experiment stations. By generating precise and synchronous triggering signals required for the facility, the multiple power modules could be discharged synchronously or in a preset time sequence. The PSTS is composed of triggering signal generator, fiber converter, expanded cell, and local sequence generator. The triggering signal generator, isolated from local device, is applied for sequential control of multi-module in the facility. The signal transmission is realized by optical fiber. A Digital Signal Processor (DSP) with specific type of TMS320F2812 is employed to design the triggering signal generator. The parameters of triggering channels and time-delay with the accuracy of 1 us could be configured through human machine interface. Local sequence generator unit is integrated in the local control unit on the basis of a Complex Programmable Logic Device (CPLD) with specific type of EPM7128. Local sequence generator is responsible for producing the time sequence signals to control and record the waveform of each power module, as well as the triggering signal waveform modulation for thyristor through expanded cell. Based on the designed system, the pulsed high magnetic field facility could be operated effectively. The test result illustrates that the system is of high performance.

Function Design and Implementation of a Central Control System of a Pulsed High Magnetic Field Facility

A user-friendly Central Control System (CCS) for the pulsed high magnetic field facility has been designed and implemented at the Wuhan National High Magnetic Field Center (WHMFC). The CCS is composed of the server, the Human Machine Interface (HMI) and the configuration tool. The controlled objects and functions of the CCS are introduced first, and then the design and implementation of key functions are given. The CCS is developed on basis of a client/server mode, so multiple users can use the system simultaneously. To achieve higher pulsed magnetic fields, a synchronous trigger sequence is used, which can trigger up to 13 power modules to be discharged into a magnet with multiple coils. Benefiting from component technology and the TCP/IP communication protocol, the CCS can monitor signals in real time and receive experimental data from recording devices running on different platforms. The test results show that the CCS meets the requirements of experiments and simplifies the control operation.

Analysis and Design of a Control System for the 100 T Pulsed High Magnetic Field Facility at WHMFC

A pulsed high magnetic field of 90.6 T has been achieved by discharging the energy in a capacitor bank to a nondestructive magnet at Wuhan National High Magnetic Field Center (WHMFC), and recently, the project for a 100-T magnetic field has been under development. The pulsed magnet with a 100-T magnetic field will be composed of three coils, which are driven by three types of power sources. Based on the existing control subsystems of these power sources, the design of the control system that can control different types of power supplies to discharge would be taken into consideration for the implementation of the 100-T magnetic field. This paper first analyzes the control process for the 100-T system, which can divided into three stages, and the time requirement for each stage. Based on the analysis, the structure and main functions of the control system are discussed, and then the main control program and the global control block are designed. To protect the safety of the system, some protection measures are finally discussed. This paper provides design bases for the realization of the control system.

Design of the power supply for the pulsed electric current sintering

The pulsed electric current sintering (PECS) is a new rapid sintering technique. As an important part of the PECS system, the pulsed electric current power supply is one of the main factors which affect the sintering result. This paper proposes a pulsed electric current power supply topology based on phase-shift full-bridge converter, which implements ZVS (zero voltage switching). By controlling the PWM output, it implements such variety output modes as pulse mode, DC mode and Pulse-DC mode. The power supply can output 700A current and 14V voltage. Its output pulse width is a minimum of 2ms, and can be adjusted by the user.

Operation Strategy and Reliability Analysis of the Control System for the Hybrid Capacitor-Battery Pulsed High Magnetic Field Facility

A hybrid capacitor-battery power supply is built at Wuhan National High Magnetic Field Center to generate a steep rising/flat top waveform, where the capacitor banks provide the sharp rising edge and the batteries maintain the flat top long pulse. A control system, which consists of a global controller and subcontrol system, is designed to ensure the reliable operation. The global controller includes a triggering unit, an interlock unit, and a data transmission unit. Each type of power source can be discharged separately through its own subcontrol system. When different powers discharge together, its own control system fulfills internal operations, and the triggering unit is responsible for generating the highest priority triggering signals, the interlock unit is applied for protecting multitype power modules. The data transmission unit is used to communicate with different power modules. Based on the designed control system, the operation strategy and reliability analysis are discussed. The result shows that the control system could greatly improve the performance of the hybrid capacitor-battery power supply.