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This paper suggests a design of pulsewidth modulation series-resonant converter (PWM SRC) for magnetron power supplies. The goal of this design is to make the PWM SRC have a wide output voltage maintaining mode 3 operation that shows good switching characteristics. To keep the mode 3 operation, a systematic design is required because the design is related to various parameters, such as resonant tank, transformer turns-ratio, magnetizing inductance, and duty-ratio. To establish the design procedure, converter analysis is performed related to the steady-state operation, input–output relationship, and critical design conditions, and several design equations are derived based on the analysis. Based on the design procedure, a PWM SRC with parallel-input-series-output-connected transformer has been designed for magnetron power supplies and verified. [ABSTRACT FROM AUTHOR]

A magnetic pulse compressor (MPC) transfers energy via $C$ – $L$ – $C$ resonance. The pulse width of the MPC is determined by the saturation inductance of the magnetic switch (MS). When using the MS, the pulse width is limited due to the stray elements. To increase the pulse compression rate, the number of stray elements must be reduced. In this paper, we propose an optimum design for an MS having the lowest impedance of stray elements, along with its analysis and experimental verification. The proposed model is designed to have a reduced magnetic path length while retaining the same saturation inductances as that of a common MS; this is accomplished by using the relationship between the magnetic field path length and the number of inductor turns. The experimental results show that the proposed MS decreases the full width at half maximum by 18% and increases the rise rate by 69%. This result demonstrates that the proposed MS increases the pulse compression rate of the MPC by reducing impedance of stray elements in the system. [ABSTRACT FROM AUTHOR]

In a magnetic pulse compressor (MPC), the saturation inductance of the magnetic switch (MS) determines the energy transfer time. Thus, in general, the number of windings on the MS is modulated to vary the saturation inductance. Changing the number of windings also changes the energy transfer time and the saturation time. In this paper, we propose and analyze an MS with multiwindings to modulate the pulse width without affecting the saturation time of the MS. The parallel structure of the multiwindings on the MS decreases the energy transfer time without affecting the saturation time. Through experiments, we show that the energy transfer time is decreased by 13% via a double winding MS. Therefore, an MS with multiwindings can be used to modulate the pulse width at the last stage of the MPC without affecting the saturation time of the MS. [ABSTRACT FROM AUTHOR]

This paper describes a high-frequency pulsed-power generator for various industrial applications such as water treatment, food and medical apparatus for sterilization, or polluted gas treatment. The system is made of silicon-controlled rectifier as a main trigger switch, capacitors, two-stage magnetic pulse compression stages, and a linear transformer to generate a maximum of 120-kV, 5-kA pulse. The parameters obtained through the development are: output voltage: 120 kV (maximum), pulse repetition ration: 300 pulse per second, pulsewidth: 0.25~\mu \texts , and mean power: 30 kW. The designed pulsed-power generator is confirmed to be used effectively for many high-voltage pulsed-power applications related to environmental industry by simulation and experiments. [ABSTRACT FROM AUTHOR]

Magnetic compression (MC) technology was recommended for tokamak to study compressed plasma and a power module have been designed here for developing its server power supplier. The minor-radius compression is one of the most effective methods to improve the performance parameters of existing tokamaks, enabling the fusion plasmas operated at high density, high temperature, and high beta. In this paper, a high-frequency and high-power supply system is proposed, used for powering coils of MC within the vacuum chamber of the experimental advanced superconducting tokamak. The basic of the power module is an ac/pulse converter, implemented by a series-resonant full-bridge circuit and controlled by pulsewidth modulated. Also, control method adopts current closed-loop proportional–integral control, which has less than 3-ms current response time in real time. The converter is analyzed and the design procedure is discussed. Experimental results obtained from a 3-kW converter prototype are presented to validate the converter’s performance with the redesigned control board. [ABSTRACT FROM AUTHOR]

A 100-kV/60-A high-voltage power supply (HVPS) has been established to energize the electron cyclotron resonance heating system for the J-TEXT tokamak. The HVPS based on the pulse step modulation technique has many advantages, including low stored energy and short protective time in case of a short circuit fault. This paper describes and provides the key design features of isolated transformers, switch power supply (SPS) modules, measurement equipment, and controllers. In this HVPS, four dry-type transformers with 36 secondary windings drive the 144 series SPS modules and isolate the high voltage between the rectifiers and the 6.3-kV ac bus. A controller based on PXI technology, which conforms to the ITER CODAC standard, has been developed to operate the series switches in each SPS module. The error signals from all the modules are monitored by the controller, and the fast protection responds to any current fault in <5~\mus. A control strategy improved from the conventional pulsewidth modulation phase-shift modulation method has also been proposed to acquire better dynamic response and stability. Experimental results show that the power supply system performs well. [ABSTRACT FROM PUBLISHER]

To achieve the maximum current rising rate, the second-generation fast control power supply (FCPS) applies voltage control mode while retaining the first-generation current tracking mode. When the power supply outputs high voltage, the accompanied frequent overcurrent protection will return the power to dc side, which leads to overvoltage protection, so the current limiting protection is applied. Experimental results prove that voltage mode can greatly improve the ability to suppress vertical unstable displacement of plasma. [ABSTRACT FROM AUTHOR]

A significant engineering upgrade of the DIII-D neutral beam system has recently completed, providing ability to smoothly and independently vary the beam voltage and current. This enables greater control of the injected beam power, torque, and plasma instability drive for fusion experiments. Modifications to the high-voltage equipment and the plasma control system were made and tested over the last year to allow beam energy to vary by as much as 20 kV over a 0.5-s period anywhere within the 45–85 kV operating range of the beams. The beam current can be made to track the voltage (keeping the perveance constant), or the current and voltage can be varied independently (scanning the perveance). The smooth variation of beam energy avoids the extremely perturbative effects of pulsewidth modulation, the only tool previously used for regulating the injected neutral beam power. With independent control of voltage and current, the beam ion velocity space can be tailored to facilitate new experiments that explore, for example, the detrimental effects of Alfvén eigenmodes. These modes are driven by energetic particles and can possibly be avoided in steady-state scenarios by timely variation of the beam energy while maintaining constant input power. A description of the modifications made to the power supply and beam controls will be presented, as well as some initial physics results employing the new variable beam energy system. [ABSTRACT FROM AUTHOR]

The required peak current and peak voltage of ITER in-vessel vertical stability (VS) coil power supply are up to 80 kA and 2.4 kV, so VS coil power supply needs a pulse width modulation (PWM) rectifier to achieve high power factor operation under the highly transient power demand of the value of 144 MW. A new maximum current control method for three-phase voltage source PWM rectifier based on its mathematical model in $d$ – $q$ frame and improved by dual-closed-loop control method has been presented. This control method meets the fast power charging demand and the dc-side voltage stabilization demand of power supply, and achieves a unity or high power factor operation; its controller is easier to be designed and implemented than dual-closed-loop control at charging mode. The advantages and feasibility of this control method have been verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper presents a novel technique for the voltage droop compensation of long pulses in solid-state bipolar high-voltage Marx generators. Considering the modularity of Marx generators the compensation consists in adding one extra stage to perform as a pulsewidth modulation circuit. This stage voltage is added to the output positive or negative pulses, and an output LfCf filter is included to smooth the voltage pulse waveform. A five-stage laboratory prototype of this circuit has been assembled using 1200-V Insulated Gate Bipolar Transistors and diodes with 1000-V dc input voltage. The circuit was operated at 50-Hz bipolar pulse rate, giving 4-kV bipolar pulses, into a resistive load, with 100- \mu \texts pulsewidth and 9.5-ms relaxation time. The circuit was able to compensate 10% of bipolar pulse voltage droop. [ABSTRACT FROM PUBLISHER]

A 100-kV/60-A high-voltage power supply (HVPS) is developed to supply the auxiliary heating system for a J-TEXT tokamak. This power supply is based on pulse step modulation (PSM) technology and consists of 144 switch modules. To fulfill the isolation, control, and protection requirements, a control system based on the PCI extensions for instrumentation is designed with the PSM technology for the HVPS. Experimental results show that the system has a good control performance and fast response. Thus, the proposed system meets the control requirement of the 100-kV/60-A HVPS. [ABSTRACT FROM AUTHOR]

High-voltage double pulse of nanosecond duration (\sim hundreds of nanoseconds) with extremely short interval (\sim tens of nanoseconds) between the pulses can be used to study the double pulse effect in nanosecond laser ablation for laser-induced breakdown spectroscopy. A 0.5-GW compact pulsed-power driver is designed using the transmission line characteristics of the pulse forming line to generate two pulses with extremely short repetition interval. The impedance of the pulsed-power driver is 22 \Omega, and it generates two flat top high-voltage pulses of 100 kV, 100 ns duration with a interpulse repetition interval of 30 ns across the matched load. [ABSTRACT FROM AUTHOR]

The initial stage of atmospheric air breakdowns in Ka-band pulsed microwave fields was observed for the microwave power increasing to a maximum within a characteristic time of ~300 ps. Pulsed microwaves were produced by relativistic BWOs with output powers of ~170 and ~500 MW (4-ns and 300-ps FWHMs, respectively). The effects of air breakdown in the fields of microwave pulses of this type are pronounced when the radiation is extracted through the vacuum window of a horn antenna and when it is channeled in passing through waveguides and quasioptical lines. Of particular interest are modes in which repetitive pulsed microwaves are generated. [ABSTRACT FROM AUTHOR]