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In this paper, the results of a 2.88-MW solid-state long-pulse modulator, which has been designed for the new linear collider at the european spallation source in Lund, are summarized. The presented modulator generates an output voltage pulse of 115 kV with a pulselength of 3.5 ms. The main components of the modular system, which include a series–parallel resonance converter, a high-voltage high-frequency transformer, and an output rectifier, are discussed. The modulator design is verified by measurements performed with a full-scale prototype, which is operated under nominal load conditions. A detailed output voltage ripple evaluation is given, and in addition, the system design has been proven by a 7- and 2/3-h heat run test. All specifications are well within the given limits, and the maximum occurring temperatures in the transformer stay below 110 °C even under worst case assumptions. The system achieves a pulse efficiency (determined by the pulse shape) of 96.78%, an overall electrical system efficiency of 91.9%, and a combined pulse system efficiency of 89%. [ABSTRACT FROM AUTHOR]

In this paper, two control strategies for voltage balancing in a modular serial parallel resonant converter modulator system, which is used in a high-voltage-pulsed power application, are presented and verified by simulations and measurements. The system is based on two series parallel resonant converter modules, forming an input series output parallel stack. To obtain the given output voltage pulse of 115 kV, nine of these input series output parallel stacks are connected in parallel at the input and in series at the output, forming an input parallel output series system. A robust input voltage balancing by an auxiliary circuit and an output voltage balancing by control is introduced and proven by measurements. In addition, an alternative approach, where the input and output voltage balancing is achieved purely by control, is given and verified by simulations. For designing the control of this system, a large and a small signal model is derived and the influence of component tolerances is investigated. [ABSTRACT FROM AUTHOR]

Modern accelerator driven experiments like linear colliders or spallation sources are supplied by RF amplifiers using klystrons. The cathode voltage for these klystrons can be generated by long pulse modulators generating highly accurate voltage pulses in the length of milliseconds. Conventional designs using pulse transformers become huge for long pulses. The series-parallel resonant converter (SPRC) topology avoids this drawback as the transformer is operating at high frequencies. This paper presents a comprehensive design approach for SPRC modules, which is based on an optimization procedure containing an electrical model of the resonant circuit and a thermal model of the semiconductors. In addition, an insulation and a leakage design procedure and a thermal model of the transformer are also presented. Finally, this procedure provides the optimal design parameters of the resonant circuit elements. With these parameters, a global optimizer chooses the optimum amount of modules connected in series and/or in parallel to fulfill the given restrictions. The efficiency of a basic SPRC-module is 94.7% with a pulsed power density of 4.63 kW/l. [ABSTRACT FROM PUBLISHER]

In this paper, the charging precision of a 40-kW 3-kV soft-switching boost converter for capacitor charging is investigated. At the beginning, an overview on the topology and the control of the converter is given. Then, two different feedback controllers are presented and compared analytically to determine their sensitivity on noisy input variables. An algorithm to investigate the charging precision is illustrated. This algorithm considers the signal-to-noise ratio (SNR) of all measured signals, the controller output limitations, quantization related errors, the finite resolution in the digital domain, and the switching signal jitter to calculate the charging precision. All effects mentioned before are analyzed separately. This analysis shows that the output voltage measurement SNR is the key parameter for the charging precision. Then, measurements are performed to verify the model used to calculate the precision. These measurements show that the measured precision is only 6% higher than the precision predicted by the model for the used setup. Finally, the charging precision of the presented converter is analyzed including all considered effects. The repetition accuracy of the converter is determined to be 8.3 ppm at an output voltage of 3 kV, neglecting the load connection and the input voltage variation during one switching cycle. [ABSTRACT FROM PUBLISHER]

In this paper, a procedure for optimal transformer design with a variable set of constraints for pulse transformers with a pulse range of 3–140 \mus is presented. During the optimization procedure, the pulse shape is analyzed in the time domain, ensuring that the pulse constraints, such as rise time and overshoot are met. For accurate prediction of the pulse shape, analytical approaches are proposed to estimate the distributed capacitance and leakage inductance of the transformer. The analytical approach is verified by 2-D-FEM simulations and measurements. The optimization procedure considers pulse, core, winding, demagnetization losses, and losses of the primary switches. First, the procedure is applied to an existing pulse transformer with specifications for SwissFEL. An improvement of 16.6% in conversion efficiency is achieved in comparison with the existing design. In a second step, the procedure is applied to specifications of the compact linear collider, which demands high conversion efficiency. The resulting optimal transformer consists of three cores with five primary turns and requires a tank volume of 0.915 m^3. In an optimal configuration, an overall conversion efficiency of 97.7% is achieved for the considered system including pulse losses. [ABSTRACT FROM AUTHOR]