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Very low frequency (VLF) high-voltage (HV) sinusoidal test waveforms are suitable for testing characteristics and insulation qualities of long buried power cables. Unlike as with conventional PWM converters, a newly developed LCC resonant inverter combined with a symmetrical three-stage voltage multiplier rectifier is introduced in this paper to generate VLF HV sinusoidal waves. Due to the wide ranges...
This paper presents educational software for a PIC microcontroller used to study and design resonant electronic ballasts. The digitally controlled resonant inverter enables students to investigate the ballast behavior when changing the values of parameters. The soft start-up sequence and control of the LCsCp resonant inverter applied to supply high intensity discharge (HID) lamps is implemented in...
In recent two decades the application of high voltage test systems using the concept of very low frequency is more and more accepted by industries. This contribution deals with the control design for a novel high voltage test system generating a true sinus test voltage of 85 kV (RMS) at 0.1 Hz based on a zero-voltage switched LCC-resonant converter and a 3-stage Cockcroft Walton voltage multiplier...
The paper describes a new three-phase to single-phase matrix converter featuring unity input power factor, very low input total harmonic distortion, and soft-switching over the full power range, for high frequency induction heating applications. A variable output pulse density modulation scheme has been proposed for stable operation of the converter, with the notable feature of requiring no on-line...
The power transistor (IGBT) is one of the most important components of the inverter of domestic induction cookers. For this application the maximum junction temperature (Tjmax) of the IGBT is one of the most critical design parameters because the cooker has to decrease the output power when the junction temperature is near to Tjmax of the device. The junction temperature (Tj) of the IGBT principally...
Resonant converters offer an efficient alternative to linear supplies for pulsed electrochemical processes. This paper presents an open loop and closed loop comparison between the dc-dc series and series-parallel resonant converters for a pulsed 500 W load. Placing restrictions on the resonant tank parameters proves necessary to achieve continuous transient waveforms. Generalized averaging is applied...
This paper presents a method to prevent voltage ringing on the main switch of a full-wave zero-current-switch quasi-resonant (ZCS-QR) boost converter during its turn-off period. The proposed method does not incorporate any dissipative snubber in order to maintain efficiency of the converter. Severe clamp diode reverse recovery current and non-zero turn-on current occurred on the former diode-clamped...
Nowadays the possibility to increase switching frequency in power converters has allowed minimizing their size and weight, and has permitted the improvement of their power density. This has been achieved by using soft-switching techniques that reduce the switching losses and the stress the switches suffer, quite of this techniques rely on resonance concept. However this increase of frequency is not...
For the European XFEL at DESY in Hamburg (Germany) a klystron modulator prototype is built, based on the proven so called ldquoBouncerrdquo principle. Although it is a well known technique, the bouncer modulator faces some difficulties on flattop stability and protection of the klystron. In this paper improvements for these problems are presented. Besides a chosen solution for constant input power...
One of the most important advantages in using piezoelectric transformers (PT) is that they operate at high frequencies with a very good efficiency, tipically higher than 95%. This paper presents a DC/DC converter based on two piezoelectric transformers which duplicates the output voltage frequency ripple, maintaining the switching frequency. Also, the converter operates at a fixed frequency, and an...
One of the major drawbacks of high-ratio step-up transformers is the high value of their secondary side capacitor. This value is reflected at the primary side giving rise to a non-desirable one. There are some converters which include this capacitor in the topology and can cope with it, and even more, they need it. Particularly, in high-voltage applications, we will find transformers with a large...
This paper describes experimental results obtained from a sliding-mode quantum controller implementation applied to a laboratory setup of a series-resonant converter. The motive for the design of the latter controller has been to achieve maximum operational efficiency. The newly formulated sliding surface indeed assures active minimization of the system energy loss in any arbitrary chosen full power...
This paper considers the calorimetric measurements of losses and the optimisation of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10 %, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms to...
This paper aims to determine the maximum frequency achievable in a 25 kW series inverter for induction heating applications and to compare, in hard switching conditions, four fast transistors IGBTs 600 A and 1200 V modules encapsulated in 62 mm from different suppliers. The comparison has been done at 25 and 125degC in a set-up. Important differences between modules have been obtained depending on...
Two bi-directional high-power dc-dc converter topologies with zero-voltage-switching (ZVS) operation over a defined load range are compared. These are the non-resonant dual-active bridge (DAB) and the dual-active series-resonant converter (DSRC) in super-resonant mode. A unified mathematical model describing both converters is presented, which treats the DAB as a boundary case of the super-resonant...
The application of pulse density modulation (PDM) control to a rectifier-series resonant inverter set makes it possible to implement an AC/AC converter with good performances (size and efficiency). However its power factor decreases when the load power varies. We propose a dual-PDM control strategy adapted to a rectifier - parallel resonant inverter set. This converter is obtained by application of...
Parasitic high frequency (HF) phenomena for adjustable speed drives (ASD) fed by inverters with fast switching semiconductors are well known in literature. Although many advantages rise when using higher switching frequencies, like lower motor harmonics and audible noise, feeding the electrical machine through long cables lead to high voltage overshoots at motor terminals due to cable-motor impedance...
In high frequency induction heating applications, the inverters used to generate the high frequency alternating current are implemented with MOSFET. In order to avoid the failure of the MOSFET intrinsic diode, each switch is formed by two extern diodes which are connected to the MOSFET, one in series, and the other one in anti-parallel with both devices. If the power regulation is achieved by using...
This paper presents a very high efficiency AC/DC/DC converter topology suitable for all those applications dealing with high power requirements and good handling of very wide input voltage variations, such as Traction auxiliary services. In particular, to enhance high conversion efficiency together with high reliability and cost reduction, the document addresses the use of a double stage power architecture...
A new firing strategy for a resonant current fed inverter based in switches formed only by IGBTs, without the series diode, is presented in this paper. It is described the behavior of the inverter topology proposed and two different strategies for its reliable operation are explained: control of the switching current level, and control of the over-current through the anti-parallel diodes. Dynamic...
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