Enrique J. Dede

Induction Heating Technology and Its Applications: Past Developments, Current Technology, and Future Challenges

Induction heating (IH) technology is nowadays the heating technology of choice in many industrial, domestic, and medical applications due to its advantages regarding efficiency, fast heating, safety, cleanness, and accurate control. Advances in key technologies, i.e., power electronics, control techniques, and magnetic component design, have allowed the development of highly reliable and cost-effective systems, making this technology readily available and ubiquitous. This paper reviews IH technology summarizing the main milestones in its development and analyzing the current state of art of IH systems in industrial, domestic, and medical applications, paying special attention to the key enabling technologies involved. Finally, an overview of future research trends and challenges is given, highlighting the promising future of IH technology.

Improving the Efficiency of IGBT Series-Resonant Inverters Using Pulse Density Modulation

This paper analyzes a high-power (50 kW) high-frequency (150 kHz) voltage-fed inverter with a series-resonant load circuit for industrial induction heating applications, which is characterized by a full bridge inverter made of insulated-gate bipolar transistor and a power control based on pulse density modulation (PDM). This power control strategy allows the inverter to work close to the resonance frequency for all output-power levels. In this situation, zero-voltage switching and zero-current switching conditions are performed, and the switching losses are minimized. An additional improvement of inverter efficiency is achieved by choosing appropriate values of the modulation index. Results are verified experimentally using a prototype for induction hardening applications. A comparative study between the PDM and the classical power control by frequency variation will be made.

A bidirectional and isolated three-phase rectifier with soft-switching operation

A bidirectional-power-flow three-phase rectifier with high-frequency isolation and all-digital control, based on the matrix converter topology, is analyzed in this paper. The selected topology consists of a bidirectional three-phase-to-single-phase reduced matrix converter with power-factor correction and a bidirectional active rectifier. The inclusion of the isolation transformer at the switching frequency permits the reduction of volume and weight. By synchronizing the commutation of both converters and adding a saturable inductor and a blocking capacitor it is possible to achieve soft commutation for most of the semiconductor elements. An all-digital control based on a digital-signal-processor and a field-programmable gate array was used to implement space-vector modulation and output current regulation. This power converter is intended to feed the low-energy correction magnet of a particle accelerator. Experimental results of a 1.5-kW 20-kHz prototype are presented to illustrate the performance of the proposed topology.

Improving the Reliability of Series Resonant Inverters for Induction Heating Applications

This paper analyzes a high-power (100-kW) high-frequency (50-kHz) voltage-fed inverter with a series resonant load circuit for industrial induction heating applications which is characterized by a full-bridge inverter composed of isolated-gate bipolar transistors and a new power control based on phase-shift (PS) control. This power control circuit incorporates a load-adaptive variable-frequency controller and automated blanking time management in order to allow the inverter to work in zero-voltage switching for all output power levels and load conditions. An important improvement of the inverter reliability is achieved by choosing an appropriate and novel switching sequence for the PS inverter. The results are verified experimentally using a prototype for induction hardening applications. A comparative study between the proposed and standard PS power control will be made.

Comparative Study of a Single Inverter Bridge for Dual-Frequency Induction Heating Using Si and SiC MOSFETs

The induction surface hardening of parts with nonuniform cylindrical shape requires a multifrequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium- and high-frequency power signals to the heating inductor. An initial study is made to select the most appropriated topology for this application. The resonant output circuit is analyzed, and a design procedure is presented. The selected inverter operation is described and simulated. Simulations are experimentally verified on a 10-kW dual-frequency resonant inverter operating at 10 and 100 kHz using MOSFETs of silicon (Si) and silicon carbide (SiC) technology. A comparative study is presented based on the measurements of power losses and the energy efficiency of the inverter using both types of MOSFETs.

High Power Resonant Inverter with Simultaneous Dual-frequency Output

Induction surface hardening of parts with non-uniform cylindrical shape requires a multi-frequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply constituted of an only inverter circuit and a specially designed output resonant circuit. The whole circuit supplies both medium and high frequency power signals to the heating inductor simultaneously

Steady-state frequency analysis of the "LLC" resonant inverter for induction heating

In this paper, the main steady-state frequency properties of the LLC circuit are described. The advantage of its use on induction heating applications is proved, in contrast with the SRI (series resonant inverter). This analysis will allow the future design of a frequency control strategy for the inverter. Finally, a simple design algorithm is proposed, which satisfies the power specifications and limits the stress current in the switches.

A multiple output regulator using the variable transformer turns ratio regulator technique

The use of a new regulation concept, parallel regulation, permits the construction of a power converter with multiple outputs that eliminates cross-regulation. The regulation principle-named variable transformer turns ratio regulator because it behaves as a transformer with an electronically controlled turns ratio-has been implemented in a zero voltage zero current power switching topology that was initially developed for space power applications. High efficiency, low mass, simplicity and low number of components are the main characteristics of the power converter.<<ETX>>

Features and design of the voltage-fed L-LC resonant inverter for induction heating

In this paper the main advantages of the L-LC resonant inverter for induction heating over the conventional voltage-fed SRI are presented: its lower transformer current levels and its short-circuit capability. The design algorithm of the L-LC is presented, and the transformation equations which allow the conversion of the SRI into the equivalent L-LC are deduced, guaranteeing the same working frequency and power dissipation with the same inverter, heating coil and piece. Experimental results are also presented, showing the continuous and reliable behavior of the inverter during the short-circuit.

An all-digital controlled AC-DC matrix converter with high-frequency isolation and power factor correction

A three-phase rectifier with high frequency isolation and four-quadrant operation is described and analyzed in this paper. The selected topology consists of a bidirectional three-phase to one-phase cycloconverter, based on the matrix converter topology, a high frequency transformer and a bidirectional active rectifier. Main features of this power converter are the ability to regenerate energy back to the utility, unity power factor at the mains and reduction of volume and weight thanks to the high-frequency isolation. An all-digital control based on a field-programmed-gate-array (FPGA) and a digital-signal-processor (DSP) was used to implement space vector modulation (SVM) and output current regulation, respectively. Experimental results verify the feasibility of the proposed converter.