N. Vishwanathan

Comparison of control methods for high frequency IH cooking applications

This paper presents the comparison of different fixed frequency control strategies for Induction Heating (IH) applications. Phase shift control method (PSM), Asymmetrical duty cycle control (ADC) method, and Asymmetrical voltage cancellation (AVC) methods are used to control the output voltage in IH applications. The performance analysis of the control methods is discussed in this paper. The MATLAB simulation results are given to validate the control schemes.

Single Inverter Configuration for Simultaneous Dual Frequency Induction Hardening with Independent Control

Summary Induction hardening is a heat treatment process which selectively heats parts of work-piece with different size and shape. Components like gears require different frequencies with inner core requiring low frequency and outer surface requiring high frequency. Simultaneous application of low and high frequency currents is desirable for proper hardening of gear. This paper proposes a two inverter topology with a load resonant circuit which can provide independent and simultaneous control of low and high frequency currents through the load coil. The load circuit is a combination of two series resonant circuits which operates at the desired low and high frequencies. Power control is achieved with phase modulation of low and high frequency inverters.

A Two Stage Power Converter Topology for High Voltage DC Power Supplies Under Pulsed Loads

Summary High voltage power supplies for radar applications are investigated, which are subjected to high frequency pulsed load (above 100 kHz) with stringent specifications (regulation < 0.01%, efficiency >85%, droop < 0.5 V/micro-sec.). As good regulation and stable operation requires the converter to be switched at much higher frequency than the pulse load frequency, transformer poses serious problems of insulation failure and higher losses. The solution to this problem as a single stage converter is very difficult. In converters operating at high voltage and high frequency, the insulation failure of high voltage transformer is very common. Skin and proximity effect result in higher power losses. Because of high turns ratio, the winding capacitance results in delays and current spikes. Hence a two-stage converter has been proposed. It isolates the HV transformer from high frequency requirement of the regulation. Its block diagram is shown in the following figure. One stage of it, namely, Base power supply(BPS), operates at low frequency and produces majority of the output voltage and power. The other one, namely, fast power supply (FPS), operating at high frequency and low output voltage supplies the remaining power and takes care ofthe transient variations of line and load and provides the required regulation. The final output voltage is obtained as sum of the outputs of BPS & FPS. Each of the BPS & FPS use phase modulated-series resonant converter as the power-processing unit with zero voltage switching (ZVS). This topology also allows load frequency variation over a certain range.

Hybrid controlled dual frequency inverter for two load induction cooking application

Abstract Induction heating applications have become more popular due to its advantages like non-contact heating, environment friendly and high efficiency. In this paper, a two load induction heating system is proposed for cooking applications. A single full-bridge inverter is powering the loads at two different frequencies. These loads are controlled independently and simultaneously. The prototype has been built and tested for 115 W of low frequency and 60 W of high frequency power. Phase shift control and pulse density techniques are used for power control. Experimental results presented are in good agreement with simulation results.

Full bridge series resonant inverter for induction cooking application

The induction heating principle has been successfully introduced for about twenty years in domestic cooking appliances. In this paper a simple power control scheme for series resonant full bridge inverter with phase shift control at constant frequency is proposed. The proposed control scheme has the output power control in efficient zero voltage switching. The control principle described in detail and the validity is verified through the simulation and experimental results at 35 kHz.

A three-output inverter for induction cooking application with independent control

Abstract In Induction Heating (IH) cooking appliances more than one output is highly desirable. A three leg inverter is proposed for three output IH cooking application. It is operating with a constant frequency of 30.5 kHz and allows the power control in loads independently. On-off control technique in cyclic manner is used. The number of switching devices per load is two (i.e. one leg per load). Thus utilization of the switching devices is improved. It can be extended for more number of loads also. A 260 W prototype has been implemented. Experimental results have good agreement with the simulation results.

Multiple-Load Induction Cooking Application with Three-Leg Inverter Configuration

Inverter configurations for multiple-load induction cooking applications need development. Inverter configurations for induction cooking applications are used in home appliances based on single coil inverters. For multiple-load configurations, multiple coils are used. They require proper inverters, which provide independent control for each load and have fewer components. This paper presents a three-leg inverter configuration for three load induction cooking applications. Each induction coil powers one induction cooking load. This configuration operates with constant switching frequency and powers individual loads. The output power of the required load is controlled with a phase-shift control technique. This configuration is simulated and experimentally tested with three induction loads. The simulation and experimental results are in good agreement. This configuration can be extended to more loads.

Design and control of two-inverter dual frequency induction hardening

Dual frequency inverters are used for induction gear hardening. Two inverter topology for dual frequency operation is considered. Design and control aspects related to dual frequency inverters are presented in this paper. Zero voltage switching aspects related to this configuration are explained. Performance of this inverter is presented along with simulation and experimental waveforms.

Class-D/E resonant inverter for multiple-load domestic induction cooking appliances

This paper presents a class - D/E resonant inverter for multiple-load domestic induction cooking appliances. Most of the induction inverter configurations used in home appliances is based on single coil inverter. In these configurations, the vessel size cannot be more than induction coil size. The proposed configuration is suitable for any size of vessel and also can be used for multiple-loads. It operates with constant switching frequency and independent control of each load. The output power of each load can be controlled with asymmetrical duty cycle control technique for class-D configuration and with asymmetrical voltage cancellation control technique for class-E configuration. The proposed configuration and control techniques are simulated and experimentally tested with two loads. Simulation and experimental results are in good agreement. This configuration can be extended to multiple-loads.

A full bridge resonant inverter with multiple loads for induction cooking application

In this paper full bridge resonant inverter with independent output power control of two loads for induction cooking application is presented. The proposed configuration can be operating with efficient ZVS by constant switching frequency and constant duty ratio of full bridge resonant inverter. By varying the duty ratio of load switch, each load output power is controlled individually. And in this proposed configuration, synchronization of load switch switching pulse with inverter output voltage is done for output power control. The proposed configuration can be extended to multiple loads. It is more reliable for multiple load induction cooking application with output power control of each load independently. For theoretical predictions, the proposed configuration of two load full bridge resonant inverter for induction cooking application with independent control of each load is simulated in MATLAB/Simulink environment.