A Unity Power Factor Induction Cooktop: Design Issues and a Novel Approach to Measurement and Elimination of Conducted EMI (IEEE)(图文)

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Barış Çolak、H

发布时间：2007-12-12   来源：IEEE

Writer：

Barış Çolak

Information Technologies and Electronics Research Institute (BİLTEN)

METU 06531 Ankara Turkey

Phone: 90 (312) 2104402 baris.colak@bilten.metu.edu.tr

H. Bülent Ertan

Middle East Technical University and BİLTEN

Electrical and Electronics Engineering Department

06531 Ankara Turkey

Phone: 90 (312) 2102359 Fax: 90 (312) 2101261

Ertan@metu.edu.tr

Abstract

The paper describes how a low cost solution is realized to the problem of controlling the operation of a resonant inverter designed for an induction cooker. The controller permits both the control of the output power level of the cooker and assures a unity power factor sinusoidal current to be drawn from the mains side. Then attention is paid to the harmonic content of the input current and conducted EMI problem. A procedure is presented, which is used for assessing and improving EMI performance of the cooker. This procedure is applicable to all types of electronic devices. The EMI measurement in this procedure uses a digital storage oscilloscope and widely used mathematical software both of which are readily available in most laboratories. Hence, the need for using an expensive noise separator or spectrum analyzer is avoided. The procedure is applied to the induction cooker system and the design steps and test results are presented. These results are compared with measurements made by a spectrum analyzer.

1. Introduction

Principle of induction heating has been used for many years for billet heating, surface heat treatment, and melting. In the recent years, less expensive power transistors capable of operating at higher frequencies made possible, the use of this principle in home appliances, such as induction cooktops. The advantage of this technology, against its counterparts is its high efficiency and flameless thus safer operation. Furthermore, fast cooking and quick reaction time of such equipment is an added advantage.

In the most general terms the operation of the inverter is as follows; a high frequency current is generated in the heating coil. This current generates a high frequency magnetic flux and induces eddy currents in a removable cookware, which is placed above the heating coil. The cookware should be made of magnetic materials, such as iron. These eddy currents directly heat the cookware and hence the food contained in the cookware.

Induction cooktop electronics however, needs to be reliable and inexpensive to compete with more conventional solutions. Furthermore, some solution must be found to comply with EMI/EMC regulations applicable to household appliances. Satisfying all these requirements is not easy especially when the cost is of prime consideration. This paper first briefly describes one such solution developed by the authors. The next issue addressed is the measurement and design of the EMI filter. This process can be quite costly and requires expensive equipment. The paper describes a novel approach, which permits the use of ordinary laboratory equipment to accomplish this task.

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