Hironobu Yonemori

On the Heating Characteristic and Magnetic Flux of a Double-Coil Drive Type Induction Heating Cooker

This paper discusses the realization of a new type induction heating (IH) cooker that uses the double-coil. Adoption of double-coil is the main point of this new IH cooker. Current whose phase differs 180 degrees with each other is supplied to a pair of this double-coil, respectively. As the result, high frequency - 2 times that of supplying current frequency-eddy current flows in the metal load. Using this new technique mentioned above, heating the non-magnetic metals that had been difficult to heat became possible. In this time, heating characteristics of proposition method is made clear. Furthermore, it has been made clear that there is close relationship between heating characteristics and magnetic flux distribution. And, as for the aluminum and the copper we found unique magnetic flux distribution. This developed method has a big merit: this method can double present highest frequency which can be obtained by the power-electronics technic. In other words, it is the epoch-making method where it can apply to also the induction heating apparatus for industry not just the IH cooker. As a conclusion, we report the fact that our system can heat the non-magnetic metals successfully

Temperature control of a double-coil drive type IH cooker by means of the PDM control provided with audio noise suppression

This paper discusses the achievement of the temperature control method of a double-coil drive type induction heating (IH) cooker. Double-coil drive type IH cooker invented by us, is the new induction heating method which can heat nonmagnetic metals. We have already proposed the PDM temperature control method which can be adopted in the proposed system. However, there gives rise to the audio noise trouble when the metal be heated. We investigated the cause of this noise. In this paper, PDM temperature control method that can suppress the audio noise is proposed. The heating characteristic of this new PDM temperature control method is described in this paper. And, active power and temperature characteristic to the PDM-duty-ratio were made clarified. As a conclusion, we report on the successful results on the PDM temperature control system that can be applied for the double-coil drive type IH cooker, which enables audio noise suppression.

Study on the high frequency acoustic noise and vibration of a pan generated by an IH cooker

This paper discusses high frequency acoustic noise generated by an IH cooker. Mechanism of the high frequency acoustic noise generation is clarified by experimental study. Recently, influence of the electromagnetic wave on the human body is worried. They symptoms some users of home electronic appliances feel are headache and nausea. There is a report that other users who are using IH cooking heater also feel these symptoms. We have discovered that the high frequency acoustic noise, which is generated from an IH cooker, indicates strong-level sound pressure. High frequency strong acoustic noise must not be ignored, because its danger on our health is reported scientifically and medical standpoints. Then, it becomes necessary to examine the suppressing method of high frequency acoustic noise. In this paper, generating mechanism of the high frequency (20 kHz∼) acoustic noise is clarified by the experiments.

Relation of gap length and resonant frequency about a double-coil drive type IH cooker

This paper studies possibility of soft switching operation through the calculation of the circuit constants in the double-coil drive type induction heating (IH) cooker, which had been proposed by us. Therefore, we experimentally clarified the effect of (a) gap length between metal load and heating coil and (b) kinds of the metal loads, on the characteristic of the drive circuit in the double-coil drive system. Double-coil drive system is an excellent new technique that can control the increase of switching loss and heating coil loss. Power device used in the IH cooker needs soft switching operation with a view to reduce the switching loss. However, soft switching operation will become impossible under the condition of (a) change of the gap length between the metal load and heating coil; and (b) change of the kinds of metal loads, because these condition brings the change of the inductance-value. So, it becomes very important to evaluate the heating coil inductance in securing the stable soft switching operation. We have focused our attention on the change of inductance-value of the heating coil caused by (a) change of the gap length between the metal load and heating coil; and (b) change of the kinds of metal loads. As the first step of deriving inductance-value, we measured both (a) resonance frequency and (b) equivalent impedance under the resonance. Then, we compared these characteristics with data on a single-coil system, and investigated the possibility of applying skills used in the single-coil system. As the result, it becomes clear that the equivalent impedance on the single-coil system and on the double-coil system shows the strong resemblance. On the other side, the equivalent impedance of the single-coil is lower than the equivalent impedance of the double-coil, and their difference becomes larger when the gap length becomes large. Resonant frequencies of the double-coil system for each gap length are about 0.7 times that of the single-coil system. From theses results, we arrived at a conclusion that the stable soft switching can be realized on the double-coil system, for the practical cooking application.