Abstract: A low-frequency electromagnetic induction heater includes a plurality of leg iron cores, a corresponding yoke iron core arranged on the leg iron cores, an induction coil wound around each leg iron core, and an iron plate or metal vessel for producing Joule heat with which the leg iron cores or induction coils are substantially in direct contact. The spaces between the yoke iron core, the leg iron cores and the induction coils are solidly filled with a resinous substrate which has been molded using molten resin. The induction heater produces less noise than other such heaters while providing a higher level of electromagnetic flux density.

Abstract: Disclosed is a low-frequency electromagnetic induction heater which comprises at least six induction coils each having a circular configuration and positioned in a circular and symmetrical configuration. The coils form three sets of coils such that each set of coils receives electrical power in a different phase from a three- phase electrical power source, such as a three-phase alternating current power source. The coils are interconnected such that the current flows from a first coil to a second other coil substantially opposed to the first coil. In a preferred embodiment, the heater consists of six coils connected in a three-phase double delta connection. This invention provides for heating of the heating element with continuous attraction to the induction coils, a substantial increase of electromagnetic flux density, prevention of noise due to electromagnetic vibration of the heating element, and high thermal efficiency.