Patent ID: 7002119

Claim:
A device of liquid heating by electromagnetic induction and shaft-circuit using three-phase industrial frequency power, comprising; an El-formed core comprising multi-layered silicon steel sheets to form a closed three-phase magnetic loop, wherein each of three core legs of the El-formed core is coiled with a primary winding to form a three-phase primary winding, that can be connected by star or delta connection with the core and the three-phase primary windings being all enclosed in a metal shell, in which a space within the shell is packed with insulating fillers to form a completely-enclosed solid body, wherein the metal shell is set along the closed three-phase magnetic loop to form a secondary side of each phase that surrounds the core and the primary winding of each phase so as to constitute a main heating body of the device, and also acts as a protecting shell and a radiator for the core and the three-phase primary winding; wherein when the secondary side of each phase is conductively connected through the same said metal shell to create an interphase short-circuit and a tree-phase short-circuit in the secondary side, a vector sum of the three-phase short-circuit comes to zero and the metal shell is at zero potential; wherein said metal shell is provided with a top tray and a bottom tray, a shell case, rectangular tubes and a connector base; the connector base being welded to one side of the shell case and leading wires of the three-phase primary windings being led from the connector base; wherein the top tray and the bottom tray are welded to top and bottom ends of the shell case respectively; of the rectangular tubes, a first rectangular tube is positioned between two phases of the three-phase primary windings and between upper and lower yokes of a corresponding said core, while a second rectangular tube is positioned between two phases of the three-phase primary windings and between the upper and lower yokes of the corresponding core; the first and second rectangular tubes passing through front and rear sides of the shell case while four sides of the front and rear ends of the rectangular tubes are respectively welded to front and rear surfaces of the shell case; wherein left and right sides of the rectangular tubes together with the shell case create separately three metal rings as secondary sides to surround the primary winding of each phase, while upper sides of the rectangular tubes together with the shell case and the top tray create separately four metal rings as secondary sides to surround the upper yoke and the lower sides of the first and second rectangular tubes together with the shell case and the bottom tray create separately two metal rings as secondary sides to surround the lower yoke; and wherein the metal rings acting as secondary sides make use of an effective length of the three-phase magnetic loop of the core so that an output power of the device is maximized.