Electric heating – Inductive heating – With power supply system
Patent
1998-09-11
2000-04-04
Jeffery, John A.
Electric heating
Inductive heating
With power supply system
219630, 219428, H05B 608
Patent
active
060464429
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a temperature controller and an starting method of an electromagnetic induction heating apparatus which possesses a heating element made of magnetic material to a temperature controller and starting method to heat and start the electromagnetic induction heating apparatus without a magnetic transformation of the heating element made of magnetic material.
BACKGROUND OF ART
A construction of a prior example concerning such kind of an electromagnetic induction heating apparatus will be described based on FIG. 6.
The electromagnetic induction heating apparatus comprises a pipe 11 formed of an insulator, a heating element 12 in a fluid introduced in the pipe 11 and a coil 13 rolled around the pipe 11, and generates heat by an electromagnetic induction caused between the heating element 12 and the coil 13. A high frequency inverter 5 with a sensorless high power factor is used as the high frequency electric current generator for making an alternating field on the coil 13. A controller 3 controls an output of the high frequency electric current generator, which includes a phase shift controling device 3a and a gate driver 3b. A temperature sensor 17 is fixed on the side of outlet of the pipe 11. A temperature regulator 2 is connected with the phase shift controling device 3a. In addition, the high frequency electric current generator includes a rectification section 22 for an alternating current power supply 21, a non-smoothing filter 23 and an inverting section 24.
Normal functions of the above mentioned electromagnetic induction heating apparatus will be described. At the time of ordinary running, a low-temperature fluid 14 is supplied from a lower side of the pipe 11. The low-temperature fluid 14 turns into a fluid 15 of the turbulent flow within the heating element 12. The fluid 15 of the turbulent flow directly exchanges heat with the heating element 12 and turns into a high-temperature fluid.
The high-temperature fluid is discharged from an upper side of the pipe 11. A temperature of the high-temperature fluid is measured by the temperature sensor 17. An instruction corresponding to a difference between the high-temperature fluid and a required temperature is output from the temperature regulator 2 to the phase shift controling device 3a. The instruction is input in the high frequency electric current generator 5 through the gate driver 3b. Then, an electric current from the high frequency electric current generator 5 is appropriately controlled. According to the direct heating type of the electromagnetic induction heating apparatus 1, a high heat conductive efficiency is achieved by making heat conductive areas of the heating elements 12 large. Hence, the time when temperature raises up till a required temperature can be shortened. In other words, a starting-up time for starting heating at the required temperature can be shortened.
The heating element 12 generates heat itself by electromagnetic induction then heats up a fluid directly. Therefore, special material is used for the heating element 12. The material of the heating element required to be a ferromagnet for generating heat by electromagnetic induction, and, to be efficient in corrosion resistance since it directly contacts with the fluid. As the material which satisfies the above conditions, there is a stainless steel of martensite group which has Cr,Fe as the principal ingredient and is proposed in a patent application No. H6-297287.
In order to further shorten the starting-up time for starting heating at the required temperature, it is proposed to heat the entire electromagnetic induction heating apparatus in advance. In this regard a fluid is filled in a pipe 11, and a heating element 12, a temperature sensor 17 and so on are in the fluid. The pipe 11, the heating element 12 and the fluid are preheated when the high frequency electric current generator 5 operates.
A significant difference results between a fluid temperature detected by the temperature sensor 17 and a real temperature of the heating e
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Microfilm of the specification and drawings annexed to the written application of Japanese Utility Model Application No. 19214/1990 (Laid-open No. 110790/1991) (Tokin Corp.), Nov. 13, 1991, p. 5, line 17 to p. 8, line 5; Figs. 1 to 4.
Microfilm of the specification and drawings annexed to the written application of Japanese Utility Model Application No. 20267/1990 (Laid-open No. 110791/1991 (Tokin Corp.), Nov. 13, 1991, p. 5, line 2 to p. 6, line 19; Figs. 1 to 4.
Dede E.J., et al.: "On the Design of Medium and High Power Current Fed Inverters for Induction Heating," proceedings of the Industry Applications Society Annual Meeting, Dearborn, Sep. 28, -Oct. 1, 1991, vol. 1, Jan. 1, 1991, Insttitue of Electrical and Electronics Engineers, pp. 1047-1053.
Kawamura Yasuzo
Uchihori Yoshitaka
Jeffery John A.
Kabushiki Kaisha Seta Giken
Pwu Jeffrey
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