Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1996-08-07
1998-09-22
Ledynh, Bot L.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
361303, 361715, 361716, 361811, 361830, H01G 438, H05K 720, H02B 101
Patent
active
058123652
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to electricity and more particularly to an apparatus for mounting and cooling capacitors.
2. Information Disclosure Statement
The appearance of power transistors and SCR's led to modifying the generators intended for inductive heating.
The supply voltages for these switching devices are usually less than 1,000 V.
As a result, the voltages supplied by transistor or SCR-based inductive heating generators are less than 1,000.times..sqroot.2, i.e. about 700 V. In practice, most of these power sources deliver voltages comprised between 250 and 700 V.
The need to use an inductor, i.e. a reactor to transfer the power from the generator to the load to be heated, necessitates the creation of a reactive power whose value is usually 8 to 40 times that of the active power.
Consequently, it is necessary to have capacitor banks combined with the inductor, with properties allowing high currents to be supplied at voltage levels less than 700 V.
The operating frequencies of these devices are usually in the range of 40 to 400 kHz.
One of the classical means to build such banks is to mount in parallel capacitors with the highest capacitance possible and capable of delivering currents of a few ten to a few hundred amperes.
Assembling a high number of elements sets several technical problems: the heating by induction of the capacitors located close to the bank output terminals. between two or several capacitors in the a bank. This phenomenon, when occurring, will destroy the bank elements. cooled by water circulation; as a consequence, the whole bank or the greatest part of it will have to be disassembled to replace a capacitor.
The parallel mounting of a large number of capacitors results in the creation of a high current that must be conveyed to the bank output terminals through connecting means designed to generate negligible ohmic and inductive voltage drops.
These conditions are difficult to achieve.
The device hereunder solves all these problems.
SUMMARY OF THE INVENTION
This system deals with a means to group power capacitors cooled by conduction into banks containing any number of elements. The purpose of this device is to reduce to a negligible value the inductance of connecting terminals as well as the magnetic field generated by the currents flowing from each capacitor. Whilst mainly intended for inductive heating applications, this device also allows the conduction of the capacitor banks to the user inductor.
The device under this invention is mainly comprised of one or several pairs of metal bars made of thermally and electrically conductive to material, including the fastening means for the capacitors and cooled by water circulation through a channel provided over the whole length of bar.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a plurality of capacitors laid out on one side of cooling bars; and
FIG. 2 illustrates a plurality of capacitors laid out on both sides of cooling bars.
DESCRIPTION OF THE PREFERRED EMBODIMENT
It will be described, as a non restrictive example, by reference to FIG. 1 showing the device according to the invention, and to FIG. 2 which shows another possible embodiment of said device.
It is mainly comprised of two or several bars (3) made of thermally and electrically conductive metal cooled by channels (4) through which water (4) flows.
The capacitors are laid out astride two bard (3) by means of fastening screws (5).
The capacitors (1) can be laid out in any number, either on one side of the cooling bars (3) as illustrated in FIG. 1, or on both sides as illustrated in FIG. 2.
The distance between the collector bars cooled by water circulation is reduced down to a gap about 1 to 5 mm wide in order to confine the magnetic field created by the current flowing from each capacitor between the bars.
The magnetic field created by the large currents flowing between the collector bars (3) becomes little disturbing in as much as the distance between the magnetic field and the location of the nearest met
REFERENCES:
patent: 4211957 (1980-07-01), Alley et al.
patent: 4499524 (1985-02-01), Shioleno
patent: 5367431 (1994-11-01), Kunishi et al.
Database WPI, Week 7651, Derwent Publications Ltd, London, GB; AN 76-M0905X & SU, A, 502 381 (Gatterman) (No Date Provided).
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