Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1996-05-31
1998-01-06
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361 86, 337 17, H02H 100
Patent
active
057061610
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to protection devices for electrical systems and, in particular, discloses a device which protects against hazardous conditions that arise through open circuits.
BACKGROUND ART
In the neon lighting industry, high tension (HT) transformers are used to supply a high voltage, typically about 15 kV, to a glass tube filled with an inert gas so as to provide illumination. Problems arise with the use of such transformers when the high tension output thereof becomes open circuit, typically due to breakage of glass tubing or through a disconnection of one or more high tension supply leads. When an open circuit occurs, the output potential of the HT winding increases dramatically and, over a period of time, typically between thirty minutes and six hours, a substantial temperature rise within the transformer can cause the transformer to fail. Where the HT output is not contained within a completed circuit, the high tension presents a fire hazard to nearby materials.
It is known to use an electronic open circuit monitor arranged at the primary winding of the high tension transformer to overcome this problem. Such a monitor is configured to identify a drop in primary winding current corresponding to the high tension secondary winding going open circuit. Upon detecting the drop, the open circuit monitor electronically disconnects the primary thereby removing any potential difference from the outputs of the secondary winding. However, such electronic devices, whilst effective, are often in practice difficult to calibrate and are relatively expensive in terms of their component count and complexity.
SUMMARY OF THE INVENTION
It is an object of the present invention to substantially overcome, or ameliorate, the abovementioned difficulties through provision of an alternative open circuit protection device.
In accordance with one aspect of the present invention there is disclosed a protection device for electrical systems, the device comprising an insulating member enclosing first and second electrical contact pieces separated by a protection member, and a biasing member for biasing at least the first contact piece to sandwich the protection member between said contact pieces, wherein the protection member is configured to disintegrate upon a predetermined potential difference being reached between the contact pieces, the disintegration of the protection member permitting the biasing member to force the contact pieces into contact thereby eliminating any potential difference therebetween.
Generally, the electrical system is a gas-filled tube lighting arrangement supplied via a high tension transformer, and at least one of the protection devices is connected between a high tension output of the transformer and earth, and is configured to withstand a normal load operating high voltage of the transformer, but to disintegrate when subjected to a no-load high-voltage caused by the high tension output going open-circuit.
Preferably, the protection member is either rigid or resilient and is configured to combust as the predetermined potential difference is applied across it. Generally, the length of the protection member determines the minimum potential difference it can withstand prior to disintegration. Also preferably the protection member can be supplemented by an accelerant which acts to increase its rate of disintegration.
BRIEF DESCRIPTION OF THE DRAWINGS
A number of preferred embodiments of the present invention will now be described with reference to the drawings in which:
FIG. 1 is a schematic view of a lighting system which incorporates two open circuit protectors of a first embodiment;
FIGS. 2 and 3 are plan and inverse plan views of one of the open circuit protectors shown in FIG. 1;
FIG. 4 is a side elevation view showing the interior of the open circuit protector of FIGS. 2 and 3;
FIG. 5 is an end elevation view of the arrangement of FIG. 4;
FIG. 6 is a cross-sectional view drawn along the lines VI--VI of FIG. 4;
FIG. 7 is a side view of an open circuit pr
REFERENCES:
patent: 2179935 (1939-11-01), Kayatt
patent: 2216974 (1940-10-01), Hogan
patent: 3026392 (1962-03-01), Louret
patent: 4275432 (1981-06-01), Napiorkowski
patent: 4355345 (1982-10-01), Franchet
patent: 5155649 (1992-10-01), Hung et al.
Patent Abstracts of Japan, E-118, p. 27, JP, A, 54-49550 (Mitsubishi Denki K.K.) 18 Apr. 1979.
Patent Abstracts of Japan, E-161, p. 86, JP, A, 54-137647 (Mitsubishi Denki K.K.) 25 Oct. 1979.
Patent Abstracts of Japan, E-121, p. 127, JP, A, 54-57143 (Mitsubishi Denki K.K.) 8 May 1979.
Gaffin Jeffrey A.
Sherry Michael J.
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