Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1987-02-03
1988-08-09
Tolin, G. P.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 58, 361 91, 361100, H02H 308
Patent
active
047632208
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an electric switch device having between two input and output terminals, a semiconductor component adapted for establishing and interrupting the passage of current between these terminals when an electrode controlling this component receives appropriate signals which are delivered by a control device receiving, on the one hand, conduction or interruption orders corresponding to normal operation and, on the other hand, disabling orders which are emitted when the intensity of the current which is measured by detection means placed in series between these terminals, undergoes an abnormal rise.
A circuit, having an operation comparable to that defined above and which is known from the patent application DE-OS No. 2 416 450 uses a semiconductor component of the triac type for feeding in regulated fashion a load having a resistive characteristic, similar to that of an incandescent lamp.
Such a load has then possible resistance variations, which are known beforehand and which are stabilized in a time close to a period; the circuit, in which it is placed, which is generally fed by a domestic mains consequently sees currents passing whose short circuit intensity can never take on excessive values; furthermore, the use of a triac as switch member has here the disadvantage of not allowing interruption of the AC current at any time in the period.
Such a device consequently does not take into account transitory phenomena such as those which appear in the power supply circuits for motors where overloads, of the order of 5 to 6 times the nominal current, may occur during a current drain which may last for about a second.
The invention relates to an industrial switch device or circuit in which the load is formed by an electric motor whose consumption may vary over a large range of values related to the nature of the masses which are to be set in motion; in such an industrial circuit, which is generally fed by the very low impedance network, the line, the switch member and the load should be protected against the effects of current overloads and against those of true short circuits which may either damage the load definitively, or cause destruction of the switch member resulting in a prolonged stoppage of production; in addition, bringing the load into service with this switch member corresponds to a category of use whose constraints are much more severe than those governing domestic apparatus.
The most widely used technique at the present time for effecting the above mentioned functions, uses an association of electromechanical products such as contact makers, thermal protection relays, contact breakers, limiters and fuses whose particular properties must be well chosen if these functions are to be perfectly fulfilled.
The invention consequently proposes providing a static industrial switch device or circuit which is capable of frequently both establishing and interrupting electronically the power supply of a load, whose impedance may vary accidently and of protecting this load and the line against the effects of current surges and short circuits.
According to the invention, the aim sought is attained because, in a conducting branch placed in parallel across the anode and the cathode of this component which belongs to one of the so called GTO families, respectively IGT and GTR, there are placed in parallel: anode and this cathode and for reversibly withstanding a high energy pulse, withstanding a high current pulse and contacts of a non repulsive mechanical switch, which is normally open, and whose closure may be provided by a high speed relay, the coil of this relay being supplied with power only when a first type of fault of limited duration appears, for which the presumed current is substantially between 1.25 times and 6 times the nominal current, and before a disabling signal is transmitted to the control electrode of the static switch, whereas this coil is not supplied with power and a permanent disabling signal is immediately delivered to this electrode when a current gradient appears greate
REFERENCES:
patent: 4275430 (1981-06-01), Seki et al.
patent: 4351014 (1982-09-01), Schofield, Jr.
patent: 4377835 (1983-03-01), Asplund et al.
patent: 4475139 (1984-10-01), Chadwick
patent: 4651251 (1987-03-01), Thiele
IEEE paper # vol. PAS-105, No. 5, May 1983, "Development of Zinc Oxide Ceramic Energy Absorbers for DC Thyristor C. B. "
Siemens Components XIX (1984) No. 6, "Capacitors for GTO Thyristors" by Goldbrunner et al.
Belbel Elie
Fechant Louis
Riotte Jaan Paul
Drucker William A.
Jennings Derek S.
La Telemecanique Electrique
Tolin G. P.
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