Intrinsically safe circuits
First Claim
1. An intrinsically safe circuit for use in a hazardous environment, the circuit comprising:
- a plurality of circuit sectors located in the hazardous environment and which are substantially isolated physically from one another by electrical insulating means, the circuit sectors being electrically connected, directly or indirectly, so as to define at least one power transfer path between each said circuit sector and at least one other said circuit sector;
power supply means located in the hazardous environment and connected to at least one said circuit sector; and
power limiting means provided between said power supply means and each said circuit sector connected thereto, wherein at least two said circuit sectors having at least one power transfer path defined therebetween have different sparking voltages and the intrinsically safe circuit further includes voltage clamping means in each said power transfer path between at least two said circuit sectors having different sparking voltages, for reducing the maximum voltage which may be applied by one of said at least two circuit sectors to another of said at least two circuit sectors.
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Accused Products
Abstract
An intrinsically safe circuit for use in a hazardous environment includes a plurality of circuit sectors (1, 2) which are substantially isolated physically from one another by an electrical insulator, such as air, and are electrically connected, directly or indirectly, so as to define at lease one power transfer path (P1) between each circuit sector (1) and the other circuit sector (2) ; and power limiting means such as resistors (R1, R2) provided in each power transfer path between the connected circuit sectors for limiting the maximum power transfer value therebetween to a value less than a predetermined threshold value at which combustion in said hazardous environment is initiated. The circuit sectors (1, 2) having at least one power transfer path (P1) defined therebetween may have different sparking voltages, in which case voltage clamping means such as Zener diodes (Z1, Z2) is provided in each power transfer path between the two circuit sectors having different sparking voltages, for reducing the maximum voltage which may be applied by one of the two circuit sectors to the other.
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Citations
17 Claims
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1. An intrinsically safe circuit for use in a hazardous environment, the circuit comprising:
- a plurality of circuit sectors located in the hazardous environment and which are substantially isolated physically from one another by electrical insulating means, the circuit sectors being electrically connected, directly or indirectly, so as to define at least one power transfer path between each said circuit sector and at least one other said circuit sector;
power supply means located in the hazardous environment and connected to at least one said circuit sector; and
power limiting means provided between said power supply means and each said circuit sector connected thereto, wherein at least two said circuit sectors having at least one power transfer path defined therebetween have different sparking voltages and the intrinsically safe circuit further includes voltage clamping means in each said power transfer path between at least two said circuit sectors having different sparking voltages, for reducing the maximum voltage which may be applied by one of said at least two circuit sectors to another of said at least two circuit sectors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- a plurality of circuit sectors located in the hazardous environment and which are substantially isolated physically from one another by electrical insulating means, the circuit sectors being electrically connected, directly or indirectly, so as to define at least one power transfer path between each said circuit sector and at least one other said circuit sector;
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16. A method of limiting power transfer in an intrinsically safe circuit for use in an hazardous environment, comprising:
- providing a plurality of circuit sectors located in the hazardous environment and which are substantially isolated physically from one another by electrical insulating means;
electrically connecting the circuit sectors, directly or indirectly, so as to define at least one power transfer path between each said circuit sector and at least one other said circuit sector;
supplying power to each said sector, directly or indirectly, so that at least two said circuit sectors having at least one power transfer path defined therebetween are provided with different sparking voltages, including connecting power supply means to at least one said circuit sector;
providing power limiting means between said power supply means and each said circuit sector connected thereto; and
providing voltage clamping means in each said power transfer path between at least two said circuit sectors having different clamping voltages, for reducing the maximum voltage which may be applied by one of said at least two circuit sectors to another of said at least two circuit sectors. - View Dependent Claims (17)
- providing a plurality of circuit sectors located in the hazardous environment and which are substantially isolated physically from one another by electrical insulating means;
Specification