Apparatus and method for protecting equipment against electrical power surges
OwnerPak Chuen Changinventor
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Abstract
Apparatus and method for protecting equipment against electrical power surges which is not `ground-centered`. A protection circuit in accordance with this invention comprises at least (a) two input terminals, (b) two fuses in series respectively, (c) a triac which is over-current activated and connected at outputs of the fuses, (d) an over-current sensor in series between one of the fuses and an output terminal, to activate the triac, and (e) a static potential limiter which is overvoltage activated and connected between the triac and a ground terminal. Each fuse is appropriately rated to blow before the activated triac or the activated static potential limiter of the protection circuit are destroyed.
Claims18
A surge protecting apparatus for protecting electrical equipment from a power surge, comprising:
- first isolation means connected in series between a first input means and a first output means;
- second isolation means connected in series between a second input means and a second output means;
- absorbing means connected in parallel between outputs of the first and second isolation means for absorbing energy delivered via the first and second isolation means when activated;
- overcurrent sensing means connected between the second isolation means and the second output means, for sensing an overcurrent and for activating the absorbing means in response to the sensed overcurrent;
- and
- a static potential limiting means connected between the absorbing means and a ground means, said second isolation means, said absorbing means and said static potential limiting means being connected at a common node, wherein
- the static potential limiting means enables said common node to be connected to ground means, in response to an overvoltage;
- and wherein,
- each isolation means is appropriately selected so that it will (a) protect the absorbing means which will be activated to become short-circuited when a predetermined level of overcurrent is detected by the overcurrent sensing means in order to prevent harmful in-circuit surge from reaching the electrical equipment via the output means, and (b) protect the static potential limiting means which prevents harmful inter-circuit voltage surge, in relation to ground potential, from reaching the electrical equipment.
A method of absorbing and isolating a harmful electrical surge, for equipment-circuit protection, comprising the steps of:
- providing a protection circuit including at least two input means, two suitably selected isolation means respectively connected in series with the two input means, a suitable absorbing means connected in parallel at the outputs of the isolation means, an overcurrent sensing means connected in series between an isolation means and one of two output means suitably connected to trigger the absorbing means, and a static potential limiting means connected to the output of one of said two isolation means, enabling said isolation means to be connected to a ground means;
- and
- employing an isolation means which is appropriately selected so that it will (a) protect the absorbing means which will be activated to become short-circuited when a predetermined level of overcurrent is detected by the overcurrent sensing means in order to prevent harmful in-circuit surge from reaching the equipment-circuit via the output means, and (b) protect the static potential limiting means which prevents harmful inter-circuit voltage surge, in relation to ground potential, from reaching the equipment-circuit.
Dependencies are inferred from the claim text.