Electricity: electrical systems and devices – Safety and protection of systems and devices – Transient responsive
Reexamination Certificate
2000-11-14
2004-01-27
Toatley, Jr., Gregory J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Transient responsive
Reexamination Certificate
active
06683770
ABSTRACT:
TECHNICAL FIELD
The present invention relates to over-voltage protection circuits. More particularly, the present invention relates to over-voltage protection circuits having metal oxide varistor (MOV) devices as the over-voltage sensing component. Even more particularly, the present invention relates to over-voltage protection circuits having metal oxide varistor (MOV) devices as the over-voltage sensing component for utilization in AC electric power distribution.
BACKGROUND OF THE INVENTION
The current state of the art electronic components (e.g., both commercial and residential computers and related equipment) accommodate transient voltage surge suppression features for protecting their highly sensitive circuits from over-voltage damage. Most transient voltage surge suppression systems today address only minor fault conditions associated with normal use and cannot handle a major over-voltage condition as would occur during loss of neutral, loss of ground, or repetitive current pulses (e.g., from a lightning strike). Typical voltage surge protection devices comprise either a plurality of fault fuses where the input is disconnected from the output. The related art surge suppression systems may involve various metal oxide varistor (MOV) and fuse combinations. MOVs are typically non-linear devices formed from composite ceramic materials (e.g., ZnO grains in combination with an amorphous material). MOVs maintain the voltage within a narrow band (i.e., varistor voltage) over a wide current range. During major over-voltage conditions, the MOVs may absorb heat so excessive such that they will rupture or explode, thereby allowing the related electronic equipment to be destroyed.
Some related art surge suppression apparatus patents include:
(1) U.S. Pat. No. 6,055,147 to Jeffries et al. which teaches a plurality of MOVs being in series with a plurality of thermal fuses;
(2) U.S. Pat. No. 5,412,526 to Kapp et al. which teaches a plurality of MOVs being in series with a plurality of thermal fuses, and the plurality of MOVs being in parallel with a plurality of resistors;
(3) U.S. Pat. No. 6,040,971 to Martenson et al. which teaches a plurality of MOVs being in parallel with one another, an MOV being in parallel with a thermal fuse, and the thermal fuse being in series with a circuit protection device having an over-voltage trip device;
(4) U.S. Pat. No. 5,388,021 to Stahl which teaches a plurality of MOVs being in parallel with a plurality of resistors and a plurality of inductors, and a plurality of MOVs being in parallel with another;
(5) U.S. Pat. No. 5,675,468 to Chang which teaches two input terminals, two fuses in series respectively, a triac, an MOV in series between one fuse and an output terminal, a static potential limiter between the triac and ground;
(6) U.S. Pat. No. 4,901,183 to Lee which teaches two MOVs being in parallel with one another, two thermal fuses being in parallel with one another, a capacitor being in parallel with an MOV, two capacitors being in parallel with one another, and two inductors being in parallel with one another;
(7) U.S. Pat. No. 6,038,117 to Dullni et al. which teaches pairs of MOVs being in parallel, a plurality of such pairs being in series with one another and in series with a relay;
(8) U.S. Pat. No. 5,534,769 to Ishii which teaches resistor-capacitor combinations; and
(9) U.S. Pat. No. 5,808,850 to Carpenter, Jr. which teaches a three-phase device having quadruplets of parallel MOVs, each quadruplet being in series with a thermal fuse and an inductor, and bulbs for an indicator light for line to ground only.
A typical problem associated with these related art inventions is that an electrician may accidentally reverse the line wire and the neutral wire, creating an extremely hazardous situation at the wall receptacle, even if the invention succeeds in disconnecting the circuit to a peripheral device. In addition, the related art patents maintain an inordinately high component count to achieve their purpose of surge suppression. Therefore, a need exists for a circuit apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration (i.e., the minimum number of components for device size reduction) which assures a rapid simultaneous disconnect of both the hot line and the neutral line.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration (i.e., the minimum number of components for device size reduction) which assures a rapid simultaneous disconnect of both the hot line and neutral power lines.
Another object of the present invention is to provide an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by opening the circuit to simultaneously disconnect both the hot line and the neutral line feeding a load when the over-voltage event occurs in any of three wire pairings: line-to-neutral (L-N), line-to-ground (L-G), or neutral-to-ground (N-G).
Accordingly, the present invention provides a single-phase over-voltage protection circuit apparatus for all AC power lines and combinations thereof. In particular, the present invention provides an apparatus and a method which prevent (1) the hazardous condition occurring at the wall receptacle, arising from accidental reversal of the line wire with the neutral wire, from adversely affecting at least one peripheral device in the line, and (2) the overheating and destruction of MOVs in an over-voltage protection circuit by providing an efficient circuit configuration which assures a rapid simultaneous disconnect of both the hot line and neutral line. The present invention achieves this by opening the circuit to simultaneously disconnect both hot line and neutral line feeding a load when the over-voltage event occurs in any of the three following wire pairings: hot line to neutral line (L-N), hot line to ground line (L-G), or neutral line to-ground line (N-G).
By example, in a single phase AC power system, the hot line (L), the neutral line (N), and ground line (G) are all paths vulnerable to destructive high voltages. The present invention protects these paths by first providing protection devices in the form of metal oxide varistors (MOVs) in parallel for each pair of wires (i.e., hot line to neutral, hot line to ground, and neutral to ground). The apparatus additionally comprises in-line fuses and a normally open relay device that disconnects both the hot line as well as the neutral line from the load. The MOV devices are activated by an over-voltage condition and upon absorbing all the extra and potentially damaging power surges and over-voltages which cause excessive current to flow, which then opens the fuse, causing de-energizing of the relay device.
Accordingly, in the event of a sufficiently high voltage (i.e., V
L-N
>120 V to 130 V), from hot line-to-neutral or hot line-to-ground, causing excessive heating of the MOV protection devices, the hot line and neutral line will be disconnected from the user's connected equipment. This disconnect is facilitated by the use of an open circuit condition of the in-line special fuses which causes de-energizing of the relay device and reversion of the relay contacts back to a normal
Benenson Boris
LaRiviere Grubman & Payne, LLP
Monster Cable Products, Inc.
Toatley , Jr. Gregory J.
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