Patent Description:
With the proliferation of low voltage direct current (DC) in applications such as solar, data centers, electric vehicle charging stations, heating and air conditioning system, as well as many residential power systems, there is an increasing need for surge protection to appropriately protect such devices from power surges. A power surge (also referred to as a "voltage surge" or "transient voltage") is an electrical transient, a short duration, high-energy impulse that is imparted on the normal electrical power system whenever there is a sudden electrical charge coupled into the electrical circuit. A power surge can originate from a variety of sources, both internal and external to an installed location, whether it is a residence, commercial building, solar array, or industrial facility.

A device that offers surge protection is a surge protection device or more commonly referred to as an SPD. An SPD is typically designed for either AC or DC applications.

The component that absorbs and passes a voltage surge inside an SPD is often referred to as a surge element. Surge elements include, but are not limited to, a metal oxide varistor (MOV), a transient voltage suppressor (TVS) diode, a thyristor surge protection device (TSPD), a gas discharge tube (GDT) and a spark gap overvoltage suppressor. Each SPD may include a plurality of surge elements connected in series, parallel, or a combination of series/parallel to achieve a particular surge rating for the SPD.

<FIG> is a circuit diagram illustrating an exemplary prior art SPD <NUM> designed to protect a DC power system having multiple DC power lines. In this illustrative embodiment of a prior art SPD the surge elements <NUM> takes the form of MOVs (metal-oxide varistors). However, it should be appreciated that the surge elements of prior art SPDs may take other forms. The negative potential (N) is common between the five DC power lines (L1-L5). The five DC power lines are isolated from earth ground (G). Each of the five surge elements <NUM> have a respective status output <NUM> for indicating whether the respective surge element has failed. SPD <NUM> also includes an alarm circuit <NUM> for outputting an external alarm signal indicative of the status of SPD <NUM>. The status outputs <NUM> of the five surge elements <NUM> are summed by alarm circuit <NUM>. If the summation of status outputs <NUM> indicates that one or more of surge elements <NUM> has failed (i.e., a surge condition has occurred), then alarm circuit <NUM> provides an alarm signal by switching the alarm output. In the illustrated example, alarm circuit <NUM> has a normally open (NO) terminal, a normally closed (NC) terminal, and a common (COM) terminal for connection with an external circuit.

One of the drawbacks of existing prior art SPDs is that separate surge elements are respectively required between each DC power line (L1-L5) and the negative potential (N), and a separate surge element is required between the negative potential (N) and ground potential (G). Thus, SPD <NUM> requires a total of six surge elements <NUM> in order to protect a DC power system having <NUM> DC power lines. The need for this large number of surge elements makes the SPD costly to manufacture and requires a significant amount of space inside a housing for the SPD.

The above-described drawbacks in SPDs designed for DC applications are also present with respect to existing SPDs designed for AC applications for use in protection of multi-line, multiphase AC power systems.

The present invention overcomes these and other drawbacks of prior art SPDs to provide an SPD with a reduced number of surge elements for protection of multi-line DC power systems. Surge protection devices in accordance with the prior art are known from, for instance, documents <CIT> and <CIT>.

In accordance with an embodiment useful for understanding the invention, there is provided a surge protection device, comprising: a plurality of power line inputs; a negative potential or neutral input; a ground potential input; a surge protection component having one or more surge elements; a rectification circuit including a plurality of diodes, wherein said rectification circuit is connected between said inputs and the surge protection component.

An advantage of the present invention is the provision of a SPD that requires fewer surge elements to protect multiple DC power lines.

Another advantage of the present invention is the provision of a SPD that can be manufactured at a lower cost.

Still another advantage of the present invention is the provision of a SPD that minimizes space requirements for an SPD housing.

Yet another advantage of the present invention is the provision of a SPD that can be implemented with less circuitry to indicate a status condition of the SPD.

These and other advantages will become apparent from the following description of illustrated embodiments taken together with the accompanying drawings and the appended claims.

The invention may take physical form in certain parts and arrangement of parts, embodiments of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein:.

Referring now to the drawings wherein the showings are for the purposes of illustrating an embodiment of the invention only and not for the purposes of limiting same, <FIG> is a circuit diagram illustrating a SPD 30A according to a first embodiment of the present invention, as configured for protecting a DC power system having a plurality of DC power lines. In the illustrated embodiment of the present invention SPD 30A is configured to protect a DC power system having up to five DC power lines. It should be appreciated that SPD 30A of the present invention may be alternatively configured for protection of greater or fewer than five DC power lines.

As illustrated, SPD 30A is generally comprised of inputs for (i) DC power lines L1-L5, (ii) negative potential N, and (iii) ground potential G; a rectification circuit <NUM>; a surge protection component <NUM> having a status output <NUM>; and an alarm circuit <NUM>. SPD 30A is adapted to handle positive voltage surges.

Rectification circuit <NUM> is comprised of a plurality of diodes associated with the inputs of SPD 30A. The anode and cathode terminals of the diodes are oriented such that SPD 30A is adapted to provide protection from positive voltage surges.

Surge protection component <NUM> is comprised of one or more surge elements. In the illustrated embodiment, the surge element takes the form of a single metal oxide varistor (MOV). However, it should be appreciated that the surge element of surge protection component <NUM> may take other forms, including, but not limited to, a transient voltage suppressor (TVS) diode, a thyristor surge protection device (TSPD), a gas discharge tube (GDT), a spark gap overvoltage suppressor, and the like. It should be understood that surge protection component <NUM> may be comprised of a plurality of surge elements connected in series, parallel, or a combination of series/parallel to achieve a particular surge rating.

In the operation of SPD 30A, the diodes of rectification circuit <NUM> steer overvoltage current above the turn-on threshold of the surge protection component <NUM> to the one or more surge elements thereof.

In the illustrated embodiment, alarm circuit <NUM> is configured with normally closed (NC), common, and normally open (NO) outputs for connection with a remote status indicator used to provide a visual and/or audible alarm to alert the user of a surge event.

Referring now to <FIG>, there is shown a current flow in SPD 30A in response to a positive voltage surge between a first DC power line (L1) and negative potential N. The current flow along path a-b-c-d is illustrated by arrows. Similarly, <FIG> shows a current flow in SPD 30A in response to a positive voltage surge between a first DC power line (L1) and ground potential G. The current flow along path a-b-c-d is illustrated by arrows.

<FIG> shows an SPD 30B according to a second embodiment of the present invention. As illustrated, SPD 30B is generally comprised of inputs for DC power lines L1-L5, negative potential N, and ground potential G; a rectification circuit <NUM>; a surge protection component <NUM> having a status output <NUM>; and an alarm circuit <NUM>.

Rectification circuit <NUM> is comprised of a plurality of diodes associated with the inputs of SPD 30B. The orientation of the anode and cathode terminals of the diodes of rectification circuit <NUM> are reversed relative to the orientation of the anode and cathode terminals of the diodes of rectification circuit <NUM>, such that SPD 30B is adapted to provide protection from negative voltage surges. The remaining elements of SPD 30B are the same as the elements of SPD 30A described above, and thus, have the same reference numbers.

In the operation of SPD 30B, the diodes of rectification circuit <NUM> steer overvoltage current above the turn-on threshold of the surge protection component <NUM> to the one or more surge elements thereof.

Referring now to <FIG>, there is shown a current flow in SPD 30B in response to a negative voltage surge between a first DC power line (L1) and negative potential N. The current flow along path a-b-c-d is illustrated by arrows. Similarly, <FIG> shows a current flow in SPD 30B in response to a negative voltage surge between a first DC power line (L1) and ground potential G. The current flow along path a-b-c-d is illustrated by arrows.

<FIG> shows an SPD 30C according to a third embodiment of the present invention. As illustrated, SPD 30C is generally comprised of inputs for DC power lines L1-L5, negative potential N, and ground potential G; a rectification circuit <NUM>; a surge protection component <NUM> having a status output <NUM>; and an alarm circuit <NUM>.

Rectification circuit <NUM> is comprised of a plurality of diodes associated with the inputs of SPD 30C. The diodes of rectification circuit <NUM> are arranged such that SPD 30B is adapted to provide protection from both positive and negative voltage surges. The remaining elements of SPD 30C are the same as the elements of SPDs 30A and 30B described above, and thus, have the same reference numbers.

In the operation of SPD 30C the diodes of rectification circuit <NUM> steer overvoltage current above the turn-on threshold of the surge protection component <NUM> to the one or more surge elements thereof.

Referring now to <FIG>, there is shown a current flow in SPD 30C in response to a positive voltage surge between a first DC power line (L1) and negative potential N. The current flow along path a-b-c-d-e is illustrated by arrows. Similarly, <FIG> shows a current flow in SPD 30C in response to a positive voltage surge between a first DC power line (L1) and ground potential G. The current flow along path a-b-c-d is illustrated by arrows.

Referring now to <FIG>, there is shown a current flow in SPD 30C in response to a negative voltage surge between a first DC power line (L1) and negative potential N. The current flow along path a-b-c-d-e-f is illustrated by arrows. Similarly, <FIG> shows a current flow in SPD 30C in response to a negative voltage surge between a first DC power line (L1) and ground potential G. The current flow along path a-b-c-d-e-f is illustrated by arrows.

In the embodiment of <FIG>, an AC multi-line, multi-phase system is shown as part of an embodiment useful for understanding the invention.

<FIG> is a circuit diagram illustrating a SPD <NUM>, as configured for protecting a multi-line AC power system having a plurality of AC power lines. In the illustrated embodiment SPD <NUM> is configured to protect a multiphase AC power system having three AC power lines. It should be appreciated that SPD <NUM> may be alternatively configured for protection of greater or fewer than three AC power lines.

As illustrated, SPD <NUM> is generally comprised of inputs for (i) AC power lines L1-L3, (ii) ground potential G, and (iii) neutral N; a rectification circuit <NUM>; surge protection components 34a, 34b, and 34c having a respective status output <NUM>; and an alarm circuit <NUM>. SPD <NUM> is adapted to handle both positive and negative voltage surges.

Rectification circuit <NUM> is comprised of a plurality of diodes associated with L1, L2, L3 and G of SPD <NUM>. The anode and cathode terminals of the diodes are oriented such that SPD <NUM> is adapted to provide protection from both positive and negative voltage surges.

Each surge protection component 34a, 34b, 34c is comprised of one or more surge elements. In the illustrated embodiment, the surge element takes the form of a single metal oxide varistor (MOV). However, it should be appreciated that the surge element of surge protection components 34a 34b, 34c may take other forms, including, but not limited to, a transient voltage suppressor (TVS) diode, a thyristor surge protection device (TSPD), a gas discharge tube (GDT), a spark gap overvoltage suppressor, and the like. It should be understood that each surge protection component 34a, 34b, 34c may be comprised of a plurality of surge elements connected in series, parallel, or a combination of series/parallel to achieve a particular surge rating.

In the operation of SPD <NUM>, the diodes of rectification circuit <NUM> steer overvoltage current above the turn-on threshold of the surge protection components 34a, 34b, 34c to the one or more surge elements thereof.

<FIG> is illustrated to show a current flow in SPD <NUM> in response to a positive voltage surge between a first AC power line (L1) and neutral N. The current flow path is illustrated by arrows. Similarly, <FIG> is illustrated to show a current flow in SPD <NUM> in response to a negative voltage surge between a first AC power line (L1) and neutral N.

<FIG> is illustrated to show a current flow in SPD <NUM> in response to a positive voltage surge between a first AC power line (L1) and a second AC power line (L2).

<FIG> is illustrated to show a current flow in SPD <NUM> in response to a negative voltage surge between a first AC power line (L1) and ground potential G.

It should be appreciated from the illustrated examples of positive and negative voltage surge conditions for SPD <NUM> that surge protection component 34a is used for protection when there is a positive voltage surge between (i) L1, L2, L3, or G and (ii) N; that surge protection component 34c is used for protection when there is a negative voltage surge between (i) L1, L2, L3, or G and (ii) N; and that surge protection component 34b is used for protection when there is a negative or positive voltage surge between any pair of inputs L1, L2, L3, and G.

Claim 1:
A surge protection device (30A, 30B, 30C), comprising:
a negative potential or neutral input;
a surge protection component (<NUM>) having one or more surge elements; and
a rectification circuit (<NUM>, <NUM>, <NUM>),
characterized by
a plurality of direct current, DC, power line inputs;
a ground potential input;
and in that
the rectification circuit (<NUM>, <NUM>, <NUM>) includes a plurality of diodes, wherein said rectification circuit (<NUM>, <NUM>, <NUM>) is connected between said inputs and the surge protection component (<NUM>).