Patent Application
20140376142
1. Field
The disclosed concept relates generally to fuses and, more particularly, to fuse assemblies. The disclosed concept also relates to strings including fuse assemblies.
2. Background Information
Fuses have been used in photovoltaic systems to protect strings from over-current conditions. One type of fuse includes a conductive element which is electrically connected in series with a protected power circuit. The conductive element heats up due to current flowing therethrough. The fuse is designed such that when the current flowing through the power circuit exceeds a predetermined level, the conductive element becomes hot enough to melt and interrupt the current flowing through the power circuit.
However, fuses in photovoltaic systems are limited to protecting strings from over-current conditions, and cannot protect strings from other faults such as, for example and without limitation, reverse current conditions. It would be beneficial to provide additional protection for strings.
There is room for improvement in fuse assemblies.
There is also room for improvement in strings.
These needs and others are met by aspects of the disclosed concept which provide a fuse assembly including a relay. These needs and others are also met by aspects of the disclosed concept which provide a string including a fuse assembly including a relay.
In accordance with aspects of the disclosed concept, a fuse assembly structured for use with a power circuit comprises: a fuse holder defining a space and including first and second terminals structured to electrically connect to the power circuit; a fuse disposed in the space defined by the fuse holder; and a relay electrically connected in series with the fuse, the relay disposed in the space defined by the fuse holder and including separable contacts, an operating mechanism structured to open and close the separable contacts, and a control circuit cooperating with the operating mechanism to cause the operating mechanism to open or close the separable contacts, wherein current flowing between the first and second terminals flows through the separable contacts and the fuse, and wherein opening the separable contacts or the fuse interrupts the current flowing between the first and second terminals.
In accordance with other aspects of the disclosed concept, a string having a feed end and a remote end comprises: a plurality of direct current electrical generating modules electrically connected in series; a power line electrically connected between the feed end and one of the direct current electrical generating modules or between two of the direct current electrical generating modules; a return line electrically connected to one of the direct current electrical generating modules at the remote end; and a number of string protectors in the power line or return line of the string, each of the number of string protectors comprising: a fuse holder defining a space and including first and second terminals structured to electrically connect to the power line or the return line; a fuse disposed in the space defined by the fuse holder; and a relay electrically connected in series with the fuse, the relay disposed in the space defined by the fuse holder and including separable contacts, an operating mechanism structured to open and close the separable contacts, and a control circuit cooperating with the operating mechanism to cause the operating mechanism to open or close the separable contacts, wherein current flowing between the first and second terminals flows through the separable contacts and the fuse, and wherein opening the separable contacts or the fuse interrupts the current flowing between the first and second terminals.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
As employed herein, the term “string” shall mean a series electrical circuit connection of a plurality of electrical generating modules.
As employed herein, the term “string protector” shall mean a protection device for a string and/or an electrical generating module of a string. The string protector includes a number of arc fault circuit interrupter (AFCI), over current, reverse current, feed forward fault, ground fault protection and/or remote shutdown functions.
As employed herein, the term “combiner box” shall mean a box, an enclosure or another suitable structure where one or both ends of a plurality of strings are fused and/or protected. A combiner box electrically combines in parallel DC current from several strings.
As employed herein, the term “direct current electrical generating module” shall mean a photovoltaic (PV) electrical generating module, a battery or a fuel cell.
As employed herein, the term “power line” shall mean a power conductor at the feed end of a string or between PV modules.
As employed herein, the term “return line” shall mean a power conductor extending from the remote end to the feed end of a string.
As employed herein, the term “feed forward fault” shall mean a fault defined by a non-zero forward current and a corresponding voltage that is significantly lower than Voc (e.g., without limitation, a voltage less than about 20% of open circuit voltage) or Vmpp (voltage at the maximum power point). For example, a feed forward fault can indicate an external short toward the feed (inverter) end of a string.
The disclosed concept is described in association with protection for PV circuits, although the disclosed concept is applicable to a wide range of DC applications, including for example and without limitation, relatively higher DC voltage circuits, such as wind power, hybrid vehicles, electric vehicles, marine systems and aircraft.
Referring to
The fuse assembly 1 further includes a fuse 20 and a relay 30 electrically connected in series between the first and second terminals 12,14. Current flowing between the first and second terminals 12,14 flows through the fuse 20 and the relay 30. Both the fuse 20 and the relay 30 are also capable of interrupting the current flowing between the first and second terminals 12,14.
The relay 30 includes separable contacts 31 which, when closed, allow current to flow between the first and second terminals 12,14, and when open, interrupt the current flowing between the first and second terminals 12,14. The separable contacts 31 include a first conductor 32, a second conductor 33, and a third conductor 34. The first and third conductors 32,34 have a fixed position and the second conductor 33 is moveable between a closed position (as shown in
The separable contacts 31 are opened and closed with an operating mechanism such as the example solenoid 35. The solenoid 35 includes an actuator 36 that is coupled with the separable contacts 31 and, in particular, the second conductor 33, which is movable. Operation attic solenoid 35 moves the actuator 36 to open or close the separable contacts 31. The solenoid 35 may be biased to hold the separable contacts 31 open when no power is provided to the solenoid 35. However, it should be appreciated that the solenoid 35 may also be biased to hold the separable contacts 31 closed when no power is provided to the solenoid 35 without departing from the scope of the disclosed concept.
The relay 30 further includes a control circuit 37 which is configured to control operation of the solenoid 35. The control circuit 37 may receive an external control signal such as a control signal from a fault detector 60 (see
The fuse holder 10 further includes a fuse access mechanism 16 which can be opened to provide access to the fuse 20 to, for example and without limitation, replace the fuse 20. However, accessing the fuse 20 when current is flowing between the first and second terminals 12,14 can create a dangerous situation. To this end, opening the fuse access mechanism 16 actuates a manual switch 17, which in turn causes the control circuit 37 to operate the solenoid 35 to open the separable contacts 31 and interrupt the current flowing between the first and second terminals 12,14. Closing the fuse access mechanism 16 actuates the manual switch 17 again causing the control circuit 37 to operate the solenoid 35 to close the separable contacts 31. The fuse holder 10 may also be structured so that a user can directly access and manually actuate the manual switch 17.
The solenoid 35 may also include an indicator 38. The indicator 38 is structured to remain inside the interior space of the fuse holder 10 when the separable contacts 31 are closed, as shown in
The fuse assembly 1 may be employed as part of a power system such as the power systems 2, 2′, and 2″ shown in respective
Each of the strings 4 further includes a string protector 50 in one of the power lines 6. The string protector 50 includes a fuse assembly, such as the fuse assembly 1 of
The fault detector 60 monitors characteristics of the power line 6 and/or the return line 7 through one or more sensors, such as the example current sensors, in order to detect a number of faults of the string 4. The fault detector 60 also outputs a control signal to the control circuit 37 in order to control the control circuit 37 to cooperate with the solenoid 35 (see
The fault detector 60 may also be integrated into the control circuit 37′ of the fuse assembly 1′, as shown in
Any number of string protectors 50 may be employed on a string 4 without departing from the scope of the disclosed concept. Referring to
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
