Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
2001-04-26
2004-11-09
Gandhi, Jayprakash N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S286000, C323S241000, C361S057000
Reexamination Certificate
active
06816758
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to switches and, more particularly, to an apparatus and method for remotely controlling the current to at least one load.
BACKGROUND OF THE INVENTION
In many industries today, such as the avionics and automotive industries, in order to protect complex and costly electrical components, systems and subsystems, electrical power systems powering these components, systems and subsystems employ circuit breakers and relays. Typically, circuit breakers interrupt the current in an electric circuit, sometimes referred to as tripping the circuit breaker, when the current through the circuit becomes higher than that allowed by the circuit breaker. Conventional circuit breakers are typically rated for a specific current level that depends upon the components in the circuit and their current tolerances. When the current through the circuit breaker exceeds the rated current level, the circuit breaker trips and interrupts the current in the circuit. In one type of conventional circuit breaker, a mechanical circuit breaker, when enough current runs through the circuit to trip the circuit breaker, a pair of contacts that are normally in contact in order to conduct current through the circuit breaker and the rest of the circuit are separated, such as by preloaded springs, thus breaking the circuit.
In addition to circuit breakers, many industries today employ relays to control the flow of current to components, systems and/or subsystems. Conventional relays are electromechanical switches that are operated by a flow of current in one circuit which controls the flow of current in another circuit. One basic conventional relay consists of an electromagnet with a soft iron bar, or armature, disposed close to the electromagnet. A movable contact is connected to the armature such that the contact is held in a normal position by a spring, or similar device. To actuate the relay, the electromagnet is energized, such as by passing a current through it, thereby exerting a force on the armature which, in turn, causes the contact to overcome the pull of the spring and move so as to either complete or break the circuit. When the electromagnet is de-energized, such as by halting the current flow through the electromagnet, the contact returns to its original, normal position.
While conventional circuit breakers and relays are used in many power systems, they pose some problems. Many conventional circuit breakers and relays allow excessive current to flow when the contacts open and close the circuit. In these circuit breakers and relays, the excessive current flow results in an electric arc that forms at the contacts, which typically erodes the contacts and can, in some instances, weld them closed. The electric arc can also result in the contacts becoming carbonized, thereby not allowing the contacts surfaces to adequately conduct electrical current. Additionally, the presence of the electric arc can add unnecessary danger to electrical devices and people around such devices in instances in which combustible gases have collected around the circuit breaker or relay.
To allow access to conventional circuit breakers and relays, in many conventional power systems, they are placed on centrally located panels in areas that are typically distant from the components, systems and/or subsystems being protected and/or controlled. This results in long cable assemblies that extend between the circuit breakers and/or relays and the components, systems and/or subsystems being protected and/or controlled. The length of the cables can additionally result in parasitic impedance, which can cause a loss of power to the system, and can increase system noise. This results in lowering the efficiency of the power system. Additionally, longer cables also increase the weight of the power system, because, as stated, the cables must reach extended lengths to control the various components and/or subsystems.
In addition to lower reliability and increased weight of conventional mechanical circuit breakers and relays, conventional mechanical circuit breakers suffer from limitations due to their material characteristics. Most of these conventional circuit breakers cannot be adjusted for different requirements without replacing the entire circuit breaker. For example, if a mechanical circuit breaker is rated for a ten amp trip and is attached to a circuit containing a component, system or subsystem rated for five amps, the ten amp rated circuit breaker would need to be replaced with a five amp rated circuit breaker to provide over-current protection for the five amp rated component, system or subsystem. Additionally, conventional mechanical circuit breakers do not allow for adjustments accounting for power-up inrush current, or adjustments in trip voltages accounting for fluctuations in the voltage drop across a mechanical circuit breaker due to temperature changes in the circuit breaker.
SUMMARY OF THE INVENTION
In light of the foregoing background, the present invention provides a programmable controller capable of interfacing with a remote master controller, where the programmable controller is capable of controlling an input current to at least one load, such as a component and/or subsystem that is proximate the programmable controller. The programmable controller of the present invention includes at least one solid-state switch capable of limiting the input current to the loads to a predetermined value at or below the maximum current rating of the solid-state switch. In one embodiment, each solid state switch includes a switching element electrically connected to a respective load to monitor and control the input current and voltage levels to the respective load, and a drive element to provide the input current to the respective load. In this embodiment, the switching element controls the input current provided by the drive element. Using a solid-state switch, such as a metal oxide semiconductor field-effect transistor (MOSFET) or an integrated gate bipolar transistor (IGBT), the programmable controller eliminates the mechanical contacts of conventional circuit breakers and relays, thus eliminating the erosion and associated problems with such contacts.
The programmable controller also includes at least one measuring element for measuring at least one parameter associated with the loads and the solid-state switches. For example, in various embodiments, the programmable controller can measure the current through the solid-state switches, the current through and voltage drop across the loads and the temperature at or around the solid-state switches. Using these parameters, the programmable controller can protect the loads and solid-state switches from damage, such as that caused by over current, over voltage, under voltage, over temperature and under temperature conditions.
The programmable controller of the present invention also includes a processing element, such as a microcontroller, electrically connected to the solid-state switches and measuring elements. The processing element is capable of controlling the solid-state switches. For example, the processing element can control the respective switches in an on mode where the solid-state switch permits a respective load to receive the input current, or an off mode where the solid-state switch prevents the respective load from receiving the input current.
In one embodiment, the programmable controller can further include a memory device electrically connected to the processing element for storing information relative to the switches and/or loads in addition to user preferences and built-in-test information. To backup the operation of the processing element, in another embodiment, the programmable controller further includes a monitoring element electrically connected to the processing element and the solid-state switches. In instances when the processing element fails to function properly by failing to control the solid-state switches, the monitoring element is capable of controlling the solid-state switches to alter the input
Hornsby Rodney M.
Maxwell, Jr. John M.
Offer Kerry Michelle
Ramsey Dale B.
Schwarz Charles R.
Alston & Bird LLP
Gandhi Jayprakash N.
The Boeing Company
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