Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
2000-09-26
2003-09-09
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S078000, C700S177000, C702S115000
Reexamination Certificate
active
06618649
ABSTRACT:
BACKGROUND OF THE INVENTION
Circuit breakers are often used to protect wiring that carries current over external power lines (i.e., from a power source) to computer systems (i.e., loads). Such circuit breakers are effective in preventing thermal events (e.g., smoke and fire) from going beyond control. A typical circuit breaker includes a connection mechanism that can be placed in one of three positions: an off position, a set position, and a tripped position.
Suppose that such a circuit breaker is installed between external power lines and wiring that leads to a computer system. When the connection mechanism of the circuit breaker is in the off position, the circuit breaker does not allow current to flow between the external power lines and the wiring leading to the computer system. When the connection mechanism is in the set position, the circuit breaker allows current below a rated trip threshold to flow through the circuit breaker between the external power lines and the wiring. If the current flowing through the circuit breaker exceeds the rated threshold, the connection mechanism of the circuit breaker “trips”, i.e., transitions from the set position to the tripped position. Once the connection mechanism of the circuit breaker transitions to the tripped position, the connection mechanism does not allow further current to flow between the external power lines and the wiring leading to the computer system in order to protect the wiring from the effects of excessive current.
In addition to the above-described conventional circuit breaker which installs between external power lines and wiring leading to a computer system (hereinafter referred to as an external circuit breaker), some computer systems include one or more circuit breakers (hereinafter referred to as internal circuit breakers) that protect circuitry within the computer systems against damage from over-current fault conditions. In general, the connection mechanism of an internal circuit breaker operates in a manner similar to that of an external circuit breaker. For example, suppose that an internal circuit breaker is installed within a computer system between a computerized device within the computer system and external wiring that leads to external power lines (perhaps through an external circuit breaker). When the connection mechanism of the internal circuit breaker is in the off position, the internal circuit breaker does not allow current to flow through it to reach the computerized device. When the connection mechanism of the internal circuit breaker is in the set position, the internal circuit breaker allows current below a rated threshold to flow through it and between the wiring leading to the external power lines and the computerized device. However, if the current flowing through the internal circuit breaker exceeds the rated threshold, the connection mechanism of the internal circuit breaker “trips”, thus moving the connection mechanism.of the circuit breaker to a tripped position. Once the connection mechanism transitions to the tripped position, the connection mechanism does not allow further current to flow through it between the wiring leading to the external power lines and the computerized device thus protecting the computerized device from excessive current.
In general, the threshold of the external circuit breaker is designed to be higher than the threshold of the internal circuit breaker protecting the computerized device of the computer system since the wiring (and other external power equipment) leading to the computer system is typically designed to carry at least as much current as that which flows through circuitry within the computer system. For example, in Europe, the external circuit breaker for a computer system can have a threshold of 32 amperes, and the internal circuit breaker for the computer system can have a threshold of 30 amperes.
Some computer system installations use multiple external circuit breakers and multiple internal circuit breakers. In one configuration, the external multi-phase power equipment that protects the wiring leading from power supply lines to such a computer system includes a multi-pole or “ganged” multi-phase circuit breaker. The connection mechanisms for the poles (the outputs or current paths provided by the circuit breaker) share common trip linkage forcing all of the connection mechanisms to reside in the same position at the same time. For example, suppose that all connection mechanisms are in the set position. If current flowing from one of the poles exceeds the threshold for the circuit breaker, the connection mechanism for that pole transitions from a set position to a tripped position preventing further current from flowing from that pole. At the same time, the trip linkage forces the connection mechanisms for the remaining poles to automatically transition from their set positions to their tripped positions. Accordingly, when one pole of the ganged circuit breaker trips, all of the poles of the ganged circuit breaker trip thus preventing any current from flowing through the ganged circuit breaker.
In contrast to the ganged external circuit breakers of the external power equipment for the computer system, multiple internal circuit breakers for the computer system are typically un-ganged. That is, the internal circuit breakers are not mechanically coupled together. Accordingly, if one internal circuit breaker trips, the other internal circuit breakers do not automatically trip. As a result, computer systems can be designed with fault tolerant power features (e.g., multiple power units) which enable the computer systems to remain powered up and operational even when one of multiple internal circuit breakers trip (e.g., when one of three internal circuit breakers that respectively protect three power units trips leaving two internal circuit breakers and two power units operational).
The above-described external and internal circuit breakers typically carry alternating current (AC). In contrast, some circuit breaker suppliers market circuit breakers designed to carry direct current (DC). In either case, circuit breaker suppliers typically rate their circuit breakers with a threshold (e.g., 1 5-amp, 30-amp, 50-amp, etc.) and a trip coil tolerance (e.g., +/−35%). Prior to releasing their circuit breakers into the stream of commerce, the suppliers can test their circuit breakers to confirm that their circuit breakers conform to their rated specifications.
In one testing approach, the supplier installs a circuit breaker in a test assembly, and places the connection mechanism of that circuit breaker into the set position. The supplier then verifies that the circuit breaker properly allows current to pass through it by providing, through the circuit breaker, a test current (e.g., from a signal generator, a transformer, etc.) that is lower than a rated threshold for that circuit breaker (e.g., 30 amperes). If the supplier is testing an AC circuit breaker, the supplier provides alternating current; if the supplier is testing a DC circuit breaker, the supplier provides direct current. Next, the supplier attempts to increase the current (e.g., incrementally) until the current exceeds the rated threshold. If the circuit breaker operates properly, the connection mechanism of the circuit breaker trips when the magnitude of the current is within a specified tolerance of the rated threshold (e.g., +/−35%), thus preventing further current from passing through the circuit breaker. If the circuit breaker does not trip within this tolerance (or if the circuit breaker tripped prematurely before the current exceeded the threshold), the supplier typically considers the circuit breaker defective and does not ship that circuit breaker. Suppliers can increase the sophistication of the tests by varying the time delays between incremental current increases and measuring time delays before the circuit breaker trips. Such data can then be plotted to provide performance curves describing the expected performance under different current conditions.
In situat
EMC Corporation
Frank Elliot
LandOfFree
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