Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With coupling means
Reexamination Certificate
2001-08-30
2003-06-10
Le, N. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With coupling means
C324S11700H, C324S531000, C324S508000, C324S142000, C324S457000, C324S213000
Reexamination Certificate
active
06577115
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention is directed to power delivery systems. More particularly, the present invention is directed to an apparatus that facilitates the measuring and testing of electrical power present in a circuit or delivered to a device and a method for assembling the apparatus.
2. Background of the Invention
While systems to monitor power characteristics of an electrical circuit have been proposed in the past, all of those systems suffered from shortcomings that prevented them from successful deployment in critical applications.
Most of the prior art devices cannot be used to measure current because any current measuring device placed over all of the conductors would result in an inaccurate reading of current because the power passing through the conductors would be out of phase and would result in a reading of nearly zero current flow.
U.S. Pat. No. 3,206,707 to Lo Vetere discloses an electronic circuit testing apparatus. The Lo Vetere apparatus is used for servicing tube-type radio and television sets. Lo Vetere teaches a length of insulated conductor having a bare uninsulated portion referred to as a breakout lead, and an insulating tubular sleeve frictionally fitted around the insulated conductor that can be slid along the conductor for covering and uncovering the bare insulated portion. See FIGS. 1 and 3 of Lo Vetere. The purpose of the Lo Vetere invention is to conveniently expose, disconnect, and reconnect live wires for test leads at point 3—3. See FIG. 1. This is also discussed in column 2, lines 59-67. The breakout lead of the '707 patent is attached to electronic tube sockets. This system, with energized bare conductors, would be unacceptable for any critical hardware. Use of the breakout lead could easily short-out the leads causing disruption of electrical service to the critical hardware. If any part of the monitoring circuitry failed, it could cause the power to fail, thus causing the critical hardware to fail.
The device disclosed in U.S. Pat. No. 3,206,707 is a testing device used for tube-type radio and television components like tubes, capacitors, resistors. See column 1, lines 30-37. It also connects to bare leads. The device disclosed in the '707 could not be used in a critical situations. The exposed wire leads and lack of mechanical protection of the conductors would likely cause short circuits.
This device is for use by trained technicians who would not be endangered by the exposed energized electrical leads. Because of the inherent danger of the easily exposed conductors, the apparatus must not be installed permanently in populated areas. (National Electrical Code: Article 110-27 “Guarding of Live Parts”)
U.S. Pat. No. 3,559,200 to Walters discloses a monitoring unit for signaling a specific condition in the circuitry supplying power to an electrical device. This patent monitors and records voltage used by an electrical device and takes action on the results.
The monitoring unit according to the '200 patent has electronic components attached to the power source that directly feed the critical hardware. If any part of the monitoring circuitry fails, it could cause the power to fail, thus causing any hardware to fail. The electronic components used in this device are part of the device and as such will become obsolete as time passes. The device disclosed in the Walters patent does not allow the removal or reinstallation of the metering and test equipment without interrupting the critical power supply.
The internal electronic circuitry of the apparatus uses the same electrical source that supplies the appliance being monitored. This can influence and affect the power delivered to the appliance. There are also discrete electrical connections shown in FIG. 4: conductor P and conductor 18 are connected; conductor G and conductor 19 are connected; and conductor N and conductor 20 are connected. These connections would impose an additional point of failure on the circuit. If, for any reason, any electronic component should fail, the result could change quality or characteristic of the incoming electrical power. The failure could even cause a short circuit and disrupt the power.
U.S. Pat. No. 3,878,458 to Muska discloses an electrical safety test apparatus for detecting leakage, current-tripping current and proper grounding. Muska U.S. Pat. No. 3,878,458 discloses a device designed for ground fault interruption. The apparatus is the forerunner of the receptacle commonly seen in bathrooms today. It uses, for its control circuit, the same electrical source that supplies the appliance being served. In doing so there are discrete electrical connections to conductors 25, 26, and 27.
This patent has electronic components attached to the power source that directly feed the critical hardware. If any part of the monitoring circuitry fails, it could cause the power to fail, thus causing the any hardware connected to it to fail as well. In contrast to the present invention, this device is specifically designed to interrupt power. The apparatus disclosed in the '458 patent does not allow metering and test equipment removal or reinstallation without interrupting the critical power supply.
U.S. Pat. No. 3,990,003 to Agee discloses a pulsed available conductor antenna-conduit electromagnetic radiator test technique for electromagnetic-shielding flaw detection in buried conduits and shielded conductors.
The electronic circuit testing apparatus disclosed in this patent is used for detecting buried conduit shielding flaws. The '003 patent does not have any provision to measure current or provide a place to install a current meter. This device only detects flaws in the outer metal covering (pipe or shield). A small antenna wire is installed in the pipe or cable assembly at the time of construction. The device reads the broadcast signal from this antenna wire through the side wall casing of the pipe or metal shield detecting flaws in the outer covering.
U.S. Pat. No. 4,182,982 to Wolf discloses a current-sensing transducer for power line current measurements. The device disclosed in the '982 patent is a current divider that is used to measure large magnitudes of AC current. Electric utilities use this device to meter industrial and commercial buildings. These types of devices are designed and built for specific needs and installed in locations locked away from the public. Once installed, these devices cannot be altered, removed or re-installed with the power on.
The transducer does not directly measure the current through the tested power line. Instead, the disclosed device estimates the total power by measuring only a small portion of the power traveling through a power line. This is because the total power is mechanically split, and the Wolf '982 device must then estimate the total power by measuring the power in the portion that has been split off of the main power line.
The Wolf '982 device also includes conductors in the power circuit. In column 7 lines 29 to 32, Wolf states: “The conductors 31 and 32 are connected to opposite terminal ends 75 of the conductive member 72 and the conductors 33 and 34 are connected to opposite terminal ends 75 of the conductive member 74.” Wolf also teaches components disposed between the conductors. In the Abstract, Wolf teaches: “A current-sensing transducer includes a conductive current divider including a branch path for conduction a fractional current proportional to a current to be sensed and being applied through the divider. A compensated transformer includes a primary circuit responsive to the fractional current and two secondary windings.” These connections would impose an additional point of failure on the circuit. If, for any reason, any electronic component should fail, the result could change quality or characteristic of the incoming electrical power. It could even cause a short circuit and disrupt the power.
U.S. Pat. No. 4,240,059 to Wolf discloses a current divider for a current sensing transducer. The device disclosed in the '059 patent is a
Bednarek Michael D.
Hamdan Wasseem H.
Le N.
Shaw Pittman LLP
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