Source: http://www.google.com/patents/US6072679?dq=D523,461
Timestamp: 2016-12-08 22:21:58
Document Index: 615631848

Matched Legal Cases: ['Application No. 08', 'Application No. 08', 'Application No. 09', 'Application No. 08', 'Application No. 09', 'Application No. 08', 'Application No. 09', 'Application No. 08']

Patent US6072679 - Electric protection systems including PTC and relay-contact-protecting RC ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAn electrical protection system includes a control element of a series combination of a PTC device thermally coupled with a resistive device, and a relay coil coupled with relay contacts. If the relay contacts are open the only way in which they can be closed is by supplying current to the relay coil...http://www.google.com/patents/US6072679?utm_source=gb-gplus-sharePatent US6072679 - Electric protection systems including PTC and relay-contact-protecting RC-diode networkAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS6072679 APublication typeGrantApplication numberUS 09/273,635Publication dateJun 6, 2000Filing dateMar 23, 1999Priority dateFeb 6, 1998Fee statusPaidAlso published asCN1201456C, CN1296657A, DE69941325D1, EP1053585A1, EP1053585B1, WO1999040663A1Publication number09273635, 273635, US 6072679 A, US 6072679A, US-A-6072679, US6072679 A, US6072679AInventorsInho MyongOriginal AssigneeMyong; InhoExport CitationBiBTeX, EndNote, RefManPatent Citations (34), Non-Patent Citations (8), Referenced by (19), Classifications (9), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetElectric protection systems including PTC and relay-contact-protecting RC-diode network
US 6072679 AAbstract
An electrical protection system includes a control element of a series combination of a PTC device thermally coupled with a resistive device, and a relay coil coupled with relay contacts. If the relay contacts are open the only way in which they can be closed is by supplying current to the relay coil through a resistance-capacitance network. A diode permits current to pass through the resistance-capacitance network to the relay coil but prevents current from flowing in the opposite direction thereby preventing relay contact chatter, contact fusing, and potential relay catastrophic failure.
1. An electrical protection system which can be connected between an electrical power supply and an electrical load to form an operating circuit, the operating circuit having an on state and an off state and comprising a current carrying line and a return line, and which when so connected protects the circuit from overcurrents, the system having a normal operating condition and a fault condition, and comprising:a. a set of relay contacts which, when the system is so connected, is connected in series between the power supply and the load, and has:i. a closed state which permits the flow of a normal current, INORMAL, when the system is in the normal operating condition, and ii. an open state which permits the flow of at most a reduced current, substantially less than INORMAL, when the system is in the fault condition; b. a resistive device which, when the system is so connected, is connected in series with the set of relay contacts and the load, and hasi. a normal state, when the current in the system does not exceed the normal current, INORMAL, by a predetermined current amount and ii. a fault state, when the current in the system exceeds the normal current, INORMAL, by the predetermined amount; c. a control element which comprises a series combination ofi. a PTC device thermally coupled with the resistive device; and ii. a relay coil coupled with the relay contacts; the series combination being connected across the power supply, between the current carrying line and the return line, with the PTC device connected to the current carrying line and the relay coil coupled to the return line; the set of relay contacts changing from its closed state to its open state, thereby causing the system to change from its normal operating condition to its fault condition, when the resistance of the PTC device increases by a predetermined resistance amount in response to the resistive device changing from its normal state to its fault state; d. a resistance-capacitance network through which current can be supplied to the relay coil, so that if the relay contacts are open, the only way in which they can be closed is by supplying current to the relay coil through the resistance-capacitance network; and e. a diode or other electrical component which permits current to pass through the resistance-capacitance network to the relay coil but which prevents it from flowing in the opposite direction. Description
This is a continuation of patent application Ser. No. 09/019,766, filed on Feb. 6, 1998, and now abandoned.
The present application is related to U.S. patent application Ser. No. 09/019,767, filed on Feb. 6, 1998, now abandoned in favor of a co-pending continuation application Ser. No. 09/274,561, filed on Mar. 23, 1999. In these related applications there are described a number of improved protection systems based on those disclosed in Ser. Nos. 08/869,905, 08/682,067 and 08/682,172. The entire disclosure of U.S. patent applications Ser. Nos. 09/019,767 and 09/274,561 is incorporated herein by reference for all purposes. The present invention provides further improvements in the systems disclosed in Ser. Nos. 08/868,905, 08/682,172 and in Ser. Nos. 09/019,767 and 09/274,561 having the same filing date as the parent of this application.
PTC devices are well known. Particularly useful devices contain PTC elements composed of a PTC conductive polymer, i.e. a composition comprising an organic polymer and, dispersed or otherwise distributed therein, a particulate conductive filler, e.g. carbon black, or a metal or a conductive metal compound. Such devices are referred to herein as polymer PTC, or PPTC, devices. Other PTC materials are also known, e.g. doped ceramics, but are not as generally useful as PTC conductive polymer, in particular because they have higher resistivities. PTC devices can be used in a number of different ways, and are particularly useful in circuit protection applications, in which they function as remotely resettable fuses to protect electrical components from excessive currents and/or temperatures. Components which can be protected in this way include motors, batteries, loudspeakers and wiring harnesses in automobiles. The use of PPTC devices in this way has grown rapidly over recent years, and continues to increase. Reference may be made for example to U.S. Pat. Nos. 4,237,441, 4,238,812, 4,315,237, 4,317,027, 4,426,633, 4,545,926, 4,689,475, 4,724,417, 4,774,024, 4,780,598, 4,800,253, 4,845,838, 4,857,880, 4,859,836, 4,907,340, 4,924,074, 4,935,156, 4,967,176, 5,049,850, 5,089,801, 5,378,407, 5,451,919, 5,451,921, and 5,645,746, and to copending commonly assigned U.S. application Ser. No. 08/900,787 (Graves et al., filed Jul. 25, 1997), now U.S. Pat. No. 5,852,397 the disclosures of which are incorporated herein by reference for all purposes.
More recently, it has been proposed to combine PTC devices with other electrical components to provide circuit protection systems which respond to faults in ways which make use of the characteristics of both the PTC device and the electrical component. Reference may be made for example to U.S. Pat. Nos. 5,666,254 and 5,689,395, and to copending commonly assigned U.S. application Ser. Nos. 08/564,465 (Duffy et al., filed Nov. 29, 1995), now U.S. Pat. No. 5,864,458, Ser. No. 08/563,321 (Duffy et al., filed Nov. 28, 1995), now Pat. No. 5,745,322 Ser. No. 08/584,861 (Duffy et al., filed Jan. 5, 1996), abandoned in favor of continuation application Ser. No. 09/145,799, filed on Sep. 2, 1998, which has been abandoned in favor of continuation application Ser. No. 09/311,785 filed on May 14, 1999 Ser. No. 08/658,782 (Duffy et al., filed Jun. 5, 1996) now abandoned 08/682,067 (Myong et al., filed Jul. 16, 1996) abandoned in favor of continuation application Ser. No. 09/156,933, filed Sep. 18, 1998 and 08/682,172 (Myong, filed July 16, 1996) and 08/868,905 (Myong, filed Jun. 4, 1997), abandoned in favor of continuation application Ser. No. 09/248,166, filed on Feb. 9, 1999 the disclosures of which are incorporated herein by reference for all purposes.
As disclosed in related applications Ser. Nos. 09/019,767 and 09/274,561 the manually-operated relay switch disclosed in 08/682,067 and 08/682,172 can advantageously be replaced by a remotely operated system, preferably an RC circuit in the line to the relay coil. However, I have discovered that if there is a short circuit in the load when the relay contacts are closed, there are some conditions under which the relay contacts can chatter (i.e. continually open and close), which can lead to the contacts welding shut, and catastrophic failure. This occurs when the fault resistance is such that the current which can flow through the short circuit exceeds the current that the power source can supply. Under these circumstances, when the relay closes onto the short circuit, the system voltage (e.g. battery voltage), drops drastically. This voltage drop causes the relay to drop out restoring the battery voltage. Immediately after this, since the battery voltage has been recovered, the relay picks up again reducing the battery voltage, and the cycle continues.
The chattering is primarily due to the fact that as the system voltage drops, the voltage across the capacitor in the RC network discharges in the reverse direction, causing the relay coil to drop out.
I have realized, in accordance with the present invention, that this problem can be solved by adding to the system a diode which will prevent the capacitor from discharging in this way, and thus will keep the relay coil energized, and the relay contacts closed, for long enough to trip the PPTC and open the relay in the desired way.
An embodiment of the invention comprises an electrical protection system which can be connected between an electrical power supply and an electrical load to form an operating circuit, the operating circuit having an on state and an off state and comprising a current carrying line and a return line, and which when so connected protects the circuit from overcurrents, the system having a normal operating condition and a fault condition, and comprising:
the set of relay contacts changing from its closed state to its open state, thereby causing the system to change from its normal operating condition to its fault condition, when the resistance of the PTC device increases by a predetermined resistance amount in response to the resistive element changing from its normal state to its fault state;
d. a resistance-capacitance network through which current can be supplied to the relay coil, so that if the relay contacts are open, the only way in which they can be closed is by supplying current to the relay coil through the resistance capacitance network; and
e. a diode or other electrical component which permits current to pass through the resistance-capacitance network to the relay coil but which prevents it from flowing in the opposite direction.
FIG. 1 is a circuit diagram according to an embodiment of the present invention; and
FIG. 2 illustrates a device in which various components in FIG. 1 are packaged.
As illustrated in FIG. 1, this invention provides an electrical protection system which can be connected between an electrical power supply and an electrical load to form an operating circuit, the operating circuit having an on state and an off state and comprising a current carrying line and a return line, and which when so connected protects the circuit from overcurrents, the system having a normal operating condition and a fault condition, and comprising:
a. a set of relay contacts 16, 17 and 18 which, when the system is so connected, is connected in series between the power supply V+and the load RL, and has:
i. a PTC device 24 thermally coupled with the resistive device Rs ; and
d. a resistance-capacitance network 28 through which current can be supplied to the relay coil, so that if the relay contacts are open, the only way in which they can be closed is by supplying current to the relay coil through the resistance capacitance network; and
e. a diode 42 or other electrical component which permits current to pass through the resistance apacitance network to the relay coil but which prevents it from flowing in the opposite direction.
As shown in FIG. 2, it is particularly preferred that this system should be in the form of a device 50 which comprises components (a), (c), (d) and (e) set out above, and which also comprises five terminals which can be connected to a power source, a normally open side of the relay, a normally close side of the relay, a load, and a switching source (e.g. an electronic control module and associated FET as described in related applications Ser. Nos. 09/019,767 and 09/274,561), respectively. The device may also have a diagnostics pin out which provides logic level voltage when the PTC device has tripped. The logic level voltage is achieved by dividing the coil in appropriate proportions. Preferably the device is a pluggable device.
Various components can be packaged in the device 50 shown in FIG. 2. For example, in FIG. 2 PTC device 24, diode 44, RC network 28 and diode 42 are packaged in device 52. Relay contacts 16, 17, 18, relay coil 25 and resistor 45 are packaged in device 54. Devices 52 and 54 are packaged in device 50.
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Inc.Apparatus to prevent damage to probe cardUS7143500Jun 25, 2001Dec 5, 2006Micron Technology, Inc.Method to prevent damage to probe cardUS7219418May 26, 2005May 22, 2007Micron Technology, Inc.Method to prevent damage to probe cardUS7358686 *Nov 14, 2002Apr 15, 2008Koninklijke Philips Electronics N.V.Method and device for driving a gas discharge lampUS7561399Feb 9, 2006Jul 14, 2009Landis+Gyr, Inc.Excessive surge protection method and apparatusUS7616420 *Dec 26, 2000Nov 10, 2009Landis+Gyr, Inc.Excessive surge protection method and apparatusUS20020080545 *Dec 26, 2000Jun 27, 2002Slater Byron J.Excessive surge protection method and apparatusUS20020196120 *Jan 24, 2002Dec 26, 2002Hopkinson Philip J.Non-energy limiting class 2 transformer with positive temperature protectionUS20030122564 *Dec 20, 2002Jul 3, 2003Byrd Phillip E.Apparatus to prevent damage to probe cardUS20030122570 *Dec 20, 2002Jul 3, 2003Byrd Phillip E.Method to prevent damage to probe cardUS20030128041 *Dec 20, 2002Jul 10, 2003Byrd Phillip E.Apparatus to prevent damage to probe cardUS20050060882 *Nov 8, 2004Mar 24, 2005Byrd Phillip E.Method to prevent damage to probe cardUS20050162103 *Nov 14, 2002Jul 28, 2005Oscar DeurlooMethod and device for driving a gas discharge lampUS20050225341 *May 26, 2005Oct 13, 2005Byrd Phillip EMethod to prevent damage to probe cardUS20060126255 *Feb 9, 2006Jun 15, 2006Landisinc.Excessive surge protection method and apparatus* Cited by examinerClassifications U.S. Classification361/93.7, 361/93.1, 361/93.9, 361/165, 361/106International ClassificationH02H3/087, H02H3/08Cooperative ClassificationH02H3/085European ClassificationH02H3/08TLegal EventsDateCodeEventDescriptionApr 5, 2000ASAssignmentOwner name: TYCO INTERNATIONAL (PA), INC., A CORPORATION OF NEFree format text: MERGER & REORGANIZATION;ASSIGNOR:RAYCHEM CORPORATION, A CORPORATION OF DELAWARE;REEL/FRAME:011682/0001Effective date: 19990812Owner name: TYCO INTERNATIONAL LTD., A CORPORATION OF BERMUDA,Free format text: 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