US20010005303A1 - Current Limiter for a network - Google Patents
Current Limiter for a network Download PDFInfo
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- US20010005303A1 US20010005303A1 US09/771,152 US77115201A US2001005303A1 US 20010005303 A1 US20010005303 A1 US 20010005303A1 US 77115201 A US77115201 A US 77115201A US 2001005303 A1 US2001005303 A1 US 2001005303A1
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/43—Programme-control systems fluidic
- G05B19/44—Programme-control systems fluidic pneumatic
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
- H02H9/025—Current limitation using field effect transistors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
- H02H3/042—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned combined with means for locating the fault
Definitions
- the present invention relates to a fieldbus network and, more particularly, to a current limiter to protect a fieldbus network from an electrical short in a spur cable or a device attached to a spur cable.
- sensors measure position, motion, pressure, temperature, flow, and other parameters related to the operation of process machinery and activities.
- Actuators such as valves and motor controllers, control the operation of the machinery and process activities.
- the sensors and actuators are remotely located from the human and computerized controllers which gather information from the sensors and direct operation of the actuators.
- a communication network links the controllers with the sensors and actuators located in the field.
- Communication utilizing digital signaling reduces the susceptibility of the communication system to noise and provides a capability for conveying a wide range of information over the communication network.
- Digital communication also permits several different devices to communicate over a single pair of wires.
- Remote devices used in connection with a digital communication system typically incorporate local “intelligence.” This permits sensors and actuators to perform diagnostic, control, and maintenance functions locally. Further, the local intelligence permits the devices to communicate directly with each other and perform some functions without the necessity of involving a central control facility, thus promoting the development of distributed control systems.
- Fieldbus is a generic term used to describe a digital, bidirectional, multidrop, serial communication network for connecting isolated field devices, such as controllers, actuators and sensors, in industrial applications.
- One such fieldbus is defined by the Instrument Society of America standard, ISA SP50.02. This system utilizes a two-wire bus to provide simultaneous digital communication and DC power to remotely located devices.
- FIG. 1 While fieldbus installations are as varied as the industrial applications with which they are used, an exemplary fieldbus installation is illustrated in FIG. 1.
- a twisted pair cable referred to as the home run 2 , connects a digital control system 4 and a DC power supply 6 with a number of devices 8 (actuators, sensors, power supplies, and local controllers) in the field.
- the digital control system 4 and the DC power supply 6 may be located in a control room 10 .
- the power supply 6 could be located in the field or at a marshaling panel. If wiring runs are long, it may be desirable to power the network from more than one point with additional power supplies 15 .
- a power conditioner 22 is necessary to isolate the DC power supplies from the bus.
- the DC power supply will attempt to maintain a constant output voltage which, in the absence of isolation, would prevent propagation of the digital signal on the network.
- the development of the digital fieldbus may also mean that controllers are located in the field.
- a terminator 16 comprising a resistor 18 and a series capacitor 20 connected across the wires of the home run cable 2 must be provided at both ends of the home run cable 2 .
- the varying voltage of the digital signal is produced when an attached device varies the current drawn from the network producing a voltage drop across the resistor 18 of the terminator 16 .
- the capacitor 20 of the terminator 16 prevents dissipation of the DC power through the terminator resistor 18 while permitting transmission of the high frequency digital signal on the bus.
- the terminators 16 serve to prevent signals from reflecting from the ends of the home run wires 2 .
- devices can be connected along the home run cable 2 with spur cables 14 that are connected to the home run by spur connectors 13 .
- the chicken foot 12 and the spur connectors 13 provide a convenient means for interconnecting the wires of the home run 2 and the spur cables 14 .
- the positive and negative wires and the shield of the spur cable 14 have been directly connected to the corresponding conductors of the home run cable 2 .
- Direct connection of the individual wires is facilitated by terminals within the chicken foot 2 and spur connection 13 connector blocks.
- the wiring of a spur cable 14 or a connected device should become shorted, neither the DC power nor the digital signals can be sent over the network and the entire network is disabled.
- Disabling the network may cause an entire plant or process to be shut down with severe economic consequences. Further, safety may make the ability to continue to monitor and control other parts of the plant or process particularly essential when one part of the system is malfunctioning. The shutting down of the entire network may also make it much more difficult and time consuming to find the short and make repairs.
- the present invention overcomes the aforementioned drawbacks of the prior art by providing a fieldbus network comprising a home run conductor; a spur conductor electrically connected to the home run conductor; and a spur current limiter interposed between the spur conductor and the home run conductor.
- the spur current limiter provides a conduction path between the spur conductor and the home run conductor in which the impedance is varied as a function of the current in the spur conductor.
- the current in the spur conductor will increase causing the impedance of the current limiter to increase.
- the increased impedance of the conduction path through the current limiter limits the current flow in the spur conductor.
- the current limiter causes the spur to appear as a large impedance so the remainder of the network can continue to function.
- a method of connecting a spur cable to a home run of a field bus network comprising connecting a home run conductor to a connecting conductor in a connecting block; connecting a spur cable conductor to an electrically conducting current limiter; and engaging the connecting block and the connecting conductor with the current limiter to electrically connect the spur conductor and the home run conductor.
- the current requirements of a spur may not be known in advance. Connecting spurs to the home run through a separate current limiter with a plug connector that engages the connecting block permits the use of a universal connecting block in assembling networks with a current limiter selected from a stock for each specific spur's operating current requirement.
- FIG. 1 is a block diagram of an exemplary field bus network installation.
- FIG. 2 illustrates a spur cable connection block incorporating the current limiter of the present invention.
- FIG. 3 illustrates a spur cable connection block with a separate, plug connected current limiter.
- FIG. 4 is a schematic diagram of a current limiter according to the present invention.
- FIG. 5 is a schematic diagram for a current limiter according to the present invention having an alternative circuit to that illustrated in FIG. 4.
- FIG. 1 An exemplary fieldbus installation is illustrated in FIG. 1.
- a shielded, twisted pair cable referred to as the home run 2 , connects a digital control system 4 and a DC power supply 6 with a number of devices 8 (actuators, sensors and local controllers) in the field.
- the digital control system 4 and the DC power supply 6 may be located in a control room 10 .
- the power supply 6 could be located in the field or at a marshaling panel. If wiring runs are long, it may be desirable to power the network from more than one point with additional power supplies 15 .
- a power conditioner 22 is necessary to isolate the DC power supplies from the bus.
- the DC power supply will attempt to maintain a constant output voltage which, in the absence of isolation, would prevent propagation of the digital signal on the network.
- the development of the digital fieldbus may also mean that controllers are located in the field.
- a terminator 16 comprising a resistor 18 and a series capacitor 20 connected across the wires of the home run cable 2 must be provided at both ends of the home run cable 2 .
- the varying voltage of the digital signal is produced when an attached device varies the current drawn from the network producing a voltage drop across the resistor 18 of the terminator 16 .
- the capacitor 20 of the terminator 16 prevents dissipation of the DC power through the terminator resistor 18 while permitting transmission of the high frequency digital signal on the bus.
- the terminators 16 serve to prevent signals from reflecting from the ends of the home run wires 2 .
- devices can be connected along the home run cable 2 with spur cables 14 that are connected to the home run by spur connectors 13 .
- the chicken foot 12 and the spur connectors 13 comprise connection blocks for interconnecting the conductors of the home run 2 and the spur cables 14 .
- the current limiter 30 of the present invention can be incorporated into the home run to spur cable connection block 33 .
- the current limiter 30 is interposed between the positive conductor 34 of the home run cable 40 (indicated by a bracket) and the positive conductor 42 of the spur cable 48 (indicated by a bracket).
- the negative conductor 36 of the home run 40 and the negative conductor 44 of the spur cable 48 and the shields 38 and 46 are directly connected in the spur cable connection block 33 .
- the connection block facilitates assembly of the network, the current requirements of the spur may not be known before installation of the network making selection of the correct connection block difficult. Further, if several spurs 48 with different current requirements are connected to a chicken foot connection, a number of different current limiters 30 may be required within a single connection block 33 .
- FIG. 3 A second technique for incorporating the spur current limiter into a fieldbus network is illustrated in FIG. 3.
- the current limiter 50 is incorporated into a separate module which include one half of a plug 51 .
- the connection block 52 incorporates the mating half of the plug connection 53 which is pre-wired to the connections for wires of the home run 57 .
- the current limiter module 50 for a particular spur connection can be selected from a supply of modules with different current limit ratings once the operating current requirement of a particular spur is known.
- the conductors 54 , 56 , and 58 of the spur cable 60 can be connected to the current limiter module 50 .
- the module 50 and the connection block 52 can be conveniently connected engaging the mating halves, 51 and 53 , of the plug.
- FIG. 4 A schematic of a circuit for the current limiter of the present invention is illustrated in FIG. 4. While operating at normal spur cable current levels, the voltage at the gate of the field effect transistor (FET) 70 is pulled low through a first resistor 72 and a light emitting diode (LED) 84 . This causes the FET 70 to conduct providing a low impedance current path through the second resistor 76 between the positive conductor 78 of the spur cable 79 (indicated by a bracket) a nd the positive conductor 80 of the home run cable 81 (indicated by a bracket).
- FET field effect transistor
- the voltage drop across the second resistor 76 provides an emitter-base bias signal responsive to current flow in the positive conductor 78 of the spur cable 79 to control conduction of the second transistor 82 .
- the value of the second resistor 76 is selected or adjusted such that under normal current requirements for the spur, the voltage drop across the second resistor 76 is less than the threshold emitter-base voltage of the second transistor 82 and the second transistor 82 does not conduct. Under this condition, the current through the LED 84 is negligible and no light is emitted.
- the increasing impedance of the FET 70 limits the current that can flow through conductor 78 of the spur cable 79 .
- the source to drain impedance of the FET 70 will increase until the voltage drop across the second resistor 76 is such that the bias signal on the second transistor 82 is at the threshold level.
- the spur has the appearance of a high impedance so that dissipation of the DC power is limited and signals on the home run 81 are not attenuated by the short circuit in the spur 79 .
- the second transistor 82 is conducting sufficient current flows through the first resistor 72 and the LED 84 to cause the LED 84 to emit light, indicating that current demand in the spur cable exceeds a normal operating or nominal level.
- the remainder of the network can continue to function in the event of a short circuit in a spur and repair crews can quickly locate and repair the malfunctioning spur.
- FIG. 5 illustrates an alternative equivalent current limiter produced with complementary transistors for the negative conductor of the fieldbus spur cable.
- the gate voltage of the FET 92 is raised through the first resistor 94 and the LED 96 causing the FET 92 to conduct.
- the second transistor 98 turns “ON” lowering the gate voltage of the FET 92 tending to turn it “OFF” increasing the impedance in the spur conductor 90 and limiting current flow.
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Abstract
A current limiter is provided to protect a fieldbus network from electrical shorts in the wiring of the spur cables and network devices attached to the spur cables. In the event of an electrical short, the impedance of the current limiter and the spur connection increases permitting the remainder of the network to continue to function. To facilitate repairs, the current limiter includes an indicator that signals excessive current in the spur. A method of connecting a spur cable to the network is provided where the spur cable is connected to a separate current limiter module that is pugged into a connector block.
Description
- This is a continuation of Application No. 09/344,408, filed Jun. 24, 1999.
- The present invention relates to a fieldbus network and, more particularly, to a current limiter to protect a fieldbus network from an electrical short in a spur cable or a device attached to a spur cable.
- In a typical industrial plant application, sensors measure position, motion, pressure, temperature, flow, and other parameters related to the operation of process machinery and activities. Actuators, such as valves and motor controllers, control the operation of the machinery and process activities. The sensors and actuators are remotely located from the human and computerized controllers which gather information from the sensors and direct operation of the actuators. A communication network links the controllers with the sensors and actuators located in the field.
- Heretofore, communication between controllers, remote sensors, and actuators in industrial applications has been by means of analog signaling. The prevailing standard for analog networking of field devices and the control room in industrial applications has been the Instrument Society of America standard, ISA S50.1. This ISA standard provides for a two-wire connection between the controller and each field device. One wire of the system carries the analog signal between the remote device and the controller. The analog signal may be converted to a digital signal useful to a computerized controller. The second wire of the circuit supplies DC power for operation of the remote sensor or actuator.
- Communication utilizing digital signaling reduces the susceptibility of the communication system to noise and provides a capability for conveying a wide range of information over the communication network. Digital communication also permits several different devices to communicate over a single pair of wires. Remote devices used in connection with a digital communication system typically incorporate local “intelligence.” This permits sensors and actuators to perform diagnostic, control, and maintenance functions locally. Further, the local intelligence permits the devices to communicate directly with each other and perform some functions without the necessity of involving a central control facility, thus promoting the development of distributed control systems.
- Fieldbus is a generic term used to describe a digital, bidirectional, multidrop, serial communication network for connecting isolated field devices, such as controllers, actuators and sensors, in industrial applications. One such fieldbus is defined by the Instrument Society of America standard, ISA SP50.02. This system utilizes a two-wire bus to provide simultaneous digital communication and DC power to remotely located devices.
- While fieldbus installations are as varied as the industrial applications with which they are used, an exemplary fieldbus installation is illustrated in FIG. 1. A twisted pair cable, referred to as the
home run 2, connects adigital control system 4 and a DC power supply 6 with a number of devices 8 (actuators, sensors, power supplies, and local controllers) in the field. Thedigital control system 4 and the DC power supply 6 may be located in acontrol room 10. The power supply 6 could be located in the field or at a marshaling panel. If wiring runs are long, it may be desirable to power the network from more than one point withadditional power supplies 15. Apower conditioner 22 is necessary to isolate the DC power supplies from the bus. The DC power supply will attempt to maintain a constant output voltage which, in the absence of isolation, would prevent propagation of the digital signal on the network. The development of the digital fieldbus may also mean that controllers are located in the field. -
Several devices 8 can be connected to thehome run 2 byspur cables 14 at a terminal referred to as achicken foot 12 which incorporates signal termination for the home run. Aterminator 16 comprising aresistor 18 and aseries capacitor 20 connected across the wires of thehome run cable 2 must be provided at both ends of thehome run cable 2. The varying voltage of the digital signal is produced when an attached device varies the current drawn from the network producing a voltage drop across theresistor 18 of theterminator 16. Thecapacitor 20 of theterminator 16 prevents dissipation of the DC power through theterminator resistor 18 while permitting transmission of the high frequency digital signal on the bus. In addition, theterminators 16 serve to prevent signals from reflecting from the ends of thehome run wires 2. - In addition to the devices connected to the home wiring at a chicken foot, devices can be connected along the
home run cable 2 withspur cables 14 that are connected to the home run byspur connectors 13. Thechicken foot 12 and thespur connectors 13 provide a convenient means for interconnecting the wires of thehome run 2 and thespur cables 14. Heretofore, the positive and negative wires and the shield of thespur cable 14 have been directly connected to the corresponding conductors of thehome run cable 2. Direct connection of the individual wires is facilitated by terminals within thechicken foot 2 and spurconnection 13 connector blocks. However, if the wiring of aspur cable 14 or a connected device should become shorted, neither the DC power nor the digital signals can be sent over the network and the entire network is disabled. Disabling the network may cause an entire plant or process to be shut down with severe economic consequences. Further, safety may make the ability to continue to monitor and control other parts of the plant or process particularly essential when one part of the system is malfunctioning. The shutting down of the entire network may also make it much more difficult and time consuming to find the short and make repairs. - What is desired, therefore, is an apparatus that causes a network spur to appear as a high impedance in the event of a short circuit in the spur, limiting the current drawn by the spur and permitting the remainder of the network to continue to function. Further, an indicator of abnormal current draw in a spur is desired to facilitate maintenance and repair.
- The present invention overcomes the aforementioned drawbacks of the prior art by providing a fieldbus network comprising a home run conductor; a spur conductor electrically connected to the home run conductor; and a spur current limiter interposed between the spur conductor and the home run conductor. The spur current limiter provides a conduction path between the spur conductor and the home run conductor in which the impedance is varied as a function of the current in the spur conductor. In the event of a short circuit in the wiring of the spur cable or a device attached to the spur cable, the current in the spur conductor will increase causing the impedance of the current limiter to increase. The increased impedance of the conduction path through the current limiter limits the current flow in the spur conductor. During current limiting operation, the current limiter causes the spur to appear as a large impedance so the remainder of the network can continue to function.
- A method of connecting a spur cable to a home run of a field bus network is provided comprising connecting a home run conductor to a connecting conductor in a connecting block; connecting a spur cable conductor to an electrically conducting current limiter; and engaging the connecting block and the connecting conductor with the current limiter to electrically connect the spur conductor and the home run conductor. The current requirements of a spur may not be known in advance. Connecting spurs to the home run through a separate current limiter with a plug connector that engages the connecting block permits the use of a universal connecting block in assembling networks with a current limiter selected from a stock for each specific spur's operating current requirement.
- The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
- FIG. 1 is a block diagram of an exemplary field bus network installation.
- FIG. 2 illustrates a spur cable connection block incorporating the current limiter of the present invention.
- FIG. 3 illustrates a spur cable connection block with a separate, plug connected current limiter.
- FIG. 4 is a schematic diagram of a current limiter according to the present invention.
- FIG. 5 is a schematic diagram for a current limiter according to the present invention having an alternative circuit to that illustrated in FIG. 4.
- An exemplary fieldbus installation is illustrated in FIG. 1. A shielded, twisted pair cable, referred to as the
home run 2, connects adigital control system 4 and a DC power supply 6 with a number of devices 8 (actuators, sensors and local controllers) in the field. Thedigital control system 4 and the DC power supply 6 may be located in acontrol room 10. The power supply 6 could be located in the field or at a marshaling panel. If wiring runs are long, it may be desirable to power the network from more than one point with additional power supplies 15. Apower conditioner 22 is necessary to isolate the DC power supplies from the bus. The DC power supply will attempt to maintain a constant output voltage which, in the absence of isolation, would prevent propagation of the digital signal on the network. The development of the digital fieldbus may also mean that controllers are located in the field. -
Several devices 8 can be connected to thehome run 2 byspur cables 14 at a connection block referred to as achicken foot 12 which incorporates signal termination for the home run. Aterminator 16 comprising aresistor 18 and aseries capacitor 20 connected across the wires of thehome run cable 2 must be provided at both ends of thehome run cable 2. The varying voltage of the digital signal is produced when an attached device varies the current drawn from the network producing a voltage drop across theresistor 18 of theterminator 16. Thecapacitor 20 of theterminator 16 prevents dissipation of the DC power through theterminator resistor 18 while permitting transmission of the high frequency digital signal on the bus. In addition, theterminators 16 serve to prevent signals from reflecting from the ends of thehome run wires 2. - In addition to the devices connected to the home run wiring at a chicken foot, devices can be connected along the
home run cable 2 withspur cables 14 that are connected to the home run byspur connectors 13. Thechicken foot 12 and thespur connectors 13 comprise connection blocks for interconnecting the conductors of thehome run 2 and thespur cables 14. - Referring to FIG. 2, the
current limiter 30 of the present invention can be incorporated into the home run to spurcable connection block 33. As illustrated in FIG. 2, thecurrent limiter 30 is interposed between thepositive conductor 34 of the home run cable 40 (indicated by a bracket) and thepositive conductor 42 of the spur cable 48 (indicated by a bracket). Thenegative conductor 36 of thehome run 40 and thenegative conductor 44 of thespur cable 48 and theshields cable connection block 33. While the connection block facilitates assembly of the network, the current requirements of the spur may not be known before installation of the network making selection of the correct connection block difficult. Further, if several spurs 48 with different current requirements are connected to a chicken foot connection, a number of differentcurrent limiters 30 may be required within asingle connection block 33. - A second technique for incorporating the spur current limiter into a fieldbus network is illustrated in FIG. 3. The
current limiter 50 is incorporated into a separate module which include one half of aplug 51. Theconnection block 52 incorporates the mating half of theplug connection 53 which is pre-wired to the connections for wires of thehome run 57. Thecurrent limiter module 50 for a particular spur connection can be selected from a supply of modules with different current limit ratings once the operating current requirement of a particular spur is known. Theconductors spur cable 60 can be connected to thecurrent limiter module 50. Themodule 50 and theconnection block 52 can be conveniently connected engaging the mating halves, 51 and 53, of the plug. - A schematic of a circuit for the current limiter of the present invention is illustrated in FIG. 4. While operating at normal spur cable current levels, the voltage at the gate of the field effect transistor (FET)70 is pulled low through a
first resistor 72 and a light emitting diode (LED) 84. This causes theFET 70 to conduct providing a low impedance current path through thesecond resistor 76 between thepositive conductor 78 of the spur cable 79 (indicated by a bracket) a nd thepositive conductor 80 of the home run cable 81 (indicated by a bracket). The voltage drop across thesecond resistor 76 provides an emitter-base bias signal responsive to current flow in thepositive conductor 78 of thespur cable 79 to control conduction of thesecond transistor 82. The value of thesecond resistor 76 is selected or adjusted such that under normal current requirements for the spur, the voltage drop across thesecond resistor 76 is less than the threshold emitter-base voltage of thesecond transistor 82 and thesecond transistor 82 does not conduct. Under this condition, the current through theLED 84 is negligible and no light is emitted. - In the event of an electrical short in the
spur cable 79 or an attached device, the current flow in thespur cable 79 will increase. With increased current flow through thesecond resistor 76 the voltage drop across theresistor 76 will increase. When the voltage drop across thesecond resistor 76 exceeds the threshold emitter-base bias of thesecond transistor 82, thetransistor 82 will conduct. The additional current flowing through thesecond transistor 82 increases the voltage drop across thefirst resistor 72 causing an increase in the voltage at the gate of theFET 70. The reduced bias of theFET 70 causes theFET 70 to tend toward an “OFF” state increasing source to drain impedance of theFET 70. The increasing impedance of theFET 70 limits the current that can flow throughconductor 78 of thespur cable 79. The source to drain impedance of theFET 70 will increase until the voltage drop across thesecond resistor 76 is such that the bias signal on thesecond transistor 82 is at the threshold level. During “current limiting” operation, the spur has the appearance of a high impedance so that dissipation of the DC power is limited and signals on thehome run 81 are not attenuated by the short circuit in thespur 79. When thesecond transistor 82 is conducting sufficient current flows through thefirst resistor 72 and theLED 84 to cause theLED 84 to emit light, indicating that current demand in the spur cable exceeds a normal operating or nominal level. As result of incorporation of the current limiter into the network, the remainder of the network can continue to function in the event of a short circuit in a spur and repair crews can quickly locate and repair the malfunctioning spur. - FIG. 5 illustrates an alternative equivalent current limiter produced with complementary transistors for the negative conductor of the fieldbus spur cable. In this case, the gate voltage of the
FET 92 is raised through thefirst resistor 94 and theLED 96 causing theFET 92 to conduct. When the current flow in the spur increases, thesecond transistor 98 turns “ON” lowering the gate voltage of theFET 92 tending to turn it “OFF” increasing the impedance in thespur conductor 90 and limiting current flow. - All the references cited herein are incorporated by reference.
- The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.
Claims (14)
1. A fieldbus network comprising:
(a) a home run conductor;
(b) a spur conductor electrically connected to said home run conductor;
and
(c) a spur current limiter interposed between said spur conductor and said home run conductor.
2. The network of further comprising an indicator that current in said spur conductor exceeds a nominal current.
claim 1
3. The network of claim I wherein said spur conductor current limiter comprises:
(a) a variable impedance conductor interposed between said spur conductor and said home run conductor; and
(b) an impedance adjuster to increase said impedance of said variable impedance conductor in response to electrical current in said spur conductor greater than a nominal current.
4. The apparatus of wherein said variable impedance conductor comprises a first transistor connected to conduct current between said spur conductor and said home run conductor and having a bias influenced by said impedance adjuster.
claim 3
5. The apparatus of wherein said impedance adjuster comprises a second transistor having a bias signal responsive to said current in said spur conductor and connected to reduce said bias of said first transistor in response to an increase in said spur conductor current.
claim 4
6. An apparatus to limit an electrical current in a spur conductor connected a home run conductor of a field bus network comprising;
(a) a variable impedance conductor electrically connecting said spur conductor to said home run conductor; and
(b) an impedance adjuster to alter said impedance of said variable impedance conductor in response to a change in current in said spur conductor.
7. The apparatus of further comprising an indicator that said electrical current in said spur conductor exceeds a nominal current.
claim 6
8. The apparatus of wherein said variable impedance conductor comprises a first transistor connected to conduct current between said spur conductor and said home run conductor and having a bias influenced by said impedance adjuster.
claim 6
9. The apparatus of wherein said impedance adjuster comprises a second transistor having a bias signal responsive to said current in said spur conductor and connected to reduce said bias of said first transistor in response to an increase in said current in said spur conductor.
claim 8
10. An apparatus to limit current in a spur conductor electrically connected to a home run conductor of a fieldbus network comprising:
(a) a first transistor electrically connected to vary the impedance of said spur conductor in response to a bias signal to said first transistor; and
(b) a second transistor electrically connected to vary said bias signal to said first transistor in response to a change in said current in said spur conductor.
11. The apparatus of further comprising an indicator that said electrical current in said spur conductor exceeds a nominal current.
claim 10
12. An apparatus to limit current in a spur conductor electrically connected to a home run conductor of a fieldbus network comprising:
(a) a first transistor electrically connected to vary the impedance of said spur conductor in response to a bias of said first transistor;
(b) a second transistor electrically connected to vary said bias of said first transistor in response to a change in said current in said spur conductor; and
(c) an indicator of said current in said spur conductor responsive to said variation of said bias of said first transistor.
13. An apparatus to connect a first conductor to a second conductor of a fieldbus network comprising:
(a) a connection block including a conductive connection between a mounting terminal for said first conductor and an first electrical connection arranged for selective engagement; and
(b) a current limiter including a conductive connection between a mounting terminal for said second conductor and a second electrical connection arranged for selective engagement with said first electrical connection of said connection block.
14. A method for connecting a first conductor and a second conductor of a fieldbus network comprising:
(a) connecting said first conductor to a conductor arranged for selective engagement;
(b) connecting said second conductor to an electrically conducting current limiter; and
(c) engaging said current limiter and said conductor arranged for selective engagement.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/771,152 US6369997B2 (en) | 1999-06-24 | 2001-01-26 | Current limiter for a network |
US09/866,187 US6519125B2 (en) | 1999-06-24 | 2001-05-24 | Current limiter for a network |
US10/295,235 US6870722B2 (en) | 1999-06-24 | 2002-11-14 | Enhanced spur cable circuit protection device and method for its implementation |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/344,408 US6366437B1 (en) | 1999-06-24 | 1999-06-24 | Current limiter for a network |
US09/771,152 US6369997B2 (en) | 1999-06-24 | 2001-01-26 | Current limiter for a network |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/344,408 Continuation US6366437B1 (en) | 1999-06-24 | 1999-06-24 | Current limiter for a network |
Related Child Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/866,187 Continuation US6519125B2 (en) | 1999-06-24 | 2001-05-24 | Current limiter for a network |
US09/886,187 Continuation US6950945B2 (en) | 2001-06-21 | 2001-06-21 | Apparatus and method for intersystem lock optimization |
Publications (2)
Publication Number | Publication Date |
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US20010005303A1 true US20010005303A1 (en) | 2001-06-28 |
US6369997B2 US6369997B2 (en) | 2002-04-09 |
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Application Number | Title | Priority Date | Filing Date |
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US09/344,408 Expired - Lifetime US6366437B1 (en) | 1999-06-24 | 1999-06-24 | Current limiter for a network |
US09/771,152 Expired - Lifetime US6369997B2 (en) | 1999-06-24 | 2001-01-26 | Current limiter for a network |
US09/866,187 Expired - Lifetime US6519125B2 (en) | 1999-06-24 | 2001-05-24 | Current limiter for a network |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/344,408 Expired - Lifetime US6366437B1 (en) | 1999-06-24 | 1999-06-24 | Current limiter for a network |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/866,187 Expired - Lifetime US6519125B2 (en) | 1999-06-24 | 2001-05-24 | Current limiter for a network |
Country Status (1)
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US (3) | US6366437B1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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CN102570433A (en) * | 2010-12-10 | 2012-07-11 | 沈阳中科博微自动化技术有限公司 | FF bus junction box |
DE102013213724A1 (en) * | 2013-07-12 | 2015-01-15 | Siemens Aktiengesellschaft | Bus connection device |
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US6268716B1 (en) * | 1998-10-30 | 2001-07-31 | Volterra Semiconductor Corporation | Digital voltage regulator using current control |
DE20005927U1 (en) * | 1999-03-31 | 2000-10-19 | Pepperl & Fuchs | Safety barrier to limit current and voltage |
US6870722B2 (en) * | 1999-06-24 | 2005-03-22 | Relcom, Inc. | Enhanced spur cable circuit protection device and method for its implementation |
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ITMI20021234A1 (en) * | 2002-06-06 | 2003-12-09 | Mhouse Srl | ELECTRIC CONTROL SYSTEM OF AT LEAST A GATE OR A GATE OR A SIMILAR ELEMENT OF AN ELECTRICALLY MOVED TYPE |
DE102004037924A1 (en) * | 2004-08-04 | 2006-03-16 | Endress + Hauser Process Solutions Ag | Modular connection device in a bus system for protecting an electrical consumer |
US20060176629A1 (en) * | 2005-02-08 | 2006-08-10 | Maris Graube | Networks for process control |
US7633733B1 (en) * | 2005-08-18 | 2009-12-15 | Moore Industries International, Inc. | Short circuit detector for fieldbus cable system network |
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TW200937828A (en) * | 2008-02-22 | 2009-09-01 | Macroblock Inc | Electricity -extraction circuit of AC/DC converter take |
GB201001867D0 (en) * | 2010-02-05 | 2010-03-24 | Kitchener Renato | Real time, non-disruptive, IEC61158-2 spur short circuit testing method for active device couplers |
EP2383622B1 (en) * | 2010-04-19 | 2013-05-29 | Siemens Aktiengesellschaft | Connection device for connecting field devices |
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US3571608A (en) * | 1969-04-04 | 1971-03-23 | Honeywell Inc | Protective circuit |
US3521087A (en) * | 1969-05-16 | 1970-07-21 | Spacelabs Inc | Current limiting circuit |
FR2504323B1 (en) * | 1981-04-16 | 1985-10-31 | Radiotechnique Compelec | SUBSCRIBER TELEPHONE EQUIPMENT PROVIDED WITH A SURGE PROTECTION DEVICE |
US4740859A (en) * | 1983-03-31 | 1988-04-26 | Leon A. Hoskamer | Transient voltage surge suppressor and line short monitor |
JPS60131033A (en) * | 1983-12-16 | 1985-07-12 | 東京電力株式会社 | Transmitting apparatus |
FR2601201B1 (en) * | 1986-07-03 | 1988-09-16 | Telemecanique Electrique | SHORT-CIRCUIT PROTECTION DEVICE FOR AN ALTERNATIVE NETWORK AND CIRCUIT-BREAKER-LIMITER SUITABLE FOR SUCH A DEVICE |
US5052935A (en) * | 1990-08-13 | 1991-10-01 | Delta Systems, Incorporated | Prewired circuit module |
US5331412A (en) * | 1990-11-27 | 1994-07-19 | Scientific-Atlanta, Inc. | Tamper resistant apparatus for a CATV system |
US5337208A (en) * | 1991-12-18 | 1994-08-09 | Nec America, Inc. | In-line AC current limiter |
US5415564A (en) * | 1992-09-14 | 1995-05-16 | Winter; Craig | Junction box for quick release mounting of electrical circuit components |
US5581801A (en) * | 1995-03-22 | 1996-12-03 | Scientific-Atlanta, Inc. | Apparatus for distributing RF signals and AC power to taps |
US5706157A (en) * | 1996-02-26 | 1998-01-06 | Reltec Corporation | Power distribution system with over-current protection |
US5757603A (en) * | 1996-06-21 | 1998-05-26 | Joslyn Electronic Systems Corporation | Electrical surge protection device |
US5775955A (en) * | 1996-09-17 | 1998-07-07 | Graube; Maris | Modular fieldbus terminal block |
-
1999
- 1999-06-24 US US09/344,408 patent/US6366437B1/en not_active Expired - Lifetime
-
2001
- 2001-01-26 US US09/771,152 patent/US6369997B2/en not_active Expired - Lifetime
- 2001-05-24 US US09/866,187 patent/US6519125B2/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102570433A (en) * | 2010-12-10 | 2012-07-11 | 沈阳中科博微自动化技术有限公司 | FF bus junction box |
DE102013213724A1 (en) * | 2013-07-12 | 2015-01-15 | Siemens Aktiengesellschaft | Bus connection device |
Also Published As
Publication number | Publication date |
---|---|
US6366437B1 (en) | 2002-04-02 |
US6519125B2 (en) | 2003-02-11 |
US20010022714A1 (en) | 2001-09-20 |
US6369997B2 (en) | 2002-04-09 |
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