CA2061957A1 - Digital circuit interrupter with an improved sampling algorithm - Google Patents
Digital circuit interrupter with an improved sampling algorithmInfo
- Publication number
- CA2061957A1 CA2061957A1 CA002061957A CA2061957A CA2061957A1 CA 2061957 A1 CA2061957 A1 CA 2061957A1 CA 002061957 A CA002061957 A CA 002061957A CA 2061957 A CA2061957 A CA 2061957A CA 2061957 A1 CA2061957 A1 CA 2061957A1
- Authority
- CA
- Canada
- Prior art keywords
- microprocessor
- circuit interrupter
- circuit
- keypad
- power system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- 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
- H02H3/006—Calibration or setting of parameters
Abstract
DIGITAL CIRCUIT INTERRUPTER
WITH AN IMPROVED SAMPLING ALGORITHM
ABSTRACT OF THE DISCLOSURE
A digital circuit interrupter having a keypad and display for entering and viewing the trip parameters utilizes a sampling al-gorithm to periodically sample the current within a protected circuit. The sampling algorithm allows a real time constant sampling interval independent of wide variations in the power system frequency.
WITH AN IMPROVED SAMPLING ALGORITHM
ABSTRACT OF THE DISCLOSURE
A digital circuit interrupter having a keypad and display for entering and viewing the trip parameters utilizes a sampling al-gorithm to periodically sample the current within a protected circuit. The sampling algorithm allows a real time constant sampling interval independent of wide variations in the power system frequency.
Description
i '3 7 - 1 - 41P~-6865 DIGITAL CIRCUIT INTERRUPTER
; WITH AN IMPROVED S~MPLING ALGORITHM
BACKGROUND o~ THE INVENTION
This invention relates to ~olid state circuit interrupters employing digital electronic trip units.
one such solid state circuit interrupter is described within U.S. Patent 4,589,052. Electronic trip units are used in such circuit interrupters and are capahle of acting on a number of programmed setpoint trip parameters to interrupt the ~ircuit being protected in a timely manner. One such e:Lectronic trip unit which allows for user interaction and which provides capability both to select trip parameters and to view the selected trip parameter~ is found within U.S.
Patent 4,672,501.
For purposes of reducing cost while main~aining accuracy and ~unctionality o~ the electroniG trip units,~microprocessors are being employed to gather information, process the information, ~nd provida a means of monitoring the information using associated digital circuity. The use of such microprocessors allows mora protection functions to be contained in 2 ~ 8 smaller-sized packages. Smaller-sized circuit interrupters ~ecause of limited space requirements do not contain the means required to enter data or to view the data being processed. The user-interfaces employed on larger~sized molded case circuit interrupters typically consist of rotatable switches with associated printed indicia to indicate the relative switch positions. The amount of area available on the front panel of such circuit interrupters is also limited and hence reduces the number of optional features requiring such switches.
U.S~ Patent No. 4,870,531 entitled "Circuit Breaker with Removable Display and Keypad", which Patent is incorporated herein for re~erence purposes, describes a user-interface unit that contains display capability for all possible circuit interrupter options by means of software located solely within the trip unit microprocessor while only displaying those parameters for which the electronic trip unit is conf igured .
U.S. Patent 4,991,042 entit:led "Digital Circuit 2 0 Interrupter with Keypad Data Entry and Display'l descrihes a circuit interrupter utilizins~ a digital keypad and display in combination with an electronic trip unit to enter and display the setpoint trip parameters. In determining the current and voltage values within the protected circuit for overcurrent and undervoltage calculations, a sampling algorithm is employed to periodically sample the current and voltage data on a continus~us basis such as described within aforementioned U . S . Patent 4, 672, 501. The sampling frequency for the sampling algorithm was provided by a fixed tim~r that is calculated to correspond with the 60Hz power system frequency. When the power system frequency operates at 60Hz, the sampling software is synchronized with the . ~
; WITH AN IMPROVED S~MPLING ALGORITHM
BACKGROUND o~ THE INVENTION
This invention relates to ~olid state circuit interrupters employing digital electronic trip units.
one such solid state circuit interrupter is described within U.S. Patent 4,589,052. Electronic trip units are used in such circuit interrupters and are capahle of acting on a number of programmed setpoint trip parameters to interrupt the ~ircuit being protected in a timely manner. One such e:Lectronic trip unit which allows for user interaction and which provides capability both to select trip parameters and to view the selected trip parameter~ is found within U.S.
Patent 4,672,501.
For purposes of reducing cost while main~aining accuracy and ~unctionality o~ the electroniG trip units,~microprocessors are being employed to gather information, process the information, ~nd provida a means of monitoring the information using associated digital circuity. The use of such microprocessors allows mora protection functions to be contained in 2 ~ 8 smaller-sized packages. Smaller-sized circuit interrupters ~ecause of limited space requirements do not contain the means required to enter data or to view the data being processed. The user-interfaces employed on larger~sized molded case circuit interrupters typically consist of rotatable switches with associated printed indicia to indicate the relative switch positions. The amount of area available on the front panel of such circuit interrupters is also limited and hence reduces the number of optional features requiring such switches.
U.S~ Patent No. 4,870,531 entitled "Circuit Breaker with Removable Display and Keypad", which Patent is incorporated herein for re~erence purposes, describes a user-interface unit that contains display capability for all possible circuit interrupter options by means of software located solely within the trip unit microprocessor while only displaying those parameters for which the electronic trip unit is conf igured .
U.S. Patent 4,991,042 entit:led "Digital Circuit 2 0 Interrupter with Keypad Data Entry and Display'l descrihes a circuit interrupter utilizins~ a digital keypad and display in combination with an electronic trip unit to enter and display the setpoint trip parameters. In determining the current and voltage values within the protected circuit for overcurrent and undervoltage calculations, a sampling algorithm is employed to periodically sample the current and voltage data on a continus~us basis such as described within aforementioned U . S . Patent 4, 672, 501. The sampling frequency for the sampling algorithm was provided by a fixed tim~r that is calculated to correspond with the 60Hz power system frequency. When the power system frequency operates at 60Hz, the sampling software is synchronized with the . ~
operating ~requency in an endless loop by means of a fixed timer. In some industrial distribution circuits, the power system frequency can vary from 40 to 80Hz such that the software loop no longer corresponds to the fixed 60Hz cycle generated by the fixed timer.
Accordingly, one purpose of the invention is to provide an electronic trip circuit interrupter having digital data entry and display wherein the operating software's endless loop period within the trip unit depends on the actual operating frequency of the circuit in real time rather than a predetermined fixed time interval.
SUMMARY OF THE INVENTION
A circuit interrupter having an electronic trip unit further includes a digital keypad and display for entering and viewing the circuit trip parameters. The operating programs within the trip unit are controlled by a variable loop time control sampling algorithm that automatically synchronizes to the power system operating frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top perspective view o~ a digital : circuit interrupter containing the improved sampling algorithm in accordance with the invention;
Figure ~ is a diagrammati~ repres2ntation of the trip unit and dis~lay circuits used within the circuit interrupter of Figure 1:
Figure 3 is a ~low chart representation of a sampling algorithm in accordance with the prior art; and Figure 4 is a flow chart representation o~ the sampling algorithm according to the inventionO
~y ~ ? ~
Accordingly, one purpose of the invention is to provide an electronic trip circuit interrupter having digital data entry and display wherein the operating software's endless loop period within the trip unit depends on the actual operating frequency of the circuit in real time rather than a predetermined fixed time interval.
SUMMARY OF THE INVENTION
A circuit interrupter having an electronic trip unit further includes a digital keypad and display for entering and viewing the circuit trip parameters. The operating programs within the trip unit are controlled by a variable loop time control sampling algorithm that automatically synchronizes to the power system operating frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top perspective view o~ a digital : circuit interrupter containing the improved sampling algorithm in accordance with the invention;
Figure ~ is a diagrammati~ repres2ntation of the trip unit and dis~lay circuits used within the circuit interrupter of Figure 1:
Figure 3 is a ~low chart representation of a sampling algorithm in accordance with the prior art; and Figure 4 is a flow chart representation o~ the sampling algorithm according to the inventionO
~y ~ ? ~
DESCRIPTION OF THE PREFERR~D ~MBODIMENT
A circuit breaker employing an electronic trip unit is depicted at lo, in Figure 1. The digital circuit ~reaker includes a circuit breaker case 11 closed by a circuit breaker cover 12 and electrical connection is made with the circuit breaker by means of the load terminals 13 at one end and through corresponding line texminals at the opposite end (not shown)a An operating handle 1~ pxovides manual intervention to open the 10 circuit breaker contacts 15 (Figure 2) which are otherwise automatically controlled by means of an electronic trip unit 16 which trip unit i5 ~ontained within the circuit breaker cover. A separate accessory cover 18 is attached to the circuit breaker cover and 15 includes one recess for receiving the keypad and display unit 17 and a separate r~cess for receiving the rating plug 19. A good description of the function o~ the accessory cover is found within U.S. Patent No. 4,75~,247 and the rating plug is described within U.S. Patent No.
4,728,914. The accessory cover includes two accessory doors 20, 21 which provide access to at least one accessoxy and to the trip actuator unit contained within the circuit breaker cover as de~cribed within aforementioned U.S. Patent No~ 4,754,247. ~he keypad and display unit 17 comprises a ~isplay ~2 and a keypad 23 which interconnect with the trip unit. Th~ trip unit circuit 24 is similar to that described within : aforementioned U.S. Patent No. 4,870,531 and is shown in : Figure 2 wherein the ROM 46, which contains the - 30 operational programs for the microprocessor 33, connects with the microprocassor over buses ~3, 47 and wherein ~he RAM 45 and NVM 48 which contain the data processed within the microprocessor also connect with the microprocessor ~ J
A circuit breaker employing an electronic trip unit is depicted at lo, in Figure 1. The digital circuit ~reaker includes a circuit breaker case 11 closed by a circuit breaker cover 12 and electrical connection is made with the circuit breaker by means of the load terminals 13 at one end and through corresponding line texminals at the opposite end (not shown)a An operating handle 1~ pxovides manual intervention to open the 10 circuit breaker contacts 15 (Figure 2) which are otherwise automatically controlled by means of an electronic trip unit 16 which trip unit i5 ~ontained within the circuit breaker cover. A separate accessory cover 18 is attached to the circuit breaker cover and 15 includes one recess for receiving the keypad and display unit 17 and a separate r~cess for receiving the rating plug 19. A good description of the function o~ the accessory cover is found within U.S. Patent No. 4,75~,247 and the rating plug is described within U.S. Patent No.
4,728,914. The accessory cover includes two accessory doors 20, 21 which provide access to at least one accessoxy and to the trip actuator unit contained within the circuit breaker cover as de~cribed within aforementioned U.S. Patent No~ 4,754,247. ~he keypad and display unit 17 comprises a ~isplay ~2 and a keypad 23 which interconnect with the trip unit. Th~ trip unit circuit 24 is similar to that described within : aforementioned U.S. Patent No. 4,870,531 and is shown in : Figure 2 wherein the ROM 46, which contains the - 30 operational programs for the microprocessor 33, connects with the microprocassor over buses ~3, 47 and wherein ~he RAM 45 and NVM 48 which contain the data processed within the microprocessor also connect with the microprocessor ~ J
over bus conductors 43, 47. The trip unit circuit interconnects with a three-phase industrial power circuit generally shown at 29 by means of three current transformers 27, signal conditioner circuit 26, corresponding conductors ~8 and bus conductors 44, 49.
Although no~ shown, corresponding potential transformers connected to signal conditioner 26 are used to measure the system voltage. The signal conditioner circuit ~6 generates both the 5 volt operating power and the analog to digital conversion of the current and voltage through the power circuit 29. The signal conditioner ~6 also measures the number of samples between zero crossings of the currents and voltages. Upon the occurrence of an overcurrent condition for a predetermined period o time, a trip signal is communicated to the signal conditioner circuit 26 over bus conductor 49 by the microprocessor.
The trip signal is output over wire conductor 32 from the signal conditioner 26 to the trip actuator 31 whi¢h operably connects with the contacts 15 by means of the wire conductor 30. As described within aforementioned U.S. Patent No~ 4,870,531, an interface circuit 25 interconnects between microprocessor 33 and the display 22 by means of wire conductors 34, 35. Power is provided to the interfac~ circuit 25 and keypad 23 by means of conductor wires 37, 38. The keypad connects with the microprocessor over wire conductors 36 and ~he interface cixcuit connects with the microprocessor over wire : conductors 35 as indicated. The keypad includes four switches (39~42) which operate as the "FUNCTION", "VALUE", "SELECT" and "ENTER" (F,V,S,~) key~ Each of the keys provides a logic level to the microprocessor in the event the key i5 closed. The software operating in the microprocessor senses the logic level of each key and determines operation o~ the display in the manner described within the aforementioned U.S. Patent 4,991,042O
The sampling algorithm used within the aforementioned U.S~ Patent 4,672,501 is depicted at 58 in Figure 3. A
fixed timer within the microprocessor which is set at 8 milliseconds is initialized (49) and the timer is started (50). The periodic calculations for various electric circuit parameters such as current and voltage RMS
values, ~or examplel is performed (51~ and a determination is made as to whether the timer is expired (52). I~ the timer is expired, the timer is again started and the loop 50-52 is continued. In the event that the timer is not expired a~tsr the calculations are per~ormed, the timer is allowed to expire before being restarted and continuing the loop (50-52). The 8 millisecond time interval corresponds to a loop time o~
one half cycle of the AC wave form of current or voltage when the power system frequency is operating at 60 Hz.
If the power system frequency increases or decreases, the timer æhould be continually adjusted to correct for the chanye in the timing interval based on predetermined loop time for a given frequency.
The sampling algorithm 59 ~depicted in Figure 4 provides a variable loop time control wherein the execution time directly depends on the actual power circuit fre~uency rather than a fixed time interval. Th~
algorithm accordingl~r allows the operating software within the microprocessor to precisely synchroniz2 with the power system ~requency in real time by waiting for a z~ro crossing to occur in one of the measured AC
parameters. The power system frequency can accordingly vaxy from as much as ~0-80 Hz without affecting the . ? ~ ~ 7 accuracy of the sampling loop. The actual powPr system fre~uency is determined by counting the number of samples taken between zero crossings of the power system voltage or current wave form from on~ phase in a three-phase system, or from the single operating pha~e in a single-phase system and determining operating frequency based on this number of samples. The frequency is calculat~d from the number of samples between zero crossings u~ing the following relation~hip:
~ = 1, Z x no. o~ samples x 256ms/sample This value is averaged over time since the numb~r of amples is an integral which does not always correspond to the exact ~requency. Upon start-up, the microprocessor is initialized (53) and a determination is made as to whether a zero crossing of the power system frequency AC wave form has occ:urred (54) by determining a negative-to-positive or a posi.tive-to-negative sign chanye. If so, the number o~ samplas between zero crossings of the wave fo~m is determined (55) the actual power system freguency is calc:ulated (56~ and the periodic calculations are per~ormed (57). If the number of sample is outside th range of 40-80 Hz, the previous : hal~ cycle number of samples is used for the frequency calculation until the next valid zero crossing count is read.
An electronic ircuit interrupter utili~ing a solid state trip unit which includes a microproces~or, is provided with a samplinq algorithm to reliably determine the electrical parameters within an associated electrical power distribution circuit whereby the sampling frequency ~ ,..3. 7 is synchronized to the power system frequency for real time determination of the electrical parameters.
:
Although no~ shown, corresponding potential transformers connected to signal conditioner 26 are used to measure the system voltage. The signal conditioner circuit ~6 generates both the 5 volt operating power and the analog to digital conversion of the current and voltage through the power circuit 29. The signal conditioner ~6 also measures the number of samples between zero crossings of the currents and voltages. Upon the occurrence of an overcurrent condition for a predetermined period o time, a trip signal is communicated to the signal conditioner circuit 26 over bus conductor 49 by the microprocessor.
The trip signal is output over wire conductor 32 from the signal conditioner 26 to the trip actuator 31 whi¢h operably connects with the contacts 15 by means of the wire conductor 30. As described within aforementioned U.S. Patent No~ 4,870,531, an interface circuit 25 interconnects between microprocessor 33 and the display 22 by means of wire conductors 34, 35. Power is provided to the interfac~ circuit 25 and keypad 23 by means of conductor wires 37, 38. The keypad connects with the microprocessor over wire conductors 36 and ~he interface cixcuit connects with the microprocessor over wire : conductors 35 as indicated. The keypad includes four switches (39~42) which operate as the "FUNCTION", "VALUE", "SELECT" and "ENTER" (F,V,S,~) key~ Each of the keys provides a logic level to the microprocessor in the event the key i5 closed. The software operating in the microprocessor senses the logic level of each key and determines operation o~ the display in the manner described within the aforementioned U.S. Patent 4,991,042O
The sampling algorithm used within the aforementioned U.S~ Patent 4,672,501 is depicted at 58 in Figure 3. A
fixed timer within the microprocessor which is set at 8 milliseconds is initialized (49) and the timer is started (50). The periodic calculations for various electric circuit parameters such as current and voltage RMS
values, ~or examplel is performed (51~ and a determination is made as to whether the timer is expired (52). I~ the timer is expired, the timer is again started and the loop 50-52 is continued. In the event that the timer is not expired a~tsr the calculations are per~ormed, the timer is allowed to expire before being restarted and continuing the loop (50-52). The 8 millisecond time interval corresponds to a loop time o~
one half cycle of the AC wave form of current or voltage when the power system frequency is operating at 60 Hz.
If the power system frequency increases or decreases, the timer æhould be continually adjusted to correct for the chanye in the timing interval based on predetermined loop time for a given frequency.
The sampling algorithm 59 ~depicted in Figure 4 provides a variable loop time control wherein the execution time directly depends on the actual power circuit fre~uency rather than a fixed time interval. Th~
algorithm accordingl~r allows the operating software within the microprocessor to precisely synchroniz2 with the power system ~requency in real time by waiting for a z~ro crossing to occur in one of the measured AC
parameters. The power system frequency can accordingly vaxy from as much as ~0-80 Hz without affecting the . ? ~ ~ 7 accuracy of the sampling loop. The actual powPr system fre~uency is determined by counting the number of samples taken between zero crossings of the power system voltage or current wave form from on~ phase in a three-phase system, or from the single operating pha~e in a single-phase system and determining operating frequency based on this number of samples. The frequency is calculat~d from the number of samples between zero crossings u~ing the following relation~hip:
~ = 1, Z x no. o~ samples x 256ms/sample This value is averaged over time since the numb~r of amples is an integral which does not always correspond to the exact ~requency. Upon start-up, the microprocessor is initialized (53) and a determination is made as to whether a zero crossing of the power system frequency AC wave form has occ:urred (54) by determining a negative-to-positive or a posi.tive-to-negative sign chanye. If so, the number o~ samplas between zero crossings of the wave fo~m is determined (55) the actual power system freguency is calc:ulated (56~ and the periodic calculations are per~ormed (57). If the number of sample is outside th range of 40-80 Hz, the previous : hal~ cycle number of samples is used for the frequency calculation until the next valid zero crossing count is read.
An electronic ircuit interrupter utili~ing a solid state trip unit which includes a microproces~or, is provided with a samplinq algorithm to reliably determine the electrical parameters within an associated electrical power distribution circuit whereby the sampling frequency ~ ,..3. 7 is synchronized to the power system frequency for real time determination of the electrical parameters.
:
Claims (10)
1. An electronic circuit interrupter comprising:
a molded plastic case and a molded plastic cover;
a pair of separable contacts within said case arranged for automatic. separation upon occurrence of an overcurrent condition through said contacts;
an electronic trip unit within said cover and arranged for electrical connection with an associated electric power distribution circuit operating at a power system frequency defining a power system frequency wave form, said electronic trip unit including a microprocessor said trip unit further containing a sampling algorithm determining said periodic time increments, said time increments beginning and ending at each zero crossing of said power system frequency wave form;
current sensing means connecting with said power distribution circuit and said microprocessor arranged for transmitting circuit current parameters to said microprocessor at periodic controlled time increments; and a ROM connected with said microprocessor storing operating programs for said microprocessor.
a molded plastic case and a molded plastic cover;
a pair of separable contacts within said case arranged for automatic. separation upon occurrence of an overcurrent condition through said contacts;
an electronic trip unit within said cover and arranged for electrical connection with an associated electric power distribution circuit operating at a power system frequency defining a power system frequency wave form, said electronic trip unit including a microprocessor said trip unit further containing a sampling algorithm determining said periodic time increments, said time increments beginning and ending at each zero crossing of said power system frequency wave form;
current sensing means connecting with said power distribution circuit and said microprocessor arranged for transmitting circuit current parameters to said microprocessor at periodic controlled time increments; and a ROM connected with said microprocessor storing operating programs for said microprocessor.
2. The circuit interrupter of claim 1 including a RAM
connected with said microprocessor storing said operational setpoints controlling said automatic separation of said contacts.
connected with said microprocessor storing said operational setpoints controlling said automatic separation of said contacts.
3. The circuit interrupter of claim 1 including an NVM
connected with said microprocessor storing setpoint values, said setpoint values being displayed and augmented without effecting said automatic contact separation.
connected with said microprocessor storing setpoint values, said setpoint values being displayed and augmented without effecting said automatic contact separation.
4. The circuit interrupter of claim 1 including a keypad and display unit within a recess formed within said cover, said keypad and display unit being connected with said trip unit for inputting operational setpoints to said microprocessor, said operational setpoints determining said automatic contact separation.
5. The circuit interrupter of claim 1 wherein said sampling algorithm determines whether said power system wave form has crossed said zero axis and if so begins to input said circuit current parameters to said microprocessor.
6. The circuit interrupter of claim 5 wherein said sampling algorithm takes a predetermined number of samples, counts further samples between zero crossing counts, and inputs said further samples to said microprocessor after said predetermined number of samples have been taken.
7. The circuit interrupter of claim 1 wherein said keypad comprises a SELECT key, a VALUE key, an ENTER key and a FUNCTION key, each of said keys connecting with said microprocessor through a corresponding ON-OFF switch.
8. The circuit interrupter of claim 3 including an accessory cover attached to said cover, said accessory cover including a slot circumferentially surrounding said keypad and display unit.
9. The circuit interrupter of claim 1 wherein said ROM
further contains frequency calculation and loop timing algorithms.
further contains frequency calculation and loop timing algorithms.
10. The invention as defined in any of the preceding claims including any further features of novelty disclosed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US666,960 | 1991-03-11 | ||
| US07/666,960 US5159519A (en) | 1991-03-11 | 1991-03-11 | Digital circuit interrupter with an improved sampling algorithm |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2061957A1 true CA2061957A1 (en) | 1992-09-12 |
Family
ID=24676248
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002061957A Abandoned CA2061957A1 (en) | 1991-03-11 | 1992-02-27 | Digital circuit interrupter with an improved sampling algorithm |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5159519A (en) |
| CA (1) | CA2061957A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0590936A3 (en) * | 1992-09-30 | 1994-06-15 | Westinghouse Electric Corp | Electrical switching apparatus with digital trip unit and automatic frequency selection |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2704064B1 (en) * | 1993-04-16 | 1995-06-02 | Merlin Gerin | Electric current measuring block. |
| US5745355A (en) * | 1996-06-25 | 1998-04-28 | Exide Electronics Corporation | Wireless selective tripping of AC power systems connected in parallel |
| DE19636338B4 (en) * | 1996-08-30 | 2004-06-03 | Siemens Ag | Circuit arrangement for monitoring an electronic tripping device for low-voltage switches |
| US5974545A (en) * | 1997-09-22 | 1999-10-26 | General Electric Company | Circuit breaker trip unit processor initialization program |
| US7086778B2 (en) * | 2000-10-09 | 2006-08-08 | Levtech, Inc. | System using a levitating, rotating pumping or mixing element and related methods |
| ES2177426B1 (en) * | 2000-11-14 | 2004-11-16 | Cima Instrumentacion, S.L. | ELECTRONIC CONTROLLER OF OPERATING TIME AND PROTECTION OF AN ELECTRICAL CHARGE. |
| US6897747B2 (en) * | 2002-05-10 | 2005-05-24 | Joseph T. Brandon | Circuit breaker |
| GB2389461A (en) * | 2002-06-06 | 2003-12-10 | Arc Technology Co Ltd | Control circuit for a solenoid actuated relay |
| US7492562B2 (en) * | 2003-09-10 | 2009-02-17 | Siemens Energy & Automation, Inc. | AFCI temperature compensated current sensor |
| US7441173B2 (en) * | 2006-02-16 | 2008-10-21 | Siemens Energy & Automation, Inc. | Systems, devices, and methods for arc fault detection |
| US7688560B2 (en) * | 2006-03-24 | 2010-03-30 | Ics Triplex Technology Limited | Overload protection method |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4319329A (en) * | 1980-02-21 | 1982-03-09 | Iowa State University Research Foundation, Inc. | Frequency measuring and monitoring apparatus, methods and systems |
| US4672501A (en) * | 1984-06-29 | 1987-06-09 | General Electric Company | Circuit breaker and protective relay unit |
| US4589052A (en) * | 1984-07-17 | 1986-05-13 | General Electric Company | Digital I2 T pickup, time bands and timing control circuits for static trip circuit breakers |
| US4804916A (en) * | 1986-10-28 | 1989-02-14 | Timothy Yablonski | Input voltage compensated, microprocessor controlled, power regulator |
| US4728914A (en) * | 1987-05-04 | 1988-03-01 | General Electric Company | Rating plug enclosure for molded case circuit breakers |
| US4754247A (en) * | 1987-06-12 | 1988-06-28 | General Electric Company | Molded case circuit breaker accessory enclosure |
| US4870531A (en) * | 1988-08-15 | 1989-09-26 | General Electric Company | Circuit breaker with removable display and keypad |
| US4991042A (en) * | 1990-03-19 | 1991-02-05 | General Electric Company | Digital circuit interrupter with keypad data entry and display |
-
1991
- 1991-03-11 US US07/666,960 patent/US5159519A/en not_active Expired - Fee Related
-
1992
- 1992-02-27 CA CA002061957A patent/CA2061957A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0590936A3 (en) * | 1992-09-30 | 1994-06-15 | Westinghouse Electric Corp | Electrical switching apparatus with digital trip unit and automatic frequency selection |
Also Published As
| Publication number | Publication date |
|---|---|
| US5159519A (en) | 1992-10-27 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Dead |