CA2034380A1 - Protection circuit for multiple phase power system - Google Patents
Protection circuit for multiple phase power systemInfo
- Publication number
- CA2034380A1 CA2034380A1 CA 2034380 CA2034380A CA2034380A1 CA 2034380 A1 CA2034380 A1 CA 2034380A1 CA 2034380 CA2034380 CA 2034380 CA 2034380 A CA2034380 A CA 2034380A CA 2034380 A1 CA2034380 A1 CA 2034380A1
- Authority
- CA
- Canada
- Prior art keywords
- circuit
- phase
- comparator
- input
- phases
- 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
- H02H3/24—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 responsive to undervoltage or no-voltage
- H02H3/253—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 responsive to undervoltage or no-voltage for multiphase applications, e.g. phase interruption
Landscapes
- Emergency Protection Circuit Devices (AREA)
Abstract
PROTECTION CIRCUIT FOR MULTIPLE
PHASE POWER SYSTEM
ABSTRACT OF THE DISCLOSURE
A protection circuit for three-phase power systems incorporates overcurrent protection along with phase loss and phase imbalance by means of common current sensing transformers. The phase loss and phase imbal-ance are determined by a pairwise comparison algorithm.
PHASE POWER SYSTEM
ABSTRACT OF THE DISCLOSURE
A protection circuit for three-phase power systems incorporates overcurrent protection along with phase loss and phase imbalance by means of common current sensing transformers. The phase loss and phase imbal-ance are determined by a pairwise comparison algorithm.
Description
203~3~
PROTECTION CIRCUIT FOR MULTIPLE
PHASE POWER SYSTEM
BACKG~OUND OF THE INVENTIQN
When electric motors are used within three-phase power distribution systems, the motor can become over-heated upon the occurrence of a condition commonly known as "single-phasing~'. The single-phasing occurs when a fuse in one phase operates to isolate the phase or the wiring within one of the phases becomes other-wise disconnected. The remaining two phases continue to feed the motor causing the motor to overheat.
Although the circuit current increases during the overheating conditions, most circuit interruption devices are not sufficiently sensitive to respond to the increased current resulting in eventual damage to the motor.
Most devices employed to interrupt circuit current upon the occasion of a single-phasing condition require separate sensing devices to measure the voltage across a set of fuses or to measure the current imbalance within the motor itself.
U.S. Patent 4,06Q,843 discloses separate sensing ~33~
PROTECTION CIRCUIT FOR MULTIPLE
PHASE POWER SYSTEM
BACKG~OUND OF THE INVENTIQN
When electric motors are used within three-phase power distribution systems, the motor can become over-heated upon the occurrence of a condition commonly known as "single-phasing~'. The single-phasing occurs when a fuse in one phase operates to isolate the phase or the wiring within one of the phases becomes other-wise disconnected. The remaining two phases continue to feed the motor causing the motor to overheat.
Although the circuit current increases during the overheating conditions, most circuit interruption devices are not sufficiently sensitive to respond to the increased current resulting in eventual damage to the motor.
Most devices employed to interrupt circuit current upon the occasion of a single-phasing condition require separate sensing devices to measure the voltage across a set of fuses or to measure the current imbalance within the motor itself.
U.S. Patent 4,06Q,843 discloses separate sensing ~33~
- 2 ~ 41PR-6663 means coupled to three-phase power lines for determin-ing the occurrence of single-phasing. U.S. Patent 4,0~1,703 describes the use of a DC ripple detecting device capable oE being utili~ed on a tllree-phase air-cuit to detect phase imbalance. U.S. Patent ~,837,654 teaches the use of signal amplifying transistors con-nected in a serial amplification configuration to detect single-phasing.
One purpose of the instant invention is to describe a circuit capable of detecting both phase loss and phase imbalance without requiring separate sensing devices apart from tha current transfoxmers used within electronic overcurrent circuit interrupt'on devices.
SUMMARY OF THE INVENTION
The invention comprises a phase loss and phase imbalance detection circuit employing a plurality of ground referenced operational amplifiers connected with current transformers to provide a trip signal output when the phase loss or phase imbalance is detected.
The operational amplifiers are arranged in accordance with a pairwise comparison algorithm and can be used independently from or in combination with standard electronic overcurrent circuit interruption devices.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic representation of a combined overcurrent, phase imbalance and phase loss protection circuit according to the invention;
Figure 2 is a diagrammatic representation of a simplified circuit for detecting phase imbalance and phase loss; and Figure 3 is a schematic representation of a circuit , 3 ~ ~
interruption circuit including an add-on modular phase loss and phase i~balance accessory in accordance with an alternative embodiment of the circuit of Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An integrated protection circuit 9 is shown in Figure 1 and includes a phase loss and imbalance detec-tion circuit lo connected with a power supply and trip circuit 11 and with a signal conditioniny clrcuit 12.
The signal conditioning circuit is connected with a - three-phase power system, one conductor of which is represented at 13, by means of a current transformer 14 that includes a primary winding 15, core 16, and sec-ondary winding 17. There are three such phase conduc-tors and current transformers although only one phase conductor is shown herein for purposes of illustration.
The secondary winding is connected with a bridge recti-fier 18 consisting of diodes D1-D4 and from there to a burden resistor R1 to generate a DC voltage propor-tional to the current through the first phase conduc-tor. Similar bridge rectifiers 19, 20 and diodes Ds-D12 connect with separate burden resistors R2 and R3 and diode D13 to provide a voltage indication of the current through the remaining two phase conductors (not shown). The voltage generated across the burden resis-tors is transmitted to the power supply and trip cir-cuit 11 over conductors 21-23. The trip circuit is similar to that described within V.S. Patent 4,589,052 entitled "Digital I2T Pickup, Time bands and Timing Control Circuits for Static Trip Circuit Breakers", which Patent is incorporated herein for purposes of reference. Upon the occurrence of an overcurrent con-dition in any of the three-phase conductors, a trip signal is generated and the circuit is interrupted in accordance with the teachings of the aforementioned ~3ll3~3~
One purpose of the instant invention is to describe a circuit capable of detecting both phase loss and phase imbalance without requiring separate sensing devices apart from tha current transfoxmers used within electronic overcurrent circuit interrupt'on devices.
SUMMARY OF THE INVENTION
The invention comprises a phase loss and phase imbalance detection circuit employing a plurality of ground referenced operational amplifiers connected with current transformers to provide a trip signal output when the phase loss or phase imbalance is detected.
The operational amplifiers are arranged in accordance with a pairwise comparison algorithm and can be used independently from or in combination with standard electronic overcurrent circuit interruption devices.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic representation of a combined overcurrent, phase imbalance and phase loss protection circuit according to the invention;
Figure 2 is a diagrammatic representation of a simplified circuit for detecting phase imbalance and phase loss; and Figure 3 is a schematic representation of a circuit , 3 ~ ~
interruption circuit including an add-on modular phase loss and phase i~balance accessory in accordance with an alternative embodiment of the circuit of Figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An integrated protection circuit 9 is shown in Figure 1 and includes a phase loss and imbalance detec-tion circuit lo connected with a power supply and trip circuit 11 and with a signal conditioniny clrcuit 12.
The signal conditioning circuit is connected with a - three-phase power system, one conductor of which is represented at 13, by means of a current transformer 14 that includes a primary winding 15, core 16, and sec-ondary winding 17. There are three such phase conduc-tors and current transformers although only one phase conductor is shown herein for purposes of illustration.
The secondary winding is connected with a bridge recti-fier 18 consisting of diodes D1-D4 and from there to a burden resistor R1 to generate a DC voltage propor-tional to the current through the first phase conduc-tor. Similar bridge rectifiers 19, 20 and diodes Ds-D12 connect with separate burden resistors R2 and R3 and diode D13 to provide a voltage indication of the current through the remaining two phase conductors (not shown). The voltage generated across the burden resis-tors is transmitted to the power supply and trip cir-cuit 11 over conductors 21-23. The trip circuit is similar to that described within V.S. Patent 4,589,052 entitled "Digital I2T Pickup, Time bands and Timing Control Circuits for Static Trip Circuit Breakers", which Patent is incorporated herein for purposes of reference. Upon the occurrence of an overcurrent con-dition in any of the three-phase conductors, a trip signal is generated and the circuit is interrupted in accordance with the teachings of the aforementioned ~3ll3~3~
~nited states Patent. The voltage generated across the burden resistors is also applied to the inputs of three operational amplifiers 24-26 in the following manner.
The voltage generated across R1 is applisd to the negative input terminal of amplifier 24 through resis-tor R4 and directly to the positive input terminal of amplifier 26. The voltage appearing across R2 is directly applied to the positive input terminal of am-plifier 24 and to the negative input terminal of amplifier 25 through resistor Rs. The voltage appearing across R3 is directly applied to the positive input terminal of amplifier 25 and to the negative input terminal of amplifier 26 through resistor R6.
The other side of resistors Rl-R3 is connected with the power supply and trip circuit 11 as well as with sys-tems ground. Integration capacitors C1-C3 are respectively connected across the negative inputs of the operational amplifiers 24-26 and their outputs as indicated. The negative input to operatlonal amplifier 24 is connected through resistor R7 and R8 to the negative input of operational amplifier 25 and through - resistor Rg to the negative input of operational amplifier 26. The negative inputs of tLe three ampli-fiers are commonly connected to one stage of a voltage divider consisting of resistors R11-R13 by means of conductor 29. The outputs of the three operational amplifiers are connected in common through diodes D14-D16 and conductor 30 to the positive input terminal of a comparator 27 and commonly connected to ground through resistor Rlo. The negative input to comparator 27 is connected to a second stage of the voltage di-vider Rll-R13 to provide a threshold comparison voltage to the comparator. A resistor R14 is connected between 2~3~3~
The voltage generated across R1 is applisd to the negative input terminal of amplifier 24 through resis-tor R4 and directly to the positive input terminal of amplifier 26. The voltage appearing across R2 is directly applied to the positive input terminal of am-plifier 24 and to the negative input terminal of amplifier 25 through resistor Rs. The voltage appearing across R3 is directly applied to the positive input terminal of amplifier 25 and to the negative input terminal of amplifier 26 through resistor R6.
The other side of resistors Rl-R3 is connected with the power supply and trip circuit 11 as well as with sys-tems ground. Integration capacitors C1-C3 are respectively connected across the negative inputs of the operational amplifiers 24-26 and their outputs as indicated. The negative input to operatlonal amplifier 24 is connected through resistor R7 and R8 to the negative input of operational amplifier 25 and through - resistor Rg to the negative input of operational amplifier 26. The negative inputs of tLe three ampli-fiers are commonly connected to one stage of a voltage divider consisting of resistors R11-R13 by means of conductor 29. The outputs of the three operational amplifiers are connected in common through diodes D14-D16 and conductor 30 to the positive input terminal of a comparator 27 and commonly connected to ground through resistor Rlo. The negative input to comparator 27 is connected to a second stage of the voltage di-vider Rll-R13 to provide a threshold comparison voltage to the comparator. A resistor R14 is connected between 2~3~3~
the positive input to the comparator and the comparator output which connects over conductor 28 to the power supp~y and trip circuit 11 to provide a trip si~nal thereto upon the occurrence of a phase loss on phase imbalance conditios.
Phase i~Dbalance and phase loss are determined within phase imbalance and the phase loss circuit lo by means of the followinq simple pairwise comparison algorithm:
PhLoss/Imbalance = B < (A-K) or A < (C-~) or C < (B-K) where A, B and C are the three phase currents and K is minimum imbalance level, or threshold.
The phase currents A, B, C are represented by the voltages generated across burden resistors Rl, R2 and R3 described earlier with respect to the signal condi-tioning circuit 12. The K factor in the expression for the phase loss algorithm constitutes a setpoint or threshold to prevent spurious and nuisance tripping caused by harmonic variations of a temporary nature unless the imbalance exceeds the setpoint by ten per-cent, for example. The current in phase B is compared to the current in phase A within the operational amplifier 24 such that the result of the comparison is directed over line 30 to the positive input to compara-tor 27 which is compared to the threshold value applied to the negative input by the second stage of the volt-age divider. In the event that the current in phase B
is less than that of phase A by the amount of the threshold value K, a trip signal is generated at the output of the comparator and operates the trip circuit via conductor 28. The current in phase C is compared U~
Phase i~Dbalance and phase loss are determined within phase imbalance and the phase loss circuit lo by means of the followinq simple pairwise comparison algorithm:
PhLoss/Imbalance = B < (A-K) or A < (C-~) or C < (B-K) where A, B and C are the three phase currents and K is minimum imbalance level, or threshold.
The phase currents A, B, C are represented by the voltages generated across burden resistors Rl, R2 and R3 described earlier with respect to the signal condi-tioning circuit 12. The K factor in the expression for the phase loss algorithm constitutes a setpoint or threshold to prevent spurious and nuisance tripping caused by harmonic variations of a temporary nature unless the imbalance exceeds the setpoint by ten per-cent, for example. The current in phase B is compared to the current in phase A within the operational amplifier 24 such that the result of the comparison is directed over line 30 to the positive input to compara-tor 27 which is compared to the threshold value applied to the negative input by the second stage of the volt-age divider. In the event that the current in phase B
is less than that of phase A by the amount of the threshold value K, a trip signal is generated at the output of the comparator and operates the trip circuit via conductor 28. The current in phase C is compared U~
to the current in phase B within operational amplifier 2S and when the current in phase C is less than that of phase B, a similar trip signal is generated. The current in phase A is compared to the current in phase C within operational amplifier 26 and a similar trip signal is outputted when the currellt in phase A is less than that of phase C.
A detailed arrangement of the phase loss and phase imbalance circuit 32 is depicted in Figure 2 wherein a threshold voltage is applied at Tl and the voltage representing phase A is applied at T2 with the voltage representing phase B applied to T3. In this arrange-ment the K factor which represents a setpoint or threshold voltage value is applied at the negative input to the ground-referenced operational amplifier 33, configured as an integrator, with the integrating capacitor C1 connecting between the output and the negative input terminal. Resistor Rl represents the voltage value of the K factor whereas the combination of the integrating capacitor Cl, less the voltage developed across the input resistor R2, sets the level of imbalance and the short time integration respec-tively. If desired, both the integratina capacitor and the input resistor can be made variable to set the values over a wide range of operating conditions. RMS
or peak detection could also be used to determine the comparison rather than the averaging method determined by means of the operational amplifier 33. In the event that phase A and phase ~ currents are equal in ampli-tude, the average siynal into the operational amplifier is zero, and the K factor assures a net negative input to the operational amplifier such that the output to 2~3~3~
A detailed arrangement of the phase loss and phase imbalance circuit 32 is depicted in Figure 2 wherein a threshold voltage is applied at Tl and the voltage representing phase A is applied at T2 with the voltage representing phase B applied to T3. In this arrange-ment the K factor which represents a setpoint or threshold voltage value is applied at the negative input to the ground-referenced operational amplifier 33, configured as an integrator, with the integrating capacitor C1 connecting between the output and the negative input terminal. Resistor Rl represents the voltage value of the K factor whereas the combination of the integrating capacitor Cl, less the voltage developed across the input resistor R2, sets the level of imbalance and the short time integration respec-tively. If desired, both the integratina capacitor and the input resistor can be made variable to set the values over a wide range of operating conditions. RMS
or peak detection could also be used to determine the comparison rather than the averaging method determined by means of the operational amplifier 33. In the event that phase A and phase ~ currents are equal in ampli-tude, the average siynal into the operational amplifier is zero, and the K factor assures a net negative input to the operational amplifier such that the output to 2~3~3~
the diode Dl remains at ground value vi~ resistor R3.
When the net voltage value of phase A exceeds the average of the phase B voltage plus the K factor, the output ramps in the positive direction and provides an input to the second comparator 34 where it is compared to a four volt reference supplied to the negative terminal. If it exceeds the four volt reference voltage, a trip signal is outputted onto ~he trip line 28.
A combined overcurrent protection, phase loss and phase imbalance circuit 59 is depicted in Figure 3 wherein the phase loss and phase i~alance circuit 48 comprises a stand-alone module which is plugged into the signal conditioning and power supply circuit 45 and the overcurrent trip circuit 50. The signal condi-tioning and power supply circuit 45 as ~ell as the trip circuit 50 are all included within ~he circuit breaker trip unit described in U.S. Patent 4,754,247 entitled "Molded Case Circuit Breaker Accessory Enclosure", which Patent is incorporated herein for purposes of reference. In the circuit breaker described in this Patent, the trip unit 60 and the actuator 57 are arranged within the circuit breaker case and are acces-sible through an accessory cover. It is contemplated that the phase loss and phase imbalance circuit 48 could be arranged in a separate recess within the circuit breaker cover and provided as an add-on acces-sory. In this arrangement, the three phases of a three-phase power circuit comprising conductors 36, 37 and 38 are protected by means of the circuit breaker contacts represented as switches Sl-S3 within each of the separate phases. Current transformers 39-41 con nect with the signal conditioning and power supply 45 .
2~3~8~
When the net voltage value of phase A exceeds the average of the phase B voltage plus the K factor, the output ramps in the positive direction and provides an input to the second comparator 34 where it is compared to a four volt reference supplied to the negative terminal. If it exceeds the four volt reference voltage, a trip signal is outputted onto ~he trip line 28.
A combined overcurrent protection, phase loss and phase imbalance circuit 59 is depicted in Figure 3 wherein the phase loss and phase i~alance circuit 48 comprises a stand-alone module which is plugged into the signal conditioning and power supply circuit 45 and the overcurrent trip circuit 50. The signal condi-tioning and power supply circuit 45 as ~ell as the trip circuit 50 are all included within ~he circuit breaker trip unit described in U.S. Patent 4,754,247 entitled "Molded Case Circuit Breaker Accessory Enclosure", which Patent is incorporated herein for purposes of reference. In the circuit breaker described in this Patent, the trip unit 60 and the actuator 57 are arranged within the circuit breaker case and are acces-sible through an accessory cover. It is contemplated that the phase loss and phase imbalance circuit 48 could be arranged in a separate recess within the circuit breaker cover and provided as an add-on acces-sory. In this arrangement, the three phases of a three-phase power circuit comprising conductors 36, 37 and 38 are protected by means of the circuit breaker contacts represented as switches Sl-S3 within each of the separate phases. Current transformers 39-41 con nect with the signal conditioning and power supply 45 .
2~3~8~
- 8 - 41P~-6663 over conductors 42-44 to provide signals to the trip circuit 50 over conductors 51, 52 for overcurrent determination. The same representative voltage signals are inputted to the phase loss and phase imbalance circuit 48 over conductors 46 and 47. ~1hen a phase loss or imbalance condition is ascertained, an output signal is provided to the trip circuit 'i0 over conductor 49. The output of the overcurrent determination from the trip circuit is inputted over conductor 53 to OR GATE 55. The output from the trip unit relative to the presence of a phase loss or phase imbalance condition is inputted to the OR GATE over conductor 5~. Upon the occurrence of either an overcurrent condition or a phase loss or a phase imbalance condition, a trip signal is applied over conductor 55 to the actuator unit 57. The actuator then interrupts the curren~ through all three conduc-tors 36-38 by means of the operative connection between the actuator and switches Sl-S3 as indicated by the control line 5B.
A simple phase loss and phase imbalance circuit has herein been described as a stand-alone circuit, an integral part of an overcurrent protection circuit as well as in the form of an add-on accessory to existing circuit breakers. The phase loss and phase imbalance circuit implements an algorithm that determines the occurrence of a phase lcss or phase imbalance condition and outputs a trip signal to interrupt all three phases of a protected three-phase power supply.
A simple phase loss and phase imbalance circuit has herein been described as a stand-alone circuit, an integral part of an overcurrent protection circuit as well as in the form of an add-on accessory to existing circuit breakers. The phase loss and phase imbalance circuit implements an algorithm that determines the occurrence of a phase lcss or phase imbalance condition and outputs a trip signal to interrupt all three phases of a protected three-phase power supply.
Claims (21)
1. A phase loss and phase imbalance circuit comprising:
a first operational amplifier having a negative input connecting with a signal from a first phase of a multi-phase power system and having a first output;
a second operational amplifier having a negative input connecting with a signal from a second phase of said multi-phase power system and having a second output; and a third operational amplifier having a negative input connected with a signal from a third phase of said multi-phase power system and having a third output, said negative input of said first amplifier being connected with a positive input of said third comparator for determining phase imbalance between said first and third phases.
a first operational amplifier having a negative input connecting with a signal from a first phase of a multi-phase power system and having a first output;
a second operational amplifier having a negative input connecting with a signal from a second phase of said multi-phase power system and having a second output; and a third operational amplifier having a negative input connected with a signal from a third phase of said multi-phase power system and having a third output, said negative input of said first amplifier being connected with a positive input of said third comparator for determining phase imbalance between said first and third phases.
2. The circuit of claim 1 wherein said negative input of said second comparator is connected with a positive input of said first comparator for determining phase imbalance between said first and second phases.
3. The circuit of claim 1 wherein said negative input of said third comparator is connected with a positive input of said second comparator for determining phase imbalance between said second and third phases.
4. The circuit of claim 1 wherein said first, second and third operational amplifier outputs are connected in common with one input of a comparator.
5. The circuit of claim 4 wherein another input of said comparator is connected with a reference voltage, said comparator providing an output signal when an integrated voltage on said first, second and third operational amplifier outputs exceeds said reference voltage.
6. The circuit of claim 5 wherein an output of said comparator is connected to a tripping mechanism for interrupting circuit current through said first, second and third phases of said multi-phase power system.
7. The circuit of claim 1 wherein said negative inputs to said first, second and third operational amplifiers are connected in common to a voltage divider network.
8. A circuit interrupter trip circuit including phase loss and phase imbalance protection comprising:
a plurality of current transformers connecting with corresponding phases of a multi-phase power system;
a plurality of rectifiers and resistors connecting with said current transformers for generating DC
voltage representations of circuit current through each of said phases;
a trip circuit connected with said resistors for determining overcurrent conditions through said phases and interrupting circuit current through said phases when said overcurrent conditions persist for a predetermined time; and a plurality of amplifiers interconnected together and connected with said resistors and said trip circuit to determine phase imbalance between said phases and input a trip signal to said trip unit upon occurrence of said phase imbalance above a predetermined threshold.
a plurality of current transformers connecting with corresponding phases of a multi-phase power system;
a plurality of rectifiers and resistors connecting with said current transformers for generating DC
voltage representations of circuit current through each of said phases;
a trip circuit connected with said resistors for determining overcurrent conditions through said phases and interrupting circuit current through said phases when said overcurrent conditions persist for a predetermined time; and a plurality of amplifiers interconnected together and connected with said resistors and said trip circuit to determine phase imbalance between said phases and input a trip signal to said trip unit upon occurrence of said phase imbalance above a predetermined threshold.
9. The circuit of claim 8 including a comparator connecting between said amplifiers and said trip circuit for determining whether said phase imbalance exceeds said threshold.
10. The circuit of claim 9 wherein said amplifiers have corresponding outputs connected in common with one input to said comparator.
11. The circuit of claim 10 wherein said amplifiers have corresponding inputs connected in common with each other and with another input on said comparator.
12. The circuit of claim 11 wherein said inputs are connected with another input through a voltage divider network.
13. The circuit of claim 12 wherein said one input connects with said comparator output through a feedback resistor.
14. A circuit for determining phase imbalance in a multi-phase power system comprising:
an amplifier configured as an integrator;
a negative input on said amplifier arranged for connecting with one phase of a multi-phase power system;
a positive input on said amplifier arranged for connecting with another phase of said power system; and an integrating capacitor connecting said negative input with an output on said amplifier for providing a threshold voltage to said negative input, whereby said amplifier provides an output signal when a voltage phase difference on said positive and said negative inputs exceeds said threshold voltage.
an amplifier configured as an integrator;
a negative input on said amplifier arranged for connecting with one phase of a multi-phase power system;
a positive input on said amplifier arranged for connecting with another phase of said power system; and an integrating capacitor connecting said negative input with an output on said amplifier for providing a threshold voltage to said negative input, whereby said amplifier provides an output signal when a voltage phase difference on said positive and said negative inputs exceeds said threshold voltage.
15. The circuit of claim 14 including a comparator having one input connecting with said amplifier output and another input connecting with a source of reference voltage, whereby said comparator provides an output signal when a signal on said one input exceeds said reference voltage.
16. The circuit of claim 15 including circuit interruption means connected with said comparator output for interrupting circuit current through said multi-phase circuit when said output signal appears on said comparator output.
17. An improved circuit interrupter of the type consisting of a case and a cover, said case including means for interrupting circuit current through a protected circuit, said cover including recess means for accepting an accessory device, wherein the improvement comprises:
an overcurrent protection trip circuit for determining overcurrent conditions within three phases of a multi-phase power circuit and activating said interrupter means when said overcurrent condition persists for a predetermined period of time; and a phase imbalance accessory device within said recess, said device including circuit means for determining a phase imbalance within said multi-phase power circuit and providing an interrupt signal to said interruption means to interrupt said circuit current.
an overcurrent protection trip circuit for determining overcurrent conditions within three phases of a multi-phase power circuit and activating said interrupter means when said overcurrent condition persists for a predetermined period of time; and a phase imbalance accessory device within said recess, said device including circuit means for determining a phase imbalance within said multi-phase power circuit and providing an interrupt signal to said interruption means to interrupt said circuit current.
18. The circuit interrupter of claim 17 including a comparator connected with said overcurrent protection trip circuit and said phase imbalance circuit means to output a trip signal to said interrupter means when either an overcurrent condition or a phase imbalance condition is detected on said multi-phase power circuit.
19. The circuit of claim 18 including a current transformer within each of said three phases for sampling circuit current and contacts within each of said phases, said contacts responding to said interruption means to interrupt said circuit current.
20. The circuit of claim 19 wherein said phase imbalance protection device is arranged within a module removably connectable with said current transformers and said overcurrent protection circuit.
21. 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 |
|---|---|---|---|
| US47133690A | 1990-01-29 | 1990-01-29 | |
| US471,336 | 1990-01-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2034380A1 true CA2034380A1 (en) | 1991-07-30 |
Family
ID=23871242
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2034380 Abandoned CA2034380A1 (en) | 1990-01-29 | 1991-01-17 | Protection circuit for multiple phase power system |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2034380A1 (en) |
| FR (1) | FR2657732A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2715010B1 (en) * | 1994-01-10 | 1996-06-21 | Telemecanique | Electronic thermal protection device. |
| EP0671798B1 (en) * | 1994-03-07 | 2001-01-24 | Schneider Electric Industries SA | Electronic thermal protection circuit |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4084406A (en) * | 1976-01-22 | 1978-04-18 | Fedders Corporation | Chiller controls |
| US4858053A (en) * | 1985-11-01 | 1989-08-15 | Square D Company | Operational amplifier having an improved feedback system including an integrator having a hurry-up circuit, and an electric motor control using the same for inverse trip selection |
-
1991
- 1991-01-17 CA CA 2034380 patent/CA2034380A1/en not_active Abandoned
- 1991-01-23 FR FR9100753A patent/FR2657732A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2657732A1 (en) | 1991-08-02 |
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