CA1310062C - Arrangement for controlling switchgear - Google Patents
Arrangement for controlling switchgearInfo
- Publication number
- CA1310062C CA1310062C CA000543494A CA543494A CA1310062C CA 1310062 C CA1310062 C CA 1310062C CA 000543494 A CA000543494 A CA 000543494A CA 543494 A CA543494 A CA 543494A CA 1310062 C CA1310062 C CA 1310062C
- Authority
- CA
- Canada
- Prior art keywords
- arrangement according
- feature
- load
- pulse
- power
- 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.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/34—Testing dynamo-electric machines
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/34—Testing dynamo-electric machines
- G01R31/346—Testing of armature or field windings
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Protection Of Generators And Motors (AREA)
- Control Of Direct Current Motors (AREA)
- Emergency Protection Circuit Devices (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
- Control Of Eletrric Generators (AREA)
- Remote Monitoring And Control Of Power-Distribution Networks (AREA)
- Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)
Abstract
ABSTRACT OF THE INVENTION
The invention relates to an arrangement for controlling and blocking a switchgear, preferably remote-controlled switchgear, in dependence on the grid state data by feeding-in an external voltage, and an evaluating circuit connected thereto, with reference and actual value. A pulse generator is provided for generating the external test pulses, and an evaluating circuit which determines the peak value of the instantaneous electric power sent to the motor. Thereby, short circuits, shorted turns and interruptions in the wiring can thereby be detected fast and accurately.
The invention relates to an arrangement for controlling and blocking a switchgear, preferably remote-controlled switchgear, in dependence on the grid state data by feeding-in an external voltage, and an evaluating circuit connected thereto, with reference and actual value. A pulse generator is provided for generating the external test pulses, and an evaluating circuit which determines the peak value of the instantaneous electric power sent to the motor. Thereby, short circuits, shorted turns and interruptions in the wiring can thereby be detected fast and accurately.
Description
-` 1310~62 2~365-2728 ARRANGEMENT FOR CONTROLLING SWITCHGEAR
sackground of the Invention The invention relates to an arrangement for control-ling switchgear, preferably remote-controlled switchgear, in dependence on state data generated by feeding an external volt-age into a load and using an evaluating circuit connected thereto to effect a comparison of reference and actual values.
The load may comprise a motor and its associated power lines.
In one known arrangement of the type mentioned a~ove (DE-OS 33 47 209), a measuring voltage is applied to the load, to which a current sensor is connected in series. By switching to the individual phases, the impedance between the individual phases and to ground is determined and the determined values are fed to a processing stage. If a small voltage is used in the arrangement, voltage flashovers and also shorted turns (which occur only at higher voltages) cannot be detected. If, however, a higher voltage is used, a relatively costly switch-ing device for switching to the individual phases is necessary since the full power must be switched.
OBJECTIVES A~D SUMMAR~ OF THE INVENTION
It is an object of the present invention to improve the above-described arrangement in such a manner that the detection of shorted turns becomes possible with a small amount of circuitry. This is achieved in a simple manner by providing a pulse generator for providing the external voltage. In order to realize an even more reliable detection of shorted turns which is insensitive to interference voltages, it is advanta-geous if the evaluation circuit evaluates power. A relatively simple and inexpensive evaluation of the power is obtained if the evaluation circuit evaluates the peak values of the instan-., ~
~31~06~
taneous power. It is advantageous if the pulse generator applies a pulse to all phases of a multi-phase group simulta-neously, or alternately. In order to make use of one pulse voltage generator and one evaluation circuit, the pulse voltage generator may be equipped with a random generator for selecting a single phase to be stressed. So that non-linear effects such as turns shorted by partial arcs in the windings can also be detected, it is advantageous if the protection or peak value of the pulse voltage corresponds approximately to that of the nominal peak voltage for the load. However, -the voltage should also be chosen not substantially higher than the peak values of the line voltage so as not to stress the windings excessively and to thereby cause shorted turns. In order to minimize the effect of stray inductances and the magnetic properties of the lamination stack, it is advantageous if the amplitude spectrum of the voltage pulse is in a frequency range of 50 to 1 kHz.
If the internal impedance of the pulse generator is large as compared to the line and in particular a motor load, a voltage as well as a current change results in the presence of shorted windings. For realizing the pulse generator with only a few components in a compact design, an arrangement is provided wherein the pulse generator consists of a capacitor which can be charged through rectifiers and which can be discharged through an electronic switch into the load lines and in parti-cular into the motor windings. In order to avoid a damped transient which decays only after a few milliseconds, it is advantageous if the output terminals of the pulse generators are shunted by a bypass diode. Thereby, the pulse is cut off after the first voltage zero crossing. A simple coupling of the evaluation circuit is provided if the bypass diode is shunted by a voltage divider and a shunt is 1 31 ~a ~2 20365~2728 connected into the line. A simple evaluation circuit is further obtained if the evaluation circuit consists of a circuit for sensing the current and the voltage, and an amplifier connected thereto as well as of a subsequent multiplier circuit which is i followed by a peak-voltage rectifier with a holding circuit. If the amplifiers are provided with adjustable gain, the evaluating circuit can be matched to the pulse generator and the motor parameters in a simple manner. In order to simplify the circuit further, it is of advantage if the evaluating circuit contains a microprocessor which triggers the pulse generator and performs the comparison with reference values as well as delivers the blocking command. A state of the art use of digital techniques with appropriate reliability is presented if an arrangement is provided in which current and voltage values are digitized and evaluated after multiplication corresponding to power waveform power, and used to generate a blocking command. For this purpose, a method has been found to be advantageous which consists of the provision that aEter the pulse generator is triggered, the peak values of the instantaneous power of the individual phaRe windings are compared with previous measured values and the blocking command is delivered in accordance with a predetermined deviation. If such values are stored in the arrangement, -the measured peak values of the instantaneous power can be corrected in dependence on the rotor position.
In accordance with a broad aspect of the lnvention there is provided an arrangement for controlling a preferably remote-controlled switchgear used for feeding power to a load, comprising a pulse generator connected to said load for feeding pulses to said load and an evaluating circuit connected to said pulse ; - 3 -131~2 20365-2728 generator to evaluate at least one response signal Erom said load indicative of the instantaneous peak power supplied to said load by said pulses from said pulse generator, said circuit including comparison means Eor comparing said response signal to preselected reference values, said comparison means generating a blocking signal for blocking the switchgear when said response signal exceeds said reference values.
In accordance with another broad aspect of the invention there is provided a method of controlling a switchgear used for providing power to a load comprising the steps of:
applying a pulse to said load;
evaluating an instantaneous peak power delivered to said load through said pulse;
comparing said instantaneous peak power with a reference value derived from previous evaluations; and generating a blocking command to block said switchgear if said instantaneous peak power exceeds said reference value by a predetermined deviation.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will be described with reference to the drawings wherein Fig. 1 shows a preferred embodiment of circuit of the pulse generator and the evaluation circuit, Fig. 2 shows the peak power as a function of the number of pulse stresses, and Fig. 3 shows an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The pulse generator with the evaluating circuit shown in Fig. 1 consists of the isolating transformer 1, the secondary side 1 31 0 ~ 6 2 20365--2728 2 of which is connected to a capacitor 5 via a rectifier 3 and a resistor 4. The capacitor is connected via the thyristor 6 to the windings 7 of the motor 8. The firing electrode of -the thyristor 6, shown by line 9, is connected to a control circuit 25. A
bypass diode 10 is connected in parallel to the output terminals of the circuit and to the winding 7 of the motor. A voltage divider 11 serves for taking off -the voltage and a shunt 12 serves for sensing the current for the evaluating circuit. The voltage divider 11 is shunted by a further capacitor 13. The current and voltage values sensed by circuit 26 are amplified via amplifiers 14, 15 and fed to a multiplier circuit 16. A peak value rectifier 17 rectifies the multiplier output. The peak rectified value is stored in a capacitor 18, and fed by an amplifier 19, to an indicating instrument 20 and a comparison circuit 21 which delivers a blocking signal. Because of the adjustable gains of the amplifiers 14, 15, the evaluating circuit can be matched to the pulse generator and the motor parameters in a simple manner.
Since the peak value reading is held, the holding member must be reset before the pulse genera-tor is triggered for a new operator.
The firing electrode 9 of the thyristor 6 can be controlled by a microprocessor in a manner not shown in detail. After the thyristor is fired, the capacitor 5 is discharged via the - 4a --1 3 ~
.1 ! motor. The frequency of the undisturbed transient is determined by the capacity and the inductance of the cable motor wiring. The evaluating circuit measures the peak value of the instantaneous power. In this connection, the number of pulses, the design of the phase winding and the rotor position ~as well as, possibly shorted turns must be considered as parameters. The stator and rotor laminations are either ¦demagnitized before the first pulse stress or are premagnetized in some direction. Since the magnetizing curve of the iron has a steep slope for small magnetic-field intensity, the inductance of the motor in this region is large (L~d~/di dB/DH). The current flowing during the pulse is thereby limited. Upon being stressed by further unipolar voltage pulses, the current and thereby, the power p increases since L
becomes smaller by the increasing magnetization. After about the fourth stress, or pulse the ualue of p no longer increases, see Fig. 2. With a possible repetition rate a final value can therefore be obtained after 82 milliseconds. No significant ¦difference of the phase windings can be detected.
,¦ The peak values of the instantaneous power p show a dependence on the rotor position which can be determined by measurements or motors with known characteristics to established reference values. By comparing the peak values of the measured power with a threshold value which is based on the reference values, conclusions can be drawn as to the state of ;the motor and its phases. If the peak values exceed the reference values, a blocking signal is sent to block the ,switchgear.
i For all possible shorted turns on'winding higher p ,'values occur than with a motor free of defects. In the case of _5_ 1 3 ~ 2 20365-2728 very large values, a terminal short or a short in the feeding cable is indicated.
In the embodiment of Figure 1, the pulses from the pulse generator are applied simultaneously to the three motor windings as shown. In the alternative embodiment of Fig. 3, three individual switches are provided, one for each phase winding, and a random generator may be used to close arbitarily any two of the three switches to test the windings. In both figures 1 and 3, the main switches to the power generators a-e not shown for the sake of clarity. Figure 2 shows the curves obtained for three different phases of a motor. The curves are not identical because of differences in measurement inaccura-cies, as well as inherent asymmetries within the motor.
Obviously numerous modifications may be made to the invention without departing from its scope as defined in the attached claim.
sackground of the Invention The invention relates to an arrangement for control-ling switchgear, preferably remote-controlled switchgear, in dependence on state data generated by feeding an external volt-age into a load and using an evaluating circuit connected thereto to effect a comparison of reference and actual values.
The load may comprise a motor and its associated power lines.
In one known arrangement of the type mentioned a~ove (DE-OS 33 47 209), a measuring voltage is applied to the load, to which a current sensor is connected in series. By switching to the individual phases, the impedance between the individual phases and to ground is determined and the determined values are fed to a processing stage. If a small voltage is used in the arrangement, voltage flashovers and also shorted turns (which occur only at higher voltages) cannot be detected. If, however, a higher voltage is used, a relatively costly switch-ing device for switching to the individual phases is necessary since the full power must be switched.
OBJECTIVES A~D SUMMAR~ OF THE INVENTION
It is an object of the present invention to improve the above-described arrangement in such a manner that the detection of shorted turns becomes possible with a small amount of circuitry. This is achieved in a simple manner by providing a pulse generator for providing the external voltage. In order to realize an even more reliable detection of shorted turns which is insensitive to interference voltages, it is advanta-geous if the evaluation circuit evaluates power. A relatively simple and inexpensive evaluation of the power is obtained if the evaluation circuit evaluates the peak values of the instan-., ~
~31~06~
taneous power. It is advantageous if the pulse generator applies a pulse to all phases of a multi-phase group simulta-neously, or alternately. In order to make use of one pulse voltage generator and one evaluation circuit, the pulse voltage generator may be equipped with a random generator for selecting a single phase to be stressed. So that non-linear effects such as turns shorted by partial arcs in the windings can also be detected, it is advantageous if the protection or peak value of the pulse voltage corresponds approximately to that of the nominal peak voltage for the load. However, -the voltage should also be chosen not substantially higher than the peak values of the line voltage so as not to stress the windings excessively and to thereby cause shorted turns. In order to minimize the effect of stray inductances and the magnetic properties of the lamination stack, it is advantageous if the amplitude spectrum of the voltage pulse is in a frequency range of 50 to 1 kHz.
If the internal impedance of the pulse generator is large as compared to the line and in particular a motor load, a voltage as well as a current change results in the presence of shorted windings. For realizing the pulse generator with only a few components in a compact design, an arrangement is provided wherein the pulse generator consists of a capacitor which can be charged through rectifiers and which can be discharged through an electronic switch into the load lines and in parti-cular into the motor windings. In order to avoid a damped transient which decays only after a few milliseconds, it is advantageous if the output terminals of the pulse generators are shunted by a bypass diode. Thereby, the pulse is cut off after the first voltage zero crossing. A simple coupling of the evaluation circuit is provided if the bypass diode is shunted by a voltage divider and a shunt is 1 31 ~a ~2 20365~2728 connected into the line. A simple evaluation circuit is further obtained if the evaluation circuit consists of a circuit for sensing the current and the voltage, and an amplifier connected thereto as well as of a subsequent multiplier circuit which is i followed by a peak-voltage rectifier with a holding circuit. If the amplifiers are provided with adjustable gain, the evaluating circuit can be matched to the pulse generator and the motor parameters in a simple manner. In order to simplify the circuit further, it is of advantage if the evaluating circuit contains a microprocessor which triggers the pulse generator and performs the comparison with reference values as well as delivers the blocking command. A state of the art use of digital techniques with appropriate reliability is presented if an arrangement is provided in which current and voltage values are digitized and evaluated after multiplication corresponding to power waveform power, and used to generate a blocking command. For this purpose, a method has been found to be advantageous which consists of the provision that aEter the pulse generator is triggered, the peak values of the instantaneous power of the individual phaRe windings are compared with previous measured values and the blocking command is delivered in accordance with a predetermined deviation. If such values are stored in the arrangement, -the measured peak values of the instantaneous power can be corrected in dependence on the rotor position.
In accordance with a broad aspect of the lnvention there is provided an arrangement for controlling a preferably remote-controlled switchgear used for feeding power to a load, comprising a pulse generator connected to said load for feeding pulses to said load and an evaluating circuit connected to said pulse ; - 3 -131~2 20365-2728 generator to evaluate at least one response signal Erom said load indicative of the instantaneous peak power supplied to said load by said pulses from said pulse generator, said circuit including comparison means Eor comparing said response signal to preselected reference values, said comparison means generating a blocking signal for blocking the switchgear when said response signal exceeds said reference values.
In accordance with another broad aspect of the invention there is provided a method of controlling a switchgear used for providing power to a load comprising the steps of:
applying a pulse to said load;
evaluating an instantaneous peak power delivered to said load through said pulse;
comparing said instantaneous peak power with a reference value derived from previous evaluations; and generating a blocking command to block said switchgear if said instantaneous peak power exceeds said reference value by a predetermined deviation.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will be described with reference to the drawings wherein Fig. 1 shows a preferred embodiment of circuit of the pulse generator and the evaluation circuit, Fig. 2 shows the peak power as a function of the number of pulse stresses, and Fig. 3 shows an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The pulse generator with the evaluating circuit shown in Fig. 1 consists of the isolating transformer 1, the secondary side 1 31 0 ~ 6 2 20365--2728 2 of which is connected to a capacitor 5 via a rectifier 3 and a resistor 4. The capacitor is connected via the thyristor 6 to the windings 7 of the motor 8. The firing electrode of -the thyristor 6, shown by line 9, is connected to a control circuit 25. A
bypass diode 10 is connected in parallel to the output terminals of the circuit and to the winding 7 of the motor. A voltage divider 11 serves for taking off -the voltage and a shunt 12 serves for sensing the current for the evaluating circuit. The voltage divider 11 is shunted by a further capacitor 13. The current and voltage values sensed by circuit 26 are amplified via amplifiers 14, 15 and fed to a multiplier circuit 16. A peak value rectifier 17 rectifies the multiplier output. The peak rectified value is stored in a capacitor 18, and fed by an amplifier 19, to an indicating instrument 20 and a comparison circuit 21 which delivers a blocking signal. Because of the adjustable gains of the amplifiers 14, 15, the evaluating circuit can be matched to the pulse generator and the motor parameters in a simple manner.
Since the peak value reading is held, the holding member must be reset before the pulse genera-tor is triggered for a new operator.
The firing electrode 9 of the thyristor 6 can be controlled by a microprocessor in a manner not shown in detail. After the thyristor is fired, the capacitor 5 is discharged via the - 4a --1 3 ~
.1 ! motor. The frequency of the undisturbed transient is determined by the capacity and the inductance of the cable motor wiring. The evaluating circuit measures the peak value of the instantaneous power. In this connection, the number of pulses, the design of the phase winding and the rotor position ~as well as, possibly shorted turns must be considered as parameters. The stator and rotor laminations are either ¦demagnitized before the first pulse stress or are premagnetized in some direction. Since the magnetizing curve of the iron has a steep slope for small magnetic-field intensity, the inductance of the motor in this region is large (L~d~/di dB/DH). The current flowing during the pulse is thereby limited. Upon being stressed by further unipolar voltage pulses, the current and thereby, the power p increases since L
becomes smaller by the increasing magnetization. After about the fourth stress, or pulse the ualue of p no longer increases, see Fig. 2. With a possible repetition rate a final value can therefore be obtained after 82 milliseconds. No significant ¦difference of the phase windings can be detected.
,¦ The peak values of the instantaneous power p show a dependence on the rotor position which can be determined by measurements or motors with known characteristics to established reference values. By comparing the peak values of the measured power with a threshold value which is based on the reference values, conclusions can be drawn as to the state of ;the motor and its phases. If the peak values exceed the reference values, a blocking signal is sent to block the ,switchgear.
i For all possible shorted turns on'winding higher p ,'values occur than with a motor free of defects. In the case of _5_ 1 3 ~ 2 20365-2728 very large values, a terminal short or a short in the feeding cable is indicated.
In the embodiment of Figure 1, the pulses from the pulse generator are applied simultaneously to the three motor windings as shown. In the alternative embodiment of Fig. 3, three individual switches are provided, one for each phase winding, and a random generator may be used to close arbitarily any two of the three switches to test the windings. In both figures 1 and 3, the main switches to the power generators a-e not shown for the sake of clarity. Figure 2 shows the curves obtained for three different phases of a motor. The curves are not identical because of differences in measurement inaccura-cies, as well as inherent asymmetries within the motor.
Obviously numerous modifications may be made to the invention without departing from its scope as defined in the attached claim.
Claims (17)
1. An arrangement for controlling a preferably remote-controlled switchgear used for feeding power to a load, comprising a pulse generator connected to said load for feeding pulses to said load and an evaluating circuit connected to said pulse generator to evaluate at least one response signal from said load indicative of the instantaneous peak power supplied to said load by said pulses from said pulse generator, said circuit including comparison means for comparing said response signal to preselected reference values, said comparison means generating a blocking signal for blocking the switchgear when said response signal exceeds said reference values.
2. The arrangement according to claim 1 wherein said load comprises a motor and its associated power lines.
3. The arrangement according to claim 2, characterized by the feature that the evaluating circuit evaluates power.
4. The arrangement according to claim 2, characterized by the feature that the evaluating circuit evaluates the peak values of the instantaneous power.
5. The arrangement according to claim 2, characterized by the feature that the pulse generator stresses all phases of the motor simultaneously by a pulse.
6. The arrangement according to claim 2, characterized by the feature that the pulse voltage generator is provided with a random generator for selecting a motor phase to be stressed.
7. The arrangement according to claim 2, characterized by the feature that the peak value of the pulse voltage corresponds approximately to the nominal motor voltage.
8. The arrangement according to claim 2 characterized by the feature that the amplitude spectrum of the pulse voltage is in a frequency range of 50 to 1 kHz.
9. The arrangement according to claim 8 characterized by the feature that the internal impedance of the pulse generator is large as compared to the load.
10. The arrangement according to claim 8 characterized by the feature that the pulse generator consists of a capacitor which can be charged via rectifier means and can be discharged via an electronic switch through windings of said motor.
11. The arrangement according to claim 2, characterized by the feature that the output terminals of the pulse generator are shunted by a bypass diode.
12. The arrangement according to claim 11 characterized by the feature that a voltage divider is connected in parallel to the bypass diode and a shunt is connected into the line.
13. The arrangement according to claim 2 characterized by the feature that the evaluating circuit consists of a circuit for sensing current and voltage, and amplifiers connected thereto as well as of a multi-plier circuit connected thereto which is followed by a peak value rectifier with a holding circuit.
14. The arrangement according to claim 2 characterized by the feature that the evaluating circuit contains a micro-processor which triggers the pulse generator, which makes the comparison with the reference values and delivers the blocking command.
15. The arrangement according to claim 3 characterized by the feature that an arrangement is provided in which current and voltage values deliver a blocking command after being digitalized and evaluated after multiplication with respect to the waveform of the power.
16. A method of controlling a switchgear used for provi-ding power to a load comprising the steps of:
applying a pulse to said load;
evaluating an instantaneous peak power delivered to said load through said pulse;
comparing said instantaneous peak power with a reference value derived from previous evaluations; and generating a blocking command to block said switchgear if said instantaneous peak power exceeds said reference value by a predetermined deviation.
applying a pulse to said load;
evaluating an instantaneous peak power delivered to said load through said pulse;
comparing said instantaneous peak power with a reference value derived from previous evaluations; and generating a blocking command to block said switchgear if said instantaneous peak power exceeds said reference value by a predetermined deviation.
17. The method of claim 16 wherein said load comprises a motor having a rotor adapted to assume various rotor positions, further comprising the step of correcting said instantaneous peak power for said rotor position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863626399 DE3626399A1 (en) | 1986-08-04 | 1986-08-04 | ARRANGEMENT FOR INFLUENCING A SWITCHGEAR |
| DEP3626399.0 | 1986-08-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1310062C true CA1310062C (en) | 1992-11-10 |
Family
ID=6306682
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000543494A Expired - Fee Related CA1310062C (en) | 1986-08-04 | 1987-07-31 | Arrangement for controlling switchgear |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0255658B1 (en) |
| JP (1) | JPS6348117A (en) |
| AT (1) | ATE84881T1 (en) |
| CA (1) | CA1310062C (en) |
| DE (2) | DE3626399A1 (en) |
| IN (1) | IN168580B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE59309599D1 (en) | 1992-03-31 | 1999-07-01 | Siemens Ag | Method and arrangement for the detection of short circuits in line branches of electrical networks |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3622882A (en) * | 1969-06-11 | 1971-11-23 | Gen Electric | Reactance circuit tester |
| US3869664A (en) * | 1973-06-08 | 1975-03-04 | Avtron Manufacturing Inc | Improved surge tester for electrical windings |
| JPS5952410B2 (en) * | 1976-01-20 | 1984-12-19 | キヤノン株式会社 | Camera operation display device |
| JPS54147441A (en) * | 1978-05-11 | 1979-11-17 | Matsushita Electric Works Ltd | Detection system of disconnection in line |
| DE3347209A1 (en) * | 1983-12-27 | 1985-07-11 | Siemens AG, 1000 Berlin und 8000 München | ARRANGEMENT FOR INFLUENCING A SWITCHGEAR |
| JPS60228971A (en) * | 1984-04-27 | 1985-11-14 | Toshiba Corp | Continuity inspection apparatus |
-
1986
- 1986-08-04 DE DE19863626399 patent/DE3626399A1/en not_active Withdrawn
-
1987
- 1987-07-22 DE DE8787110611T patent/DE3783680D1/en not_active Expired - Fee Related
- 1987-07-22 AT AT87110611T patent/ATE84881T1/en active
- 1987-07-22 EP EP87110611A patent/EP0255658B1/en not_active Expired - Lifetime
- 1987-07-31 JP JP62193627A patent/JPS6348117A/en active Pending
- 1987-07-31 CA CA000543494A patent/CA1310062C/en not_active Expired - Fee Related
- 1987-07-31 IN IN593/CAL/87A patent/IN168580B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IN168580B (en) | 1991-05-04 |
| DE3783680D1 (en) | 1993-03-04 |
| ATE84881T1 (en) | 1993-02-15 |
| EP0255658B1 (en) | 1993-01-20 |
| DE3626399A1 (en) | 1988-02-11 |
| EP0255658A1 (en) | 1988-02-10 |
| JPS6348117A (en) | 1988-02-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |