CA1195382A - Error-compensated high-voltage transformer - Google Patents
Error-compensated high-voltage transformerInfo
- Publication number
- CA1195382A CA1195382A CA000391036A CA391036A CA1195382A CA 1195382 A CA1195382 A CA 1195382A CA 000391036 A CA000391036 A CA 000391036A CA 391036 A CA391036 A CA 391036A CA 1195382 A CA1195382 A CA 1195382A
- Authority
- CA
- Canada
- Prior art keywords
- transformer
- voltage
- amplifier
- secondary winding
- impedance
- 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
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/144—Measuring arrangements for voltage not covered by other subgroups of G01R15/14
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R17/00—Measuring arrangements involving comparison with a reference value, e.g. bridge
- G01R17/02—Arrangements in which the value to be measured is automatically compared with a reference value
- G01R17/06—Automatic balancing arrangements
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Transformers For Measuring Instruments (AREA)
- Details Of Television Scanning (AREA)
- Emergency Protection Circuit Devices (AREA)
- Amplifiers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A high-voltage transformer has a secondary wind-ing connectable to a load and having a measuring series impedance for producing a small voltage drop proportional to the load current. An error-compensating amplifier has an input circuit connected across the measuring impedance and an output connected in series with the secondary wind-ing to compensate for errors introduced by the load.
A high-voltage transformer has a secondary wind-ing connectable to a load and having a measuring series impedance for producing a small voltage drop proportional to the load current. An error-compensating amplifier has an input circuit connected across the measuring impedance and an output connected in series with the secondary wind-ing to compensate for errors introduced by the load.
Description
1 The present invention relates in general to high-voltage transformers, and in particular to -trans-formers in which the transmission error is compensated by means of an amplifier.
~ n unloaded voltage transformer produces at the terminals of its secondary winding a voltage corre-sponding to the so-called open-circuit transformation ratio. As soon as the secondary winding of the trans-former is connected to a load, a voltage drop will re-sult which changes the open-circuit secondary voltage and introduces the aforementioned transmission error.
In order to keep the load-dependent deviations o:E the secondary voltage within the desired limits, the active parts of the transformer, such as coils and the iron core, are designed with corresponding dimensions. These measures, however, particularly in high-voltage transformers, are costly and, moreover, the insulation problems are increased, inasmuch as the insulation is directly proportional to the size and weight of these active parts. From prior art, transformers circuits are known in which the transmission errors in the secondary winding are more or less compen-sated by various circuits elements.
For example, a device is known in which the sec-ondary circuit of a voltage transformer is connected in series with an impedance Zl corresponding to the short-circuit impedance of the secondary circuit, this impedance Zl being connected in series with a coupling impedance Z2 in the input of an amplifier; the coupling impedance is again connected in series with an impedance of the output circuit of the ampliEier, the output impedance being similar ~2-~ 6~5 ~ ~
1 to the input impedance Zl The amplifier delivers at its output an electromotive force which compensates the voltage drop across the impedance Z] and simultaneously the voltaye drop caused by the transformer itself, so that the secondary voltage transformed from the primary voltage exhibits prac-tically no error due to the load.
This known device utilizes a difference measuring process which, due to its sensitivity, is susceptible to disturbances and unreliable operation. The measuring imped-ance of such differential measuring circuits is too largeand consequently, in case of failure in the amplifier, the error voltage in the transformer may increase to such a level that the transformer is made unusable in a practical appli-cation.
Also known is a compensation circui-t for reducing the load dependence of a voltage transformer. In this prior-art circuit, the load-dependent voltage is coupled back into the primary circuit with such a phase as to reduce the error.
This kind of compensation is effective when the load alter-nates between zero and a maximum value while the nominalvoltage remains constant. Nevertheless, this prior-art compensation circuits is effective also during the upward and downward devia-tion of the primary voltage~ and thus introduces a measuring error into the secondary circuit when the load remains constant.
Also known are automatic devices for reducing transmission errors in voltage transformers, in which trans-ducers and amplifiers are connected in the secondary current circuit. The elimination of transmission errors caused by the load in such devices is effected by means of a correction ~Ca53~2 1 voltage dependent both upon the load current and on the secondary voltage. The correction voltage is employed as an input signal for a transducer connected in the secondary circuit. Since the transducer employed is connected im-mediately in the secondary circuit, the full secondary current flows therethrough and consequently it must be designed to withstand a considerable power. The switching conditions of the transducers are influenced by the trans-mission errors to be compensated, and consequently this solution provides only a reduction of the transmission error but not its complete elimination.
Furthermore, a device is known which employs two auxiliary voltage transformers arranged in the primary cir-cuit of the hi~h-voltage transformer. The secondary voltage of one of the auxiliary transformers is applied to the input of an amplifier, and the output of the amplifier is connect-ed to the secondary winding of the out auxiliary transformer.
The first auxiliary transformer serves for the generation of an open-circuit reference voltage which is compared with the secondary voltage of the other, loaded auxiliary trans-fer, to produce a difference signal which as to its magni-tude and phase corresponds to the transmission error and is employed for the compensation of such error. In this prior-art compensation device, however, it is practically impossible to drive one of the auxiliary transformers in a no-1oad con-dition, and consequently in practical applications the afore-mentioned operational principle is not completely successfulO
In addition, this known arrangement is very expensive.
Devices are also known which amplify low signals on the secondary winding of the high-voltage transformer to ~ ~a~3~z 1 a desired value. The total power, however, is delivered by the amplifier, and the transformer serves only as a control element. Consequently, such power amplifiers have to meet high operational requirements as to their stability with respect to time and temperature and with respect to the phase error between their input and output circuits. The last-mentioned parameters for the amplified power must always be kept within the tolerance range of the desired class of accuracy.
It is therefore a general object of the present invention to overcome the aforementioned disadvantages.
More particularly, it is an object of the inven-tion to provide an improved error-compensated high-voltage transformer which eliminates the transformation errors and which is effective both in the open-circuit or no-load con-dition of the secondary circuit and in the loaded condition of the same.
In keeping with these objects, and with others which will become apparent hereafter, one feature of -the invention resides, in an error-compensated high-voltage transformer having a secondary circuit, in a combination which comprises a measuring impedance connected in series with the secondary circuit to produce a small voltage drop from the secondary current in the same vector direction, an amplifier having its input connected across the measur-ing impedance and an output connected in series wlth the secondary winding. With advantage, the ampoifier is power-supplied by means of a transformer from the secondary circuit.
~30 In principle, the accurancy of the compensating ~S38~
1 circuit of the voltage transformer must be kept within a predetermuned operational range, such as within 0.8 to 0.2 multiple of the phase voltage in the case of single-phase transformers (minimum and maximum measuring voltage). The transformer itself is during operation subject to a substan-tially increased accuracy range. For instance, the last-mentioned transformer operates up to 1.9 times the phase voltage. The maximum operational voltage together with the nominal load of the transformer determines the required load-ing capacity of the amplifier. For instance, if the inputof the amplifier is connected to a transformer which is designed such that the saturation of its iron core is at-tained slightly above the current corresponding to the max-imum measuring voltage at a nominal load, then the ampli-fied voltage increases only slightly with currents or volt-ages exceeding the maximum measuring voltage. It is suf-ficient to design the amplifier for a loading capacity which only slightly exceeds the value of the maximum measur-ing voltage at a nominal load. As a consequence, there re-sults a substantial saving in the design of the amplifier.This saving is apparent from the following example:
Single-phase transformer for nominal power 60 VA
Operational voltage between 0.22 to 1.9 Un Measuring voltage in the range of 0.8 to 1.2 Un (Un = phase voltage) If the transformer or converter produces during its rated operation an error of for instance 6%, then in order to achieve an accurancy class of 0.5, it is necessary to pro-duce a compensation power of about 5~, corresponding to 3 VA.
-5~
1 Without the aforementioned adjustment of the transducer tothe input of the amplifier, the maximum loading capacity of the amplifier would have to be about 1.92 3, that is approximately 11 VA.
By using impedance transformers at the input and output sides of the amplifier, the measurement at a reduced accuracy can take place even if the amplifier becomes dis-abled. It is of advantage that each secondary winding of respective impedance transducers is bridged by a measuring impedance. These measuring impedances are dimensioned such that, in case of failure of the amplifier, a sufficient de-crease of the transmission impedance is produced. As a re-sult, the transmission error typically remains within ac-ceptable limits. This feature is unattainable in all con-ventional error-compensating systems.
Due to the additional impedances connected paral-lel to the windings of the transformers in the secondary cir-cuit, the vector position of the compensating voltage trans-mitted by the measuring transformers can be regulated. This adjustability of the vectors of the compensating voltage in turn makes it possible that ~he error compensa-tion be carried out in the ampllfier itself. It is of advantage when ~he compensation voltage delivered by the amplifier is combined with an additional compensation voltage from a series-connected capacitor. In this manner, the orientation of -the vector of the compensation voltage at the output of the amplifier is adjustable within a broad range, because this voltage counteracts the phase shift of the compensation volt-age. Consequently, only low requirements are placed on the arnplifier for the transmission of phase of signals and the 5;:~2 1 same holds true for the vector conditions of the vol-tage applied to the input of the amplifier.
The aforementioned capacitor can be connected either directly or via a transformer in series with the secondary circuit of the high--voltage transformer. The error-compensation method of this invention enables also a partial compensation of the errors, so that a residual error of an arbitrary magnitude and vectorial direction is preserved.
The amplifier can be power-supplied from the secondary winding of the high-voltage transformer. This power-supply connection causes an additional load on the high-voltage transformer. The resulting additional trans-formation error, however, is compensated in the manner de-scribed above.
The novel features which are considered charac-teristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description o~ specific embodiments when read in connection with the accompanying drawingO
FIG. 1 is a schematic circuit diagram of one embodiment of the error-compensated transformer of this invention; and FIG. 2 and 3 show, respectively, another two embodiments of this invention.
In the Figures, reference numeral 1 indicates the secondary winding of a high-voltage trans~ormer or 3~
transducer connected to terminals 2' of à load 2, An amplifier 3 has an input 4 which is connected across a measuring impedance 5.
The impendance 5 is connected in series with the secondary winding 1 and the output 6 of -the amplifier is connected in series with the impedance 5 and the load 2. The impedance 5 produces only a small voltage drop from the load current, and the amplifier is designed so that its output 6 compensates automatically all voltage losses resulting from the application of load 2. The amplifier is power-supplied from a circuit 7.
A preferred embodiment of this invention is shown in FIGS. 2 and 3, where measuring transformers 8 and 9 have primary windings connected in series with the secondary winding l and the load ~.. The secondary windings of measuring transformers 8 and 9 are bridged by resistances 10 and 11 and connected respectively to the input 4 and the output 6 of amplifier 3. The resistances 10 and 11 adjust the phase conditions of the compensation voltage. An additional transformer 12 is connected in series with the secondary winding l and its secondary circuit is bridged by a capacitor 13. The additional tr.ansformer 12 serves for the generation of the additional compensation voltage.
The operation of the error compensated circuit will be explained by way of an example with reference to FIG. 2.
Assuming a load 2 of 60 VA at a rated voltage lO0/ ~ 3, the secondary winding 1 of a non-compensated high voltage transformer would show 3% voltage drop due to ohmic component and a 3% voltage drop to a reactive component of the transmission path.
According to this invention, -these voltage drops are compensated in such a manner as to allow a voltage accuracy of 0.2 at the nominal output of 60 VA. The value of capacitor ~ is 0.082 microfarad; the winding ratio of transformer 12 is 24/3648; the value of resistor 10 is l ohm; the winding ratio.of transformer 8 is 2l/5;
the wlnding ratio of transformer 9 is 111/24; the frequency i.s 50 Hz;
the resistance ll in this example is 117 ohms; and the amplifi.er 3 is designed for an input voltage of 0.25 vol-ts and for an outpu-t voltage f 8 volts.
_ g _ S3~Z
The linearity and angular accuracy of the amplifier are set to be 1.25 times the nominal value of the input voltage, as far as in this range the error of the amplification factor of the amplifier is not higher than ~2,5% and its phase displacement l1'~5 does not exceed -~60 minutes. From 0~ 5 up to 1,9 times the rated ,, _ value of the input voltage, the voltage error may rise up to -~10%
without any limitation to the phase displacement. The alternating current at 50 Hz, which at a load of 60 VA corresponds to 1.03 A, causes a voltage drop of 3% across the capacitor 13. This voltage drop compensates the reactive voltage drop in the transformer 12.
The resistance 10 (value 1 ohm) which is connected to the input terminals of the amplifier 3 and via the transformer 8 with the turn ratio 21/5 to the load 2, produces at the current of 1.03 ~ a voltage of 0.25 V is produced across the resistance 10 at the input of amplifier 3. This voltage is amplified to 8 volts.
The output voltage at the amplifier 3 is introduced via the transformer 9 (with the turn ratio 111/24) into the load circuit 2. Since the transformed voltage is in opposite phase to the ohmic voltage drop of 1.73 volts corresponding to the aforementioned 3% drop of the rated voltage in the load circuit, the latter voltage drop of 3% in the transformer is thus compensated. As a result, the amplifier is loaded with an active power of 1.03 (~) X 24/111 X 8 (V) = 1.78 (W).
The resistance 11 across the secondary winding of transformer 9 is preferably constituted by the impedance of a capacitor of 27 microfarads which at 50 Hz has an impedance of 117 ohms. At the primary winding of transformer 9, this impedance amounts to 5.36 ohms and as a result a voltage drop due to the load current of 1.03 amperes is applied to the load to compensate reactive voltage drop in case of a failure of the amplifier 3~ The capacitance 11 causes a supplementary Load on the amplifier of 82/117 (ohm) = 0.547 YA.
~9a-S~
FIG. 3 illustrates a circuit similar to that of FIG. 2, in which a voltage regulator 14 is connected across the secondary winding 1 and the regulated voltage is used for feediny the amplifier 3.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
-9b-Laa~3B~
1 While the invention has been illustrated and described as embodied in a high-voltage error-compensated transformer, i.t is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
~ n unloaded voltage transformer produces at the terminals of its secondary winding a voltage corre-sponding to the so-called open-circuit transformation ratio. As soon as the secondary winding of the trans-former is connected to a load, a voltage drop will re-sult which changes the open-circuit secondary voltage and introduces the aforementioned transmission error.
In order to keep the load-dependent deviations o:E the secondary voltage within the desired limits, the active parts of the transformer, such as coils and the iron core, are designed with corresponding dimensions. These measures, however, particularly in high-voltage transformers, are costly and, moreover, the insulation problems are increased, inasmuch as the insulation is directly proportional to the size and weight of these active parts. From prior art, transformers circuits are known in which the transmission errors in the secondary winding are more or less compen-sated by various circuits elements.
For example, a device is known in which the sec-ondary circuit of a voltage transformer is connected in series with an impedance Zl corresponding to the short-circuit impedance of the secondary circuit, this impedance Zl being connected in series with a coupling impedance Z2 in the input of an amplifier; the coupling impedance is again connected in series with an impedance of the output circuit of the ampliEier, the output impedance being similar ~2-~ 6~5 ~ ~
1 to the input impedance Zl The amplifier delivers at its output an electromotive force which compensates the voltage drop across the impedance Z] and simultaneously the voltaye drop caused by the transformer itself, so that the secondary voltage transformed from the primary voltage exhibits prac-tically no error due to the load.
This known device utilizes a difference measuring process which, due to its sensitivity, is susceptible to disturbances and unreliable operation. The measuring imped-ance of such differential measuring circuits is too largeand consequently, in case of failure in the amplifier, the error voltage in the transformer may increase to such a level that the transformer is made unusable in a practical appli-cation.
Also known is a compensation circui-t for reducing the load dependence of a voltage transformer. In this prior-art circuit, the load-dependent voltage is coupled back into the primary circuit with such a phase as to reduce the error.
This kind of compensation is effective when the load alter-nates between zero and a maximum value while the nominalvoltage remains constant. Nevertheless, this prior-art compensation circuits is effective also during the upward and downward devia-tion of the primary voltage~ and thus introduces a measuring error into the secondary circuit when the load remains constant.
Also known are automatic devices for reducing transmission errors in voltage transformers, in which trans-ducers and amplifiers are connected in the secondary current circuit. The elimination of transmission errors caused by the load in such devices is effected by means of a correction ~Ca53~2 1 voltage dependent both upon the load current and on the secondary voltage. The correction voltage is employed as an input signal for a transducer connected in the secondary circuit. Since the transducer employed is connected im-mediately in the secondary circuit, the full secondary current flows therethrough and consequently it must be designed to withstand a considerable power. The switching conditions of the transducers are influenced by the trans-mission errors to be compensated, and consequently this solution provides only a reduction of the transmission error but not its complete elimination.
Furthermore, a device is known which employs two auxiliary voltage transformers arranged in the primary cir-cuit of the hi~h-voltage transformer. The secondary voltage of one of the auxiliary transformers is applied to the input of an amplifier, and the output of the amplifier is connect-ed to the secondary winding of the out auxiliary transformer.
The first auxiliary transformer serves for the generation of an open-circuit reference voltage which is compared with the secondary voltage of the other, loaded auxiliary trans-fer, to produce a difference signal which as to its magni-tude and phase corresponds to the transmission error and is employed for the compensation of such error. In this prior-art compensation device, however, it is practically impossible to drive one of the auxiliary transformers in a no-1oad con-dition, and consequently in practical applications the afore-mentioned operational principle is not completely successfulO
In addition, this known arrangement is very expensive.
Devices are also known which amplify low signals on the secondary winding of the high-voltage transformer to ~ ~a~3~z 1 a desired value. The total power, however, is delivered by the amplifier, and the transformer serves only as a control element. Consequently, such power amplifiers have to meet high operational requirements as to their stability with respect to time and temperature and with respect to the phase error between their input and output circuits. The last-mentioned parameters for the amplified power must always be kept within the tolerance range of the desired class of accuracy.
It is therefore a general object of the present invention to overcome the aforementioned disadvantages.
More particularly, it is an object of the inven-tion to provide an improved error-compensated high-voltage transformer which eliminates the transformation errors and which is effective both in the open-circuit or no-load con-dition of the secondary circuit and in the loaded condition of the same.
In keeping with these objects, and with others which will become apparent hereafter, one feature of -the invention resides, in an error-compensated high-voltage transformer having a secondary circuit, in a combination which comprises a measuring impedance connected in series with the secondary circuit to produce a small voltage drop from the secondary current in the same vector direction, an amplifier having its input connected across the measur-ing impedance and an output connected in series wlth the secondary winding. With advantage, the ampoifier is power-supplied by means of a transformer from the secondary circuit.
~30 In principle, the accurancy of the compensating ~S38~
1 circuit of the voltage transformer must be kept within a predetermuned operational range, such as within 0.8 to 0.2 multiple of the phase voltage in the case of single-phase transformers (minimum and maximum measuring voltage). The transformer itself is during operation subject to a substan-tially increased accuracy range. For instance, the last-mentioned transformer operates up to 1.9 times the phase voltage. The maximum operational voltage together with the nominal load of the transformer determines the required load-ing capacity of the amplifier. For instance, if the inputof the amplifier is connected to a transformer which is designed such that the saturation of its iron core is at-tained slightly above the current corresponding to the max-imum measuring voltage at a nominal load, then the ampli-fied voltage increases only slightly with currents or volt-ages exceeding the maximum measuring voltage. It is suf-ficient to design the amplifier for a loading capacity which only slightly exceeds the value of the maximum measur-ing voltage at a nominal load. As a consequence, there re-sults a substantial saving in the design of the amplifier.This saving is apparent from the following example:
Single-phase transformer for nominal power 60 VA
Operational voltage between 0.22 to 1.9 Un Measuring voltage in the range of 0.8 to 1.2 Un (Un = phase voltage) If the transformer or converter produces during its rated operation an error of for instance 6%, then in order to achieve an accurancy class of 0.5, it is necessary to pro-duce a compensation power of about 5~, corresponding to 3 VA.
-5~
1 Without the aforementioned adjustment of the transducer tothe input of the amplifier, the maximum loading capacity of the amplifier would have to be about 1.92 3, that is approximately 11 VA.
By using impedance transformers at the input and output sides of the amplifier, the measurement at a reduced accuracy can take place even if the amplifier becomes dis-abled. It is of advantage that each secondary winding of respective impedance transducers is bridged by a measuring impedance. These measuring impedances are dimensioned such that, in case of failure of the amplifier, a sufficient de-crease of the transmission impedance is produced. As a re-sult, the transmission error typically remains within ac-ceptable limits. This feature is unattainable in all con-ventional error-compensating systems.
Due to the additional impedances connected paral-lel to the windings of the transformers in the secondary cir-cuit, the vector position of the compensating voltage trans-mitted by the measuring transformers can be regulated. This adjustability of the vectors of the compensating voltage in turn makes it possible that ~he error compensa-tion be carried out in the ampllfier itself. It is of advantage when ~he compensation voltage delivered by the amplifier is combined with an additional compensation voltage from a series-connected capacitor. In this manner, the orientation of -the vector of the compensation voltage at the output of the amplifier is adjustable within a broad range, because this voltage counteracts the phase shift of the compensation volt-age. Consequently, only low requirements are placed on the arnplifier for the transmission of phase of signals and the 5;:~2 1 same holds true for the vector conditions of the vol-tage applied to the input of the amplifier.
The aforementioned capacitor can be connected either directly or via a transformer in series with the secondary circuit of the high--voltage transformer. The error-compensation method of this invention enables also a partial compensation of the errors, so that a residual error of an arbitrary magnitude and vectorial direction is preserved.
The amplifier can be power-supplied from the secondary winding of the high-voltage transformer. This power-supply connection causes an additional load on the high-voltage transformer. The resulting additional trans-formation error, however, is compensated in the manner de-scribed above.
The novel features which are considered charac-teristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description o~ specific embodiments when read in connection with the accompanying drawingO
FIG. 1 is a schematic circuit diagram of one embodiment of the error-compensated transformer of this invention; and FIG. 2 and 3 show, respectively, another two embodiments of this invention.
In the Figures, reference numeral 1 indicates the secondary winding of a high-voltage trans~ormer or 3~
transducer connected to terminals 2' of à load 2, An amplifier 3 has an input 4 which is connected across a measuring impedance 5.
The impendance 5 is connected in series with the secondary winding 1 and the output 6 of -the amplifier is connected in series with the impedance 5 and the load 2. The impedance 5 produces only a small voltage drop from the load current, and the amplifier is designed so that its output 6 compensates automatically all voltage losses resulting from the application of load 2. The amplifier is power-supplied from a circuit 7.
A preferred embodiment of this invention is shown in FIGS. 2 and 3, where measuring transformers 8 and 9 have primary windings connected in series with the secondary winding l and the load ~.. The secondary windings of measuring transformers 8 and 9 are bridged by resistances 10 and 11 and connected respectively to the input 4 and the output 6 of amplifier 3. The resistances 10 and 11 adjust the phase conditions of the compensation voltage. An additional transformer 12 is connected in series with the secondary winding l and its secondary circuit is bridged by a capacitor 13. The additional tr.ansformer 12 serves for the generation of the additional compensation voltage.
The operation of the error compensated circuit will be explained by way of an example with reference to FIG. 2.
Assuming a load 2 of 60 VA at a rated voltage lO0/ ~ 3, the secondary winding 1 of a non-compensated high voltage transformer would show 3% voltage drop due to ohmic component and a 3% voltage drop to a reactive component of the transmission path.
According to this invention, -these voltage drops are compensated in such a manner as to allow a voltage accuracy of 0.2 at the nominal output of 60 VA. The value of capacitor ~ is 0.082 microfarad; the winding ratio of transformer 12 is 24/3648; the value of resistor 10 is l ohm; the winding ratio.of transformer 8 is 2l/5;
the wlnding ratio of transformer 9 is 111/24; the frequency i.s 50 Hz;
the resistance ll in this example is 117 ohms; and the amplifi.er 3 is designed for an input voltage of 0.25 vol-ts and for an outpu-t voltage f 8 volts.
_ g _ S3~Z
The linearity and angular accuracy of the amplifier are set to be 1.25 times the nominal value of the input voltage, as far as in this range the error of the amplification factor of the amplifier is not higher than ~2,5% and its phase displacement l1'~5 does not exceed -~60 minutes. From 0~ 5 up to 1,9 times the rated ,, _ value of the input voltage, the voltage error may rise up to -~10%
without any limitation to the phase displacement. The alternating current at 50 Hz, which at a load of 60 VA corresponds to 1.03 A, causes a voltage drop of 3% across the capacitor 13. This voltage drop compensates the reactive voltage drop in the transformer 12.
The resistance 10 (value 1 ohm) which is connected to the input terminals of the amplifier 3 and via the transformer 8 with the turn ratio 21/5 to the load 2, produces at the current of 1.03 ~ a voltage of 0.25 V is produced across the resistance 10 at the input of amplifier 3. This voltage is amplified to 8 volts.
The output voltage at the amplifier 3 is introduced via the transformer 9 (with the turn ratio 111/24) into the load circuit 2. Since the transformed voltage is in opposite phase to the ohmic voltage drop of 1.73 volts corresponding to the aforementioned 3% drop of the rated voltage in the load circuit, the latter voltage drop of 3% in the transformer is thus compensated. As a result, the amplifier is loaded with an active power of 1.03 (~) X 24/111 X 8 (V) = 1.78 (W).
The resistance 11 across the secondary winding of transformer 9 is preferably constituted by the impedance of a capacitor of 27 microfarads which at 50 Hz has an impedance of 117 ohms. At the primary winding of transformer 9, this impedance amounts to 5.36 ohms and as a result a voltage drop due to the load current of 1.03 amperes is applied to the load to compensate reactive voltage drop in case of a failure of the amplifier 3~ The capacitance 11 causes a supplementary Load on the amplifier of 82/117 (ohm) = 0.547 YA.
~9a-S~
FIG. 3 illustrates a circuit similar to that of FIG. 2, in which a voltage regulator 14 is connected across the secondary winding 1 and the regulated voltage is used for feediny the amplifier 3.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
-9b-Laa~3B~
1 While the invention has been illustrated and described as embodied in a high-voltage error-compensated transformer, i.t is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
Claims (8)
1. An error-compensated high-voltage transformer circuit comprising a secondary winding with load terminals;
at least one measuring impedance connected in series with the secondary winding for producing a small voltage drop proportional to the load current; an amplifier having an input circuit connected across said measuring impedance, and an output circuit connected in series with the secondary winding.
at least one measuring impedance connected in series with the secondary winding for producing a small voltage drop proportional to the load current; an amplifier having an input circuit connected across said measuring impedance, and an output circuit connected in series with the secondary winding.
2. An transformer as defined in claim 1, wherein said measuring impedance includes a coupling transformer having its primary winding connected in series with said secondary winding, and the secondary winding of the coupling transformer being connected to the input of said amplifier.
3. A transformer as defined in claim 2, further including a second coupling transformer having a primary winding connected in series with said secondary winding and the secondary winding of said second transformer being con-nected to the output of said amplifier.
4. A transformer as defined in claim 2, wherein the coupling transformer at the input of said amplifier has an iron core saturable by a magnetic flux resulting from the load current which is higher than the rated current of the high-voltage transformer corresponding to the desired accuracy.
5. A transformer as defined in claim 4, further including an additional coupling transformer having a primary winding connected in series with said secondary winding of the high-voltage transformer and the secondary winding of the additional coupling transformer being connected to said capacitor.
6. A transformer as defined in claim 3, wherein the secondary winding of at least the coupling transformer at the input of said amplifier is bridged by an impedance for adjusting the vector orientation of the tapped input voltage for the amplifier.
7. A transformer as defined in claim 1, further including a voltage regulator connected to said secondary winding of the high-voltage transformer and connected for supplying power to said amplifier.
8. A transformer as defined in claim 3, wherein the secondary winding of the second coupling transformer at the output of said amplifier is bridged by an impedance for adjusting the vector orientation of the output voltage of said amplifier.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0583080A AT389397B (en) | 1980-11-28 | 1980-11-28 | ERROR COMPENSATED VOLTAGE CONVERTER FOR HIGH VOLTAGE |
| ATA5830/80K1.21E | 1980-11-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1195382A true CA1195382A (en) | 1985-10-15 |
Family
ID=3580004
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000391036A Expired CA1195382A (en) | 1980-11-28 | 1981-11-26 | Error-compensated high-voltage transformer |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0053581B1 (en) |
| AT (2) | AT389397B (en) |
| CA (1) | CA1195382A (en) |
| DE (1) | DE3175859D1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT397741B (en) * | 1990-07-18 | 1994-06-27 | Franz Dipl Ing Dr Zach | Measurement device for mixed currents of defined origin |
| CN108279369B (en) * | 2017-12-22 | 2020-10-16 | 中国科学院微电子研究所 | Method for testing transient current and thermal distribution unevenness of multi-chip parallel circuit |
| CN111983541B (en) * | 2020-07-22 | 2023-12-26 | 中国电力科学研究院有限公司 | Method and device for calculating load error of multi-winding electromagnetic voltage transformer |
| CN115407255B (en) * | 2022-11-03 | 2023-02-03 | 云南电网有限责任公司 | Current transformer error online monitoring device and method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE615752C (en) * | 1933-07-29 | 1935-07-12 | Walter Hohle Dr Ing | Method for testing current transformers with the aid of a standard transformer with the same transmission ratio using a differential circuit |
| FR860170A (en) * | 1939-06-15 | 1941-01-08 | Alsthom Cgee | Further development of electrical measurement transformers and their use |
| DE1061433B (en) * | 1958-02-25 | 1959-07-16 | Licentia Gmbh | Measuring transducer testing device based on the differential method |
| DE1220036B (en) * | 1962-06-01 | 1966-06-30 | Licentia Gmbh | Circuit for reducing the error of a measuring voltage converter or divider |
| US3419788A (en) * | 1964-12-28 | 1968-12-31 | Superior Electric Co | Automatic voltage regulator |
| US3497793A (en) * | 1966-07-05 | 1970-02-24 | Ind Elettriche Di Legnano Spa | Error compensation apparatus for instrument transformers |
-
1980
- 1980-11-28 AT AT0583080A patent/AT389397B/en not_active IP Right Cessation
-
1981
- 1981-11-19 DE DE8181810464T patent/DE3175859D1/en not_active Expired
- 1981-11-19 AT AT81810464T patent/ATE25150T1/en not_active IP Right Cessation
- 1981-11-19 EP EP81810464A patent/EP0053581B1/en not_active Expired
- 1981-11-26 CA CA000391036A patent/CA1195382A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ATE25150T1 (en) | 1987-02-15 |
| EP0053581A1 (en) | 1982-06-09 |
| DE3175859D1 (en) | 1987-02-26 |
| AT389397B (en) | 1989-11-27 |
| EP0053581B1 (en) | 1987-01-21 |
| ATA583080A (en) | 1989-04-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4581691A (en) | Balanced constant current sensing circuit inherently immune to longitudinal currents | |
| US3753094A (en) | Ohmmeter for measuring the internal resistance of a battery and directly reading the measured resistance value | |
| CA1295023C (en) | Current ratio device | |
| JPH02254369A (en) | Static watt-hour meter | |
| US5260644A (en) | Self-adjusting shunt regulator and method | |
| US4130790A (en) | Ferroresonant transformer power supply | |
| CA1195382A (en) | Error-compensated high-voltage transformer | |
| US4213083A (en) | Circuit arrangement for compensating transmission errors of a transformer | |
| US3497793A (en) | Error compensation apparatus for instrument transformers | |
| CA1038033A (en) | Ferroresonant voltage regulating circuit | |
| US4417198A (en) | Average responding RMS indicating type transducer | |
| US3303412A (en) | Current regulated power supply with compensating means for extraneous shunting current paths across the load | |
| US4286211A (en) | Direct current detecting device using saturable reactors | |
| US5113140A (en) | Microprocessor-controlled high-voltage capacitance bridge | |
| US2814773A (en) | Voltage regulator | |
| US4477772A (en) | Frequency compensator for a current-comparator capacitance bridge | |
| US3701008A (en) | Phantom burden arrangement for current transformer calibration | |
| US3532964A (en) | Load compensated instrument potential transformer of improved accuracy | |
| US2891214A (en) | Ideal transformer | |
| US3848178A (en) | Combined power and instrument potential transformer | |
| US3895287A (en) | Low cost voltage regulating relay | |
| JPH02112210A (en) | Electronic inductor | |
| Slomovitz | Electronic compensation of voltage transformers | |
| US3433976A (en) | Parametric amplifier | |
| US3416076A (en) | Voltage regulating means for impedance bridge measuring circuits |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |