Arrangement and method for accurately sensing voltage of a high-impedance source and supplying power to a variable burden

• US 5,220,495 A
• Filed: 09/18/1991
• Issued: 06/15/1993
• Est. Priority Date: 09/18/1991
• Status: Expired due to Term

• Current Assignee: S&C Electric Company
• Original Assignee: S&C Electric Company
• Inventors: Zulaski, John A.
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US07/761,590
• Time in Patent Office: 636 Days
• Field of Search: 323/220, 323/223, 323/225, 323/226, 323/358, 323/359, 363/84, 307/130, 307/131, 320/32, 324/126
• US Class Current: 363/84
• CPC Class Codes: G01R 15/144 Measuring arrangements for voltage not covered by other subgroups of G01R15/14
• CPC Class Codes: G05F 1/613 using semiconductor devices in parallel with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: H02H 1/063 primary power being supplied by fault current

Abstract

An arrangement is provided for accurately sensing the source voltage of a high-impedance source while supplying a variable burden. A current-sensing element is connected in series with a load circuit across a high-impedance source. The load circuit includes a variable burden load. A shunt regulator is connected with the variable burden load and is arranged to operate so that the combination of the shunt regulator and the variable burden present a controlled, nearly constant burden to the high-impedance source. The source voltage of the high-impedance source is sensed via the voltage across the series current-sensing element. While the output voltage is directly proportional to the burden, the output current is essentially unaffected by small variations in the burden. Thus, the current through the series current-sensing element is utilized to accurately sense the voltage of the high-impedance alternating-current source while also supplying the variable burden load such as a battery, electrical circuitry, and a switch operator.

Claims

1. An arrangement for accurately measuring the source voltage of a high-impedance source while supplying a variable burden load comprising:

a current-sensing element, the series combination of said current-sensing element and the variable burden being connected to the high-impedance source; and

a voltage regulator being connected with the variable burden so as to maintain a constant voltage across the variable burden, the voltage developed across said current-sensing element accurately representing the voltage of the high-impedance source, said current-sensing element comprising a current transformer.

2. The arrangement of claim 1 wherein the variable burden includes a load supply circuit and a variable load, said voltage regulator comprising shunt regulator means being connected across the variable load.

3. An arrangement for accurately measuring an input voltage to a circuit supplying a load circuit including a variable burden load comprising:

voltage sensor means connected to the input voltage and providing an output generally representative of the input voltage, said output of said voltage sensor means having the characteristics of a high-impedance source so as to behave as an ideal voltage source in series with an impedance of high magnitude such that the voltage of said output varies significantly with changes in load and is not an accurate representation of the input voltage in the presence of variations in the load on said output,

a sensing element connected in series with said output of said voltage sensor means and the load circuit, the voltage developed across said sensing element being utilized to represent the input voltage; and

voltage regulator means being connected with the variable burden load for maintaining a constant voltage to the variable burden load.

4. In an alternating current power system having a source that supplies a circuit having a variable load, an arrangement for sensing the voltage of the source comprising:

voltage sensor means connected to the source and providing an output generally representative of the source voltage, said output of said voltage sensor means having the characteristics of a high-impedance source in series with an impedance of high magnitude such that the voltage of said output varies significantly with changes in load and is not an accurate representation of the source voltage in the presence of variations in the load on said output;

load supply circuit means for supplying the variable load;

a sensing element connected in series with said output and said load supply circuit means;

means for sensing the voltage developed across said sensing element as a measure of the source voltage; and

shunt regulator means connected across the variable load for maintaining constant voltage across the variable load in response to variations in the impedance presented by the variable load to thereby present a controlled, nearly constant burden to said output and improve the accuracy of the sensed voltage signal.

5. A method for accurately measuring the source voltage of a high-impedance source that supplies a load circuit including a variable load comprising sensing the voltage developed across a current-sensing element connected in series with the source and the load circuit to provide an output that accurately represents the source voltage, and maintaining the voltage across the variable burden at a predetermined level.

6. An arrangement for measuring the source voltage of a high-impedance source while supplying a load comprising:

current-sensing means being connected in series circuit relationship with the series combination of the high-impedance source and the load, the voltage developed across said current-sensing means providing an output representing the source voltage of the high-impedance source, the source being an alternating-current source;

the load including a variable load portion and rectifying means, the rectifying means including means for supplying the variable load portion; and

voltage regulator means connected across the variable load portion for maintaining a constant voltage across the variable burden.

7. The arrangement of claim 6 wherein said current-sensing means comprises a resistor.

8. The arrangement of claim 6 wherein said current-sensing means comprises a current transformer.

9. The arrangement of claim 6 wherein said voltage regulator means is of the shunt-regulating type.

10. The arrangement of claim 6 wherein the alternating-current source operates at a source frequency, the arrangement further comprising filter means connected across said current-sensing means for attenuating frequencies other than the source frequency.

11. An arrangement for accurately measuring an input voltage to a load circuit supplying a variable burden load comprising:

voltage sensor means connected to the input voltage and providing an output generally representative of the input voltage, said output of said voltage sensor means having the characteristics of a high-impedance source in series with an impedance of high magnitude such that the voltage of said output varies significantly with changes in load and is not an accurate representation of the input voltage in the presence of variations in the load on said output;

sensing means; and

voltage regulator means, said sensing means and said voltage regulator means being connected in series with each other and in series combination with said output of said voltage sensor means, said voltage regulator means comprising means for providing supply connections to supply the variable burden load, the voltage developed across said sensing means being utilized to represent the input voltage.

12. The arrangement of claim 11 wherein said voltage regulator means comprises means for maintaining a constant voltage across the variable burden load.

13. The arrangement of claim 11 wherein said voltage regulator means comprises shunt regulator means being connected across the variable burden load.

14. The arrangement of claim 11 wherein said voltage regulator means comprises means for presenting an essentially constant burden to said output of said voltage sensor means while the burden of the variable burden load changes.

15. In an electrical power system having a high-impedance source that supplies power to a load circuit having a variable load portion, an arrangement for sensing the source voltage of the source comprising:

shunt regulator means connected across the variable portion; and

signal providing means for providing a sensed-voltage signal representing the voltage of the source, said signal-providing means including sensing means connected in series circuit relationship between the source and the load circuit, the voltage developed across said sensing means representing the voltage of the source, the source being an alternating-current source and the load circuit including a rectifying arrangement having an output being connected to supply said shunt regulator means.

16. A method for accurately measuring the source voltage of a high-impedance source that supplies a variable load comprising the steps of:

supplying the variable load from a voltage regulator that is connected in series with the source and a current-sensing element;

maintaining the voltage across the variable load at a predetermined constant level; and

measuring the voltage developed across the current-sensing element to provide a representation of the source voltage of the high-impedance source.

17. The method of claim 16 wherein the high-impedance source operates at a predetermined source frequency and said measuring step comprises filtering the voltage developed across the current-sensing element to pass the predetermined source frequency relative to other frequencies.

18. The method of claim 16 wherein the high-impedance source operates at a predetermined source frequency and said measuring step comprises outputting the voltage at the predetermined source frequency.