GB2221313A - Multiplier for use in instantaneous power measurement systems - Google Patents

Multiplier for use in instantaneous power measurement systems Download PDF

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Publication number
GB2221313A
GB2221313A GB8817714A GB8817714A GB2221313A GB 2221313 A GB2221313 A GB 2221313A GB 8817714 A GB8817714 A GB 8817714A GB 8817714 A GB8817714 A GB 8817714A GB 2221313 A GB2221313 A GB 2221313A
Authority
GB
United Kingdom
Prior art keywords
instantaneous
multiplier
power measurement
amplifier
voltage
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.)
Granted
Application number
GB8817714A
Other versions
GB8817714D0 (en
GB2221313B (en
Inventor
P G Williams
A J Wilks
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OMEGA ELECTRIC Ltd
Original Assignee
OMEGA ELECTRIC Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by OMEGA ELECTRIC Ltd filed Critical OMEGA ELECTRIC Ltd
Priority to GB8817714A priority Critical patent/GB2221313B/en
Publication of GB8817714D0 publication Critical patent/GB8817714D0/en
Priority to PCT/GB1990/000134 priority patent/WO1991011725A1/en
Publication of GB2221313A publication Critical patent/GB2221313A/en
Application granted granted Critical
Publication of GB2221313B publication Critical patent/GB2221313B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00—Arrangements for measuring electric power or power factor
    • G01R21/133—Arrangements for measuring electric power or power factor by using digital technique
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06J—HYBRID COMPUTING ARRANGEMENTS
    • G06J1/00—Hybrid computing arrangements

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • Mathematical Physics (AREA)
  • Automation & Control Theory (AREA)
  • Evolutionary Computation (AREA)
  • Fuzzy Systems (AREA)
  • Software Systems (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

In a power measurement system a signal representing the instantaneous value of the current (i) is applied to a programmable resistance (6) in the input to an amplifier (7), and the value of the resistance (6) is selected (5) on an instantaneous basis in accordance with the rectified (1), analogue to digital (3) converted, value of the instantaneous voltage (v). A detector (2) determines the phase of the applied voltage and operates a reversing switch (8) for negative voltage (v). The output of a summing amplifier (10) then represents true instantaneous power. <IMAGE>

Description

DESCRIPTION INSTANTANEOUS MULTIPLIER FOR USE IN POWER MEASUREMENT SYSTEMS This invention relates to an instantaneous multiplier for use in power measurement systems such as solid state electricity meters.
Solid state electricity meters generally require a four quadrant multiplier to compute the actual power waveform with varying voltage, current and power factor of the load. This is generally achieved using a four quadrant multiplier based upon the variable transconductance principle. Unfortunately such four quadrant multipliers suffer from drift problems and linearity errors.
Alternatively digital sampling techniques can be employed, but these suffer with phase errors due to the inherent delays associated with the techniques.
Optical multipliers to date suffer from inherent slow response times, which render them useless for instantaneous calculation as is required in dynamic power measurement.
According to the present invention a multiplier can be made which will allow the instantaneous calculation of power in an AC system.
A specific example will now be described with reference to the accompanying drawing.
Figure 1 shows in block diagram form a fast multiplier using a full wave rectifier, analogue to digital converter, a digitally programmable resistor, a phase detector, a solid state changeover switch, and a number of operational amplifiers.
Referring to Figure 1 the instantaneous AC voltage v is applied to a full wave rectifier (1) and a phase detector (2). The output of the full wave rectifier is applied to an analogue to digital converter (3) and the output of this is in turn applied to a digitally programmable resistor (4) consisting of a number of analogue switches (5) and a weighted resistor network (6), alternatively the network (6) could be based upon an R-2R system which is known to those in the art.
A voltage signal representative of the instantaneous AC current i is applied to the digitally programmable resistor and hence the output of the amplifier (7) will be the resultant of instantaneous current multiplied by the rectified value of the applied voltage by virtue of the input resistance to amplifier (7) being made to vary with the rectified value of the applied voltage.
In order to correctly calculate the active power supplied to a load the phase of the applied voltage is determined by the detector (2) which then operates the analogue changeover switch (8) so that the output of the amplifier (7) is inverted by amplifier (9) for negative excursions of the instantaneous voltage v. Hence the output of the summing amplifier (10) will be a true representation of instantaneous power.

Claims (3)

1. An instantaneous multiplier for electrical power meters based upon the use of a variable resistance within an amplifier circuit, said variable resistance being made variable with the voltage applied to a load on an instantaneous basis.
2. An instantaneous amplifier as in Claim 1 constructed using an analogue to digital converter and a digitally programmable resistor to produce a variable resistance within an amplifier circuit.
3. A multiplier as in Claim 1 or Claim 2 using a phase canparator and solid state switch to correct for loss of phase information in one of the multiplicands as a result of rectification.
GB8817714A 1988-07-26 1988-07-26 Instantaneous multiplier for use in power measurement systems Expired - Fee Related GB2221313B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB8817714A GB2221313B (en) 1988-07-26 1988-07-26 Instantaneous multiplier for use in power measurement systems
PCT/GB1990/000134 WO1991011725A1 (en) 1988-07-26 1990-01-30 Instantaneous multiplier for use in power measurement systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8817714A GB2221313B (en) 1988-07-26 1988-07-26 Instantaneous multiplier for use in power measurement systems

Publications (3)

Publication Number Publication Date
GB8817714D0 GB8817714D0 (en) 1988-09-01
GB2221313A true GB2221313A (en) 1990-01-31
GB2221313B GB2221313B (en) 1993-02-24

Family

ID=10641079

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8817714A Expired - Fee Related GB2221313B (en) 1988-07-26 1988-07-26 Instantaneous multiplier for use in power measurement systems

Country Status (2)

Country Link
GB (1) GB2221313B (en)
WO (1) WO1991011725A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2686994A1 (en) * 1992-02-04 1993-08-06 Sagem ELECTRONIC COUNTER FOR ELECTRICAL ENERGY CONSUMPTION.
FR2702581A1 (en) * 1993-03-12 1994-09-16 Sagem Multiplier circuit with potentiometers and electric energy meter incorporating such a circuit.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4101966A (en) * 1977-03-28 1978-07-18 Communications Satellite Corporation 4-quadrant multiplier
EP0008630A1 (en) * 1978-07-17 1980-03-19 Siemens Aktiengesellschaft Power/frequency converter with a microcomputer

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4058768A (en) * 1977-01-07 1977-11-15 General Electric Company Two-way electronic kWh meter
US4079313A (en) * 1977-04-18 1978-03-14 Allen-Bradley Company Digital watts transducer
US4486707A (en) * 1982-09-24 1984-12-04 Sangamo Weston, Inc. Gain switching device with reduced error for watt meter
US4535287A (en) * 1983-03-25 1985-08-13 General Electric Company Electronic watt/watthour meter with automatic error correction and high frequency digital output
CH673714A5 (en) * 1985-05-02 1990-03-30 Zellweger Uster Ag
GB8624926D0 (en) * 1986-10-17 1986-11-19 Gen Electric Co Plc Electric power measuring devices
US4795974A (en) * 1987-07-24 1989-01-03 Ford Motor Company Digital energy meter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4101966A (en) * 1977-03-28 1978-07-18 Communications Satellite Corporation 4-quadrant multiplier
EP0008630A1 (en) * 1978-07-17 1980-03-19 Siemens Aktiengesellschaft Power/frequency converter with a microcomputer

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2686994A1 (en) * 1992-02-04 1993-08-06 Sagem ELECTRONIC COUNTER FOR ELECTRICAL ENERGY CONSUMPTION.
EP0555141A1 (en) * 1992-02-04 1993-08-11 Sagem Sa Electronic energy consumption meter
FR2702581A1 (en) * 1993-03-12 1994-09-16 Sagem Multiplier circuit with potentiometers and electric energy meter incorporating such a circuit.
EP0616292A1 (en) * 1993-03-12 1994-09-21 Sagem Sa Multiplier circuit with resistor networks and an electric energy meter incorporating such a circuit
US5446374A (en) * 1993-03-12 1995-08-29 Societe D'applications Generales D'electricite Et De Mecanique -Sagem Potentiometer multiplier circuit, and an electrical energy meter including such a circuit

Also Published As

Publication number Publication date
WO1991011725A1 (en) 1991-08-08
GB8817714D0 (en) 1988-09-01
GB2221313B (en) 1993-02-24

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19960726