CA1175487A - Means for sensing the ratio between the line voltage and the frequency of an a.c. network - Google Patents
Means for sensing the ratio between the line voltage and the frequency of an a.c. networkInfo
- Publication number
- CA1175487A CA1175487A CA000350515A CA350515A CA1175487A CA 1175487 A CA1175487 A CA 1175487A CA 000350515 A CA000350515 A CA 000350515A CA 350515 A CA350515 A CA 350515A CA 1175487 A CA1175487 A CA 1175487A
- Authority
- CA
- Canada
- Prior art keywords
- input signal
- integrating
- frequency
- signal
- voltage amplitude
- 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
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/10—Measuring sum, difference or ratio
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/04—Measuring peak values or amplitude or envelope of ac or of pulses
-
- 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
- G01R31/343—Testing dynamo-electric machines in operation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/46—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to frequency deviations
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Measurement Of Current Or Voltage (AREA)
- Measurement Of Resistance Or Impedance (AREA)
- Protection Of Static Devices (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
A device for determining the AC line voltage amplitude/frequency characteristic of an AC network, comprising a circuit for integrating an input signal, having a certain voltage amplitude and frequency, and re-presentative of the line voltage and frequency of the AC
network. The integrating circuit repeatedly integrates the input signal to obtain an integrated signal proportional to the maximum voltage amplitude of the input signal and representative of the voltage amplitude/frequency ratio of this input signal. The device also comprises a circuit responsive to the input signal for repeatedly generating control signals defining an initial and end points of the integration of this input signal as a function of its frequency such that a phase angle between the initial and end points, and a phase angle between each initial point and an immediately preceding zero passage of the input signal, are at least substantially constant. An electronic switch is responsive to the control signals for controlling the respective initiation and termination of the integra-ting of the integrating circuit to provide integration intervals between respective initial points and successive end points. An output signal of the device is provided by a circuit responsive to the integrated signal, which output signal is by itself representative of the voltage amplitude/
frequency ratio characteristic of the AC line.
A device for determining the AC line voltage amplitude/frequency characteristic of an AC network, comprising a circuit for integrating an input signal, having a certain voltage amplitude and frequency, and re-presentative of the line voltage and frequency of the AC
network. The integrating circuit repeatedly integrates the input signal to obtain an integrated signal proportional to the maximum voltage amplitude of the input signal and representative of the voltage amplitude/frequency ratio of this input signal. The device also comprises a circuit responsive to the input signal for repeatedly generating control signals defining an initial and end points of the integration of this input signal as a function of its frequency such that a phase angle between the initial and end points, and a phase angle between each initial point and an immediately preceding zero passage of the input signal, are at least substantially constant. An electronic switch is responsive to the control signals for controlling the respective initiation and termination of the integra-ting of the integrating circuit to provide integration intervals between respective initial points and successive end points. An output signal of the device is provided by a circuit responsive to the integrated signal, which output signal is by itself representative of the voltage amplitude/
frequency ratio characteristic of the AC line.
Description
1 ~7548~
This invention relates to means connected to an a.c. network for sensing a voltage therein and for pro-viding a signal which is proportional to the ratio between the line voltage and the frequency of the network. Such a means may be used, for example, for excitation measurement in connection with motors, generators and transformers.
A known means of the above-mentioned kind, des-cribed in U.S. Patent N 3,546,534, is based on the prin-ciple of sensing the voltage across a circuit comprising a capacitor with a relatively great capacitance in series with an ohmic resistor and which is connected to the se-condary side of a transformer, the primary side of which is connected to the a.c. network.
The present invention provides a means of the above-mentioned kind which has a greater accuracy while at the same time is less space-demanding, than the known means.
More particularly, according to the present in-vention, there is provided a device for determining the AC
line voltage amplitude/frequency characteristic of an AC
network, comprising:
means for integrating an input signal, having a voltage amplitude U(in) and frequency F, and representative of the line voltage and frequency of the AC network, for repeatedly integrating this input signal to obtain an in-tegrated signal U(l max) proportional to the maximum voltage amplitude of U(in) and representative of the voltage amplitude/frequency ratio of the input signal;
means responsive to the input signal for repeated-ly generating control signals aefining an initial point and an endpoint of the integration of the input signal as a function of the frequency F such that a phase angle between the initial and end points, and a phase angle between each initial point and an im~ediately preceding zero ~assage of the input signal , are at least substantially constant;
electronic switching means responsive to the ~ 17548~
control signals for controlling the respective initiation and termination of the integrating of the means for inte~
grating to provide integration intervals between respective initial points and successive end points; and means responsive to the integrated signal to provide an output signal that by itself represents the voltage amplitude/frequency ratio characteristic of the AC
line.
Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which Figure 1 is a circuit diagram of a first embodi-ment of the means in accordance with the invention, Figure 2 is a series of graphs showing certain voltage characteristics for the means of Figure 1, Figure 3, which is disposed on the same sheet of drawings as Figure 1 is a circuit diagram of a second embodiment of the means in accordance with the invention, and Figure 4, which is disposed on the same sheet of drawings as Figure 1, is a pair of graphs showing voltage characteristics for the means of Figure 3.
In the means shown in Figure 1, the numerals 10 and 11 designate two input terminals across which there is applied an alternating voltage Uin, which is proportional to and uniform with the line voltage of an a.c. network.
The terminal 11 is connected to the O-level of the alter-nating voltage. An integrator l is arranged to be fed with the alternating voltage Uin. The integrator 1 comprises an amplifier 12 and an integration capacitor 13, which is connected between the output terminal of the amplifier 12 and the negative input terminal thereof. The capacitor 13is connected in parallel with an electronic switch 14 which is controlled by means of a zero detector 15, which com-prises two cascade-connected amplifiers 15' and 15" . The input of the zero detector 15 is also connected to the ~ .
1 17548~
input terminal 10 of the a.c. network. The voltage (U15~
appearing between the output of the zero detector 15 and the O-level is shown in Figuré 2, which also shows the curve for Uin. The voltage U15 is supplied to a control terminal of the electronic switch 14 via a diode 16, which is connected in parallel with a resistor 17'. The switch 14 does not receive a closing control signal immediately the voltage U15 passes through zero but only after a short delay interval, due to the need to accumulate a charge in a delay capacitor 17. Discounting this delay interval, the capacitor 13 will be short-circuited for the entire ~ 17548~
negative half-cycle of the alternating voltage Uin. The output voltage (Ul) of the integrator 1 will then be zero, or practically zero, for each negative half-cycle of the alternating voltage Uin, which means that the voltage Uin is integrated between an initial point in the vicinity of the zero passage when the voltage changes from a negative to a positive value and an end point when the next zero passage occurs. The value of this integral is represented by the voltage ulmax across the capacitor 13 at the end of the charging interval and is proportional to the product of the amplitude of the voltage Uin and the period T, i.e.
ulmax = kl.Uin.T. Or, expressed in terms of the frequency f of the a.¢. network, gives ulmax = kl.Uin/f.
Of course, it is possible to monitor that the relation-ship between the voltage and frequency of the a.c. network does not exceed a permissible value by observing ulmax on an oscillograph screen. However, usually an output value in the form of a voltage proportional to ulmax is desired and this can be obtained by connecting the voltage ul to a maximum value indicator. Such an indicator is included in the means shown in Figure 1 and comprises an electronic switch 18, a deriving means 19, a copying capacitor 20, which is arranged to be charged to and thus "copy'l the voltage ulmax, and a proportional amplifier 21, which is arranged to be controlled by the voltage appearing across the copying capacitor 20. The deriving means 19 reacts only on the zero passage of the output voltage ul5 from plus to minus on the basis of the signal delivered by the zero detector 15 and gives a corresponding very brief 3 voltage pulse ulg, to the control input of the electronic switch 18, which is then closed and held closed for a brief time interval corresponding to the width of the pulse ulg. The copying capacitor 20 then acquires, during this brief time interval, a potential which, in relation to the O-level, is equal to ulmax. This potential is supplied to the input of the amplifier 21, the output voltage u21 of which then becomes proportional to ul~ax.
From the foregoing descrip~ion,it will be appreciatedthat the 1 ~7548~
integrator 1 repeatedly integrates the ~bsolute value of the voltage Uin between an initial point and an end point of the voltage curve, the phase angle between the initial point and end point and the phase angle between each initial 5 point and the immediately preceding zero passage of the voltage being at least substantially constant.
The embodiment shown in Figures 3 and 4 differs from that shown in Figure 1 substantially in that -the integration capacitor is bridged by a rectifier element instead of the electronic switch 14 shown in Figure l.
The means shown in Figure 3 comprises an integrator 31, a zero-indicator 32, a deriving means 33, an electronic switch 34, amplifiers 35, 36 and 37, capacitors 38 and 39, rectifier elements 40, 41 and 42 and resistors 43, 44, 45, 15 46, 47 and 48.
The zero indicator 32 and the deriving means 33 form a peak value indicating detector together with the elec-tronic switch 34, the capacitor 38 and the amplifier 35, the output voltage u35 of the amplifier 35 being proportional 20 to the potential of the integration capacitor 39 above a reference levelO During a negative half-cycle of the alternating voltage Uin, the integrator 31 is supplied by said voltage. During the positive half-cycle of the voltage, the integration capacitor 39 is discharged to the 25 reference level.
This invention relates to means connected to an a.c. network for sensing a voltage therein and for pro-viding a signal which is proportional to the ratio between the line voltage and the frequency of the network. Such a means may be used, for example, for excitation measurement in connection with motors, generators and transformers.
A known means of the above-mentioned kind, des-cribed in U.S. Patent N 3,546,534, is based on the prin-ciple of sensing the voltage across a circuit comprising a capacitor with a relatively great capacitance in series with an ohmic resistor and which is connected to the se-condary side of a transformer, the primary side of which is connected to the a.c. network.
The present invention provides a means of the above-mentioned kind which has a greater accuracy while at the same time is less space-demanding, than the known means.
More particularly, according to the present in-vention, there is provided a device for determining the AC
line voltage amplitude/frequency characteristic of an AC
network, comprising:
means for integrating an input signal, having a voltage amplitude U(in) and frequency F, and representative of the line voltage and frequency of the AC network, for repeatedly integrating this input signal to obtain an in-tegrated signal U(l max) proportional to the maximum voltage amplitude of U(in) and representative of the voltage amplitude/frequency ratio of the input signal;
means responsive to the input signal for repeated-ly generating control signals aefining an initial point and an endpoint of the integration of the input signal as a function of the frequency F such that a phase angle between the initial and end points, and a phase angle between each initial point and an im~ediately preceding zero ~assage of the input signal , are at least substantially constant;
electronic switching means responsive to the ~ 17548~
control signals for controlling the respective initiation and termination of the integrating of the means for inte~
grating to provide integration intervals between respective initial points and successive end points; and means responsive to the integrated signal to provide an output signal that by itself represents the voltage amplitude/frequency ratio characteristic of the AC
line.
Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which Figure 1 is a circuit diagram of a first embodi-ment of the means in accordance with the invention, Figure 2 is a series of graphs showing certain voltage characteristics for the means of Figure 1, Figure 3, which is disposed on the same sheet of drawings as Figure 1 is a circuit diagram of a second embodiment of the means in accordance with the invention, and Figure 4, which is disposed on the same sheet of drawings as Figure 1, is a pair of graphs showing voltage characteristics for the means of Figure 3.
In the means shown in Figure 1, the numerals 10 and 11 designate two input terminals across which there is applied an alternating voltage Uin, which is proportional to and uniform with the line voltage of an a.c. network.
The terminal 11 is connected to the O-level of the alter-nating voltage. An integrator l is arranged to be fed with the alternating voltage Uin. The integrator 1 comprises an amplifier 12 and an integration capacitor 13, which is connected between the output terminal of the amplifier 12 and the negative input terminal thereof. The capacitor 13is connected in parallel with an electronic switch 14 which is controlled by means of a zero detector 15, which com-prises two cascade-connected amplifiers 15' and 15" . The input of the zero detector 15 is also connected to the ~ .
1 17548~
input terminal 10 of the a.c. network. The voltage (U15~
appearing between the output of the zero detector 15 and the O-level is shown in Figuré 2, which also shows the curve for Uin. The voltage U15 is supplied to a control terminal of the electronic switch 14 via a diode 16, which is connected in parallel with a resistor 17'. The switch 14 does not receive a closing control signal immediately the voltage U15 passes through zero but only after a short delay interval, due to the need to accumulate a charge in a delay capacitor 17. Discounting this delay interval, the capacitor 13 will be short-circuited for the entire ~ 17548~
negative half-cycle of the alternating voltage Uin. The output voltage (Ul) of the integrator 1 will then be zero, or practically zero, for each negative half-cycle of the alternating voltage Uin, which means that the voltage Uin is integrated between an initial point in the vicinity of the zero passage when the voltage changes from a negative to a positive value and an end point when the next zero passage occurs. The value of this integral is represented by the voltage ulmax across the capacitor 13 at the end of the charging interval and is proportional to the product of the amplitude of the voltage Uin and the period T, i.e.
ulmax = kl.Uin.T. Or, expressed in terms of the frequency f of the a.¢. network, gives ulmax = kl.Uin/f.
Of course, it is possible to monitor that the relation-ship between the voltage and frequency of the a.c. network does not exceed a permissible value by observing ulmax on an oscillograph screen. However, usually an output value in the form of a voltage proportional to ulmax is desired and this can be obtained by connecting the voltage ul to a maximum value indicator. Such an indicator is included in the means shown in Figure 1 and comprises an electronic switch 18, a deriving means 19, a copying capacitor 20, which is arranged to be charged to and thus "copy'l the voltage ulmax, and a proportional amplifier 21, which is arranged to be controlled by the voltage appearing across the copying capacitor 20. The deriving means 19 reacts only on the zero passage of the output voltage ul5 from plus to minus on the basis of the signal delivered by the zero detector 15 and gives a corresponding very brief 3 voltage pulse ulg, to the control input of the electronic switch 18, which is then closed and held closed for a brief time interval corresponding to the width of the pulse ulg. The copying capacitor 20 then acquires, during this brief time interval, a potential which, in relation to the O-level, is equal to ulmax. This potential is supplied to the input of the amplifier 21, the output voltage u21 of which then becomes proportional to ul~ax.
From the foregoing descrip~ion,it will be appreciatedthat the 1 ~7548~
integrator 1 repeatedly integrates the ~bsolute value of the voltage Uin between an initial point and an end point of the voltage curve, the phase angle between the initial point and end point and the phase angle between each initial 5 point and the immediately preceding zero passage of the voltage being at least substantially constant.
The embodiment shown in Figures 3 and 4 differs from that shown in Figure 1 substantially in that -the integration capacitor is bridged by a rectifier element instead of the electronic switch 14 shown in Figure l.
The means shown in Figure 3 comprises an integrator 31, a zero-indicator 32, a deriving means 33, an electronic switch 34, amplifiers 35, 36 and 37, capacitors 38 and 39, rectifier elements 40, 41 and 42 and resistors 43, 44, 45, 15 46, 47 and 48.
The zero indicator 32 and the deriving means 33 form a peak value indicating detector together with the elec-tronic switch 34, the capacitor 38 and the amplifier 35, the output voltage u35 of the amplifier 35 being proportional 20 to the potential of the integration capacitor 39 above a reference levelO During a negative half-cycle of the alternating voltage Uin, the integrator 31 is supplied by said voltage. During the positive half-cycle of the voltage, the integration capacitor 39 is discharged to the 25 reference level.
Claims (7)
1. A device for determining the AC line voltage amplitude/frequency characteristic of an AC network, comprising:
means for integrating an input signal, having a voltage amplitude U(in) and frequency F, and represen-tative of the line voltage and frequency of said AC net-work, for repeatedly integrating said input signal to obtain an integrated signal U(1 max) proportional to the maximum voltage amplitude of U(in) and representative of the voltage amplitude/frequency ratio of said input signal;
means responsive to said input signal for repeatedly generating control signals defining an initial point and an end point of the integration of said input signal as a function of said frequency F such that a phase angle between said initial and end points, and a phase angle between each initial point and an immediately preceding zero passage of said input signal, are at least substan-tially constant;
electronic switching means responsive to said control signals for controlling the respective ini-tiation and termination of the integrating of said means for integrating to provide integration intervals between respective initial points and successive end points; and means responsive to said integrated signal to provide an output signal that by itself represents the voltage amplitude/frequency ratio characteristic of the AC line.
means for integrating an input signal, having a voltage amplitude U(in) and frequency F, and represen-tative of the line voltage and frequency of said AC net-work, for repeatedly integrating said input signal to obtain an integrated signal U(1 max) proportional to the maximum voltage amplitude of U(in) and representative of the voltage amplitude/frequency ratio of said input signal;
means responsive to said input signal for repeatedly generating control signals defining an initial point and an end point of the integration of said input signal as a function of said frequency F such that a phase angle between said initial and end points, and a phase angle between each initial point and an immediately preceding zero passage of said input signal, are at least substan-tially constant;
electronic switching means responsive to said control signals for controlling the respective ini-tiation and termination of the integrating of said means for integrating to provide integration intervals between respective initial points and successive end points; and means responsive to said integrated signal to provide an output signal that by itself represents the voltage amplitude/frequency ratio characteristic of the AC line.
2. A device according to claim 1, in which the initial points and the end points each occur at a zero passage of said input signal, and the phase angle between each successive initial point and end point is substantially 180 degrees.
3. A device according to claim 2, wherein said means for integrating includes an integration capacitor for repeatedly integrating said input signal, and said electronic switching means includes a controlled electronic on/off switch connected to said integration capacitor to control the charge and discharge thereof to provide a charging interval at the initial points and a discharging interval at the end points to terminate the integrating capacitor discharge before the immediately succeeding initial point occurs; and said means for generating a control signal includes detector means responsive to the polarity of said input signal to generate said control signal only during every second half-cycle of said input signal to establish an on or off condition of said controlled electronic on/off switch.
4. A device according to claim 2, further comprising an electronic switch responsive to said control signals and said means for integrating includes an inte-gration capacitor for repeatedly integrating said input signal, and said means for providing an output signal in-cludes a copying capacitor adapted to be connected to said integration capacitor through said electronic switch, and wherein said means for generating control signals includes a zero passage detector responsive to said input signal to provide zero passage output signals representative of every second zero passage of said input signal, and further including means responsive to said zero passage output signals for generating said control signals.
5. A device according to claim 2, further comprising a diode responsive to said control signals and connected between said means for generating control signals and said electronic switching means.
6. A device according to claim 4, in which said zero passage detector includes at least one amplifier for amplifying and clipping said input signal to provide said zero passage output signals.
7. A device according to claim 1, wherein said means for integrating repeatedly comprise means for in-tegrating the absolute value of said input signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7903585A SE416757B (en) | 1979-04-24 | 1979-04-24 | DEVICE CONNECTING TO AN AC POWER NETWORK TO FEEL THE VOLTAGE IN THIS AND TO PROVIDE AN OUTPUT VALUE PROPORTIONAL TO THE RELATIONSHIP BETWEEN THE NETWORK'S LINE POWER AND FREQUENCY |
| SE7903585-3 | 1979-04-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175487A true CA1175487A (en) | 1984-10-02 |
Family
ID=20337884
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000350515A Expired CA1175487A (en) | 1979-04-24 | 1980-04-23 | Means for sensing the ratio between the line voltage and the frequency of an a.c. network |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1175487A (en) |
| CH (1) | CH650079A5 (en) |
| DE (1) | DE3014096A1 (en) |
| FR (1) | FR2455285A1 (en) |
| GB (1) | GB2049959B (en) |
| SE (1) | SE416757B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3044020A1 (en) * | 1980-11-22 | 1982-06-03 | Hermann Dr. 3171 Rötgesbüttel Lühr | Magnetometer with digital display - uses pulse integration and has premagnetising and induction coils on single core |
| KR850000683A (en) * | 1983-06-30 | 1985-02-28 | 카다야마 히도하지로 | Voltage detection device of variable frequency power system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3546534A (en) * | 1968-01-31 | 1970-12-08 | Gen Electric | Overexcitation relay |
| US3717818A (en) * | 1972-01-10 | 1973-02-20 | J Herbst | Instantaneous voltage detector |
-
1979
- 1979-04-24 SE SE7903585A patent/SE416757B/en not_active IP Right Cessation
-
1980
- 1980-04-01 CH CH254780A patent/CH650079A5/en not_active IP Right Cessation
- 1980-04-12 DE DE19803014096 patent/DE3014096A1/en not_active Withdrawn
- 1980-04-21 FR FR8008873A patent/FR2455285A1/en active Granted
- 1980-04-23 CA CA000350515A patent/CA1175487A/en not_active Expired
- 1980-04-23 GB GB8013451A patent/GB2049959B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3014096A1 (en) | 1980-11-13 |
| FR2455285A1 (en) | 1980-11-21 |
| GB2049959B (en) | 1983-01-12 |
| CH650079A5 (en) | 1985-06-28 |
| SE416757B (en) | 1981-02-02 |
| SE7903585L (en) | 1980-10-25 |
| FR2455285B1 (en) | 1985-04-19 |
| GB2049959A (en) | 1980-12-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |