JPS5852575A - Power-factor transducer - Google Patents

Abstract

PURPOSE:To realize a transducer having high accuracy without being influenced by a temperature of a circuit to be measured, by executing addition and subtraction of each DC voltage being proportional to a power of a phase difference of 2 AC inputs, and reference voltage, in a prescribed ratio. CONSTITUTION:An AC input of a phase diffenence (phi) is applied to a terminal 1 and 2, respectively, is waveform-shaped by a comparator 11 and 12, its exclusive OR is taken by a gate 13, and square wave voltage 53 of a duty ratio being proportional to the phase difference (phi) is obtained. The voltage 53 passes through a switch S1 and a filter A1, is converted to DC voltage E21, and is supplied to S2. In the same way, voltage E22 being proportional to phi<2> is obtained and is supplied to S3. Moreover, voltage E23 being proportional to phi<3> is obtained. Subsequently, the voltage E22 and E23 are subjected to addition and subtraction in the prescribed ratio, respectively, with reference voltage Ez by an adding and subtracting circuit AD, and DC voltage being proportional to a power-factor of a circuit to be measured is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power factor transducer that outputs a DC voltage proportional to the power factor of a circuit under test.

Conventionally, a power factor transducer has a phase discrimination circuit that outputs a DC voltage proportional to the phase difference φ between two AC inputs, and a polygonal line approximation using a diode, etc. φcrs d '9;!
It consisted of a switching circuit.

However, the φ-
The ctf1$F m circuit has poor conversion accuracy and is affected by ambient temperature changes and temporal drift, so it was not suitable for high-precision power factor measurement (τ).

This invention was made by paying attention to the actual situation of two series, and by using a power circuit of the phase difference φ using a switch m'fe+' and a filter circuit, -
The present invention attempts to provide a highly accurate power factor transducer that performs one-possible φ conversion.

Here, the power factor before φ is expressed in terms of the power of the phase difference φ.

When the residence φ is subjected to Taylor expansion with respect to ≠, it can be expressed as the following equation (1).

In general, power factor transducers have blade factors of 0.5 to 0.5 in practice.
Since it is sufficient to be able to measure the range of 1, the power factor range is α5~
It is also possible to express φ as shown in the following equation (2) with respect to φ.

Residenceφ middle 1-α522φ+0.068φ...(2)
By substituting specific numerical values into equation (2), the φ-determined φ conversion accuracy is determined, and Table 1 shows a comparison between the enclosed φ value and the true value of possible φ based on equation (2).

Table 1 As shown in Table 1, the part φ value obtained by equation (2) has a small error with respect to the true residence φ value.

Therefore, the circuit of the present invention is configured to calculate equation (2).

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the power factor transducer of the present invention, in which (1) and (2) are input terminals to which AC human power 41 and 42 of the circuit under test are applied, respectively;
111 and θ are input terminals (1) and (2), respectively.
), a comparator that shapes the waveform of the AC input applied to the
i+31 is a gate that outputs the exclusive OR of the outputs of the comparators (111 and (121); S+, 82, and S3 are switches that are turned on only when the voltages of the respective control terminals G+, Gz, and G3 are high; AT;

A2 and A3 are filters that smooth the input signal, EZ is the reference DC voltage, Q]), (a) and (to) are the phase difference φ
, AD is the terminal where the DC voltage proportional to φ, -1 and φ8 is obtained, respectively, and AD is the reference voltage EZ and the terminal (H).
An adding/subtracting circuit adds and subtracts the DC voltages outputted to and - respectively at a ratio based on equation (2) above, and (2) is an output terminal that takes out a DC voltage proportional to the power factor.

In the power factor transducer circuit configured in this way, the input terminals (1) and (2) are connected to each other as shown in FIG.
AC input 41 with phase difference φ as shown in 1) and (2)
and 42 are applied. These inputs are input by comparators (11) and G21, respectively, as shown in Fig. 2 (3).
And the waveforms are shaped into rectangular wave voltages 51 and 52 shown in (4). These rectangular wave voltages 51 and 52 are exclusive-ORed with a gate (G)H, and a rectangular wave voltage 53 having a duty ratio proportional to the phase difference φ shown in FIG. 2 (5) is obtained. The square wave voltage 53 is applied to control terminals Gj, G2 and G3 of switches S+, S2 and S3.

First, switch S1 is activated when the rectangular wave voltage 53 is high.
N and the reference voltage KZi is passed through, and an output 61 having a peak value Kz as shown in FIG. 2 (6) is obtained.

This output 61 is smoothed by the filter A1, and the DC voltage E2+ is proportional to the input phase difference φ as shown in the following +3) formula.
is converted to

E21= 1' -Ez...+3)π This voltage Fi2+ is supplied to the switch S2, and in the same way as the switch S1, the peak value E2 is set as shown in FIG. 2 (7).
1 output 62 is obtained. This output 62 is filter A2
The input phase difference φ is smoothed by the following equation (4).
is converted into a DC voltage Fi22 proportional to φ☆.

=<-j! -5·Ez (4)π This voltage Fj22 is supplied to the switch S5, and in the same way, an output 68 having a peak value B22 as shown in FIG. 2 (8) is obtained. This output 63 is smoothed by a filter A3 and converted into a DC voltage 1123 proportional to φ8 with respect to the input phase difference φ as shown in the following equation (5).

=(11ge·E····(5) π The DC voltages E22 and B2M and the reference voltage ILz obtained in the above manner are added and subtracted by 2 and 1 to the addition/subtraction ratio Kl by the addition/subtraction circuit AD. , the next (6)
An output Fi2s shown by the formula is obtained.

F225=Ez-K 1E22 +2 B2 sK,
+ B2 (In formula 01, □= (1,522,--=0.06
If F9 F8 is selected as 8, the output E25 shown in equation (6) will be added and subtracted at the same ratio as in equation (2), and will be proportional to the power factor of the input.

Here, in the circuit of FIG. 1, as shown in FIG. 2 (5) to (8), the output of the load 1 is not considered, but the switch S
, , Sz and B3 are respectively connected to control terminals a1. If a2 and G3 are configured to output inverted voltages to filters Al, A2 and A3, respectively, when a2 and G3 are low, the outputs E2+, E22 and B25 of filters Al, A2 and A3, respectively, are as follows. 1311i) and 00 formula.

φ−(π−φ) E 2 + = −−−Fiz π = (”−1) Ez−031 π m−(π− B22= −・Ft21 π ==(2$ 1)s , Ez π − -(4 generations -4$ +1)EZ -04)F9
π B25=φ−(π−φ), B22 π Next, B21. B22. 23 and the reference voltage Ez at the addition/subtraction ratio M+, M2. M
5 and M4, an output E25 shown by the following equation (16) is obtained.

E2s=M+Ez++M2E22+23+λ4t for M3
Kz=((rt)M1+(a, -71) M2+<
'? ”, pr-Juji-3) Ms4-M4) Bz2φ
4φ24φ +j藺φJFiz ... (+6) In the (+6) formula, -Mi +M2-M50M4=11-M + -
--M2 10-Ms = 6', 'M2 +-MS
=0.522π π π
If F9 π98[3=α068 is selected, addition/subtraction πB will be calculated at the same ratio as in equation (2), and an output proportional to the power factor will be obtained as in equation (6).

In addition, in FIG. 1, the phase discrimination circuit composed of gate 1B and switch S1 is
It is designed to output a rectangular wave voltage with a duty ratio proportional only to the magnitude of the phase difference φ, but as is commonly used, one of the inputs can be phase-shifted by a total of π/2 to discriminate the phase. Therefore, even when configured to output a rectangular wave voltage with a duty ratio that increases or decreases in response to phase lag and advance, the φ-circle φ conversion can be performed by similarly calculating A2 and A8 with respect to the phase difference -. This is possible and is also included in this invention.

In such a case, the output voltage 75 of the filter A3 in FIG. 1 is reversed around the zero phase rudder, so it can also be realized by inserting an absolute value circuit or the like into the input section 03) of the adder/subtractor circuit AD. It is.

According to this invention as above, with a simple cycle 1δ hinoki,
It provides a DC voltage proportional to the power factor of the circuit under test, and because it does not use elements that cause drift such as diodes, it provides a highly accurate power factor transducer that is stable against changes in ambient temperature, etc. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a power factor transducer according to the present invention on the positive axis side, and FIG. 2 is a waveform diagram of each part in FIG. 1. In the figure, (1) and (2) are input terminals, (11Q21
is a comparator, 031 is a gate, (c) is an output terminal,
81 to S5 are switches, A1 to AS are filters, AD is an addition/subtraction circuit, and Fiz is a reference voltage. Agent Makoto Kuzuno - Procedural amendment (spontaneous) Mr. Commissioner of the Japan Patent Office■, Small case indication Patent application No. 151811/1982 2
, Name of the invention Power factor transducer 3, Person making the amendment 5, Detailed explanation of the invention column 66 of the specification to be amended Contents of the amendment (1) The specification is corrected as follows. (2)

Claims (2)

[Claims] (1) A phase discrimination circuit that outputs a rectangular wave voltage with a duty ratio proportional to the phase difference between two AC inputs of the circuit under test;
A filter circuit that smoothes the output of this phase discrimination circuit and outputs a DC voltage proportional to the phase difference φ, a first switch circuit connected to the output end of this filter circuit, and a first switch circuit connected to the output end of this first switch circuit. a first filter circuit connected;
a second switch circuit connected to the output end of the first filter circuit; a second filter circuit connected to the output end of the second switch circuit; and a reference voltage and the output of the first filter circuit. It is characterized by comprising an adding/subtracting circuit that adds and subtracts the voltage and the output voltage of the second filter circuit at a predetermined ratio, and the first switch circuit and the second switch circuit are switched on and off based on the output of the phase discrimination circuit. power factor transducer. (2) The addition/subtraction circuit adds or subtracts the reference voltage, the output voltage of the filter circuit, the output voltage of the first filter circuit, and the output voltage of the second filter circuit at a predetermined ratio. Claim No. 1 (1)
) Power factor transducer described in section 2.