JPS63103976A - Current effective value measuring circuit for cycle control type electric power controller - Google Patents

Abstract

PURPOSE:To accurately measure a current effective value by finding the effective value of an intermittent current from the output voltage signal and threshold signal of a frequency counter and a holding circuit. CONSTITUTION:The intermittent current after cycle control is converted by a comparator 11 into a rectangular wave signal which is at H level for the duration of a current exceeding a threshold level and a wavelength measuring circuit 12 converts it into a voltage signal proportional to the duration of the rectangular wave signal. This voltage signal is held by a holding circuit 13 until the leading point of a next voltage signal and inputs this voltage signal and the threshold signal to find the crest value of a sine wave current waveform. Then, an arithmetic circuit 15 is provided which computes the effective value of the intermittent current from the found crest value and the output signal of the frequency counter 14 which inputs the output signal of the circuit 11 and outputs the effective value. The effective value of the intermittent current is therefore found from two instantaneous values of a sine wave current waveform in either half cycle of each intermittent current cycle, so the effective value can be measured without distorting the intermittent current waveform.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention controls the main sirisk on and off in synchronization with the voltage zero phase of a variable current power source, and reduces the number of cycles of load current in a repetition period. The present invention relates to a circuit for measuring the average effective value of the output intermittent current of a cycle control (alternating current) single force adjustment device.

[Prior art and its problems]

The cycle control power regulator is a system that controls the load current on and off in synchronization with the zero phase of the AC power supply voltage, so it has less harmonic interference than a phase control power regulator, and the control equipment Because the configuration can be simplified, it is mainly used to control electric heat in a wide range of fields such as heat treatment processing, drying ovens, glass processing, plastic processing, and food processing as a power adjustment device for small-scale resistive loads. The effective direct weight e of the output intermittent current of the cycle control power regulator is the blowback period of the intermittent current To, and the intermittent [
All instantaneous values of flow 1. When the intermittent flow period kTt is made up of an integer number of cycles during the needle return cycle, it is usually defined by the following equation.

In other words, the effective value e of the intermittent VL flow is the ratio of the conduction period T1 to the repetition period TO of the intermittent current (hereinafter T1/
It changes depending on the To f load factor. Therefore, when measuring the effective value of intermittent current using an indicating ammeter for measuring the effective value of alternating current, there is a problem that the meter pointer vibrates when the load factor is low, making it difficult to measure with high precision. be. In addition, if you take measures such as increasing the time constant of the measurement circuit to avoid vibration of the pointer, there will be a delay error in the response and a decrease in measurement accuracy at high load factors. The reality is that there is no known measuring device or measuring circuit that can accurately measure the effective value regardless of the magnitude of the load factor.

[Object of the Invention] The present invention has been made in view of the above-mentioned situation.
Effective 1fL' of c style? ! :11L of cycle control type power adjustment device that can measure accurately regardless of the magnitude of negative # rate
The purpose of this invention is to provide a current effective value measurement circuit.

[Key points of the invention]

The present invention provides cycle-controlled intermittent 11. A comparator circuit that uses the current as a human input signal converts it into a square wave signal that remains at H level for the duration of the current exceeding a predetermined threshold, and a wavelength measurement circuit converts it into a voltage signal proportional to the duration of the square wave signal. Then, this voltage signal is held by a hold circuit until the next voltage signal rises, and the peak value of the sine wave current waveform is calculated based on a predetermined formula using this voltage signal and the threshold signal as human input signals. and an arithmetic circuit that calculates and outputs the effective value of the intermittent current from the obtained wave height 1 frequency and the output signal of a frequency counter which uses the output signal of the comparator circuit as a human signal. It is possible to obtain the effective value of the intermittent current by using the instantaneous 11i of the sine wave current waveform of either half cycle of each intermittent tll cycle at two points. Therefore, the correct effective value can be obtained without distorting the intermittent current waveform. It is designed to be measurable.

[Embodiments of the invention]

The present invention will be explained below based on an example of Mi.

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention. In the figure, 1 is a cycle-controlled power regulator, and v
The main thyristor 2 connected to the L source voltage waveform 8 and the sine wave current waveform 4 emitted seven times, and the main thyristor 2 at '+Jl voltage 8
Cycle control circuit 3 that controls on/off at voltage zero phase
By intermittently controlling the main thyristor 2 on and off in accordance with a predetermined load factor, a waveform of 9 W is applied to the resistive load 5 arranged on the load side of the main thyristor 2.
It is configured to supply an intermittent current shown by . 10 is a current effective value measuring circuit for an intermittent current of 9 W, which is connected to the output side of the main thyristor 2 via the current transformer 6; , a comparator circuit 11 that is connected and outputs a square wave signal that is at H level for the duration of the intermittent current exceeding a predetermined threshold; Wavelength measurement circuit 12. A hold circuit 16 holds the output voltage signal level of the wavelength 6111 foot circuit 12 until the next rise of the square wave signal, and a frequency f=i/ To
a frequency counter 14 that generates seven next voltage signals in proportion to;
The output signals of the frequency counter 14 and the hold circuit 13 and the threshold signal 1 of the comparator circuit 11
1Ak and calculates the effective value e of the intermittent current based on a predetermined formula.

Figure 42 is an input and output waveform diagram of the comparator circuit,
The operation of the embodiment circuit will be explained using FIG. In the figure, 9W is the output intermittent current waveform of main thyristor 2, and 11W
is the output square wave pulse waveform of the comparator circuit 11, and for every repetition period To, the period T! The intermittent flow of 9W is 1
Intermittent current 9 indicates a state in which only one cycle flows, and therefore the frequency of the intermittent current is f = 1/To.
The wave height of W is expressed as p, the effective value is expressed as e, and the instantaneous value is expressed as 1. The threshold value in the comparator circuit 11 is set to 11
Assume that the current transformation ratio t'' of the current transformer 6 is 1. When an intermittent current of 9 W is input to the comparator circuit 11, the
rises at the time t1 when the instantaneous value 1 reaches the threshold IIIL, and the instantaneous value 1 falls to the threshold 11 [L]. and stand down. 1.
A square wave pulse 11W that maintains the H level for -1□ time is output and sent to the wavelength measurement circuit 12.

It is converted into a voltage signal of ts=A (V), and A (V) is held in the hold circuit 16 until the next voltage rises, and the threshold negative signal 11A=1 is sent to the arithmetic circuit 14.
a voltage signal corresponding to z; and 1. −t1==A(
v) A signal is generated manually.

By the way, the sine wave AC voltage 80 of the power supply 4 in FIG.
Since the frequency is known, tl and (ts-ts)
=(A+tx) The instantaneous values of the intermittent m flow 9W at the phase are both threshold values 11, and are expressed by the following equation.

■p gin ωt□:Ipthω(A+tz)=”・
...(2) ωt□=m ” 1□/Ip・
・・・・・・・・・・・・(3) (1) , (21
From the formula, the threshold value of 1 ri is expressed by the following formula.

1s = engineering psfn (QI A+(dn ”
it/engineering p)) ...(4) Therefore, (
4) The peak value of the intermittent current 9 W that satisfies the formula p f can be determined by the arithmetic circuit 15 using the input signal 11 and (t, tl)=A. In addition, once the wave peak value p is determined, the instantaneous value 1 of the intermittent current 9W can be obtained by applying formula (2) mutatis mutandis, so the effective value θ of the intermittent current 9W can be calculated using (1)
It can be determined using the formula. That is, the square of the instantaneous value 1 of the intermittent current is integrated over the current period T□, and this integrated value and the output frequency f of the frequency counter 14 are
By finding the square root of the product with =1/To, (
1) Find the effective value Ie of the intermittent current defined by 2.

It can be output.

In the current effective value measuring circuit configured as described above, since it is a resistive load, there is no phase difference between the power supply voltage and the load current, and an intermittent current waveform that can easily maintain a sinusoidal waveform is created using a predetermined method. Detection is performed using the threshold value 11, the duration of exceeding this threshold value (ts tl) = A, and the output signal of the frequency counter, and the effective value is determined by a theoretical calculation consisting of a combination of the detection signals. Accurate effective values can be obtained without changing or distorting the current. In addition, since the hold circuit can maintain the intermittent current of the human input signal Ai of the arithmetic operation circuit,
It is possible to continuously output the effective direct output color code regardless of the load factor of the intermittent flow, and therefore eliminates pointer vibration etc. even when measuring the effective value output No. 15 with an indicating instrument. Therefore, highly accurate measurements can be made.

〔Effect of the invention〕

As described above, the present invention uses a comparator circuit to detect the duration of an intermittent flow exceeding a predetermined threshold, converts it into a voltage signal that lasts during a repetition period using a wavelength measuring circuit and a hold circuit, and Signal and threshold negative signal and 2
The current effective value is calculated and outputted based on a predetermined formula by a calculation circuit that receives the output signal of the frequency counter as an input signal. As a result, by specifying two instantaneous values corresponding to the threshold of the sine wave m light waveform, the peak value, instantaneous value, and effective value of the sine wave current can be determined based on theoretical calculations. In addition, it has become possible to continuously output the effective output signal using the hold circuit even during the pause period of the intermittent storm flow, which eliminates the vibration of the pointer of the indicating instrument in the prior art.

It is possible to provide a current measurement circuit for a cycle-controlled power regulator having a resistive load that can accurately measure the effective value of intermittent current regardless of the load factor of the load current.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a signal waveform diagram in the embodiment. DESCRIPTION OF SYMBOLS 1... Cycle control power regulator, 2... Main thyristor, 6... Cycle control circuit, 6... Current transformer,
DESCRIPTION OF SYMBOLS 10... Current effective value measurement circuit, 11... Comparator circuit, 12... Wavelength measurement circuit, 13... Hold circuit, 14... Frequency counter, 15... Arithmetic circuit, 9W... Intermittent current waveform, 11W...square wave pulse, To...repetition period, T,...current flow period, 1□・
...Threshold value, 1. -11... Duration.

Claims (1)

[Claims] 1) In a cycle control type power regulating device that outputs an intermittent current consisting of an integer cycle by controlling on/off of an alternating current flowing through a resistive load with a voltage zero phase, the current flowing during the conduction period is used as an input signal and a predetermined signal is output. A comparator circuit that outputs a square wave signal that remains at H level for a duration of a current exceeding a threshold, and a frequency counter that receives the output square wave signal of the comparator circuit and outputs a voltage signal proportional to the average frequency per unit time. , a wavelength measurement circuit that receives the output square wave signal of the comparator circuit and outputs a voltage signal proportional to the duration of the H level, and a hold that holds the output voltage signal of this wavelength measurement circuit until the next voltage signal rises. and an arithmetic circuit that receives the output voltage signals of the hold circuit and the frequency counter and the threshold signal, calculates and outputs the effective value of the intermittent current based on a predetermined formula. Current effective value measurement circuit for cycle-controlled power regulator.