JPS5886614A - Controller for direct current feeding device - Google Patents

Abstract

PURPOSE:To realize an economical device while improving reliability and facilitating construction by calculating a DC current from an AC current through simulation, and using it as an actual value current signal. CONSTITUTION:A load current is detected at an AC side as a DC voltage signal iac proportional to an AC current Iac through a current detector 13, rectifier 14, and resistance 15 connected as a load. The voltage signal iac is shaped by a load simulation circuit 16 into a current waveform equivalent to a welder DC current Idc, and its output is converted by a current value arithmetic circuit 17 into the effective value (or mean value) of the current, which is compared with a reference current value IR to control a current regulator 2 by a phase controller 9 through an amplifier 8 so that the deviation is brought to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION VS Technical Field of the Invention The present invention relates to a control device for a DC power supply device, and more specifically, the present invention relates to a control device for a DC power supply device, and more specifically, the present invention relates to a control device for a DC power supply device, and more specifically, the present invention relates to a control device for a DC power supply device. The control device of the DC power supply device supplies the controlled DC power to the DC power source 91.

(2) Prior Art As an example of this type of device, the circuit configuration of a conventional DC type melting current control device is shown in Figure 1. Phase-controlled AC power is supplied to the primary @ of the transformer 3 through a current regulator consisting of
: Connect the ffi circuit and supply its rectified output to the DC load, that is, the welding Iat pole jK.

Molten III machine electrode part! The current detector 4 detects the direct current flowing through the oscillator 4, and the detected signal is amplified by the amplifier 7.

The load current actual value detected in this way is compared with a current reference value R, and the deviation thereof is supplied via an amplifier t to a phase controller D. This phase controller controls the energization phase of the If flow regulator so that the deviation becomes zero, that is, the actual current value becomes equal to the current reference value RK.

(3) Problems with conventional techniques This conventional flK had the following drawbacks.

The welding DC current is generally a large current of 1 to 3 oKh, so it is difficult to secure a place to insert the current detector, and the current detector is large, making it economically disadvantageous. .

■ The distance between the installation location of the control device, which houses the current control circuit, electrical and air valves, and the installation location of the welding machine body, which houses the transformer and rectifier circuit, is often several tens of meters (transformer Since a current of several tens of times flows through the secondary 111, it is necessary to arrange the wiring at the shortest distance), so in the method of detecting the DC side current, i! The IE line distance will be longer, causing problems such as noise, and construction costs will increase.

(→Object of the Invention) Therefore, an object of the present invention is to provide a control device for a DC power supply device that does not have such drawbacks.

(j1 Structure of the Invention In order to achieve this object, the present invention realizes an economical device by calculating the ffi current 1fl [current from the alternating current side current by similation and using it as the current actual value signal. (77 Embodiments of the Invention The present invention will be described in detail below with reference to FIG. 2 showing one embodiment.The main circuit portion of FIG. 2 is functionally as follows. It is substantially the same as the one in figure wk1, but for convenience of explanation, it is partially shown as an equivalent circuit.In other words, the illustration of the transformer is omitted here, and the AC side including that part is shown. An inductance IO is inserted into the alternating current circuit.

In addition, the DC side circuit including the load is DC - inductance /
/ and DC side load resistance 12. If the value of inductance/l is R and the value of load resistance/J is R, then
The DC side time constant is ! It is expressed as ＝し乍.

The load current of this device is determined by a current detector such as a current transformer on the AC side.
3. It is detected as a DC voltage signal iaa proportional to the AC current Iac through a resistor 15 connected to the rectifier /l and its load 17. This voltage signal 1ac is the 7th load simulation circuit/AK from the welding machine DC side current Id
The current waveform sum equivalent to 0 is converted, and the output thereof is converted by the current value calculation circuit 77 into the effective value (or average value) of the current, and compared with the current reference X.

The current regulator is controlled by a phase controller via an amplifier l so that the deviation becomes zero.

The phase controller drives the timer circuit /I by the pulse P output in synchronization with the ON signal of the electric valve, and outputs the output signal ? , , P to obtain the currents HII mxs and t, which will be described later, and compare them with the time constant of the DC side main circuit using the comparison calculation (b) path 19, so that the time constant of the time constant selection circuit 1 becomes the DC current calculated above. −Selected to match the time constant of the main circuit,
The switching circuit is configured to switch the time constant of the self-contained construction lag circuit 16.

The operation of the control circuit shown in FIG. 2 will be explained according to FIG.

V is the output voltage on the DC side, Ia is the output voltage of the self-defense power ignition circuit 14 that is connected to the DC power supply device aC, and 1lLe is the output voltage a obtained by rectifying the AC current Iaa.
The voltage proportional to oK, Vg, indicates the firing pulse that turns on/off the electric valve with a current of 11111 isJ.

When the electric valve of the current regulator is turned on by the ignition pulse Vg at time t1, a positive voltage Va is output to the DC machine, and an AC current ac begins to flow (see signal 1ao). Since the AC/2 current side inductor 10 in the welding machine device is significantly smaller than the DC current/ductance, the current is rapidly commutated from the WI ring current of the rectifier circuit to the AC side.

The DC voltage Va and AC m'tt* Iac both increase in a proportional relationship, and the DC voltage Va
When the pressure becomes zero, the AC m*flow aQ rapidly decreases. However, the DC@current 1c circulates through the rectifier circuit regardless of the AC 111 because of the DC expansion A/ductor/S//, and the current 1c circulates through the rectifier circuit at 1 time t! During the period from t4 to t4, the signal attenuates according to the specific PIT=L/R. Here, it is assumed that the value of AC 1llllj current aa at time t is 8.

From the phase controller, when the ignition pulse vg rises '1il
It rises at time t, which is slightly opposite to l t .

Time 1. A falling pulse P is output at a slightly later time t. The timer circuit /l outputs a pulse P when the pulse P rises and outputs a pulse P when the pulse P falls.

Based on the pulse PIsP, the comparison calculation circuit 19 turns on the valve at once with the ignition pulse vg at time t4,
At time t when the AC side current Mac rises, the cautious 2 of the AC side current Mac is detected, and then at time 1. and number 19
Time interval 1=1. -1 Find snow.

Time 1. What is the main circuit DC current between ~t4? == L/
Since it K therefore attenuates, the following relational expression holds true.

From equation (1), the time constant T is expressed as follows. In this way, the main circuit time constant T can be determined from the value of f1+"ff1e".

Since the comparison calculation circuit 19 calculates equation (2), a microprocessor is normally used in the comparison calculation circuit/9jfC. Set the value of engineering,, engineering, to 0-. Quantize to a value of about 2 seals, calculate 1nXM, 1n4 in advance and write it!
To measure time t, the gate opens at time 1 and closes at time t and 6 (at time t and 6). This can be done by using a method that counts the lock pulses.

Therefore, the solution to equation (2) can be obtained by subtraction and division, which are the original functions of a microprocessor. The time constant obtained in this way will be equal to 〒.If we add the time constants of '5 load simulation circuit/base, we will get load simulation circuit/40 hours? Since it is possible to make them all match by setting the number and the time constant on the DC side of the main circuit, the current at the output d of the load shift circuit L is calculated by the current value calculation circuit 77, and the DC l! Find I1w flow me. In this way, the direct current side main circuit current is not directly detected, but can be detected by passing the AC side current through the precious load reduction circuit.

As explained above, by providing a minor loop in which the time constant of the load input shore circuit 14 always matches the time constant of the DC load circuit, it is possible to calculate the DC side current only from the AC side current. Become.

(Variation of the Invention FIG. 1 shows an embodiment in which the circuit snowmaking shown in FIG. 1 is realized using a computer.

In this embodiment, the load signal line 73 circuit 16
The output 1a of is digitized through a converter 30,
Calculation +1! (hereinafter referred to as OPU) 3/This day from IIC! (l P T131 calculates a current value from this data and outputs it through three D/A converters. On the other hand, pulse P!

P, the output is given as an interrupt input to OPU3/,
The current values I and 1 shown in FIG. 3 are read, calculated, and output to the time constant selection circuit 1. In the figure below, current caution 1
, * Since a method is adopted in which the output d of the shore circuit 16 is used as a load source, the filter of the load simulation circuit 16 is reset by the pulse P1. This situation is shown in Figure 5.

No.! The figure shows the detailed structure of the load construction/inversion circuit 4 and the switching circuit shown in Figure 1, and Figure 1 shows how the filter capacitor 7 is reset by operating the switch S with the pulse P.

The diode is preferably a rational diode (one with no voltage drop in the If direction), and can be realized by a circuit using an operational amplifier. The code/de/system 7 includes elements and resistors 9, 30 for simulating the inductance of the main circuit on the DC side.

3/ constitutes a capacitor phantom discharge circuit and determines the time constant. A normal switch on the folding line 9 and 30! 3
corresponds to a switching circuit worker, and is a switch.

The time constant changes depending on the phantom on/off. operational amplifier a
t is a buffer amplifier. The resistor SS and the switch circuit are a circuit for resetting the CO/D/S hook at time t4. For example, the load shift/circuit has a time constant K shown by the solid line in Figure 4 d, and the DC main circuit is a broken line. Assuming that the time constant is as shown in , time 1. In order to obtain the accurate current value
ao) It is operated to match 4C.

Although a single-phase main circuit has been described above, it goes without saying that the present invention can also be applied to a DC-main circuit having a multi-phase half-wave rectifier circuit or a multi-phase full-wave rectifier (b) path.

Furthermore, although only a portion of the circuit shown in Figure 1 is processed by a computer, it is also possible to implement the entire circuit shown in tI/L using a computer.

(N Effects of the Invention As explained above, according to the present invention, the small current of the transformer on the AC side - the next - can be detected using a simple method such as a current transformer, without directly detecting the large current in the main circuit on the DC side. Since it is possible to detect using a current detector and calculate the DC-main circuit current indirectly by using the load oscillation circuit, it is very economical, and at the same time, it can be detected at the control device side rather than at the load end. Since the current can be detected, the construction work is very simple.Furthermore, in the case of robot welding parts, the main circuit on the DC side has many moving parts, and reliability decreases significantly due to wiring breaks, but with the present invention, Since the current can be detected from the fixed side, reliability is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional control device, FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a line diagram for explaining the operation of the device shown in FIG. 2, and FIG. 1 is a circuit diagram of the main part showing another embodiment of the present invention, No. tlfi is a circuit diagram showing details of the main part of the device shown in FIG.
7) Diagram to clarify the work. C... AC fII heavy source, C... Current-rectifier, 3... Ratio transformer, Hiroshi... Rectifier Lc! l road,! ...Welding Sakaki electrode part, R...Phase control...Current detector, /6...Load shunt N circuit, 17...Current value calculation circuit, l
G...Tai-O circuit, 19...Comparison calculation circuit, Koto...
・Time constant selection circuit, 30... ~ Converter, 31...
Computer (OPU), jco...D/A converter.

Claims (1)

[Claims] Control of the amount of DC power supply equipment that supplies a controlled DC current obtained from an AC power source through a current adjustment aI and rectifier circuit consisting of a controllable electric valve to a DC load having an inductor. In the device. A current detection device detects the load current on the AC side, and a DC current flowing through the DC load including the off period of the current regulator is simulated according to the detection output of the current detection device and a simulated time constant of the DC load. a load simulator 1 circuit that is erected; a controller that controls the current regulator so that the DC current erected by the load simulator 1 circuit matches a target value; The detected alternating current value x1 at time t when the voltage of the alternating current power supply applied to the valve is zero, and the detected alternating current value I! at time t immediately after the controllable electric valve is turned on! Further, the time constant of the DC load is calculated from the time interval t ("t4-"t) of the two AC current detection values I, , I, and the time constant of the load simulation: i17 circuit is calculated as follows. 1. A control device for a DC power supply device, characterized in that a control device for a DC power supply device is provided with a simple switching device for switching to suit a calculated time constant T.