Triac controller for welding machine. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / welding equipment

 Comments on the article

This device uses load power control using a triac included in the primary winding of the power transformer. The circuit is also suitable for controlling other AC appliances, such as heaters, high power incandescent lamps, electric motors, etc.

Figure 1 shows a functional diagram consisting of a transformer Tr2 and a triac (triac) TC1, and Figure 2 shows the change in currents and voltages.

In the first period of the mains voltage, the minimum voltage value is set (Fig. 2, part 1), in the second, the maximum value (Fig. 2, part 2).

In the course of measurements, the secondary winding was loaded with an incandescent pump with a power of about 100 W. The "behavior" of the curves can be interpreted as follows:

• the voltage between the electrodes MT1-MT2 of the triac (Fig. 2, a) increases until it opens. Then the voltage between the electrodes drops to almost zero and remains so until the end of the half-cycle. The same thing happens in the next half-cycle;
• the change in current between the minimum and maximum values ​​\u2b\uXNUMXb(Fig. XNUMX, b) occurs evenly (resistance Rs is the equivalent resistance of the connecting wires). With increasing current, the visible jump disappears near the zero crossing of the voltage;
• the change in voltage in the primary winding of the transformer (Fig. 2, c) has a complex shape, which gradually approaches a sinusoidal one.

The connection diagram of the welding transformer is shown in Fig.3.

The scheme additionally contains:

• network noise filter;
• triac control circuit.

The device uses an industrial welding transformer (Тг2). The primary winding coil is designed for 220 V with a nominal induction of about 1.5 T. The no-load current at a mains voltage of 230 V is about 3 A. The no-load voltage on the secondary winding is 50 V. The low short-circuit voltage is compensated by a shunt coil with a larger number of turns than the secondary winding. The purpose of this controller is to continuously regulate the welding current.

The mains noise filter consists of coils L1, L2 and capacitors C1, C2. In addition to filtering, its task is to reduce the current pulses that occur when the arc is turned on. Coils reduce the voltage supplied to the transformer by about 3 ... 6 V. The number of turns of the coils is given for an inductance of 2,4 mH, with a value of A=6200 nH/turn2. The triac can be replaced by any other that can withstand the full voltage of the network and the maximum current. Target C3-R1 filters the RF interference generated by the triac.

The supply voltage of the triac control circuit is created by the transformer Tr1 with the diode bridge Gr. The trapezoidal shape of the voltage is formed by resistors R2. R3 and zener diode D1. The voltage in each half-cycle drops to zero. This synchronizes the simister start target.

The parameters of the generator on the unijunction transistor T1 are determined by the values ​​of P, R4 and C4. The values ​​of P and R4 I determined empirically. Resistance 22 + 33 kOhm creates the minimum welding current, 33 kOhm - the maximum achievable from the network. P values ​​\u47d 4 kOhm. R4.7 \u230d 2 kOhm correspond to the good operation of the transformer from 4 V. The TCXNUMX thyristor provides the necessary current to open the triac. In the absence of a unijunction transistor, it can be replaced by an analogue with two bipolar ones. included according to the scheme shown in Fig. XNUMX

Regulator design. The regulator circuit is placed on two printed circuit boards made of one-sided fiberglass. The larger board contains the noise filter, triac, and power supply for the control circuit. On the smaller board is the thyristor control circuit itself.

The drawing of the first board is shown in Fig.5, and the placement of parts is shown in Fig.6.

The control circuit uses a potentiometer with a plastic shaft. The potentiometer leads are at mains potential, so this axis provides the required isolation. The drawing of the second board is shown in Fig. 7, the placement of parts is shown in Fig. 8. The boards are connected to each other by three wires.

(click to enlarge)

This design is practical from many points of view:

• simplifies the placement of boards in the device case;
• makes it easier to set up circuits

In the manufacture of printed circuit boards, the presence of mains voltage must be taken into account, so it is necessary to maintain sufficient distance between the tracks. In addition, due to high currents, the connecting contacts must have an appropriate load capacity. Coil attachment points L1, L2 are reinforced with tubular rivets 02,5 mm. At the connection points N, L, N1, MT2, flat contacts for high currents are installed (simply soldering to the foil is not enough, since the foil can overheat and peel off the board). We additionally solder a tinned wire onto the tracks of the power unit board. Assuming that the conductor foil has a width of 7 mm and a thickness of 0,02 ... 0,03 mm, we get a cross section of only about 0,2 mm2, and the permissible current load through the conductor is 20 A/mm2. We cover the foil sides of the scheme with varnish.

Filter coils L1, L2 have dimensions of 046x28 mm. They are placed in a pot core with A=6200. The coils contain 19.75 turns of 01.5mm enameled wire. The turns on the windings are placed exactly in two rows. Nothing prevents you from making filter coils of a different shape, it is only important that the wire with a guarantee withstand a maximum current of 16 A. The triac radiator is made of a heat sink for a powerful transistor.

Adjustment. We test the circuits with care, since almost every part of them is under the network potential. In our work, we use a network cable equipped with insulated contacts. The manufactured boards are not initially connected to each other. We power the circuits from a mains socket equipped with a separate switch. In any case, we leave the mains voltage on only as long as it is necessary for measurements. First, we measure the supply voltage of the control circuit. It must correspond to the stabilization voltage of the zener diode D1. This voltage is not critical (values ​​​​in the range of 10 ... 15V are suitable).

With the mains voltage off, we connect the three wires of the control circuit and connect the welding transformer to the contacts N1 and MT2. When the mains voltage is switched on, the voltage and current can be changed using the potentiometer P. applied to the transformer. The shape of the curves corresponding to Fig. 2a, b and c is controlled using an oscilloscope.

Author: B.DEMETER

See other articles Section welding equipment.

<< Back

Latest news of science and technology, new electronics:

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive Hyundai Sonata plug-in hybrid 23.11.2015 Hyundai announced the start of sales of its 2016 Sonata Plug-in Hybrid hybrid vehicle. The machine is equipped with a four-cylinder Nu GDI engine with a displacement of 2,0 liters. The power of this power plant is 154 horsepower; torque reaches 190 newton meters. The internal combustion engine in the Sonata Plug-in Hybrid is paired with an electric motor with a power of 50 kW. The total power of the hybrid unit is 202 horsepower. The electric motor is powered by a new 9,8 kWh lithium polymer battery pack. Only on electric traction, the car can cover a distance of up to 43 km. Recharging the batteries can be carried out from the mains using a charger for 120 or 240 V. In the first case, the process takes about nine hours, in the second - less than three hours. It is claimed that on one tank of gasoline and a fully charged battery pack, the car is capable of covering a distance of up to 960 km. The standard equipment of the model includes 17-inch alloy wheels, multimedia system with 8-inch touch screen and navigation, high-quality speakers, and blind spot monitoring system. The hybrid car starts at $34.

Other interesting news:

▪ The biological clock regulates the functioning of the immune system

▪ quantum integrated circuit

▪ Languages ​​of the future

▪ folding battery

▪ Wet memory

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Preamplifiers. Article selection

▪ article Karataev, Karataevshchina. Popular expression

▪ article Which of the continental water bodies is the deepest on Earth? Detailed answer

▪ article Compass points, angular markings. Travel Tips

▪ article Acoustic guitar pickups. Encyclopedia of radio electronics and electrical engineering

▪ article Two for the price of one. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024