In any specialized store selling electrodes and welding equipment you can find a welding inverter. You can purchase it at a fairly high price, but if you have basic knowledge in electronics and know how to handle a soldering iron, you can assemble a welding inverter with your own hands, which will not yield to the factory equivalent.
Scheme of the device welding inverter.
Initially, you should become familiar with all the main nuances and aspects of this case: diagrams, drawings, instructions and the assembly process itself.
Homemade welding inverter
Homemade welding inverter is designed for long-term work, it can work with electrodes with a diameter of 4 mm. Among its advantages can be noted a large stock of current. The scheme of such a device is a single-ended inverter that operates on processor control and uses digital induction. The characteristics of the inverter are presented below:
- The maximum amount of current at which the welding inverter can perform work reaches 220 A.
- The no-load current is 30 A.
- Supporting induction mode is a three-digit indicator.
- His work can be done with power from a household network of 220 V.
Among its features are:
The scheme of the welding inverter.
- You can adjust the current at which welding is performed, it varies from 30 to 220 A.
- You can display current and temperature.
- One of its important functions is the "anti-stick", this function performs the action of switching off the device when the electrode starts to stick.
- Schemes homemade inverters will add the ability to hot start and idling.
- You can turn on the sleep mode on the inverter.
- One of the features of such a device will be the possibility of removing events occurring in it using a three-digit indicator. This system is fully automated.
The scheme of this welding inverter consists of three main blocks:
- The first unit, which is necessary to create an inverter, power supply.
- The second component of the circuit is the rectifier unit.
- The final unit is the inverter itself.
To create an inverter yourself and complete the implementation of the scheme, you will need to purchase microcontrollers and other cards that will be required for its assembly.
The power unit diagram is shown in Figure 1.Back to table of contents
Creating power supply for welding inverter
Figure 1. Diagram of the power unit.
The power supply and the necessary software are installed separately from the main structure. As a rule, they are separated by a sheet of metal through which the connecting elements pass. Those elements that are used to control the key switching relay are broken into pairs and twisted. They are soldered in the nearest possible place to the outputs of the transistors. When choosing wires worth paying attention to their length, which should not exceed 15 cm, the cross-sectional area gives only a small amount of loss and attenuation of the signal.
The power supply of the welding inverter is presented in a classic form. To make it, you will need to wind the primary winding on the transformer core, after which you should wind a second winding on top of it, which will function as a screen consisting of the same type of wires. When winding the screen, it should completely cover the area of the primary winding, and the direction of winding should be identical. To separate these windings used varnished cloth or building tape. A welding inverter, which is made by yourself, will require tuning from you; this will be done in the power supply unit by selecting the resistance R1. It should be selected until the power sets a voltage of 20 V.Back to table of contents
Power part of the inverter do it yourself
Simplified circuit of the power part of the welding inverter.
This block is executed without changes, all the necessary data you can get according to the scheme. For normal and efficient operation of the welding inverter, you need to select suitable radiators for the input and output rectifiers, as well as for power switches. In the manufacture of the inverter should install the keys on the copper substrate. In addition, radiators should be chosen more powerfully, since the working time of the inverter will depend on their power and efficiency.
The sensor should be installed near the radiator, which in the course of its operation heats up more than the others. Chips that perform regulation of the entire inverter, are based on the pulse-width modulation controller. In this case, one channel is used for data transmission, which is used to control the current in the arc. The value of the current sets a special microcontroller that operates at a frequency of 75 kHz. When the system is heated, capacitor C1 will notify the processor of any violations. The value of the current on the welding machine depends on what value the capacitor will produce.Back to table of contents
The work of the welding inverter cooling system
Unlike the factory versions, this inverter will turn on the fan with its own hands every time it is turned on for a fraction of seconds. This will occur due to the switching of the capacitor relays, which, in turn, causes the closure of some transistors. Before the temperature exceeds 40 °, your cooling system will be turned off.
Scheme of the internal device of the inverter.
After this threshold is exceeded, the fans will begin to cool the entire system and stop their operation when the temperature in the system is normal and reaches 35 °. When the temperature of the internal processors reaches 60 °, the pulse width modulation will be limited. And when the temperature becomes critical and exceeds the threshold of 73 °, the pulse-width modulation will stop working. After the fans cool the system and bring the temperature to 50 °, the pulse-width modulation operation will resume.
The inverter’s full operation will begin after the temperature has dropped to 35 °. In this case, the cooling system will stop its impact and turn off. The antistik function described above will always work and display data on reports on the indicator screen. If you want to disable or enable the hot start function, you can use the relay, while the mode currently in use will be displayed on the screen. When you increase or decrease the current, this data will also be displayed on the board, there is some delay in switching, which is half a second. When the hot start mode is on, you will not be able to increase the effective current value. The inverter circuit is designed to analyze the work of the electrode when it sticks or when selecting a mode and display this information on the board.Back to table of contents
Before starting a homemade device, it is first necessary to configure the equipment to work effectively. First you need to disconnect from the mains power unit. Further it is necessary to connect only the power supply unit in a network and to make its setup. At the same time, eights should appear on the monitor with a dot in the lower digit. We connect the power to the oscilloscope, while using the first and second outputs.
We tune the oscilloscope to work bipolar pulses and set the frequency to 50 kHz. The time division should be one and a half microseconds. Next, check the voltage at the gate of the keys. On the oscilloscope screen should appear rectangular pulses with a width of not more than 500 nanoseconds, the value of the voltage amplitude should be about 15 V.
If you did everything correctly and configured the power supply to the required values, you will need to collect the entire circuit and turn it on. At the beginning, as in the first case, you will see eights. After the relay closes on the screen, you will see a current value of 120 A. If this does not happen, the voltage that is applied to the wires exceeds the threshold value of 100 V. To eliminate this, check each block of the circuit with an oscilloscope or multimeter .
When you have found the cause of the problem and eliminated it, perform the operation again to the required indicator value.
In the event that you have achieved the required current value, you should check the operation of the instruments. To do this, try to change the value of the current, you can check the value issued by the capacitor C1. It must be changed identically to the current. If you have any difficulties, you should fix the problem. When you have checked the operation of all the systems and adjusted them, you can start working on a new welding inverter.