What is a welding power source or welder?
All arc-welding processes require a continuous supply of electrical current in sufficient amount (amperage) and of proper voltage to maintain an arc. This current may be either alternating (AC) or direct (DC), but it must be supplied to the welding electrode through a device that enables its precise control. Only when the welding current is carefully controlled can the desired welding arc characteristics and thus maximum welding efficiency – be obtained. The controlling device is called a Welding Power Source or Welder or Welding Machine.
Type of polarity and Welding process
he following may be used as a guide to select the proper power source based on the type of current.
1. Gas metal-arc welding
2. Flux-cored arc-welding
3. Exx60 type electrodes
4. Exx15 type electrodes
1. Fast freeze applications
2. Fast follow applications
3. Welding stainless steel
4. Nonferrous electrodes
5. Surfacing with high alloy electrodes
1. Fast fill applications
2. Iron powder electrodes except out of
3. position welding
4. Where arc blow is a problem
AC or DC depending on the application
1. Gas tungsten-arc welding
2. Submerged-arc welding.
Types of Welding Machine or Welder
Various types of power sources provide a range of voltage across the welding arc from 10 Volts, usually minimum voltage for starting an arc – to approximately 45 volts. The currents supplied through the &power source may range from less than 10 amp to & 1500 amp or more, the higher currents for automatic welding. Based on power type, polarity types and functions, the Welding Power source or welder are classified into:
- Welding Transformer
- Welding thyristor
- Welding Rectifier
- Welding Converter
- DC Generator
- Switched mode power supplies
Now, all the welding machines no matter for which welding process are based on these above 4 types. Further, based on welding process the welding machines types used for welding operation in industries are:
- Stick Welding or SMAW Welding Machine
- Gas welding Machine
- TIG Welding Machine
- MIG-MAG or FCAW Welding Machine
- SAW Welding Machine
- Plasma arc Welding Machine
- Laser Welding machine
- Resistance Welding Machine
- Stud Welding Machine
- Plastic Welding Machine
- Friction Welding Machine
- Projection Welding Machine
- Electron Beam Welding Machine
- Electroslag welding Machine
- Seam Welding Machine
- Flash Welding Machine
- Ultrasonic welding Machine
- Spot Welding Machine
Types of Welding Machine or Welder based on Electrical/ Electronic characteristics
Transformer Welder (AC Transformer power Source)
The transformer welder is a voltage step-down transformer that changes high voltage, low-amperage AC input current to low voltage, high-amperage AC welding current. Transformer welders usually operate on single-phase power. Most AC power produced in the United States is 60-hertz, and each time the polarity changes the voltage goes through zero, which tends to create an unstable condition in the arc. This problem, however, has been solved by designing better transient characteristics in the welder and better AC electrodes. An example of welding transformer is shown in the below figure.
Rectifiers for converting AC current to DC have been developed to a stage of efficiency and reliability. A single-phase rectifier welder is a transformer welder with a rectifier added to obtain a DC output. Adjustment of the welding current is through the AC section, as described for transformer welders. The output characteristic can be either constant or variable voltage. Welders built especially for gas metal-arc welding have adjustments for changing both the slope of the output curve and the reactance in the circuit for better performance when welding with short-circuiting transfer.
Rectifier welder is the step-down transformer, in which three-phase AC is fed to rectifier units which, in turn, feed DC to a single output circuit. The output can be either variable or constant voltage, but only DC is available since the AC is three-phase and cannot be used for welding. Rectifier uses either diode or thyristor or transistors for converting the AC to DC for welding output. Direct current (DC) offers to use welding polarity for welding operations either DCEP (Direct current electrode positive) or DCEN (Direct current electrode negative). A choking device at the end allow current and voltage adjustment.
In the direct-current generator, an armature rotates in an electrical field. Current is generated in the armature and is taken off for use through a commutator. The armature is rotated either by an electric motor or an internal combustion engine. The speed of rotation of the armature and the electrical design of the generator change the output characteristics. The arc characteristics of a generator can be precisely controlled. This fact lends DC welding more versatility than AC welding. Polarity of the electrode can be changed with a flip of a switch.
The DC motor-generator welder is driven by AC utility power. It can provide either variable or constant voltage, or a single unit may provide both types of output. The motor is usually a three-phase induction motor. The variable-voltage type is a compound generator with a series field that causes the voltage to decrease as the current is increased. Two adjustments can be made to change the welding current:
- For a given voltage, the output current can be changed by adjusting the series field. This produces an output change, and is sometimes called the “current” control.
- For a given current control setting, the output can be changed by adjusting the shunt field. This produces. an output change.
Welding Analog Power Supply
Analog power supply are latest technology in welding power sources by using dedicated and sophisticated electronic circuits. This allows very fine tuning of welding parameters such as current, voltage, arc length, type of current, pulse current output, and storing the welding programs in the welder database. These machines also offers synergic welding supply.
A single welder (welding machine) can be used for AC, DCEP & DCEN along with pulse welding parameters controls, thus allowing good welds. Although, the cost of such machines is very high compare to other such as welding transformer or welding rectifiers.