[thrive_headline_focus title=”Understanding the differences between voltage and current” orientation=”center”]
When you’re welding using an electric arc it’s important to understand that you have to pay attention to both voltage and current. The design of most machines nowadays allows for the maintenance of both but, doesn’t really allow for the use of one of them at a time.
Now, when using a direct current power supply, you have the option of using either one that’s constant voltage or constant current. You’ll usually find yourself using constant voltage equipment for either a wire-fed or semi-auto process such as FCAW or GMAW; this mainly because of the constant voltage that is required to run either of these welding processes. The need for a constant voltage arises from the need for a constant arc length, which is directly affected by the voltage of a machine.
Constant voltage equipment directly affects the wire feed rate, wire diameter, and electrode stick-out. So, in order to increase your wire feed speed or diameter, you will have to increase the current of your machine. Keep in mind that increasing the current of your machine also increase the penetration of your machine. But, if you increase the stick-out but keep the same wire-speed you will run into resistance in the electrode while also reducing the current, which reduces penetration.
If you want to stay away from burn-through, it’s imperative that you increase your stick out, which will subsequently reduce penetration and current.
Constant current equipment is typically used for welding processes that require manual attention, such as SMAW. A constant Current power supply is known for providing a consistent current to the machine.
What is the relationship between current and voltage?
Voltage and current are considered 2 fundamental qualities of electricity. Voltage is the cause and current is the effect.
Voltage between 2 points is equal to the electrical potential difference between each point. It is called the emf or electromotive force, which is responsible for the movement of electric current (electrons) through a circuit. The flow of electrons forced into motion by voltage is called current. Voltage is representative of the potential for each coulomb of electric charge to do work.
Video credits go to MadgeTech, Inc. It talks about the difference between voltage and current.
Circuit
Voltage sources have 2 points that each have a difference in electrical potential. When there is a closed loop between both of these points, it’s called a circuit, and the current can flow. In the absence of the circuit the current won’t flow even if voltage is present.
Units and symbols
An uppercase italic I represents current. The unit of measurement is amps (ampere), and this is symbolized by A. The SI unit for current is Coulomb/second. 1 ampere is equal to 1 coulomb/second.
An ampere of current is representative of one coulomb of electrical charge (6.24 x 10^18 charge carriers) moving past a certain point in the circuit in a single second. The name of the decide used to measure current is an Ammeter.
An uppercase italic V symbolizes voltage.
1 volt is equal to 1 joule/coulomb.
One volt drives one coulomb (6.24 x 10^18) charge carriers, like electrons, through the resistance of a single ohm in a second. The voltmeter is used to measure voltage.
Fields and intensity
Electric currents produce magnetic fields. The stronger the current is, the more intense the magnetic field will be.
Voltage produces an electrostatic field. As voltage increases between 2 points the electrostatic field will become more intense. As the distance between 2 points increases, with them having a given voltage with respect to one another, the electrostatic intensity will decrease between the 2 points.
Comparison Chart
| Current | Voltage | |
|---|---|---|
| Symbol | I | V |
| Definition | Current is the rate at which electric charge flows past a point in a circuit. In other words, current is the rate of flow of electric charge. | Voltage, also called electromotive force, is the potential difference in charge between two points in an electrical field. In other words, voltage is the "energy per unit charge”. |
| Unit | A or amps or amperage | V or volts or voltage |
| Relationship | Current is the effect (voltage being the cause). Current cannot flow without Voltage. | Voltage is the cause and current is its effect. Voltage can exist without current. |
| Measuring Instrument | Ammeter | Voltmeter |
| SI Unit | 1 ampere =1 coulomb/second | 1 volt = 1 joule/coulomb. (V=W/C) |
| Field created | A magnetic field | An electrostatic field |
| In series connection | Current is the same through all components connected in series. | Voltage gets distributed over components connected in series. |
| In a parallel connection | Current gets distributed over components connected in parallel. | Voltages are the same across all components connected in parallel. |
