After reading many books on welding that mention current and polarity setting I got more confused than when I began! On top of that I have been at a job interview that required a written test on this subject. The way the test was written had me confused and questioning what I know. That should not have happened because before I started welding I went through two years of electrical school! Why does everyone make it so confusing when it is so simple!
Let's break down the two current types. First there is D/C or direct current and then A/C or alternating current. Wow just two of them! How could this be so difficult to understand?
Direct current or D/C is the type of electricity that your car battery has. D/C flows from one direction to the other. Direct current flows just like water and has only one direction.
A/C or alternating current is what your home uses and it changes direction many times in a second. In your home A/C changes from positive to negative about 60 times a second. With alternating current it does not matter witch terminal is (+) positive or (-) negative because the current changes direction many times in a second! No matter how you hook up your welding leads with A/C it will not matter.
When it comes to polarity types they only apply to direct current. Direct current flows just like water. It flows from the (-) negative terminal to the (+) positive terminal. The easiest way to remember this is the (-) negative side is always losing and the (+) positive side is always gaining. Think of it as pouring water from a pitcher to a glass. The pitcher or (-) terminal is losing water and the glass or (+) is gaining the water.
The way polarity direction applies to D/C welding is based on how much heat is concentrated on your electrode. The two polarity types are DCEP or direct current electrode positive and DCEN or direct current electrode negative. DCEP concentrates 2/3 of the heat on the electrode and DCEN concentrates 2/3 of the heat onto the metal that is welded. Think of polarity types in terms of water flowing from a pitcher to a cup. If you take the pitcher of water and pour it into a glass, the glass receiving the water gets most of the friction. So in this case the pitcher is the negative side and the glass is the positive side. The side that is gaining water is the side with the most friction. In comparison to welding, this is the side most of the heat is concentrated on.
There is a bit more to current and polarity types but getting the fundamental understanding is the first step. Later on the rest will come naturally. Once you start thinking about electricity in terms of water flowing it all becomes simple. Just take the time to think about how water would act and then learn what types of current and polarity types are used for different welding processes and why.
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