When you are dealing with the electricity that is coming into your factory or building, you may think that there isn't a whole lot that you have to know about it. However, electricity isn't the same no matter what. You may have to have a current transformer to make the electricity be something that you can work with. But, what is a current transformer?
Before you understand what a current transformer is, you have to understand the alternating current that runs through the various transmission wires. Alternating current will periodically switch direction flow. Direct current is always flowing in one straight line, but when you compare DC to AC, AC will have a wave line that goes up and down, meeting the straight line of the direct current at the midpoint. Generally, the frequency of the electricity running through the transmission lines is somewhere between 50 and 60 Hz. The amount of voltage can vary, depending on the type of wire and where it is going. However, high voltage generally can't be used in most settings. That's where current transformers come into play.
The way that the current transformer works is that it takes in the current that is coming across the transmission line and then transfers it to a lower current. The way that this works is that the transformer has two poles inside the transformer's body. The two poles are both wrapped in copper wires. The primary pole only has a few wire wraps and is set for the same amount of voltage as the incoming power. The secondary pole has more wraps on it. That allows the current to step down from the incoming voltage to another voltage. For example, the primary pole may have the voltage of 500 but the wraps around the secondary pole make it so that the power leaving the transformer is 250. The transformers can be used in series so that the power transforms from 500 down to 110 in several steps. Current transformers can be used in a lot of places. including going from high voltage transmission lines down to residential transmission lines, and then from the residential transmission lines to your house or building.
Electricity can be tricky to deal with. It is more efficient to send it long distances at higher voltages, but the higher voltage can make it unusable in most places. A current transformer with 4 20ma output makes it possible to use.