Constant Current Defined
T&R Electrical Supply Company Incorporated is in the business of electricity. In our daily lives, we may take electricity for granted. But in business, understanding all of its properties is crucial to success and safety. Today we're discussing the difference between constant current and constant voltage with Kent Miller, a registered professional engineer that's been working with T&R for over 40 years.
Kent graduated from the University of Arkansas in 1960 and was inducted into the Arkansas Academy of Electrical Engineering in 1981. Kent was a charter member of the Institute of Electrical and Electronics Engineers (IEEE), and has been a senior member since 1983. You could say he's an expert in the industry.
Constant Current versus Constant Voltage
"In general, the difference between the constant current and constant voltage is based on the whether the voltage or current varies across the load," Kent explains. A constant current system fluctuates the voltage to maintain a constant flow of energy. A driver circuit is used as a current regulator when a component has a constant current. It contains a feedback loop to adjust the current to hold a set value. Usually there is some sort of voltage limiter circuit to keep the voltage below a fixed value. Applications for a constant current include: LED's, florescent lamps, shielded metal arc welding, and gas tungsten arc welding.
By contrast, constant voltage contains a feedback loop to adjust voltage to hold a set value. Usually it also has some sort of current limiter circuit, or a fuse to protect against too much current being drawn. It provides the ability to fluctuate output current while maintaining a set voltage, for example in welding. Constant voltage reduces weld 'splash' and is often used to weld rounded parts.
Currents, Voltage and Transformers
In the case of T&R Electrical Supply, let's talk about current in our transformers. "The constant current transformer, or regulator, supplies the same current from a dead short to the maximum voltage it can supply," said Miller. "It is normally used for supplying current to series streetlights in downtown areas where constant current is desired. However, several years ago most cities have retired replaced these lights with 120, 240, or 277 volt bulbs instead."
On the other hand, constant voltage transformers are used in hospitals today, for x-ray machines, where voltage fluctuations cannot be tolerated. Another application would be most utility companies, who use voltage regulators. Although these are not actually "constant voltage" transformers, they can regulate the output voltage to approximately one to two percent of input voltage.
T&R Electric Supply Company is a dependable supplier of transformers and other high voltage electrical apparatus to municipalities, REA's, investor-owned utilities, commercial and industrial customers. For more information, call 1(800)843-7994 inside the US and 1(605)534-3555, and let one of our experienced salespeople help you today!
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