A frequency converter, often known as a variable frequency drive (VFD), is a piece of electric equipment that converts the alternating current (AC) on a certain frequency to the alternating current (AC) of another frequency. There might be a slight voltage change with the use of a frequency converter, and if it does happen, it is secondary to the primary goal of the frequency converter because the conversion of voltage in AC is a lot easier to achieve than the principal frequency conversion.
In the beginning, frequency converters were motor-generator sets with vacuum tubes or mercury arc rectifiers. However, with the invention of solid-state electronics, the world of frequency converters has changed completely. At this point, these frequency converters have a rectifier stage where direct current is produced before there s an inversion process which turns it to AC of the results we are looking for.
If there is a need for voltage conversion, then the frequency converter will be fitted with an AC input or output circuitry, which provides the necessary galvanic isolation between the input AC circuits as well as the output circuits. Finally, there can be proper addition of DC circuitry to improve the converter's ride through slight outages in input power. There are different frequency converters with different power capacities ranging from watts to megawatts.
Applications of Frequency Converters
There are many applications of frequency converters; let's take a look at some of them, shall we:
Frequency converters are used for the conversion of bulk AC power from a specific frequency to another and mostly when we have different adjacent power grids operating with different frequencies.
There are different types of frequency converters. We have the variable-frequency drive (VFD) converter, which is a type of converter used for controlling the speed of AC motors such as fans and pumps. As we know, the speed of these AC motors depends on the frequency of the AC power supply, which is why the change in frequency causes a change in speed. This allows easy energy saving because the fans and pumps are now designed to change to match needs without excessive power consumption.
Another type of frequency converter is the cycloconverter which changes frequency directly specifically because the conversion process involves an initial AC-DC conversion before a DC-AC conversion. Compared to the variable frequency converter, the cycloconverter allows for direct frequency conversion without any stage in-between.
In the airline industry, frequency converters are used in planes to ground the 400hz power in airplanes while it is not in the air. These converters are also used for the provision of in-air wall current for use by passengers who would like to use power to charge devices like their phones and laptops. When it comes to renewable energy systems, frequency converters are important parts of doubly-fed inductor generators as used in modern multi-megawatt class wind turbines.
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