Frequency Converter

A frequency converter, also known as a frequency changer, is a device that converts the frequency of an alternating current (AC) from one value to another. Besides changing the frequency, these devices may also alter the voltage, but this can be considered incidental to their primary function. Voltage conversion of AC is much simpler to achieve than frequency conversion.

Types of Frequency Converters

Frequency converters can be broadly classified into static, rotating, and combined types.

1. Static Frequency Converters: These can be further subdivided into electromagnetic and rectifier types. Electromagnetic frequency converters are based on changing the shape of a sinusoidal alternating voltage using magnetic nonlinear elements, such as chokes and transformers with saturable cores. They are often used as frequency dividers and multipliers . Rectifier-type converters often employ transistors and thyristors as rectifiers, and are primarily used in radio-engineering equipment. Their power rating can be as high as 2 to 3 kilovolt-amperes (kVA).

2. Rotating Frequency Converters: These converters can be built either as two machines or as one machine. The two-machine type usually combines an electric driving motor and a generator of alternating or direct current. Their efficiency can reach 85 percent, and their power ratings range from 30 to 800 kVA.

Applications of Frequency Converters

Frequency converters find usage in various applications, including:

1. Power Grids: They are used for converting bulk AC power from one frequency to another when two adjacent power grids operate at different utility frequencies.

2. Variable-Frequency Drives: A variable-frequency drive (VFD) is a type of frequency changer used for speed control of AC motors. The speed of a synchronous AC motor is dependent on the frequency of the AC power supply. Therefore, changing frequency allows the motor speed to be varied.

3. Aerospace and Airlines Industries: Often airplanes use 400 Hz power, so a 50 Hz or 60 Hz to 400 Hz frequency converter is needed for use in the ground power unit used to power the airplane while it is on the ground.

4. Renewable Energy Systems: In renewable energy systems, frequency converters are an essential component of doubly fed induction generators (DFIGs) as used in modern multi-megawatt class wind turbines.

Frequency Converter Technology

There are two basic types of Frequency Converters: Rotary Frequency Converters and Solid State (Static) Frequency Converters. Rotary Frequency Converters use electrical energy to drive a motor. On the other hand, Solid-state frequency converters take the incoming AC and convert it to direct current (DC).

A Rotary Frequency Converter is manufactured with the use of a Motor Generator and a Solid State (Static) Frequency Converter is manufactured with the use of semiconductors and power stages. The Rotary machine is brute force as opposed to the Static machine.

In conclusion, frequency converters are crucial devices in various industries due to their ability to convert the frequency of an alternating current. They are particularly important in applications that require the control of motor speed, synchronization of different power grids, and in the operation of specific equipment in the aerospace industry.