Variable frequency power supplies and frequency converters are both frequently used in industrial production. So how much do you know about the differences between the two? Let's take a look today.
What is a variable frequency power supply?
A variable frequency power supply converts AC power from the mains through AC→DC→AC conversion, outputting a pure sine wave with adjustable frequency and voltage within a certain range. It differs from variable frequency speed controllers used for motor speed control, and also from ordinary AC voltage regulators.
There are two main types of frequency converters: linear amplifier type and SPWM switching type.
What is a frequency converter?
A frequency converter mainly consists of rectification (AC to DC), filtering, inversion (DC to AC), braking unit, drive unit, detection unit, and microprocessor unit. The frequency converter adjusts the output voltage and frequency by switching its internal IGBTs , providing the required power voltage according to the actual needs of the motor, thereby achieving energy saving and speed regulation. In addition, the frequency converter has many protection functions, such as overcurrent, overvoltage, and overload protection. With the continuous improvement of industrial automation, frequency converters have been widely used.
The difference between variable frequency power supply and variable frequency drive
Variable frequency power supplies (VFDs) are widely used devices that combine AC and DC circuits with AC filtering. They can simulate the power grid specifications of different countries and provide export-oriented electrical manufacturers with clean, reliable, low-harmonic-distortion, and highly stable sinusoidal voltage and frequency outputs for design, development, production, and testing. VFDs closely approximate ideal AC power supplies, capable of outputting the voltage and frequency of any country's power grid. In contrast, frequency converters, composed of AC-DC-AC (modulated wave) circuits, are technically called variable frequency speed controllers. Their output voltage waveform is a pulsed square wave with numerous harmonic components; the voltage and frequency change proportionally and cannot be adjusted separately, failing to meet the requirements of AC power supplies. Therefore, they are generally not suitable for use as power supplies and are typically only used for speed control of three-phase asynchronous motors .
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