Frequency Converter
A frequency converter, also known as a variable frequency drive (VFD), frequency inverter, or AC drive, is an electronic device that controls the speed and torque of electric motors by varying the frequency and voltage of its power supply.Energy saving and precise control can be achieved. Frequency converters are widely used in various equipment in industrial production, such as fans, pumps, compressors, etc., as well as air conditioners and washing machines in household appliances. Its expertise lies in providing reliable motor control and technical support for optimizing energy utilization, providing users with efficient and reliable equipment operation and production process optimization.
While adjusting the speed of electric motors to meet production process requirements, frequency converters also deliver significant energy-saving effects, especially in applications involving fan and pump loads. They provide functions for soft starting and soft stopping, which can:
Save on investments in soft start equipment.
Eliminate mechanical impacts during equipment startup.
Extend the service life and maintenance cycles of equipment.
Reduce starting current.
Eliminate impacts on adjacent equipment during startup.
Decrease the demand for power supply capacity during startup.
Thus, the application of frequency converters offers comprehensive social and economic benefits, including cost savings on operations and contributions to energy conservation and emission reduction.
Classification of Frequency Converters
(1)By Voltage Level of the Working Power Supply
Frequency converters' working power supplies are divided into high voltage and low voltage.
High voltage frequency converters have voltage levels such as 3KV, 6KV, 10KV, etc.
Low voltage frequency converters have voltage levels such as 220V, 380V, 660V, 1140V, etc.
Most converters have three-phase AC input and output, with only a few low-power converters using single-phase input and three-phase output.
(2)By the Nature of the DC Power Supply
Voltage-type frequency converter: Utilizes a large capacitor in the intermediate DC link for filtering. The capacitor stores electric field energy at peaks (higher voltage) and releases it at troughs (lower voltage), maintaining a relatively stable DC link voltage with smaller internal resistance, acting as a voltage source. This type is often used where load voltage varies greatly.
Current-type frequency converter: Employs an inductor in the intermediate DC link as an energy storage element for filtering. The inductor stores magnetic field energy at peaks (higher current) and releases it at troughs (lower current), keeping the DC current stable. With larger internal resistance, it exhibits characteristics of an approximate current source, hence the name current-type frequency converter. It is often used where load current varies greatly.
(3)By the Method of Electrical Energy Conversion
AC-DC-AC frequency converter: Converts power frequency AC to DC through a rectifier, then converts the DC to adjustable frequency and voltage AC. ANYHZ is an example of an AC-DC-AC frequency converter.
AC-AC frequency converter: Operates without a rectifier, directly converting power frequency AC to adjustable frequency and voltage AC, also known as a direct frequency converter.