A frequency converter is a power control device that uses frequency conversion technology and microelectronics technology to control an AC motor by changing the frequency of the motor's power supply.
A frequency converter mainly consists of a rectification unit (AC to DC), a filter, an inverter (DC to AC), a braking unit, a drive unit, a detection unit, and a 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.
Classification of frequency converters
1. Classified by input voltage level
Frequency converters can be classified into low-voltage and high-voltage frequency converters according to their input voltage level. Common low-voltage frequency converters in China include single-phase 220V frequency converters, three-phase 220V frequency converters, and single-phase 380V frequency converters. High-voltage frequency converters commonly use 6 kV and 10 kV transformers, and the control method is generally a high-low to high-voltage frequency converter or a high to high-voltage frequency converter.
2. Classification by frequency conversion method
Frequency converters are classified into AC-AC converters and AC-DC-AC converters according to their frequency conversion methods. AC-AC converters directly convert mains frequency AC power into AC power with controllable frequency and voltage, hence the name direct-type converters. AC-DC-AC converters first convert mains frequency AC power into DC power through a rectifier, and then convert the DC power into AC power with adjustable frequency and voltage; therefore, they are also called indirect-type converters.
3. Classification by the nature of DC power supply
In AC-DC-AC inverters, based on the nature of the DC power supply during the process of converting the main circuit power supply into DC power supply, inverters are classified into voltage-source inverters and current-source inverters.
Common frequency setting methods for frequency inverters include: operator keypad setting, contact signal setting, analog signal setting, pulse signal setting, and communication setting. Each of these methods has its advantages and disadvantages, and the appropriate method must be selected based on actual needs. Different frequency setting methods can also be combined and switched according to functional requirements. With the continuous improvement of industrial automation, frequency inverters have been widely used.
