Working principle of VFD
The working principle of frequency converters is to apply the principles of frequency conversion technology and microelectronics technology to control the power control equipment of AC motors by changing the frequency of the motor's working power supply.
The working principle of the inverter mainly includes three processes: rectification, filtering and inverter:
Rectifier: Converts the input AC power to DC power. This step is usually achieved by a three-phase bridge rectifier circuit, which uses the unidirectional conductivity of the rectifier diode to convert alternating current to direct current.
Filtering: The rectified DC is filtered to remove the pulsating components and get a smooth DC voltage. The filter circuit usually uses high-capacity electrolytic capacitors or inductors.
Inverter: The filtered direct current is converted into alternating current with adjustable frequency and voltage through the inverter, which is supplied to the motor. The inverter is the core part of the inverter, which is composed of power semiconductor devices such as IGBTs. By controlling the on-off of these devices, alternating current of the required frequency and voltage can be generated.
The power supply used is divided into AC power supply and DC power supply. Generally, DC power supply is mostly obtained by AC power supply through transformer transformation, rectification and filtering. AC power accounts for about 95% of the total power used by people.
A frequency converter is a device that converts industrial frequency power sources (50Hz or 60Hz) into AC power sources of various frequencies to achieve variable speed operation of the motor. The control circuit controls the main circuit, the rectifier circuit converts AC power into DC power, the DC intermediate circuit smooths and filters the output of the rectifier circuit, and the inverter circuit converts DC power back into AC power.
