The supplier of the frequency converter braking unit reminds you that the frequency converter is a power control device that uses frequency conversion technology and microelectronics technology to control AC motors by changing the frequency of the motor's working power supply. The frequency converter is mainly composed of rectification (AC to DC), filtering, inversion (DC to AC), braking unit, driving unit, detection unit, microprocessor unit, etc. The frequency converter adjusts the voltage and frequency of the output power supply by disconnecting the internal IGBT, providing the required power supply voltage according to the actual needs of the motor, thereby achieving energy saving and speed regulation. In addition, the frequency converter also has many protection functions, such as overcurrent, overvoltage, overload protection, etc. With the continuous improvement of industrial automation, frequency converters have also been widely used.
Classification of frequency converters
There are various classification methods for frequency converters. According to the working mode of the main circuit, they can be classified into voltage type frequency converters and current type frequency converters; According to the switch mode classification, it can be divided into PAM controlled frequency converters, PWM controlled frequency converters, and high carrier frequency PWM controlled frequency converters; According to the working principle, it can be classified into V/f control frequency converter, slip frequency control frequency converter, vector control frequency converter, etc; According to their usage, they can be classified into general-purpose frequency converters, high-performance dedicated frequency converters, high-frequency frequency converters, single-phase frequency converters, and three-phase frequency converters.
VVVF: Change voltage, change frequency CVCF: Constant voltage, constant frequency. The AC power supply used by various countries, whether for households or factories, has a voltage and frequency of 400V/50Hz or 200V/60Hz (50Hz), and so on. Usually, a device that converts AC power with fixed voltage and frequency into AC power with variable voltage or frequency is called a "frequency converter". In order to generate variable voltage and frequency, the device first needs to convert the alternating current of the power supply into direct current (DC).
The frequency converter used for motor control can change both voltage and frequency.
Working principle of frequency converter
We know that the expression for the synchronous speed of an AC motor is:
n=60 f(1-s)/p (1)， Where:
N - speed of asynchronous motor;
F - frequency of asynchronous motor;
S - motor slip rate;
P - Number of poles of the electric motor.
According to the formula, the speed n is proportional to the frequency f. As long as the frequency f is changed, the speed of the motor can be changed. When the frequency f changes within the range of 0-50Hz, the range of motor speed adjustment is very wide. The frequency converter is an ideal high-efficiency and high-performance speed regulation method that adjusts the speed by changing the frequency of the motor power supply.