A frequency changer frequency converter is an electrical device used to change the frequency of alternating current. In addition, it has an auxiliary function to change the alternating current voltage.
According to the classification of the working mode of the main circuit, it can be divided into voltage type inverter and current type inverter;According to the classification of switching mode, it can be divided into PAM control inverter, PWM control inverter and high carrier frequency PWM control inverter;According to the classification of working principle, it can be divided into V F control inverter, slip frequency control inverter and vector control inverter, etc.;According to the classification of use, it can be divided into general-purpose inverter, high-performance special inverter, high-frequency inverter, single-phase inverter and three-phase inverter.
The composition of frequency conversion speed regulation
In order to realize frequency conversion speed regulation, there must be an AC power supply with adjustable frequency, but the power system can only provide AC power with a fixed frequency, so a set of frequency conversion devices is needed to complete the task of frequency conversion. Historically, there have been rotary inverter units, but they are rarely used today due to many disadvantages. Modern frequency converters are made of high-power electronics. Compared with the rotary frequency conversion unit, it is called a static frequency conversion device, which is the central link of the frequency conversion speed regulation system.
A frequency conversion speed regulation system is mainly composed of static frequency conversion device, AC motor and control circuit 3 parts, and the input of static frequency conversion device is a three-phase single-phase constant frequency, constant voltage power supply, and the output is a three-phase alternating current that the frequency and voltage can be adjusted. As for the control circuit, the frequency conversion speed regulation system is much more complex than the DC speed regulation system and other AC speed regulation systems, which is due to the electromagnetic relationship between the controlled object - the induction motor itself and the control of the frequency converter are more complex. Therefore, most of the control tasks of the frequency conversion speed control system are undertaken by the microprocessor.
The inverter is mainly used in industrial control for speed regulation and start control of asynchronous motors
Why can the rotation speed of the asynchronous motor be changed freely?
Synchronous speed of asynchronous motor: n = 60fp
n: Synchronization speed.
f: Power frequency.
p: The number of poles of the motor.