The difference between variable frequency speed regulator and inverter

A variable frequency speed regulator is a device that converts industrial frequency power (50Hz or 60Hz) into AC power of various frequencies to achieve variable speed operation of the motor. The control circuit completes the control of the main circuit, the rectifier circuit converts AC power into DC power, the DC intermediate circuit smoothes and filters the output of the rectifier circuit, and the inverter circuit converts DC power into AC power.

The variable-frequency drive (VFD) 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 inverter is mainly composed of rectification (AC to DC), filtering, inversion (DC to AC), braking unit, drive unit, detection unit, and microprocessor unit.

Generally, the speed regulator is used to adjust the speed of the DC motor, that is, to change the amplitude of the DC motor armature voltage, n (speed) = k × U (armature voltage). Its control structure is relatively simple.

The frequency converter is also a speed regulator, which is basically used for three-phase asynchronous motors. n (speed) = 60 × f (power frequency) ÷ 2p (number of pole pairs) × (1-u). It can not only adjust the output voltage, but also the frequency.

The above are their main differences.

The differences are as follows:

1. The inverter speed regulation changes the speed of the motor by changing the power supply frequency supplied to the motor, thereby changing the speed of the load. The power supply that was originally directly input to the three-phase asynchronous motor is first connected to the inverter. The industrial frequency AC power is rectified and inverted inside the inverter through electronic conversion technologies such as PWM to become a frequency-controllable AC power that is input into the motor. When the motor is running, the frequency can be adjusted through V/F control, output torque control, vector control and other control methods to change the loop current and achieve energy-saving operation. Especially when the motor is lightly loaded, the energy-saving effect is obvious. It is an energy-saving product that has been widely promoted and applied.

⒉ The speed regulator is for single-phase motors and is divided into single-phase DC control, single-phase AC control and single-phase DC-AC control. The speed and rotation speed of the motor are adjusted by changing the resistance and capacitance of the winding. This speed regulation is not an energy-saving speed regulation method and does not change the output of the power supply. The most widely used products are household electric fans.

This is also the reason why frequency converters cannot replace DC speed regulators in many high-precision control situations.

Variable frequency speed regulator and frequency converter are synonymous. Their functions are to control the speed and torque of the motor. They control the running state of the motor by changing the voltage and frequency of the power supply. It can be said that the difference between them is only the different names, and there is no essential difference. However, in different applications, they are sometimes distinguished. Variable frequency speed regulator refers more to high-power frequency converters in industrial applications, while frequency converters tend to refer to low-power frequency converters for household appliances.

In short, whether it is a variable frequency speed regulator or a frequency converter, their function is to control the motor speed and torque, improve the efficiency of the motor, reduce energy consumption, and at the same time improve the smoothness and reliability of the motor's operation.