2. First, convert three-phase or single-phase alternating current into direct current (DC); Then direct current (DC) is converted into three-phase or single-phase alternating current (AC). The inverter changes the output frequency and voltage at the same time, that is, it changes n0 on the motor running curve, so that the motor running curve moves down in parallel. Therefore, the inverter can make the motor get a larger starting torque with a smaller starting current, that is, the inverter can start a heavy load.

3. The frequency converter has the basic functions of voltage regulation, frequency modulation, voltage stabilization and speed regulation. It adopts modern science and technology, which is expensive but has good performance, complex internal structure and simple use, so it is not only used to start motors, but also widely used in various fields, including various powers, shapes, volumes and uses. With the development of technology and the reduction of cost, frequency converters will be more widely used.

Extended data:

Classification:

1, classified by input voltage level.

Inverter can be divided into low-voltage inverter and high-voltage inverter according to the input voltage level. Common low-voltage inverters in China include single-phase 220V inverter, three-phase 220V inverter and I-phase 380V inverter. 6kV and 10kV transformers are commonly used in high voltage converters, and the control mode is generally changed by high and low frequency converters or high and low frequency converters.

2. Classification by frequency conversion.

Frequency converters are divided into AC-AC frequency converters and AC -DC frequency converters according to frequency conversion modes. AC-AC converter can directly convert power frequency AC into AC with controllable frequency and voltage, so it is called direct inverter. AC-DC-AC frequency converter is also called indirect frequency converter, which first converts power frequency alternating current into direct current through rectifier device, and then converts direct current into alternating current with adjustable frequency and voltage.

3. According to the nature of DC power supply.

In AC-DC-AC inverter, DC power supply can be divided into voltage inverter and current inverter according to the process of converting the main circuit power supply to DC power supply.