The frequency converter is a power control device that uses frequency conversion technology and microelectronics technology to control the AC motor by changing the frequency of the motor's working power supply. The frequency converter is mainly composed of a rectifier (AC to DC), a filter, an inverter (DC to AC), a brake unit, a drive unit, a detection unit, and a microprocessor unit.

Working principle of frequency converter

The inverter can be divided into voltage type and current type inverter. The voltage type is an inverter, which converts the DC power of the voltage source into AC power, and the filter of the DC loop is a capacitor. The current mode converts the DC of the current source into AC inverter, and its DC loop filter is an inductor. It is a rectifier, a rectifier and an inverter. The main circuit of the inverter consists of a rectifier, a smoothing circuit and an inverter. It is a "rectifier" that converts the industrial frequency into DC power, and a "smoothing circuit" that absorbs the voltage pulsation generated by the converter and inverter.

The role of the frequency converter

1. The inverter can adjust the power of the motor and realize the variable speed operation of the motor, thereby achieving the purpose of saving electricity. Examples are reflected in centrifugal fans and water pumps. When the inverter is used for centrifugal fans and water pumps, operators can easily control the flow as needed, thereby saving energy.

2. The inverter can reduce the voltage fluctuation in the power line and avoid the phenomenon of equipment tripping or abnormal operation once the voltage is abnormal.

3. The inverter can reduce the impact on the power grid, thereby effectively reducing reactive power loss and increasing the effective power of the power grid.

4. The inverter can also reduce the wear between the transmission parts in the machinery, reduce costs to a certain extent, and improve the stability of the system.

5. In addition, the control function of the transformer is very complete, and it can be well coordinated or used with other control devices to achieve centralized monitoring and real-time control, solving many problems of system compatibility for users.

Wiring of control circuit

The control circuit of the inverter can be divided into two types: analog and digital

1. The control circuit terminals should be wired with shielded wires or twisted pairs, and should be wired separately from the main circuit and high-voltage circuit (including 200V relay program circuit).

2. Since the frequency input signal of the control circuit is a small current, in order to prevent poor contact during contact input, the small signal contact should use two parallel nodes or double contacts.

3. The control circuit connection generally uses 0.3 ~ 0.75 square meters of cable.

Ground connection

1. Because there is leakage current in the inverter, the inverter and motor must be grounded to prevent electric shock.

2. The inverter grounding terminal is dedicated. For the connection of the grounding wire, a tinned crimping terminal should be used. When tightening the screw, be careful not to damage the screw buckle.

3. Tin plating does not contain lead.

4. The grounding cable should be as thick as possible and must be equal to or greater than the specified standard. The grounding point should be as close to the inverter as possible, and the shorter the grounding wire, the better.