What is a frequency converter?

Frequency converter is a kind of power control equipment which uses power electronics technology to change the power supply frequency and voltage of motor and realize motor speed control. It is widely used in energy saving and speed control systems of industrial loads such as fans, pumps and compressors.

The core functions of a frequency converter

• Motor speed regulation: stepless speed regulation from low speed to high speed can be realized by adjusting the output frequency to meet the requirements of different working conditions.

• Energy saving and consumption reduction: for square torque loads such as fans and pumps, speed regulation can greatly reduce energy consumption (compared with valve/baffle regulation, the energy saving rate can reach 20%-60%).

• Soft start/soft stop: avoid large current impact when the motor is started directly, protect the motor and power grid, and prolong the service life of the equipment.

• Protection against overload, overcurrent, overvoltage, etc.: Integrate multiple protection functions to improve the safety of equipment operation.

Core working principle

The frequency converter is mainly composed of four parts: rectifier unit, filter unit, inverter unit and control unit：

• Rectification: converting alternating current (AC) of the power grid into direct current (DC);

• Filtering: Smoothing the rectified DC voltage to reduce voltage fluctuation;

• Inverter: the control unit drives the power switching device (such as IGBT) to invert the direct current into alternating current with adjustable frequency and voltage;

• Control: according to external instructions (such as analog signals and communication signals), the output frequency and voltage are accurately adjusted to realize motor speed regulation.

Core components and their functions

Key parameters for selection

• Rated capacity/rated current: it needs to match the rated current of the motor (the rated current of the inverter should be ≥1.1 times the rated current of the motor)

• Voltage level: according to the rated voltage of the motor (such as 220V, 380V, 660V, 1140V, etc.);

• Control mode: V/F control (universal type, suitable for fans and pumps) and vector control (high-precision speed regulation, suitable for cranes, machine tools, etc.);

• Protection grade: selected according to the installation environment (for example, IP20 is suitable for the control cabinet and IP54 is suitable for the dusty site);

• Communication function: whether it supports industrial buses such as Modbus, Profibus and Profinet to meet the integration requirements of automation systems.

Typical application scenarios

• HVAC: variable frequency speed regulation of fans and pumps to realize accurate control of temperature and pressure;

• Metallurgical mines: speed regulation and energy saving of belt conveyors and hoists;

• Mechanical manufacturing: speed control of machine tool spindle and production line conveying equipment;

• Municipal engineering: energy-saving operation of water supply system pumps and sewage treatment aeration fans.

High-Performance Closed-Loop Vector Inverter (One of our VFDs)

The SHBF700 series offers a comprehensive range of models with a power spectrum spanning 0.75–630 kW. This high-performance inverter features robust protection mechanisms, ensuring reliable quality, high load capacity, and low temperature rise.
Designed with an enclosure smaller than industry standards, it enables broader application versatility. Backed by advanced hardware design, the product also delivers powerful external control and application functions.

Product Features：

• Frequency Reference Methods:
  Digital setting, Analog input setting, Serial communication setting, Multi-speed setting, PID setting, etc.

• Built-in PLC functionality and PID control

• Professional-grade constant pressure water supply and constant temperature control applications, with arbitrarily settable automatic sleep and wake-up functions.

• Multi-speed control function: 8-speed control, 16-speed control

• Four sets of linear acceleration and deceleration times, which can be switched according to requirements, with a maximum resolution of 0.01s

• Quick Multi-function Key: A user-definable shortcut key for versatile operations.

• Current and Overvoltage Limiting: Software-defined current limiting and overvoltage functions are available. The system can automatically adjust to load variations, keeping the output current within the set limits and preventing nuisance tripping.

• Automatic Voltage Regulation (AVR): Automatically maintains a constant output voltage even when the input grid voltage fluctuates.

• he system provides dozens of comprehensive protection functions, including:、Short-circuit protection、Software current limiting & Fast current limiting、Software over-current protection、Over-temperature protection、Over-voltage and Under-voltage protection、Phase loss protection (for both input and output)

• Standard Dual Digital Keypads: Two keypads can be connected simultaneously. The system features automatic type recognition and supports hot swapping.

• Independent trial time timer

Specifications

Rated Voltage: Single-phase 220V / Three-phase 220V / Three-phase 380V

Power Rating: Single-phase 220V (0.75 – 5.5 kW)

Three-phase 220V (0.75 – 7.5 kW)

Three-phase 380V (7.5 – 15 kW)

Three-phase 380V (18.5 – 630 kW)