Apiary

Frequency converters (PC), or inverters, today occupy a key place in the automation and control systems of electric drives. Thanks to them, enterprises can significantly improve energy efficiency, increase equipment resource and provide flexible control of electric motors in a wide variety of technological processes. Modern frequency converters are used in pumps, ventilators, compressors, transport systems, CNC machines, bottling lines, lifting equipment and many other areas.

In this article, we will consider in detail, what is a frequency converter, its structure, appointment, types, functional capabilities, as well as the main selection criteria for industrial tasks.

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What is a frequency converter??

A frequency converter is an electronic device, which changes the frequency and amplitude of the alternating voltage, which is supplied to the electric motor. Since the speed of rotation of most asynchronous motors is proportional to the frequency of the supply, The inverter allows you to smoothly adjust the revolutions, providing precise and energy-efficient drive control.

The main tasks of frequency converters:

• smooth start and stop of the engine;
• adjustment of rotation speed in a wide range;
• saving electricity due to load optimization;
• protection of the electric motor against overloads, overheating, phase distortions and other emergency situations;
• increasing the resource of mechanical units and reducing wear and tear of equipment.

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The principle of operation of the frequency converter

A typical structure of an inverter consists of three main blocks:

1. Rectifier

This element converts the alternating voltage of the network into a constant one. It can be unmanageable (on diodes) or managed (of thyristors).

2. DC link

This is where voltage is smoothed and stabilized. It usually contains filter capacitors, chokes and protective elements.

3. Inverter

The main functional unit, which forms an alternating voltage of the required frequency and amplitude. Works on power IGBT transistors, controlled by special modulation algorithms (PWM).

Algorithms of IF operation allow not only to change the frequency and voltage, and implement complex control modes — from vector control to engine positioning, making them a versatile automation tool.

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Types of frequency converters

Frequency converters are classified according to various parameters.

1. By type of electric motor:

• for asynchronous motors (the most common);
• for synchronous motors (including PMSM, motors with permanent magnets);
• universal (support several types of engines).

2. By power:

• low-power inverters (to 2,2 kW) — for pumps, fans, small mechanisms;
• Middle (2,2–90 kW) — for most industrial equipment;
• high-powered (from 90 kW and above) — for large fans, compressors, conveyors, lifting mechanisms.

3. By type of control:

• scalar (V/F) - simple, available, suitable for speed regulation;
• vector - provide precise control of torque and dynamics;
• servo drives — for high precision and positioning tasks.

4. By design:

• modular;
• panel;
• cabinet solutions;
• specialized series for pumps, compressors, fans.

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The main functions of frequency converters

A modern inverter performs a much wider set of functions, than simply adjusting the frequency:

Smooth start and stop

Reduces shock loads on mechanics and electrical network.

Engine protection:

• from a short circuit;
• from current overload;
• from overheating of the windings;
• from a phase break;
• from a decrease or increase in voltage.

Energy saving

It is especially effective in pumping and ventilation systems. Change the speed of everything to 20% can reduce electricity consumption to 50%.

Automatic control

The inverter can work:

• by analog signals 0–10 V or 4–20 mA,
• on digital inputs,
• by network protocols (Modbus, Profibus, CANopen, Ethernet).

Built-in PID regulators

Allows you to control processes by pressure, expense, temperature or level without additional controllers.

Braking modes

• dynamic braking;
• energy recovery (in certain models).

Such functions make frequency converters a universal tool for a wide range of automation tasks.

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Advantages of using frequency converters

The use of IF gives enterprises a number of significant advantages:

1. Energy saving up to 60%

Thanks to speed regulation according to the actual load.

2. Reduction of mechanical wear of equipment

Smooth start and precise control reduce shock loads, extending the life of engines, bearings, belts and other elements.

3. Increasing the productivity of processes

Optimal speed of rotation allows to achieve precise technological parameters.

4. Equipment protection

The inverter provides comprehensive electrical motor protection, reducing the risk of accidents.

5. Reduction of starting currents

The starting current of the motor can decrease from 600% nominal value up to 120–150%.

6. Integration into automation systems

Support for digital protocols allows the use of inverters in complex SCADA/PLC systems.

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Where frequency converters are used?

Frequency converters are widely used in industry, utility sector and private automation systems:

• water supply and drainage pumping stations;
• ventilation and air conditioning (HVAC);
• compressor equipment;
• conveyor lines and transport systems;
• food production;
• woodworking and metalworking machines;
• elevators, taps, lifting mechanisms;
• oil and gas and chemical industry;
• mining industry;
• packing and filling lines.

Thanks to their versatility, inverters confidently occupy a place in all areas of automation.

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How to choose a frequency converter?

To choose the optimal inverter for a specific task, must be taken into account:

1. Nominal power of the electric motor

The converter is chosen with a margin of 10–20%.

2. Type of load

• ventilators / pumps are a light load;
• conveyors - the average;
• extruders, mills is difficult.

3. Speed ​​control range

The more complex the requirements, the more necessary vector or servo drivers.

4. Availability of management interfaces

Modbus, Ethernet, CANopen, Profibus etc.

5. Operating conditions

Temperature, humidity, dustiness, the need for IP55 or IP66 protection.

6. Special functions

PID regulator, pump protection, multi-pump modes, energy saving, torque control.

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Conclusion

Frequency converters are an integral part of a modern industrial electric drive. They provide smooth, accurate and energy-efficient control of electric motors, reduce operating costs and increase equipment reliability. Due to their wide functionality, inverters are used in almost all industries — from pumping stations to complex automated lines.

On the website "" you can get advice on choosing a frequency converter, choose equipment for a specific task and order components for automation systems.