Specific Applications of Inverters in 32 Industrial Sectors

An inverter (also known as a variable-frequency drive, VFD) is an electrical control device that applies frequency conversion technology and microelectronics to control AC motors by adjusting the frequency of the motor’s power supply. With the continuous improvement of Industrial Automation, inverters have been widely used.  

Specifically, an inverter (Variable-frequency Drive, VFD) integrates frequency conversion technology and microelectronics. It controls AC motors by changing the frequency of the motor’s operating power supply and mainly consists of rectification (AC to DC), filtering, inversion (DC to AC), braking unit, drive unit, detection unit, and microprocessing unit. The inverter adjusts the voltage and frequency of the output power through the switching of internal IGBTs, providing the required power voltage according to the actual needs of the motor. This not only achieves energy saving and speed regulation but also enables multiple protection functions, such as overcurrent, overvoltage, and Overload Protection. Driven by the rising level of industrial automation, inverters have gained extensive application across various fields.  

Based on years of industry experience, inverters can be applied in 32 typical industrial sectors, including: air conditioning loads, crusher loads, large kiln/calciner loads, compressor loads, rolling mill loads, converter loads, hoist loads, roller table loads, pump loads, cranes, dump truck loads, wire drawing machine loads, transport vehicle loads, elevator and overhead tourist vehicle loads, feeder loads, stacker-reclaimer loads, fan loads, mixer loads, spinning machine loads, and special power supply loads.  

The following is a detailed analysis of their specific applications in these sectors:  

1. Application of Inverters in Air Conditioning Loads

Central air conditioning systems are widely used in office buildings, shopping malls, supermarkets, and factories. During the summer peak electricity consumption period, air conditioners account for a large proportion of power usage. In hot weather, the electricity consumption of air conditioners in cities like Beijing, Shanghai, and Shenzhen accounts for over 40% of peak-hour electricity. Therefore, using frequency conversion devices to drive the chilled Water Pumps, cooling water pumps, and fans of air conditioning systems is an effective energy-saving technology. Currently, many companies specializing in air conditioning energy conservation have emerged nationwide, with frequency conversion speed regulation as their core energy-saving technology.  

2. Application of Inverters in Crusher Loads

Crushers and ball mills are widely used in the metallurgical, mining, and building materials industries. The application of frequency conversion technology in such loads has yielded significant results.  

3. Application of Inverters in Large Kiln/Calciner Loads

For large industrial rotary kilns (converters) in metallurgy, building materials, and caustic soda production, DC motors, commutator motors, slip ring motors, cascade speed regulation, or intermediate frequency units were commonly used for speed control in the past. However, these methods either involve slip rings or have low efficiency. In recent years, many enterprises have adopted frequency conversion control, achieving excellent results.  

4. Application of Inverters in Compressor Loads

Compressors are also widely used loads. Low-voltage compressors are commonly used in various industrial sectors, while high-voltage and large-capacity compressors are extensively applied in iron and steel (e.g., oxygen generators), mining, chemical fertilizers, and ethylene production. The adoption of frequency conversion speed regulation offers advantages such as low starting current, energy conservation, and extended equipment service life.  

5. Application of Inverters in Rolling Mill Loads

In the metallurgical industry, large rolling mills traditionally used AC-AC inverters. In recent years, AC-DC-AC inverters have become more prevalent, and the adoption of AC systems for rolling mills has become a trend—especially for light-load rolling mills. For example, the multi-stand aluminum rolling mill at Ningxia National Aluminum Products Factory uses general-purpose inverters, which enable low-frequency loaded starting, synchronous operation between stands, constant tension control, and simple and reliable operation.  

6. Application of Inverters in Hoist Loads

Frequency conversion speed regulation ensures stable and reliable operation of hoist loads. Blast furnace hoisting equipment in ironworks is a key device for transporting ironmaking raw materials, requiring smooth starting/stopping, uniform acceleration/deceleration, and high reliability. Previously, cascade speed regulation, DC speed regulation, or rotor series resistance speed regulation were commonly used, which had low efficiency and poor reliability. Replacing these methods with AC inverters achieves ideal results.  

7. Application of Inverters in Converter Loads

For converter loads, replacing DC units with AC frequency conversion systems simplifies operations, enhances reliability, and ensures stable operation.  

8. Application of Inverters in Roller Table Loads

Roller table loads are mostly used in the iron and steel metallurgy industry. The adoption of AC motor frequency conversion control improves the reliability and stability of the equipment.  

9. Application of Inverters in Pump Loads

Pump loads are numerous and widely used, including water pumps, oil pumps, chemical pumps, mud pumps, and sand pumps. They range from low-voltage, small-to-medium-capacity pumps to high-voltage, large-capacity pumps.  

Many water supply companies use frequency conversion speed regulation for water pumps; chemical and fertilizer industries apply it to chemical pumps and reciprocating pumps; and non-ferrous metal industries use it for mud pumps—all achieving excellent results.  

10. Application of Inverters in Crane and Dump Truck Loads

Loads such as cranes and dump trucks require large torque, stable operation, frequent forward/reverse rotation, and high reliability. Frequency conversion devices can meet these requirements when controlling cranes and dump trucks.  

11. Application of Inverters in Wire Drawing Machine Loads

Wire drawing machines for steel wire production require high-speed, continuous operation. With a steel wire strength of 200Kg/mm², the speed regulation system demands high precision, high stability, and synchronization.  

12. Application of Inverters in Transport Vehicle Loads

Frequency conversion technology works well for loads like raw coal transport vehicles in coal mines and molten steel transport vehicles in steel plants. It enables fast starting/stopping, strong overload capacity, and flexible forward/reverse rotation—ensuring even coal stacking, accurate weight control (avoiding overloading or underloading), minimal manual operation, improved raw coal production efficiency, and energy conservation.  

13. Application of Inverters in Elevator and Overhead Tourist Vehicle Loads

As elevators are passenger-carrying devices, their drive systems require high reliability, frequent acceleration/deceleration, and forward/reverse rotation. Enhancing the dynamic performance and reliability of elevators improves passenger safety, comfort, and operational efficiency. Previously, DC speed regulation was widely used for elevators; in recent years, AC motor frequency conversion speed regulation has gradually become mainstream—both in Japan and Germany. Many domestic elevator manufacturers, such as Shanghai Mitsubishi, Guangzhou Hitachi, Qingdao Fuji, and Tianjin Otis, have adopted AC frequency conversion speed regulation. Additionally, many existing elevators have been retrofitted with frequency conversion systems.  

14. Application of Inverters in Feeder Loads

Feeders are widely used in metallurgy, electric power, coal, and chemical industries—whether disc feeders or vibrating feeders. The application of frequency conversion speed regulation yields significant results. For example, the disc feeder in the sulfuric acid production line at the Dyestuff Factory of Jilin Chemical Industry Co., Ltd. originally used slip speed regulation, which had low low-frequency torque, frequent failures, and frequent jamming. After adopting frequency conversion speed regulation, the asynchronous motor ensures high reliability and energy conservation. More importantly, the closed-loop control with a temperature transmitter guarantees accurate material conveying, preventing excessive oxidant delivery (which could cause overheating and accidents) and ensuring orderly production.  

15. Application of Inverters in Stacker-Reclaimer Loads

Stacker-reclaimers are key equipment for stacking and reclaiming materials in coal yards, docks, and mines. They enable automatic stacking and semi-automatic reclaiming, improving equipment reliability and ensuring stable operation without impact or vibration. During reclaiming, the rotation speed is adjusted according to the 1/cosφ principle, which enhances the bucket wheel reclaiming efficiency and the uniformity of coal transportation via belts—making it well-received by workers.  

16. Application of Inverters in Fan Loads

Fan loads are numerous and widely used in industries such as steel, electric power, non-ferrous metals, mining, chemicals, textiles, chemical fibers, cement, and papermaking. In the past, air volume was often adjusted by changing the baffle opening, which wasted significant electricity. The adoption of frequency conversion speed regulation not only saves energy but also reduces mechanical wear and extends equipment service life.  

17. Application of Inverters in Mixer Loads

Mixers are widely used in the chemical and pharmaceutical industries. Replacing other speed regulation methods with frequency conversion speed regulation offers numerous benefits.  

18. Application of Inverters in Spinning Machine Loads

Spinning processes are complex, involving multiple stations and requiring tension control (and in some cases, position control). The application of frequency conversion speed regulation achieves excellent results.  

19. Application of Inverters in Special Power Supply Loads

Many power supplies—such as experimental power supplies and aircraft drive power supplies (400Hz)—can be implemented using frequency conversion devices. This approach offers advantages such as low investment, quick results, small size, and simple operation.  

20. Application of Inverters in Paper Machine Loads

For paper machines in China’s papermaking industry, those requiring high precision mostly use SCR DC speed regulation, while others use slip ring motors or commutator motors. However, the presence of slip rings and carbon brushes leads to low reliability and precision, resulting in backward papermaking machinery (with a typical speed of only around 200m/min, far lower than the 2000m/min of foreign equipment). Therefore, the adoption of frequency conversion technology for paper machines has become an inevitable trend.  

21. Application of Inverters in Laundry and Ironing Equipment Loads

Washing machines and ironing equipment in large hotels previously used mechanical speed regulation or pole-changing speed regulation, which could only provide one or several fixed speeds—making them unsuitable for fabrics requiring repeated washing and ironing. The adoption of frequency conversion speed regulation greatly improves the efficiency of washing machines.  

22. Application of Inverters in Musical Fountain Loads

Musical fountains, which attract many visitors, rely on frequency conversion control to adjust the height and volume of water jets.  

23. Application of Inverters in Grinding Machines and Other Mechanical Loads

The spindle motors of grinding machines require high rotational speeds, which in turn demand high power supply frequencies (e.g., 200Hz, 400Hz, or even 800Hz). In the past, the power supply for spindle motors was mostly provided by intermediate frequency units, which were large, low-efficiency, noisy, and imprecise.  

24. Application of Inverters in Cigarette Machine Loads

Previously imported cigarette machines in the tobacco industry (such as Molins 8 and Molins 0) did not support stepless speed regulation. Therefore, the tobacco industry mainly needed to address stepless speed regulation and reliability issues. Frequency converters offer a simple technical solution with straightforward operation and significant results.  

25. Application of Inverters in Vibration and Noise Reduction Loads

Many loads—such as large air compressors and intermediate frequency units—generate high noise and vibration. The application of frequency conversion technology can reduce vibration and noise to meet relevant standards.  

26. Application of Inverters in Printing and Dyeing Machine Loads

Most printing and dyeing machinery consists of multi-unit combined equipment. Process requirements dictate that all units operate synchronously at the same linear speed while maintaining constant tension; otherwise, quality issues such as fabric breakage, wrapping, uneven color, insufficient color fastness, and excessive shrinkage may occur. In the past, both shared-power and separate-power printing and dyeing machinery used DC speed regulation systems.  

Due to the inherent drawbacks of DC motors, the printing and dyeing industry has gradually adopted AC frequency conversion technology. Rotary screen printing machines—composed of fabric feeding units, printing units, drying room conveyor belt units, and fabric winding units—are among the most complex speed regulation systems in the printing and dyeing industry. The adoption of frequency conversion speed regulation enables speed chain control, ensuring excellent synchronization, high precision, and high reliability.  

27. Application of Inverters in Injection Molding Machine Loads

Injection molding machines are key equipment for plastic processing and molding, with large quantities and high power consumption. Previously, energy-saving methods mostly involved switching from delta (△) connection to star (Y) connection, which had limited effectiveness. The adoption of frequency conversion speed regulation does not alter the original structure of the injection molding machine. Instead, it controls the pressure or flow of the oil pump during various processes (e.g., mold clamping, mold closing, injection, pressure holding, demolding, and mold opening), achieving an energy saving rate of 20% to 52%. This technology has effectively replaced the previous proportional valve throttling speed regulation method, significantly reducing energy consumption. Many injection molding factories in the Pearl River Delta have retrofitted their equipment with frequency conversion systems. When retrofitting injection molding machines, attention should be paid to accelerating mold clamping (to avoid reduced output) and harmonic interference at the input and output terminals.  

28. Application of Inverters in Environmental Protection Loads (e.g., Sewage Treatment)

Growing attention is being paid to environmental protection, as it is crucial to the living environment of humanity. This has led to the development of clean energy and “green cities.” Frequency conversion speed regulation can be applied to three types of environmental protection loads: industrial sewage treatment, waste-to-energy power plants, and the control of industrial smoke, exhaust gas, and dust.  

29. Application of Inverters in Production Lines (e.g., Glass, Ceramics, Pharmaceuticals, Beverages, Food, and Packaging)

The adoption of frequency conversion speed regulation in production lines for glass, ceramics, pharmaceuticals, beverages, food, and packaging has achieved excellent results.  

30. Application of Inverters in Offshore Oil Drilling Platform Loads

AC motor frequency conversion speed regulation is far superior to DC speed regulation for oil drilling—especially in dusty and sandy environments—due to the higher reliability of AC motors. Offshore oil drilling platforms require frequency conversion speed regulation devices.  

31. Application of Inverters in Submersible Electric Pump Loads

Submersible electric pumps are used for oil extraction in oilfields. These pumps operate in oil wells over 1,800 meters deep and mostly use power-frequency full-voltage starting and constant-speed operation, which has the following drawbacks:  

•Excessively high starting current, which may damage motor insulation;  
•Impact torque generation, which may damage the pump structure;  
•Sudden high suction force of the pump, which easily draws in sand and causes pump jamming.  

Additionally, the lack of a voltage stabilization system and large fluctuations in downhole liquid level lead to unstable voltage and current, causing over-excitation or under-excitation of the submersible motor and resulting in failures.  

32. Application of Inverters in Polyester Chip Loads

Polyester chips are one of the main products in the petrochemical industry. Frequency conversion speed regulation offers high precision, facilitates control of multiple control points, and ensures stable and reliable operation. Its application improves product quality and brings significant benefits to enterprises. Many enterprises have adopted frequency conversion speed regulation technology during capacity expansion.
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