introduction
With the increasing maturity and widespread application of high-voltage frequency converters (VFDs), their application scope and depth have been continuously strengthened. The demand for energy-saving applications of VFDs in high-risk environments such as high temperature, high humidity, high dust, strong corrosion, high electromagnetic noise, and vibration is growing. At the same time, facing the urgent needs of energy conservation and emission reduction, objective factors such as construction cycles, engineering safety and quality, and application space limitations in many projects have, to varying degrees, constrained the smooth implementation of high-voltage frequency converter energy-saving projects and the achievement of sustainable development goals.
Addressing the series of problems arising from and brought about by the application of high-voltage frequency converters, it is crucial to propose a comprehensive and integrated solution that takes into account the overall design and production of frequency converters and provides a better technical guarantee for high-voltage frequency conversion energy-saving projects. This is one of the important topics that needs to be studied at present.
Application Status Analysis
Addressing the operational environment issues of high-voltage frequency converters is of significant practical importance for improving their operational safety, stability, reliability, and economic viability. A statistical analysis of the current application status of high-voltage frequency converters of 1600kW and below reveals the following key characteristics:
(1) Of the total number of high-voltage motors in operation in China, those below 1600kW account for approximately 69% of the total number of full-power motors, indicating a large number of applications. In accordance with the current national requirements for building a conservation-oriented society and sustainable development, the vast majority require energy-saving retrofits by adding high-voltage frequency converters to achieve energy conservation and consumption reduction. Of these, over 77% require the construction of new buildings for equipment operation; only a few projects can utilize existing building structures, and these are often limited by spatial constraints or require increased project investment.
(2) With the widespread application of high-voltage frequency converters in industries such as cement, steel, metallurgy, mining, petrochemicals, and power, harsh environmental conditions such as high temperature, high dust, high humidity, high corrosion, and large diurnal temperature differences have become increasingly prominent in their impact on the safe and fault-free operation of frequency converters, leading to increasingly serious situations of equipment shutdown, production disruptions, and huge economic losses. Furthermore, addressing the operating environment of high-voltage frequency converters is crucial, especially in field operations and special working conditions. According to a report published by the U.S. military on the impact of the electrical environment on the safety of electronic equipment, 80% of equipment failures were attributed to environmental factors, including 55% due to temperature, 25% to humidity, 12% to dust, and 13% to vibration and electromagnetic noise; only 20% of equipment failures were caused by circuit design and component quality issues. This clearly demonstrates the significant impact of the environment on the safety of electrical equipment. Figures 1-3 show the impact of the environment on the main components of frequency converters.
(3) High-voltage frequency converters generate 3-4% heat loss during operation. A solution for controlling the operating temperature of the frequency converter is needed to ensure it operates under permissible environmental conditions. Long-term temperature variations, humidity, and dust directly degrade the characteristics of electronic components such as circuit board resistors and capacitors, potentially leading to malfunctions. Power electronic devices are even more sensitive to temperature, and temperature-related factors can directly cause them to malfunction. Altitude and temperature variations also necessitate derating, which is essentially a temperature-related issue. Therefore, special consideration and solutions are needed for the heat dissipation of the frequency converter's operating environment.
(4) Due to the special production environments such as mines, chemical plants, oil extraction, and offshore platforms, the application of high-voltage frequency converters needs to address a series of special working conditions, including explosion-proof, corrosion-proof, moisture-proof, salt spray-proof, high-temperature exposure-proof, ultra-low temperature operation, and skid-mounted transportation. Especially in production settings such as oil extraction and offshore oil platforms, all structures are skid-mounted; permanent building construction is not feasible. Therefore, providing a complete and comprehensive integrated technical solution is essential for the implementation of high-voltage frequency converter projects. The goal is to ensure that the equipment can be used directly upon placement and can be easily moved after use.
In summary, solving environmental problems in high-voltage frequency conversion applications should mainly include the following aspects, and should meet the corresponding technical standards and requirements shown in the attached table.
Technical solutions
To address the environmental challenges of high-voltage frequency converters in applications, including electrical, cooling, civil engineering, and low-voltage power distribution, there is an urgent need to develop a new product that integrates multiple technologies such as refrigeration, heating, environmental control, fire safety, space utilization, engineering mechanics, skid-mounted enclosure structure, and power distribution. This product would fundamentally solve all the problems required for frequency converter applications from the design and manufacturing stage. It would eliminate the direct impact of environmental factors on equipment operational safety, stability, reliability, lifespan, and power electronic component failure rates. Furthermore, by controlling environmental conditions, it would improve product performance, slow down high-temperature aging, and extend service life and mean time between failures (MTBF). Simultaneously, it must be easily movable and transportable, eliminating the need for on-site installation and commissioning, and allowing for convenient direct transport and use with equipment used in oil drilling and extraction.
This type of product must be independent of ordinary high-voltage frequency converters, yet closely integrated with them. Achieving integrated installation of multiple technologies and equipment, and developing a fully assembled frequency converter suitable for direct on-site use, will solve the following problems:
(1) The technical control process and engineering level are controllable.
The on-site equipment installation and spatial environment are determined through a streamlined production process. This minimizes the impact of environmental factors on product operational reliability and improves system operational stability.
(2) Product quality assurance is more controllable
Because the equipment is assembled and debugged before leaving the factory, it is fixed in place. Therefore, once it is in place on site, it can be powered on and used. The engineers become the delivery verification point for equipment operation and factory inspection, which is no longer a repetition of the production process but an extension of product quality assurance.
(3) The project execution cycle is more controllable
Because product manufacturing addresses on-site installation and space requirements during the manufacturing process, it eliminates the need for complex on-site engineering issues such as building, lighting, power distribution, waterproofing, civil construction, quality control, construction safety, and project supervision.
(4) Project quality is controllable
By adopting unified control procedures, technical standards, and professional personnel, the impact of uncertainties such as technical standards, personnel skills, and project quality on equipment environment and operational stability and reliability during on-site project implementation is avoided.
(5) Equipment transportation and storage are more convenient and energy-saving.
Previously, equipment needed to be packaged at the factory and unpacked on-site, resulting in waste of wood that could not be reused. Now, with integrated manufacturing, the equipment's appearance serves as both packaging and the building structure upon arrival, eliminating the need for warehouse storage and allowing it to be placed in open space.
(6) The project construction period is controllable
With the inverter featuring an outdoor, fully-assembled enclosure, the equipment can be installed immediately upon arrival at the site. Once the site location is determined, unloading and installation can be completed on-site. This eliminates the need for on-site organization of unpacking, transportation, and placement, shortening the equipment delivery and operation cycle by two-thirds.
(7) Simple electrical construction
The outdoor frequency converter provides an external high and low voltage terminal box, which can be directly connected to the field wiring, making the construction of the frequency converter as simple as the installation and wiring of a motor.
(8) Shorter equipment commissioning cycle
Once the equipment arrives and wiring is completed, it can be powered on and tested. There is no need to repeat the equipment assembly and inspection work.
(9) The equipment space environment is completed in one step.
There's no need to solve problems related to cooling, dehumidification, lighting, power distribution, fire protection, emergency lighting, and emergency ventilation. The equipment is manufactured with these solutions tailored to your specific needs.
Achieve energy savings in packaging, storage, and transportation, avoiding waste caused by the non-reusability of equipment packaging boxes. Embodies the concept of environmental protection and energy conservation, saving on wood consumption.
Feasibility application analysis
Outdoor integrated structure box-type frequency converter (abbreviated as: outdoor box-type frequency converter) is a new type of frequency converter that is manufactured and installed directly in a skid-mounted box structure, and integrates multiple technologies and equipment into a whole. It is suitable for direct on-site use outdoors.
The successful development of the outdoor box-type frequency converter structure has solved the investment cost problem in the application of high-voltage frequency converters and improved the system's adaptability. The enclosure structure of the outdoor frequency converter increases the protection level of the frequency converter from IP20 to IP43, fully meeting the application requirements of the frequency converter in harsh environments such as high dust, high temperature, and hazardous gases, and is suitable for use in highly polluted and harsh environments such as field operations, petroleum, petrochemical, mining, and cement industries.
Meanwhile, outdoor box-type frequency converters solve numerous problems in frequency conversion application environments, including electrical, cooling, civil construction, and low-voltage power distribution. They are designed and manufactured as a whole, eliminating the need for cumbersome on-site construction and multi-disciplinary coordination. More importantly, the use of box-type frequency converters provides space and a simpler means to solve external problems. Frequency conversion control and energy saving are directly integrated into the enclosure, allowing for direct application near motors, inlet baffles, valves, and other equipment requiring energy-saving modifications, eliminating the need for large-scale changes and construction costs. This makes the implementation costs of turnkey projects controllable and project investment costs traceable.
The emergence of outdoor box-type frequency converters has solved the problem of frequency converters needing to be installed and debugged on-site. Currently, high-voltage frequency converters are usually transported in separate parts, and then assembled, wired, and debugged on-site. This introduces uncertainty into the process control of whole-machine assembly and testing during production, which involves multiple independent departments for implementation and process control, and finally inspection and shipment by the quality department.
By assembling engineering products into a complete production process, not only are repetitive tasks simplified and labor costs saved, but more importantly, product quality becomes more controllable upon arrival at the site. The previous method of secondary disassembly and assembly is replaced by engineering personnel becoming the final quality control step after the product has undergone factory inspection and is transported to the site for operation. This replaces the repetitive process of simple reassembly, inspection, debugging, and commissioning. In this way, quality control during factory production is transformed into a crucial link in ensuring product quality on-site. Previously, disassembling and transporting equipment partially blocked the transmission of factory inspection results, preventing 100% transfer. This is now ensured through the training and management of on-site engineering technicians. It's even simpler than installing a high-voltage motor. On-site, all that's needed is to connect the high-voltage cable and it's ready to use, solving the problem of needing to install and debug the frequency converter on-site.
It is evident that the emergence of outdoor enclosure frequency converters provides a manufacturing platform for engineering applications of frequency converters. Project implementation no longer relies on on-site engineering but can be directly provided through manufacturing, significantly reducing project implementation cycles and costs. This allows projects to be manufactured like products, pioneering a new application model for high-voltage frequency converters. The integration level is higher, the technology integration and equipment compatibility are better, and the controllability of project implementation has increased from 35% in engineering implementation to over 80%, truly achieving standardized process control and standardized project management.
Conclusion
The development of outdoor box-type frequency converters represents an integrated embodiment of high-voltage frequency converter application technology, truly transforming engineering products into manufactured products and achieving standardization in process control and project management. The integrated box-type frequency converter structure applied to the converter body is another successful transfer and technological innovation of engineering application technology, holding significant practical importance in broadening the application fields and directions of high-voltage frequency converters.
