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Shredding is an essential step in the processing of solid industrial and municipal waste (recyclable waste). There are several levels of shredding depending on the recyclable materials. Shredders are involved in the recycling process.
Though they are intended for the same purpose, shredders are different by design and are divided into grinders:
- with one shaft;
- with two shafts; and
- with four shafts.
The main applications for shredders are:
Bulky waste, including old cars;
- scrap metal;
- household waste;
- industrial hazardous waste;
- waste tires;
- plastic; and
- cardboard.
Triol Corporation sees the following technological and economic challenges facing the shredder owner
- Equipment lifetime extension
Straight motors start and no torque limitation leads to accelerated motor and mechanism degradation, which leads to additional repair costs and increased costs of recyclable materials processing.
- Non-stop process
The appearance of abnormal equipment shutdowns related to the quality of the supply network and delayed recyclables supply lead to an increase in processing costs, which reduces the competitiveness in the market.
- Operation in weak power mains
Unacceptable mains voltage sags and emergency shutdowns caused by non-standardized mains parameters can lead to penalties for exceeding peak power consumption and can result in additional financial losses.
- Energy consumption optimization
High competition in the recycling market requires the maximum reduction of costs for the technological process. One of the major items forming the recycling price is the electricity consumed by the equipment. Its consumption reduction leads to a decrease in the cost of processing.
- Reducing the recycling cost
The recycling market requires constant cost minimization to maintain competitiveness. Non-optimal technological process, forced downtime and large (peak) power consumption greatly influence the cost of processing industrial and domestic wastes and their optimization, which is the enterprise's priority task.
- Work in conditions of high air humidity and conductive dust
The creation of dust is possible during waste recycling of conductive materials, which means that equipment with IP20, IP31, IP41 enclosures is unsuitable for use. It is necessary to use protected equipment that allows one to work in harsh environments.
- Installation in a limited space
Recycling facilities are not always able to allocate enough space to install new equipment, and the new building construction for a frequency drive can cost around $50,000, which is not acceptable to the end-user. Therefore, the preferred option for the end-user is equipment with a minimal footprint that can be installed in an existing facility.
- Adapting to the possibilities of local ventilation and equipment maintenance
Existing production facilities include communications, particularly the ventilation system, so the preferred option for the end-user would be one that allows the newly installed frequency drive to be integrated into the existing ventilation system.
- Outdoor application
Some end-user objects have no possibility of placing the frequency drive indoors. But the construction of a new room may be economically unreasonable or fundamentally impossible. Yet the newly installed equipment must be operated in the open air with an environmental temperature from -40 ° C to +40 ° C and almost 100% humidity.
The vector mode with the author's algorithms with motor torque limitation and motor speed control in Triol frequency drives provide reliable motor protection against overload and shaft breakage.
If a difficult to shred material enters the shredder, the motor develops a high torque. When the value of the torque generated by the motor reaches the limit value, the frequency drive reduces the motor speed to ensure a safe value of torque and, accordingly, the motor current.
Torque limitation algorithm
The brake application and release at 200% torque limit setpoint without shaft block.
Accurate torque and motor speed control provide a reduction in motor speed when the torque limit algorithm is triggered, allowing the material to be shredded at a lower speed without stopping the shredder.
Another interesting solution is the wedging mode with a smooth change of the shredder rotation direction in case of hard-to-grind waste. The mode allows one to grind the material without jamming the shredder by rotating it back and forth and to continue working without stopping.
Wedging mode
The kinetic buffering mode ensures the stable operation of the Triol VFD performing with an asynchronous motor, in case of the deep and asymmetrical supply voltage sags, and even in case of complete voltage failure.
In the advanced mode, the frequency drive performance is maintained by consuming a part of the kinetic energy of the rotating mechanism and then instantly restoring the set operating mode of the mechanism when the power supply is recovered. The operation time of the frequency drive in this mode for the shredder can be 5-10 periods of the mains voltage.
The Triol VFD operation oscillogram when the supply voltage sags are as follows:
The vector mode is based on the motor mathematical model and ensures smooth mechanism launch even at full load with nominal launch currents and without mechanical stress at launch. This allows using power cables for the motor and the frequency drive with a smaller cross-section, which reduces the possibility for damage and extends the service life of the shredder. Accordingly, this process reduces the cost of implementation, maintenance and repair of the shredder.
The two-stage power transformation in the Triol AT24 and AT27 frequency drives eliminate the negative effects of sags, fluctuations and mains voltage asymmetry.
The Triol AT27 VFDs are fully compliant with IEEE 519 standard without installing additional input filters and reactive power compensators. For the AT24 low-voltage frequency drives it is possible to install input passive filters.
The AT27 input current harmonics spectrum
The total THD of the current consumption does not exceed 5%.
The vector mode algorithm with shredder speed optimization reduces total motor power consumption through high-precision control and motor magnetic flux optimization. This reduces shredder power consumption by up to 10%.
The picture presents the result of the measurement of the apparent power on different frequencies with the rated current.
Energy consumption decrease
Another original algorithm by Triol allows one to reduce the shredder's power consumption by limiting peak operating modes and reducing consumption during technological downtime.
Depending on the technological process, the ratio of operating time to waiting time for recyclables may reach energy savings of up to 18%. The Triol AT27 frequency drive determines the optimum power consumption point for the shredder based on its operating cycle.
Reducing the cost of processing is also achieved by integrating the VFD and the entire shredder system into the shredding process automation system via RS-485 (Modbus RTU) and Ethernet serial communication interfaces. This is possible due to the advanced external interface of the frequency drives Triol AT24 and Triol AT27 series.
The regulation of the shredder drive motor speed depends on the volume of waste on the conveyor belt and the volume of shredded waste removed from the shredder. This process eliminates equipment downtime, ensures equal power consumption, limits the mains distortion, optimizes energy consumption, and increases productivity. As a result, all these parameters become available online to the shredder operator, allowing him to make accurate and timely decisions, leading to reducing costs for recycling.
The Triol AT27 line MV with IP66 (NEMA4) protection and the AT24 line UH with IP55 protection are solutions for recycling applications with high dust environments, including conductive dust. Both solutions have a dedicated cooling circuit, ensuring that the VFD will operate smoothly and reliably even in the toughest environments.
The Triol VFD AT27 line ED has the smallest dimensions in the world among variable frequency drives of its class at 4.2-13,8 kV.
The AT27 line ED saves on average 25-30% of the space used by the VFD. Read more about the design features of the AT27 ED line in our article "Dimensions of the AT27 Triol as the first competitive advantage." This advantage provides the opportunity to decrease the investment in the equipment location and reduce the return on investment.
The VFD Triol AT24 Line SD is a compact solution with all necessary options installed inside the cabinet. The minimum width of the cabinet with high power density and the possibility to install several frequency drives close together makes the AT24 SD suitable in any technical room.
The VFD Triol AT24 Line SD is a compact solution with all necessary options installed inside the cabinet. The minimum width of the cabinet with high power density and the possibility to install several frequency drives close together makes the AT24 SD suitable in any technical room.
The cooling fans are located entirely on the roof, making it easy to arrange the heat extraction of the Triol VFD by connecting the ventilation system directly to the roof of the VFD around the fans. The heat generated by the VFD in operation will not heat up the room but will be immediately discharged from the room, ensuring long-term and trouble-free equipment operation.
A wide range of AT27 lines for outdoor installation allows one to choose the best solution for the existing outdoor operation, thereby avoiding building additional constructions and saving significant investment costs in the future.
The technical advantages of the Triol AT24 and Triol AT27 VFDs enable a technological breakthrough in shredder operation and solve the owner's above-mentioned challenges.
