Permanentmagnet-Synchronmotoren maximieren Effizienz

Ensuring efficiency is important in every industry. This applies even more to critical infrastructure facilities such as sewage treatment plants that run continuously. Therefore, the selection of the optimal geared motor to efficiently meet these requirements can represent a convincing combination of economy and increased environmental protection. This is exactly what Bauer Gear Motor, a leading brand of the Altra Industrial Motion Corporation, has achieved for an eccentric screw pump in the Bayreuth sewage treatment plant in Germany.

Bauer Gear Motor is a global leader in geared motor technology – always one step ahead when it comes to supplying high-performance drives with a high degree of efficiency. Since the company was founded in 1927, Bauer Gear Motor has focused on optimal motor and gearbox solutions that offer operators application security while safeguarding investments (return on investment, ROI) and optimizing overall energy consumption.

This is important for the field of water treatment. In Bayreuth, progressive cavity pumps are required to operate almost continuously 365 days a year. With such requirements, an unsuitable motor can result in high costs for the operator. Oversizing the motor, combining it with the wrong components, missing the operating point or choosing the wrong gearing can have a negative effect on long-term energy efficiency. The specification of an optimal drive solution for this application in cooperation with the pump manufacturer was the challenge of the plant operator for Bauer.

As you would expect from a global technology leader, Bauer had a solution. In cooperation with the pump manufacturer, Bauer discovered that the installed 15 kW IE3 asynchronous motor (ASM) can be reduced to a 5.5 kW IE3 drive using PMSM technology.

Just reducing the size of the motor naturally increases energy efficiency, but the real advantage lies in the design of the PMSM drives from Bauer. An exceptionally efficient rotor design with special permanent magnets offers energy savings and improved environmental compatibility compared to conventional motors. Heat losses from the rotor are eliminated and the total losses are reduced by 25%, resulting in a consistent increase in motor efficiency of over 10% compared to competitive drives. These properties ensure a high level of efficiency even with varying operating requirements.

Other eccentric screw pumps in the sewage treatment plant are still operated with ASM variants, so that Bauer and the operator were able to make a direct comparison. When both the ASM and the PMSM variants are operated at constant speed at 25 Hz, the PMSM provides a higher level of efficiency across the entire characteristic curve, especially at low loads. At variable speed under part load conditions, the PMSM was even more efficient. At low speed and load, the PMSM achieves an efficiency of 85%, while the ASM only achieves 65%. This illustrates the wide range of partial loads and speeds that the PMSM, which is efficient due to its design, covers.

The advantages for the application are manifold. Eccentric screw pumps work at different speeds and operating points depending on the requirements, which corresponds to the wide partial load and speed range of the PMSM. In addition, this area offers a higher overload capacity, which is advantageous if another pump fails on site and the same operating requirements are distributed among fewer pumps. If the installed motors offer a higher overload capacity, this requirement can easily be met and availability ensured. A high starting torque is another typical PMSM characteristic that is important when pumping liquids. The miniaturization of the motor also makes future maintenance easier as the smaller motor can easily be replaced if necessary.

The main advantage for the operator, however, was the increase in efficiency across the entire range of requirements. An improvement in overall efficiency of at least 10% over the annual operating cycles led to considerable cost savings of up to € 9,000 per pump per year and in addition to environmental benefits. In addition to savings in energy costs, the operator can easily comply with limit values ​​for CO ₂ emissions, which are becoming increasingly strict in all industrial sectors. In combination with the design-related performance and reliability of the PMSM, which is predestined for variable operating conditions, the operator moves in the optimal efficiency range.

Captions:

Image 1: Eccentric screw pumps work at different speeds and operating points depending on the requirements, which corresponds to the wide partial load and speed range of the PMSM.

Fig. 2:  The attached frequency converters send a constant data stream to the programmable logic controller (PLC) via the PROFINET connection. In this way, the status of each individual unit can be monitored remotely.

Image 3:  Bauer Gear Motor offered an innovative permanent magnet synchronous motor (PMSM) solution that offers improved efficiency and greater economy for a sewage treatment plant in Bayreuth, Germany.