The “efficiency booster” for heat pumps
KEB’s high-speed drives operate turbo compressors
With the increasing use of heat pumps, the turbo compressor – as a key component of the heat pump – is also coming under greater focus. The specific technical requirements of these compressors are particularly striking: the control of high speeds is just as essential as, for example, motor protection. With the COMBIVERT F6 high-speed drives, KEB Automation has created a solution that is optimised for use in modern heat pumps and helps to increase the system’s efficiency.
More than two-thirds of energy consumption in industry is accounted for by the generation of process heat – the thermal energy required, for example, to melt, dry or heat materials. This makes the provision of heat for production, conversion and processing operations by far the largest industrial energy consumer. At the same time, the use of innovative technologies offers significant potential for savings and opportunities to decarbonise process heat.
Modern heat pumps offer an attractive option for converting waste heat into climate-neutral energy. Temperatures in the range of 100 to 200 degrees Celsius are not uncommon. Efficient permanent magnet motors form the heart of the heat pumps in this process. They operate at high speeds and enable high efficiency, which is particularly evident in applications with a small temperature range.
Why drives are used in heat pumps
These high speeds also mean that not every drive controller is designed to handle the drive tasks. KEB has therefore developed the COMBIVERT F6 High-Speed Drives specifically for such applications. “The High-Speed Drives control all types of motors at high speeds of up to 120,000 revolutions per minute, either without a sensor or with a sensor. This meets the requirements for the reliable operation of compressors in heat pumps,” says Thomas Tottleben, Sales Engineer at KEB Automation.
Power ratings of up to 450 kW, motor currents of 800 A and output frequencies of up to 2,000 Hz for maximum precision are possible. The aim is to be able to provide high torque across the entire speed range at all times. In combination with the speed monitoring integrated into the drives and the appropriate sine wave filtering technology, motor protection and optimal system performance are ensured. “We see the drive controllers as an integral part of an overall system comprising the drive, load control and sensor technology. This also means that the frequency inverter reacts immediately to load changes or faults,” says Tottleben. It is not only the high speeds of turbo compressors in heat pumps that make the appropriate inverter technology necessary; the possibility of stepless speed control also plays an important role. Thanks to demand-based load control, the heat pump can compress more or less refrigerant as required. The result: higher efficiency in partial-load operation and a significant reduction in electricity consumption.
Soft start protects components
The use of high-speed drives in heat pumps also leads to lower maintenance costs thanks to the soft start. “With our drive solutions, we control the start-up of the motor and can thus minimise electrical and mechanical stresses. To achieve this, the COMBIVERT F6 high-speed drives increase the voltage step by step, resulting in a smooth and gentle start-up of the motor,” says Tottleben. Mechanical shocks and load peaks can be avoided in this way. This protects the motor windings and mechanical components and, overall, leads to a longer service life for both the turbo compressor and the heat pump – whilst also reducing operating costs here, as less energy is used during start-up.
