AC Motor Controllers and Drives
Capacity Controls support reciprocating compressors. .
Press Release Summary:
Eliminating electromagnetic compatibility issues, entry-level CRII Mechanical Capacity Control has no influence on network quality in buildings. Modulation range for 2, 4, and 6-cylinder compressors is 10–100%. With VARISPEED Series, integrated suction gas-cooled frequency inverter and compressor form compact unit and all components are factory mounted. Control enables small and medium-sized reciprocating compressors to be operated at frequency up to 87 Hz.
Original Press Release:
Efficient Capacity Controls for Cost Savings
Depending on an application’s operating conditions and refrigerant, two solutions are available for capacity control in reciprocating compressors
VARISPEED – the convenient solution: compressor and frequency inverter are a unit
CRII – the inexpensive solution: mechanical capacity control
Nuremberg/Sindelfingen, -- Flexibility and an extensive range of applications take priority at BITZER, the compressor specialist, including when it comes to its technologies for capacity control in reciprocating compressors. Refrigeration and air conditioning engineers can choose between the VARISPEED compressor series with integrated frequency inverter or speed control provided by the CRII mechanical capacity control. The different concepts offer individual benefits, increase energy efficiency and reduce life cycle costs.
Each application is unique, which is why BITZER refrigeration compressors, like the capacity controls, are specially tailored for specific requirements. Both mechanical capacity control and capacity control based on speed adjustment have their specific benefits under the prevailing operating conditions.
Frequency inverters fundamentally have a soft start characteristic combined with low starting currents when starting the compressor. What’s more, they don’t work in stages and are therefore the optimal solution in terms of control, as the desired evaporation temperature can be selected with the utmost precision. If part-load operation is the primary mode, systems with an electronic frequency inverter are more efficient than mechanical systems due to limited switch cycles. A disadvantage compared to mechanical capacity control: the investment costs for electronic frequency inverters are somewhat higher.
CRII: the inexpensive path to optimised capacity control
The CRII mechanical capacity control, which BITZER developed from its predecessor, the CR capacity control, is the entry-level model and an inexpensive variant. Now it boasts much fewer control deviations and a much larger range of control. Compared with compressors operated with frequency inverters, the CRII achieves somewhat lower efficiency levels in the lower part-load range. However, this is of little importance when it comes to systems with several compressors and large-volume cooling positions. The modulation range for two, four and six-cylinder compressors is between 10 and 100 per cent. BITZER presented its mechanical capacity control, including for transcritical CO2 applications, for the first time at the Chillventa 2016 trade fair in Germany. One of the benefits of the CRII capacity control: electromagnetic compatibility is not an issue and the mechanical solution has no influence on network quality in buildings.
VARISPEED: the compact solution
The VARISPEED product series is the most simple frequency inverter solution for small and mediumsized reciprocating compressors, as it represents a compact, reliable and convenient option: the suction gas-cooled frequency inverter and the compressor form a compact unit and all the components are factory mounted, making separate installation a thing of the past. The components are fully wired, optimised for EMC – refrigeration and air conditioning engineers don’t have to put any thought into mounting or the frequency inverter and motor wiring. Due to their special design, VARISPEED compressors can be operated at a frequency of up to 87 Hz.
BITZER US, Inc. is a subsidiary of the BITZER Group of 36 companies. BITZER is the world’s largest independent manufacturer of A/C and Refrigeration compressors with sales companies and production sites for reciprocating, screw, and scroll compressors as well as pressure vessels all over the globe. In 2015, 3,400 employees generated sales of 686 million euros.