Next generation: Variable-speed compressors
Why use a variable-speed system?
Refrigeration compressors are normally selected to correspond with maximum expected system loads. Since loads vary throughout the day and throughout the year, the compressor designed for maximum load turns out to be oversized during long stretches (it has been estimated that on average systems are running partially loaded more than 65% of the time).
The conventional regulation systems to compensate for this excess capacity are on/off control,pressure-regulation unloading valves or hot-gas bypass. In comparison with these methods,the Maneurop® variable-speed compressor offers a superior energy-efficient solution.
Improved process control and accuracy
In a normal hermetic refrigeration compressor, the electrical motor and crankshaft rotate at a speed of 2900 rpm (50 Hz), which locks the compressor into a single fixed capacity. In a Maneurop® variable-speed compressor, motor rotation speed may be varied from 1800 to 5400 rpm. Capacity is controlled directly at the source, thereby eliminating any temperature overshoot.
Smaller-sized compressor
The built-in variable speed function pertains to both speed increase and speed reduction.
Thanks to speed increase,the selection of a variable-speed compressor can be scaled back several sizes smaller than a comparable compressor running at fixed speed. The nominal compressor capacity can then be easily aligned with the nominal system heat load.
Speed reduction provides the opportunity,during periods of low system load, for compressor capacity to be decreased, consequently reducing power consumption. Moreover, on/off cycling can be reduced to the bare minimum or avoided altogether.
Lower operating costs
Energy savings generated from doing away with the need to design compressors that meet extreme conditions encountered just a few days a year.
Energy savings generated from doing away with the need to operate an oversized compressor for extended periods of time.
Energy savings generated thanks to VTZ compressor + AKD converter capacity being so well synchronized with the actual heat load for enhanced system efficiency, not only over short periods... but all year round!
Precise regulation and low noise
The Maneurop® variable-speed compressor progresses smoothly from minimum to maximum capacity range. No predefined capacity increments have been built in, a feature that allows precisely maintaining the desired evaporating temperature and room or process temperature while keeping fluctuations to a minimum. Accurate temperature control remains the key to quality food processing activities and food storage.
During nighttime hours as heat losses diminish, the compressor runs at lower speeds, thereby generating less noise. Moreover, the bothersome system start-stop noises will, to a large extent, be eliminated.
Variable speed: Great opportunity for saving energy
One of the most attractive aspects of variable-speed technology lies in its energy savings potential.The inverter-driven, variable capacity concept is used today in several refrigeration applications, yet could still be employed on a much wider scale.
Many different refrigeration and process cooling applications feature thermal load profiles that suggest their suitability for innovative, variable-capacity systems employing specialized Maneurop® VTZ compressors and Danfoss AKD frequency inverters.
