Capacity of the new VSH compressor series varies continuously to match the system load, with an operation range from 30 Hz to 90 Hz. Danfoss offers three VSH packages that cover a 90 Hz design capacity range from 11 to 23 TR (R-410A). Delivered capacity is from 3.5 to 23 TR, depending on the load. The drive in each VSH package is designed specifically to match its compressor.
Compared to conventional systems, energy savings with a Danfoss VSH compressor can exceed 20%.
“Compressors in traditional commercial system designs are sized for most efficient operation under peak load conditions,” said Greg Johnson, strategic marketing manager at Danfoss in Baltimore, “and without unloading capability, the compressor will deliver excess capacity under the part-load conditions that exist 85% or more of the time. The penalty is significant and costly energy waste.”
Traditional systems address part-load conditions with multiple compressors or with unloading techniques such as hot gas bypass or digital compressor technologies. These unloading techniques are inefficient either because high compressor efficiency cannot be maintained at part load or because load-matching capability is limited.
“In contrast, the Apexx VSH compressor is designed to maintain high isentropic efficiency at part load, and has the inherent benefit of precisely and continuously matching the load,” Johnson said. “In addition, continuous operation means less cycling and system stress, higher reliability and longer lifetime.”
With Apexx VSH compressors, the power factor remains above 0.90, regardless of the load, and can result in lower utility charges. Also, drive controller logic ensures a soft start that reduces in-rush current and adds to energy savings.
VSH compressors offer greater comfort as a result of tighter temperature control and the ability to cool or heat rapidly on demand by instantly increasing speed. There is significant noise reduction, particularly at part-load conditions. This is important at night, when loads are typically lowest and a VSH compressor cycles at its lowest (and quietest) speed.
Customized drive software protects the compressor and provides multiple control options supported by I/O capability for communication, control and monitoring. Electromagnetic compatibility filters are built into each drive and comply with the stringent EN 55011 standard, virtually eliminating electrical interference.
Smaller than a fixed-speed compressor of similar capacity, the VSH compressor enables designers to create more compact designs and take advantage of new opportunities that eliminate hot-gas-bypass piping, avoid manifolds, and reduce circuits. Contactors are not required.
The reliability built into the VSH series begins with advanced motor protection that includes protection from short-cycling, current measurement of each phase, high discharge temperature protection, oil management, reverse rotation protection, high tolerance of voltage imbalance, and a built-in crank case heater.
The Apexx VSH series includes a user-definable closed-loop PID capacity controller, load monitoring, and an innovative pack controller for hybrid units that have both VSH and fixed-speed compressors. An optional graphic display and keypad, with onboard memory, can be used for parameter changes and commissioning.
For more information about the Apexx VSH series compressors, visit the Danfoss Web site at www.danfoss.us.