Direct current (dc) input variable-speed compressors are used in a variety of mobile applications, including climate control, which offers significant savings.

You can count on good climate control equipment to do two things - cost a fortune and increase ridership. If you would like another option your alternative is poor climate control equipment that costs a fortune and reduces ridership. Not the most appealing of choices but one all to familiar to design and maintenance engineers throughout the world. It's not so much the initial cost, but the ongoing operation and maintenance that really adds up. Energy cost alone can stress operating budgets. Given the significant cost and absolute necessity of good climate control, it would seem to be one of the most logical places to focus cost-cutting research and development.

Significant savings

Rather surprisingly, this has not been the case. Certainly there have been improvements in controls systems and the adoption of more environmentally friendly refrigerants. However, the major components, most notably the compressor and drive motor, have remained essentially unchanged for several decades. Now, thanks to recent advances in brushless dc motor (BLDC) design and in motor control, there is reason for optimism. The emergence of compact, variable-speed, hermetically sealed air conditioning compressors has the potential to provide significant advantages in every aspect of climate control. With the opportunity to reduce energy consumption by 30 - 40 per cent and cut maintenance costs in half, some of the world's leading ac system engineers are starting to wake up to the potential.
In addition to saving money, variable-speed compressor technology can also improve rider comfort by offering a more temperature stable environment.
Masterflux is delivering direct current (dc) input variable-speed compressors for use in a variety of mobile application. Climate control engineers who replace their simple-speed open-drive units with one of the new compressors will gain some immediate advantages. However, it is important to recognise the most important benefits will only be obtained by fully incorporating the technology into the overall system design. The best systems will use more sophisticated micro-processor-based controls to anticipate changes in heat load and regulate compressor and blower speed accordingly. By taking advantage of the dc input capability, engineers can simplify their power input and eliminate the problematic inductive startup surges of an ac induction motor. Since the compressor is hermetically sealed it is now possible to completely eliminate refrigerant leaks if the hermetic concept is carried through to the other components.

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Masterflux is based in Annapolis, MD, USA. www.masterflux.com