German railway company Deutsche Bahn AG, selected SR Drive^® powered air-cycle air conditioning for its latest ICE 3 high speed passenger trains.  The move to aerospace HVAC technology comes in response to growing concerns over the environmental impact of chemical refrigerants.

Air-cycle air conditioning is based on the simple concept of cooling air by forcing it to expand as it passes through a turbine.  In response to growing concerns over the environmental impact of chemical refrigerants, air-cycle systems have been applied into the railway market to meet today’s growing demand for environmentally friendly, reliable and easily maintainable air conditioning equipment.  In aircraft, air conditioning is powered by compressed air bled from the engines, however in a train, a high efficiency SR Drive^® motor drives a compressor to provide the source of air.

Air is compressed in two stages, firstly by the SR Drive^® motor compressor and then by the compressor side of a cold air unit.  The same air is continually cooled and returned around the circuit, transferring its cooling effect via heat exchangers into the carriages.
The variable speed SR Drive^® motor provides a soft start for the system and precisely matches the thermal load of the train carriages.  At maximum cooling, the motor power is 40kW at a speed of 23,000 rev/min.  

The unit is operated from a 670Vdc power converter and weighs less than conventional air conditioning, allowing it to be entirely roof mounted.