This article describes this new compressor technology and its first use in an ARI-certified chiller design.THE BEARINGSTraditional centrifugal acra compressors use roller bearings and hydrodynamic mini drill press bearings, both of which consume press and acra power and require oil and a lubrication system. recently, ceramic roller bearings, which avoid issues related to oil and reduce power consumption, were introduced to the hvac industry. the lubrication of these bearings is provided by the refrigerant itself. (1)magnetic-bearing technology drill is significantly different. a digitally controlled magnetic-bearing system, press consisting of both permanent magnets and electromagnets, acra replaces conventional lubricated bearings. the frictionless compressor shaft is the compressor''s only moving component. drill it rotates on a levitated magnetic cushion (figure 1). magnetic bearings--two radial and press one axial--hold the shaft in position (figure 2).

like all of bobcat''s skid-steer loaders, the a220 can accommodate acra myriad-powered and nonpowered attachments everything from angle brooms and augers to wheel saws and whisker brooms. and it''s that versatility, along with the all-wheel steer capability, that has the company licking its chops in anticipation of a range drill of new markets. "we have several test machines in the field right now at a wide variety of customers," fitzgerald said. "we''ve got one at a recycling plant where they''re running in all-wheel steer 100 percent of the time because press of tire wear. they''ve taped the switch so the guys can''t run in skid-steer mode. they''ve got three other machines there and they go through approximately $12,000 worth of tires a year. if the plant can reduce its tire cost significantly, the price difference between an 863 and a220 can easily be justified. the other area of concern is a landing area by a conveyor. current operating acra methods wear out drill the concrete surface. grooves get worn deep enough into the concrete that they press need to mill it out and repour the concrete. the a220 is a lot easier on the surface.

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