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Control method and apparatus for a centrifugal chiller using a variable speed impeller motor drive

  • US 5,355,691 A
  • Filed: 08/16/1993
  • Issued: 10/18/1994
  • Est. Priority Date: 08/16/1993
  • Status: Expired due to Term
First Claim
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1. A controller for adjusting the capacity of a variable capacity centrifugal compressor driven by a motor, the controller adapted for adjusting the capacity of the compressor in response to demand while minimizing electric power consumption and avoiding surge conditions, comprising:

  • means for establishing a dimensionless plot of possible points of compressor operation relating the pressure coefficient and the capacity coefficient of the centrifugal compressor;

    means for determining the current operating point of the centrifugal compressor on the plot;

    means for determining a region of actual surge on the plot;

    means for plotting a dynamic surge boundary control curve proximate the region of actual surge; and

    means responsive to variations of the region of actual surge and the surge boundary control curve for controlling compressor capacity by varying the opening of the inlet guide vanes and varying the speed of the compressor to move the operating point of the compressor proximate the surge boundary control curve.

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