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EP-4244487-B1 - SURGE CONTROL SYSTEMS AND METHODS FOR DYNAMIC COMPRESSORS

EP4244487B1EP 4244487 B1EP4244487 B1EP 4244487B1EP-4244487-B1

Inventors

  • PEREVOZCHIKOV, MICHAEL M.
  • SWALLOW, MATTHEW J.

Dates

Publication Date
20260506
Application Date
20211210

Claims (8)

  1. A system (400) comprising: a dynamic compressor (100, 404) comprising: a motor (108, 406) having a driveshaft (104) rotatably supported within the dynamic compressor (100); and a compression mechanism (106, 116, 407) connected to the driveshaft (104) and operable to compress a working fluid upon rotation of the driveshaft (104); a variable frequency drive -VFD- (416) including a sensor (408) configured to sense a current (901) provided to the motor (406); a speed sensor (417) configured to detect a speed of the motor; and a controller (410) connected to the motor (108, 406), the controller (410) comprising a processor (411) and a memory (412), wherein the memory (412) stores instructions that program the processor (411) to: operate the motor (108, 406) using the VFD (416) to compress the working fluid; receive signals representing the current (901) from the VFD (416) to the motor (406); and determine when a surge event has occurred based at least in part on the received signals representing the current (901) from the VFD (416) to the motor (406) by determining a difference between a previous current and a present current based on the received signals representing the current (901) from the VFD (416) to the motor (406) exceeds a surge threshold, characterized in that the surge threshold is a variable threshold and the instructions program the processor (411) to determine the surge threshold based at least in part on the detected speed of the motor (406) when the signal representing the present current is received.
  2. The system (400) of claim 1, wherein the memory (412) stores further instructions that program the processor (411) to determine the previous current by averaging a plurality of the signals representing the current (901) from the VFD (416) to the motor (406) that are received by the processor (411) before receiving a signal from the VFD (416) representing the present current from the VFD (416) to the motor (406).
  3. The system (400) of claim 1, wherein the memory (412) stores further instructions that program the processor (411) to determine a magnitude of the surge based on the difference between the previous current and the present current.
  4. The system (400) of claim 3, wherein the memory (412) stores further instructions that program the processor (411) to store an indication of the occurrence of the surge event and the determined magnitude of the surge in the memory (412).
  5. The system (400) of claim 1, wherein the dynamic compressor (100, 404) is a centrifugal compressor (100), and the compression mechanism is an impeller (106, 116).
  6. The system (400) of claim 5, wherein the system is an HVAC system, and the working fluid is a refrigerant.
  7. A method (1200) of detecting occurrence of a surge event in a dynamic compressor (100, 404) including a motor (108, 406) and a compression mechanism (106,116, 407) connected to the motor (108, 406) and operable to compress a working fluid upon operation of the motor (108, 406), the method (1200) comprising: operating (1201) the motor (108, 406) to compress the working fluid; receiving (1202) signals representing the current (901) provided to the motor (108, 406) to operate the motor (108, 406); and determining (1203) when a surge event has occurred based only on the received signals representing the current (901) provided to the motor (108, 406) and a surge threshold by: determining a difference between a previous current and a present current based on the received signals representing the current (901) provided to the motor (108, 406); and determining the surge event has occurred when the difference exceeds the surge threshold, characterized in that the surge threshold is a variable threshold, and determining (1203) when a surge event has occurred comprises determining the surge threshold based at least in part on a detected speed of the motor (108, 406) when the signal representing the present current is received.
  8. The method (1200) of claim 7, wherein determining the previous current comprises averaging a plurality of the signals representing the current (901) provided to the motor (108, 406) that are received before receiving a signal representing the present current being provided to the motor (108, 406).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS FIELD The field of the disclosure relates generally to control systems, and more particularly, to control systems for machines including dynamic compressors. BACKGROUND Dynamic compressors, including centrifugal compressors, are used in many applications, such as HVAC. Centrifugal compressors have a driveshaft operatively connected to a motor between compression mechanisms or impeller stages that is supported by gas foil bearings. The driveshaft can be positioned between impeller stages so the impellers are rotated at a rotation speed to compress the refrigerant to a selected pressure in an HVAC system. The compressor bearings are typically provided with one or more features to reduce friction between the compressor bearing and the driveshaft. Once the shaft is spinning fast enough, gas pushes the foil away from the shaft so that no contact occurs. The shaft and gas foil bearing are separated by the gas's high pressure, which is generated by the rotation that pulls gas into the bearing via viscosity effects. A high speed of the shaft with respect to the gas foil bearing is required to initiate the gas gap, and once this has been achieved, no contact should occur. These bearings have several advantages over other bearings including reduced weight, stable operation at higher speeds and temperatures, low power loss at high speeds, and long life with little maintenance. Compressor surge events cause accelerated wear of the compressor and compressor components, including bearings. Surge is a characteristic behavior of a dynamic compressor that can occur when the head developed by the compressor is insufficient to overcome the system pressure at the discharge of the compressor. Once surge occurs, the output pressure of the compressor is drastically reduced, resulting in flow reversal within the compressor. When a dynamic compressor surges, there is an actual reversal of gas flow through the impeller. The surge usually starts in one stage of a multistage compressor and can occur very rapidly. Compressors are especially susceptible to surge events during startups and shutdowns due to the lower operating speeds. The severity of surge events and the damage they cause increases with compressor speed. This background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. JP H11 62887 A, WO 2014/191051 A1, EP 2 765 313 A1, US 2017/002820 A1, US 5 746 062 A and US 4 581 900 A are all relevant prior art documents. SUMMARY According to the present invention, a system comprising a dynamic compressor capable of determining when a surge event has occurred according to claim 1 and a method of detecting occurrence of a surge event in a dynamic compressor are provided. Preferred embodiments thereof are provided in the dependent claims One aspect of the present invention is thus a system which, inter alia, includes a dynamic compressor, a variable frequency drive (VFD), and a controller. The dynamic compressor includes a motor having a driveshaft rotatably supported within the dynamic compressor, and a compression mechanism connected to the driveshaft and operable to compress a working fluid upon rotation of the driveshaft. The VFD includes a sensor configured to sense a current provided to the motor. The controller is connected to the motor and includes a processor and a memory. The memory stores instructions that program the processor to operate the motor using the VFD to compress the working fluid, receive signals representing the current from the VFD to the motor, and determine when a surge event has occurred based at least in part on the received signals representing the current from the VFD to the motor. Claimed, as part of the system, is a controller for a dynamic compressor that includes a motor and a compression mechanism connected to the motor and operable to compress a working fluid upon operation of the motor. The controller includes a processor and a memory. The memory stores instructions that program the processor to operate the motor to compress the working fluid, receive signals representing the current provided to the motor to operate the motor, and determine when a surge event has occurred based at least in part on the received signals representing the current provided to the motor. Another aspect of the present invention is a method of detecting occurrence of a surge event in a dynamic compressor including a motor and a compression mechanism connected to the motor and operable to compress a working fluid upon operation of the motor. The method include