KR20230119662A - Surge Control Systems and Methods for Dynamic Compressors - Google Patents

Abstract

The system 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 coupled to the driveshaft and operable to compress a working fluid upon rotation of the driveshaft. (compression mechanism). The VFD includes a sensor configured to sense the current provided to the motor. The controller is coupled to the motor and includes a processor and memory. The memory operates the motor using the VFD to compress the working fluid, receives signals representing current from the VFD to the motor, and the received signal represents current from the VFD to the motor. stores instructions that program the processor to determine when a surge event has occurred based at least in part on

Description

Surge Control Systems and Methods for Dynamic Compressors

This application claims priority to U.S. Provisional Patent Application Serial Nos. 17/247,724 and 17/247,725, filed on December 21, 2020, the disclosures of which are incorporated herein by reference in their entirety.

The field of the present disclosure relates generally to control systems, and more specifically to control systems for mechanical devices comprising dynamic compressors.

Dynamic compressors, including centrifugal compressors, are used in many applications such as HVAC. Centrifugal compressors have a driveshaft supported by gas foil bearings, interlocked to a motor between the compression mechanisms or impeller stages. A drive shaft is positioned between the impeller stages so that the impellers are rotated at a rotational speed to compress the refrigerant to a selected pressure in the HVAC system. Compression bearings typically have one or more functions to reduce friction between the compression bearing and the drive shaft. Once the shaft turns fast enough, the gas pushes the foil away from the shaft and no contact occurs. Shaft and gas foil bearings are separated by the high pressure of the gas generated by rotation which draws the gas into the bearing by viscosity effects. A high rotation of the shaft relative to the gas foil bearing is required to initiate the gas gap, and once this is achieved no contact occurs. These bearings have several advantages over other bearings: reduced weight, stable operation at high speeds and temperatures, low power loss at high speeds and long life time with little maintenance. will be.

Compressor surge events accelerate the wear of compressor components including the compressor and bearings. Surge is a characteristic action of a dynamic compressor that occurs when the compressor's head is insufficient to overcome the system pressure at compressor discharge. Once a surge occurs, the output pressure of the compressor is significantly reduced, resulting in flow reversal within the compressor. A surge in the dynamic compressor actually creates a reverse flow in the gas flow through the impeller. Surges usually originate in one stage of a multistage compressor and can occur very rapidly. Compressors are particularly vulnerable to surge events during startup and during shutdown because of their low operating speeds. The severity of surge events and the damage they cause increases with compressor speed.

This background section is provided with the intention of introducing the reader to various technical aspects that may be related to various aspects of the present disclosure, described and/or claimed below. It is believed that this discussion will 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 descriptions are to be read to this effect and not to the effect of an admission that they are prior art.

One aspect of the present disclosure is a system that 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 coupled to the driveshaft and operable to compress a working fluid upon rotation of the driveshaft. (compression mechanism). The variable frequency driver includes a sensor configured to sense a current provided to the motor. The controller is connected to the motor, and the controller includes a processor and memory. The memory operates the motor using the VFD to compress the working fluid, receives signals representing current from the VFD to the motor, and the received signal represents current from the VFD to the motor. stores instructions that program the processor to determine when a surge event has occurred based at least in part on

Another aspect is a controller for a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor. The controller includes a processor and memory. The memory operates the motor to compress the working fluid, receives signals representative of a current supplied to the motor for operating the motor, and transmits at least to the received signals representative of the current supplied to the motor. Stores instructions that program the processor to determine, in part, when a surge event has occurred.

Another aspect is a method for detecting the occurrence of a surge event in a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor. The method includes operating the motor to compress the working fluid, receiving signals representative of current supplied to the motor to operate the motor, and the received signal representing current supplied to the motor. determining when a surge event occurred based only on the s and the surge threshold.

Another aspect is a system comprising a dynamic compressor and controller. The dynamic compressor includes a motor having a drive shaft rotatably supported within the dynamic compressor and a compression mechanism connected to the drive shaft and operable to compress a working fluid upon rotation of the drive shaft. The controller is connected to the motor, and the controller includes a processor and memory. The memory operates the motor to compress the fluid at a motor speed greater than the predicted minimum surge speed plus a control margin, and determines when surge events have occurred. and storing in the memory an indicator of each surge event that the processor determines has occurred and programming the processor to determine whether or not to take a protective action when the processor determines that a surge event has occurred. Save.

Another aspect is a controller for a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor. The controller includes a processor and memory. The memory compresses the fluid at a motor speed greater than the minimum surge speed predicted by operating the motor plus an adjustment margin, determines when surge events have occurred, and determines when surge events have occurred, and each of the surge events determined by the processor to have occurred. Stores an indicator of a surge event in the memory and stores instructions that program the processor to determine whether or not to take protective action when the processor determines that a surge event has occurred.

Another aspect is a method for controlling a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor. The method includes operating the motor to compress the working fluid at a motor speed greater than the predicted minimum surge speed plus a control margin, determining when surge events have occurred, and determining when the processor has occurred. storing an indicator of each surge event it determines, and determining whether or not to take protective action when the processor determines that a surge event has occurred.

There are various improvements to the features mentioned in relation to the aforementioned aspects. Additional features may be incorporated into the foregoing aspects. These improvements and additional features may exist individually or in combination. For example, various features discussed below in connection with any of the illustrated embodiments may be incorporated into any of the foregoing aspects, singly or in combination.

The following figures illustrate various aspects of the present disclosure.
1 is a perspective view of an assembled compressor;
FIG. 2 is a cross-sectional view of the compressor taken along line 2-2 in FIG. 1 with the outer conduit removed.
FIG. 3 is a cross-sectional view through a sleeve of the bearing housing shown in FIG. 2, showing a foil bearing assembly retained within the sleeve of the bearing housing using a pair of retaining clips; The drive shaft supported in the assembly) is illustrated.
4 is a cross-sectional view of another embodiment of a bearing housing suitable for use in the compressor of FIG. 1, retained within the bearing housing between a retaining lip formed within the bearing housing at one end and a retaining clip at the other end; A drive shaft supported in a foil bearing assembly is illustrated.
5 is an exploded view of the components of the foil bearing assembly arranged relative to the bearing housing and drive shaft.
6 is a block diagram of a control system for a dynamic compressor.
7 is a surge current characteristic graph for a dynamic centrifugal compressor.
8 is a speed graph for a dynamic centrifugal compressor.
9 is a current graph for a dynamic centrifugal compressor.
10 is a graphical relationship between current swing percent and speed percent for a dynamic centrifugal compressor.
11 is an operating map of a dynamic centrifugal compressor.
12 is a flow chart of a method for determining when surge events have occurred for a dynamic centrifugal compressor.
13 is a flow diagram of an exemplary embodiment of the method of FIG. 12 .
14 is a flowchart of a method for determining whether or not to take protective action when a surge event occurs for a dynamic compressor.
15 is a flow chart of an exemplary embodiment of the method of FIG. 14 .
Corresponding reference characters throughout the drawings indicate corresponding parts.

For brevity, examples will be given of centrifugal compressors with gas foil bearings (GFB). However, the methods and systems described herein may be applied to any suitable dynamic compressor. In the surge control system of the dynamic compressor, monitoring surge event occurrences, monitoring the number of surge events that have occurred, monitoring the severity of surge events, and determining surge thresholds ( surge thresholds, determining the relationship between motor speed and surge events, adjusting control margins to provide a larger surge margin, and Deciding whether or not to take protective action, such as generating alerts, stopping operation of machinery, etc., can prevent damage and increase the life of the centrifugal compressor. These steps make it possible to more accurately schedule preventive maintenance, increase the sensitivity of anti-surge controls, and reduce surge severity at start-up by holding the centrifugal compressor at a lower speed until stable. improve reliability by limiting surge severity, allow the system to continue to provide cooling by increasing the runtime in the centrifugal compressor before faulting and shutting down, and estimate maps ( By limiting the severity of surges by activating an unloading device upon detection of surges instead of estimated maps, reliability is improved, further preventing catastrophic failures of centrifugal compressors.

Referring to FIG. 1 , a compressor exemplified in the form of a two-stage refrigerant compressor is indicated by reference numeral 100 . Compressor 100 generally includes a compressor housing 102 defining at least one sealed cavity within which each stage of refrigerant compression is performed. The compressor 100 has a first refrigerant inlet 110, a first refrigerant outlet 114 for introducing refrigerant vapor into a first compression stage (not referenced in FIG. 1), A refrigerant transfer conduit 112 for transferring refrigerant from a first compression stage to a second compression stage, and a second refrigerant inlet 118 for introducing refrigerant vapor into a second compression stage (not referenced in FIG. 1). ) and a second refrigerant outlet 120. The refrigerant conveying conduit 112 is interlockingly connected to the first refrigerant outlet 114 and the second refrigerant inlet 118 at opposite ends, respectively. The second refrigerant outlet 120 delivers compressed refrigerant from the second compression stage to a cooling system in which the compressor 100 is included.

Referring to FIG. 2 , compressor housing 102 houses first compression stage 124 and second compression stage 126 at opposite ends of compressor 100 . The first compression stage 124 includes a first compression mechanism 106 configured to apply kinetic energy to the refrigerant entering through the first refrigerant inlet 110 . In some embodiments, the first compression mechanism 106 is an impeller. The kinetic energy imparted to the refrigerant by the first compression mechanism 106 increases as the refrigerant velocity decreases as it is transported into a sealed cavity formed in the volute 132 (eg, a diffuser). converted to refrigerant pressure. Similarly, the second compression stage 126 includes a second compression mechanism 116 configured to apply kinetic energy to the refrigerant transported from the first compression stage 124 entering through the second refrigerant inlet 118 . In some embodiments, the second compression mechanism 116 is an impeller. The kinetic energy imparted to the refrigerant by the second compression mechanism 116 increases as the refrigerant velocity decreases as it is transported into a sealed cavity (eg, a diffuser) formed in the volute 132. converted to refrigerant pressure. The compressed refrigerant exits the second compression stage 126 through the second refrigerant outlet 120 (not shown in FIG. 2).

Referring to FIG. 2 , the first stage compression mechanism 106 and the second stage compression mechanism 116 are connected at opposite ends of the drive shaft 104 . The drive shaft 104 is linked to a motor 108 located between the first stage compression mechanism 106 and the second stage compression mechanism 116, so that the first stage compression mechanism 106 and the second stage compression mechanism 106 and the second stage compression mechanism 106 The compression mechanism 116 of the is rotated at a selected rotational speed to compress the refrigerant exiting the second refrigerant outlet 120 (not shown in FIG. 2 ) to a preselected mass flow. Any suitable motor may be included in compressor 100, including but not limited to an electric motor. The drive shaft 104 is supported by gas foil bearing assemblies 300 located within the sleeve 202 of each bearing housing 200/200a, as described in further detail below. Each bearing housing 200/200a includes a mounting structure (not shown) for connecting the bearing housing 200/200a to the compressor housing 102, as illustrated in FIG. .

Referring to FIG. 2 , each bearing housing 200/200a supports a drive shaft 104, and the drive shaft 104 protrudes through the bearing housing 200/200a to oppose the sleeve 202, and is compressed. Mechanism 106 is coupled to the protruding end of drive shaft 104 . Referring to FIGS. 3 and 5 , a gas foil bearing assembly 300 is positioned within a cylindrical bore 206 in the bearing housing 200 . The drive shaft 104 is snugly mounted within a gas foil bearing assembly 300, which has an outer compliant foil or foil layer 302 positioned adjacent the inner wall of the sleeve 202. , an inner flexible foil or foil layer 306 (also referred to as 'top foil') located adjacent to the drive shaft 104 and a bump located between the inner foil layer 306 and the outer foil layer 302. and a bump foil or foil layer 310 . The foils or layers 302/306/310 of the gas foil bearing assembly are sized to accommodate the drive shaft 104 with relatively little or no gap as determined by existing foil bearing design methods. It constitutes an essentially cylindrical cylindrical tube. Components of foil bearing assembly 300, such as outer foil layer 302, inner foil layer 306, and bump foil layer 310, may be any suitable components that allow foil bearing assembly 300 to function as described herein. material can be made. Suitable materials include, by way of example and not in a limiting sense, metal alloys. In some embodiments, for example, each of the outer foil layer 302, inner foil layer 306, and bump foil layer 310 is made of stainless steel (eg, 17-4 stainless steel).

Referring back to FIG. 3 , the foil bearing assembly 300 in the illustrated embodiment is designed to prevent axial slip of the layers 302/306/310 within the cylindrical bore 206 of the sleeve 202. and a pair of foil keepers 312a/312b positioned adjacent opposite ends of the layers 302/306/310. A pair of foil retaining clips 314a/314b positioned adjacent to the foil keepers 312a/312b locks the layers 302/306/310 within the cylindrical bore 206 in a locking axial position ( locked axial position) respectively. The clips 314a/314b for fixing the foil may be detachably connected to the bearing housing 200.

In other embodiments, as shown in FIG. 4 , each bearing housing 200a is integrally formed (eg, cast) with the bearing housing 200a and defines a cylindrical bore 206 . and a foil retaining lip 214 projecting radially inwardly from the radial inner surface 204 . In the illustrated embodiment, the foil fixing lip 214 is located proximate the compression mechanism end 216 of the cylindrical bore 206 adjacent the compression mechanism 116 (shown in FIG. 2). The foil clamping lip 214 is sized and dimensioned to protrude a radial distance from the radial inner surface 204 overlapping at least a portion of the layers 302/306/310 of the foil bearing assembly 300. there is. The foil anchoring lip 214 can extend completely along the circumference of the radial inner surface 204 or the foil anchoring lip extends over a portion of the circumference of the radial inner surface 204 and extends over an adjacent radial inner surface 204. It may contain two or more segments separated by spaces that are flush with. The bearing housing 200 (not shown in FIG. 4) may be similarly formed.

The foil bearing assembly 300 of the embodiment illustrated in FIG. 4 includes layers 302/306 to prevent axial movement of the layers 302/306/310 within the cylindrical bore 206 of the sleeve 202. / 310) and a single foil fixing clip 314 located adjacent to the ends and opposite the foil fixing lip 214. In this embodiment, the foil clamping clip 314 is formed in a circumferential groove 212 formed in the radial inner surface 204 of the cylindrical bore 206 proximate the motor end 218 of the cylindrical bore 206. fitted to fit

Foil clamping lip 214 is provided in a cylindrical bore proximate to compression mechanism end 216, including but not limited to a location immediately adjacent to an opening of cylindrical bore 206 in compression mechanism end 216. (206). Alternatively, the foil fixing lip 214 may be positioned on a cylindrical surface proximate to the motor end 218, including but not limited to a location immediately adjacent to the opening of a cylindrical bore 206 in the motor end 218. It can be located within any area of bore 206. In these embodiments, the foil securing clip 314 is positioned within the radial inner surface 204 of the cylindrical bore 206 proximate the compression mechanism end 216, in an arrangement essentially reversal of the arrangement illustrated in FIG. 4 . It fits into the formed outer circumferential groove 212.

Referring to FIG. 4 , the foil bearing assembly 300 is installed within the bearing housing 200 by inserting the foil bearing assembly 300 into the cylindrical bore 206 of the bearing housing 200 at the motor end 218. The foil bearing assembly 300 is then axially pushed into the cylindrical bore 206 toward the compression mechanism end 216 until the layers 302/306/310 contact the foil holding lip 214. A foil retaining clip 314 is then fitted into the circumferential groove 212 near the motor end 218 of the cylindrical bore 206 to secure the foil bearing assembly 300 in place.

In other embodiments, any suitable method for securing the foil bearing assembly 300 within the sleeve 202 may be used. Non-limiting examples of suitable methods include keepers and securing clips, adhesives, set screws and any other suitable securing method.

Bearing housings 200/200a include radial bearings, thrust bearings and proximity probes, pressure transducers, including but not limited to sensing elements (not shown) used as feedback for passive and active control schemes such as thermocouples, key phasers and the like It can further function as a mounting structure for various components.

The form of the foil bearing assembly 300 is not limited and may be provided in any suitable form. For example, the foil bearing assembly 300 may be provided with two layers, three layers, four layers or an unlimited number of additional layers. The bump foil 310 of the foil bearing assembly 300 may be formed from a radially elastic structure to provide a resilient surface for the drive shaft 104 to rotate during operation of the compressor 100. The bump foil 310 has an array of deformable bumps or other features designed to deform or rebound under intermittent compressive radial loads and intermittent compressive radial loads. It can be formed from any suitable radially elastic structure, including but not limited to any other elastically resilient material capable of compressing and repelling under pressure. The bump foil 310 can be connected to at least one adjacent layer, including but not limited to at least one of the outer layer 302 and the inner layer 306 . In some embodiments, bump foil 310 may be connected to both outer layer 302 and inner layer 306 . In some embodiments, bump foil 310 may be free floating and not connected to any layer of foil bearing assembly 300 .

Referring to FIG. 6 , an exemplary embodiment of a system 400 includes a dynamic compressor 404 . In an embodiment, the dynamic compressor is a centrifugal compressor. In other embodiments, the dynamic compressor is an axial compressor. System 400 includes a compressor 404 having a compressor housing 405 , an unloading device 401 , a user interface 415 and a controller 410 . The compressor includes a motor 406 , a compression mechanism 407 , a gas foil bearing 409 and a speed sensor 417 . The system 400 further includes a variable frequency drive (VFD) having a motor interface 413 in communication with a current sensor 408 and a motor 406 . In some embodiments, VFD 416 operates under control of controller 410 . In some embodiments, VFD 416 is part of controller 410 . In an exemplary embodiment, the compression mechanism 407 is an impeller and the dynamic compressor 404 is a centrifugal compressor. In other embodiments, the compression mechanism 407 is blades and the kinetic compressor 404 is an axial compressor. Compressor 404 and compressor housing 405, including motor 406, compression mechanism 407 and gas foil bearing 409, may be manufactured similarly to compressor 100 described in FIGS. 1-5 or Or it could be made in another way. Compressor 404 is not limited to any particular structure in system 400. Compressor 404 includes a controller 410 for controlling the operation of compressor 404 and determining when a surge event has occurred and whether or not to take protective action when one or more surge events have occurred. The controller 410 includes a processor 411 , a memory 412 and an unloading interface 414 . Memory 412 includes instructions executed by processor 411 to perform methods that control compressor 404 and determine if and when a surge event has occurred and whether or not to take protective action in response. include them

The unloading device 401 in the system 400 controls the load on the compressor to limit the severity of surge events during start-up and shut-down routines and detected surge events. load) is eliminated and/or reduced. In an exemplary embodiment, the unloading device 401 is a bypass valve. Bypass valves, such as refrigerant bypass valves, provide an alternate path for gas and thus prevent pressure rise in compressor 404 no matter how slowly compressor motor 406 accelerates during start-up and decelerates during shutdown. stop and limit potential surging. In other embodiments, the unloading device 401 is an expansion valve. In other embodiments, the unloading device 401 is a variable orifice or a diameter valve such as a servo valve and pulse width modulation configured to control opening and closing according to a duty cycle. -width-modulated: PWM) valves or solenoid valves, or fixed orifice valves. In other embodiments, the unloading device 401 may be a variable diffuser or a variable inlet guide vane (VIGV), but is not limited thereto. Although various types of unloading devices are described herein, unloading device 401 may be any suitable device or combination of devices that reduces the load on compressor 404 .

The unloading device 401 is interlocked with the controller 410, the controller 410 being configured to control at least one operating parameter of the unloading device 401, such as opening a bypass valve. Current sensor 408 measures the current in motor 406, and controller 410 detects spikes in the measured current in motor 406 to determine if and when a surge event in compressor 404 has occurred and when the compressor It is determined whether the surge event of 404 has occurred. Controller 410 determines when the surge event has ended and normal operation resumes when the measured current in motor 406 is substantially constant. Other embodiments may use other techniques such as detecting changes in voltage, detecting changes in pressure, sensing vibrations caused by a surge, or the like, to generate and terminate surge events. can be detected. The controller 410 further determines whether or not to take protective measures when a surge event occurs. Non-limiting examples of sensors suitable for use in one or more control designs include temperature sensors, pressure sensors, flow sensors, current sensors, voltage sensors, rotational rate sensors ) and any other suitable sensors.

The control system 400 includes a motor interface 413 for connecting the VFD 416 to the motor 406, an interface for connecting the controller 410 to the VFD 416, and an unloading device for the controller 410 ( and an unloading interface 414 to access 401). Processor 411 then determines when a surge event has occurred based at least in part on the received signals representing the current from VFD 416 to motor 406 and takes protective action when the processor determines that a surge event has occurred. It can execute instructions stored in memory 412 to determine whether to take or not.

The control system 400 includes a user interface 415 configured to output (eg, display) and/or receive information (eg, from a user) associated with the system 400 . In some embodiments, user interface 415 is configured to receive activation and/or deactivation input from a user to activate and deactivate (ie, turn on and off) or otherwise enable operation of system 400. . Moreover, in some embodiments, user interface 415 provides, for example and without limitation, severity alerts, occurrence alerts, fault alerts ) and motor speed alerts, as well as one or more operating characteristics of the system 400, including the condition of the gas foil bearing 409 and any other suitable information. It is configured to output information associated with them.

User interface 415 may include any suitable input devices and output devices that enable user interface 415 to function as described herein. For example, user interface 415 may include, but is not limited to, a keyboard, mouse, touch screen, joystick(s), throttle(s), buttons, switches, and/or other input devices. don't Moreover, the user interface 415 may include, for example and without limitation, a display (eg, a liquid crystal display (LCD) or organic light emitting diode (OLED) display), speakers, indicator lights, output devices including instruments and/or other output devices. Moreover, user interface 415 may be part of another component, such as a system controller (not shown). Other embodiments do not include user interface 415 .

In some embodiments, system 400 may be controlled by a remote control interface. For example, system 400 may include a communication interface (not shown) configured for connection to a wireless control interface that enables remote control and activation of system 400 . The wireless control interface may be implemented on a portable computing device such as a tablet or smartphone.

Controller 410 is generally configured to control the operation of compressor 404. Controller 410 controls operation through programming and instructions from other devices or controllers or is integrated with control system 400 through a system controller. In some embodiments, for example, controller 410 receives user input from user interface 415 and controls one or more components of system 400 in response to those user inputs. For example, controller 410 can control motor 406 based on user input received from user interface 415 .

Controller 410 may be any suitable computer and/or computer, including any suitable combination of computers, processing units, and/or the like, which may be communicatively coupled to each other and may be operated independently or in conjunction with one another. /or other processing units in general (eg, controller 410 can make up all or part of a controller network). Controller 410 may include one or more modules or devices, one or more of which may be housed within system 400 or located remotely from system 400 . Controller 410 may be part of compressor 404 or may be separate or part of a system controller in an HVAC system. Controller 410 and/or components of controller 410 may be integrated or incorporated into other components of system 400 . In some embodiments, for example, controller 410 may be incorporated into motor 406 or unloading device 401 . Controller 410 includes one or more processor(s) 411 and associated memory device(s) configured to perform various computer-implemented functions (e.g., calculations, decisions, and functions disclosed herein) ( 412) may be included. The term 'processor' as used herein refers to integrated circuits as well as controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs) and other programmable circuits. Additionally, memory device(s) 412 of controller 410 may include computer readable media (eg, RAM), computer readable non-volatile media (eg, flash memory), floppy disk, compact disk read May be or include memory element(s) including, but not limited to, dedicated memory (CD-ROM), magneto-optical disk (MOD), digital versatile disc (DVD), and/or other suitable memory elements. can do. Such memory device(s) 412, when executed by processor(s) 411, enable controller 410 to control system 400, control the operation of motor 406, , receiving inputs from the user interface 415, providing output to the operator via the user interface 415, controlling the unloading device 401, and/or other suitable computer implemented functions. It may generally be configured to store suitable computer readable instructions that cause or configure it to perform various functions described herein, including but not limited to.

Referring to FIG. 7 , a surge current characteristic graph 600 during startup is shown, including a speed curve 601 and a motor current curve 602 . 7 illustrates accelerating the motor speed to a first speed and running the motor 406 at the first speed for a time period 605 . While the motor 406 is running at a first speed during the time period 605 , a region of possible surge 603 has been identified as oscillations in the motor current curve 602 . The compressor 404 is held at the first speed until the current oscillation pattern of the surge stops (604), and the compressor 404 is marked for full start-up.

8 and 9 are traces of signals used by the system to detect the occurrence of a surge (eg, during time period 605 in FIG. 7). 8 is a speed graph 800, and FIG. 9 is a current graph 900. Referring to FIG. 8, the actual speed 801 of the motor of the compressor is shown along with a baseline speed line 803, which serves as a reference point for determining whether a surge has occurred. can be used The baseline speed line 803 is also known as the speed set point or commanded speed. Referring to FIG. 9 , the actual current 901 and the average current 902 provided to the motor (detected using current sensor 408 ) are shown. Average current 902 may be the current detected immediately prior to the surge event, the average of all current measurements prior to the surge event, the average of a predetermined or variable number of current measurements prior to the surge event, or any other suitable current average. When compressor 404 enters a surge event, mass flow through the compressor is rapidly reduced, thereby reducing the load on compressor 404 and increasing the speed of unloaded motor 406 to baseline speed line 803. make it rise upwards VFD 416 then lowers actual current 901 through a control algorithm in response to the increased speed to bring actual speed 801 back to the baseline speed line 803. As the surge ends, the load on compressor 404 (and motor 406) returns, causing speed 801 to drop rapidly. The VFD 416 increases the current to return the speed of the motor to the baseline speed 803. The result is a characteristic overshoot of the actual current 901, observed at the end of the surge event in FIGS. 8 and 9, before the speed and current return to their approximate pre-surge levels. (characteristic overshoot) and undershoot of the actual speed (801). The drop of the actual current 901 from the average current 902 is used by the controller to detect the occurrence of a surge event. When the change in current from average current 902 exceeds a threshold value, the controller determines that a surge event has occurred. Speed graph 800 represents speed surge severity 802 and current graph 900 represents current surge severity 904 during a surge event. The current surge severity is the difference between the average current (902) and the minimum current (903). The severity of each surge event may be recorded in memory 412 .

Referring to FIG. 10 , an exemplary graphical relationship 1100 between current swing percentage and speed percentage is shown to illustrate the threshold current swing for detection of a surge event. there is. A linear surge curve 1103 represents a threshold for detection of a surge. The current swing on or above the linear surge curve 1103 (e.g., surge severity 904 in FIG. 9) at the current speed of the compressor (expressed as a percentage of maximum speed) is the occurrence of a surge event. is determined to represent If the current swing is below the linear surge curve 1103, no surge event is detected. Alternatively, only current swings above the linear surge curve 1103 may be considered surge events, and current swings below the linear surge curve may not be considered surge events.

Referring to FIG. 11 , an operating envelope or operating map 1000 of an exemplary dynamic centrifugal compressor 404 is shown. Operational map 1000 graphically estimates and shows the performance of the compressor in terms of flows, heads and speeds. The map shows head versus inlet mass flow rates as a percentage of their values at the design point of the compressor 404 . The inlet mass flow rate is a measure of the amount of working fluid, such as refrigerant, flowing through the compression mechanism 407 . Head is the total pressure ratio of exit pressure to inlet pressure. Operational map 1000 shows a plurality of compressor speed lines 1007 . In this example, there are five speed lines 1007 from 110 percent design speed down to 70 percent design speed, where each line is separated by a 10 percent difference. While these specific speed lines are shown in this example, any number of speed lines in any other percentages of the compressor design may be shown for any type of compressor.

The surge limit line 1004 represents the maximum loading condition before surging occurs in the surge area 1006 (ie, to the left of the surge limit line 1004). Surge control line 1003 approximates a maximum loading condition under which compressor 404 can operate safely without risk of running into a surge. The surge control line 1003 is defined by the surge margin 1005 from the surge limit line 1004. By operating to the right of the surge control line 1003 the compressor can avoid surging. An operating point 1009 of operating map 1000 for compressor 404 is shown as the intersection of the speed line, inlet mass flow rate, and total pressure ratio. For example, the operating point 1009 shown in the operating map 1000 is at 80 percent inlet mass flow rate, 108 percent head, and 100 percent speed. If a surge occurred while operating at operating point 1009, the surge margin 1005 would be increased, for example by an amount 1008, to shift the surge control line 1003 to a new surge control line 1002. can A choke line 1001 is shown in motion map 1000 .

Referring to FIG. 12 , a method 1200 for determining when a surge event has occurred is shown. The method 1200 begins at step 1201 in which a VFD 416 is used to operate a motor 406 to compress a working fluid. In some embodiments, the working fluid is a refrigerant. Once the motor is operating ( 1201 ), the method 1200 proceeds to step 1202 of receiving signals representing current to the motor 406 from the VFD 416 . The method 1200 concludes with determining ( 1203 ) when a surge event has occurred based at least in part on received signals representative of current from VFD 416 to motor 406 . The method 1200 is implemented on a control system 400 as shown in FIG. 6 . In particular, controller 410 implements method 1200 via processor 411 using instructions stored on memory 412 . A measurement of current to motor 406 is provided by a current sensor 408 included with VFD 416 . Other embodiments may use any other suitable detection or estimation of the current provided to motor 406 . In step 1201 of operating the motor 406, compression of the working fluid is performed by the compression mechanism 407.

Determining that a surge event has occurred (step 1203) includes determining the difference between the previous current and the current current based on received signals representing the current from VFD 416 to motor 406. In some embodiments, the previous current from VFD 416 to motor 406 is received by processor 411 prior to receiving a signal from VFD indicating the current current from VFD 416 to motor 406. determined by averaging a plurality of signals representing the current into (406). A surge event occurred when the difference between the previous current and the current current exceeds the surge threshold. For example, the surge threshold is a variable threshold (eg, as shown in FIG. 10 ) and can be preloaded into controller 410 by the user and later changed via user interface 415 . It can be. The variable surge threshold is determined based, at least in part, on a detected speed from speed sensor 417 of motor 406 when a signal representing the current current is received. In other embodiments, determining the difference between the previous current and the current current based on the received signals representing the current from the VFD 416 to the motor 406 depends on the difference between the previous current and the current current. It includes determining the size of the surge based on Processor 411 stores in memory 412 an indicator of the occurrence of a surge event and the determined size of the surge.

Referring to FIG. 13 , a flowchart 1300 of an exemplary embodiment of a method 1200 from FIG. 12 for determining a surge event is shown. Flow diagram 1300 begins when compressor 404 starts up. Flow diagram 1300 depicts cases of normal operation and start-up operation of compressor 404 when determining whether a surge event has occurred. The compressor 404 starts operating, and the current sensor 408 measures the current current ( ) is continuously measured, and the speed sensor 417 has a speed ( ) is measured continuously. When the compressor 404 is operating, the N previously measured currents ( ) is a rolling data set stored in the raw memory 412. rolling data set ( ) over a period of time to generate a subset. It may contain N currents previously measured before. rolling data set ( ) is generated and stored in memory 412, the rolling average This rolling data set ( ) is generated during the time period associated with The 'rolling average' is the average of a series of measured current values with a fixed subset size. Current values over a period of time ( ) The first average for the first subset of ( ) is taken by the controller 410, this subset is either shifted forward and modified, or modified by subtracting the first current value in the rolling data set and adding the new (e.g., most recent) current value, so that the new subset is generated over different time intervals and stored in memory 412. This is done continuously over the entire current data set over the life of the compressor 404. subsets ( The rate at which ) is generated and stored may be set by the OEM or tuned by the user through the user interface 415. The controller 410 calculates the rolling average ( ) and current current ( ) difference between ( ) is calculated. Controller 410 then checks whether compressor 404 is in a start-up operating state. When the compressor 404 is in start-up operation, the difference is a preset start-up current, ) compared to In some embodiments, the start-up current ( ) is 2 amps. In other embodiments, the start-up current ( ) is any other suitable fixed or variable current. difference( ) is the start-up current ( ), a surge event was detected. If a surge event is detected, the occurrence of the surge event is stored in memory 412 . If the compressor is in normal operating condition, the controller 410 determines the detected speed of the compressor 404 ( ) based on the surge threshold current, ) to determine Surge critical current ( ) is obtained using the graphical relationship 1100 between the current swing percent and the speed percent of the compressor 404 described above in FIG. 10 . That is, in an exemplary embodiment, the surge threshold current ( ) is the detected speed ( ) is the percent current swing of the linear surge curve 1103 at a percent speed. Other embodiments may define the threshold by absolute speed, absolute current swing, or any suitable combination. Some embodiments may list surge threshold currents in a lookup table or in any other suitable format. difference( ) is the surge threshold current ( ), then a surge event has occurred and has been detected. If a surge event has occurred, the occurrence of the surge event is stored in the memory 412 and the associated difference ( ) is stored in the memory 412 as the surge severity. During start-up and normal operation of compressor 404, if no surge event is detected, compressor 404 will continue either start-up or normal operation until a surge event is detected with a new subset of future measured currents. Continue.

Referring to FIG. 14 , a method 1400 is shown for determining whether or not to take protective action when a processor 411 determines that a surge event has occurred. The method 1400 occurs after the method 1200 shown in FIG. 12 determines that a surge event has occurred. While the previous method 1200 may be used concurrently to determine the occurrence of surge events, method 1400 may be used in any situation where a surge event has been detected (by any detection means) in a kinetic compressor. The method 1400 includes operating the motor 406 to compress the work fluid at a motor speed greater than the predicted minimum surge speed plus a control margin (1401). starts from The method proceeds to step 1402 of determining when surge events have occurred. In some embodiments, this step can use method 1200 to determine that a surge event has occurred. The method 1400 proceeds to step 1403 of storing in memory 412 an indication of each surge event that processor 411 determines has occurred. The method 1400 concludes with step 1404 where the processor 411 determines whether or not to take protective action when determining that a surge event has occurred. In some embodiments, the protective action includes generating an alert. The alert may be a warning signal sent to a remotely located system controller, a visual or audible alert located close to the compressor, or any other suitable alert. In some embodiments, the protective action includes stopping the motor 406. In some embodiments, the protective action includes adjusting the adjustment margin. Similar to the previous method 1200, the method 1400 is implemented on a control system 400 as shown in FIG. In particular, controller 410 implements method 1400 via processor 411 using instructions stored on memory 412 . Compression of the working fluid in step 1401 of operating the motor 406 is achieved by the compression mechanism 407 .

If the determining step 1404 of the method 1400 concludes that generating an alert is a protective action required after the processor 411 determines that a surge event has occurred, in various embodiments the following steps may be more drunk Generating an alert may include generating an occurrence alert when the number of surge events the indicator stored in memory 412 is greater than or equal to an occurrence alarm limit. Generating an alert may include generating a fault alert when the number of surge events in which the indicator is stored in memory 412 is greater than or equal to a fault limit - Here, the failure limit is greater than the occurrence alarm limit -. When a failure notification is generated, an adjustment margin, such as adjustment margin 1005 of operational map 1000 shown in FIG. 11, is increased for dynamic compressor 404 in some embodiments. In some embodiments, the indicator of each surge event includes an indicator of the magnitude of the surge event, and generating an alert is such that the sum of the magnitudes of determined surge events stored in memory 412 is a severity alarm limit. ) greater than or equal to triggering a severity alert. Generating the alert further includes generating a fault alert when a sum of magnitudes of determined surge events stored in memory 412 is greater than or equal to a severity fault limit - where the severe failure limit is greater than the severe alarm limit in some embodiments -. Then, as described above, when a failure notification is generated, the adjustment margin can be increased. In some embodiments, generating an alert occurs when the speed of the motor 406 during the surge event exceeds the sum of the expected minimum surge speed, control margin, and charge margin. occurs Then, as described above, when a notification is generated, the adjustment margin is increased.

If the determining step 1404 of the method 1400 concludes that stopping the motor 406 is a protective action required after determining that a surge event has occurred - where an indicator of each surge event is Including size - the method may include: In some embodiments, stopping the motor 406 occurs when the number of detected surge events is greater than or equal to an occurrence shutdown threshold. Alternatively or additionally, the motor 406 can be stopped when the sum of the magnitudes of the determined surge events is greater than or equal to an accumulation shutdown threshold.

Referring to FIG. 15 , a flowchart 1500 of an exemplary embodiment of a method 1400 from FIG. 14 for determining whether or not to take protective action when a surge event occurs in a dynamic compressor 404 is shown. there is. Flow diagram 1500 shows a surge event is detected. Once detected, the surge count N is incremented to N = N + 1. At the same time, surge severity accumulation is calculated as the surge count N increases to N = N + 1. The cumulative surge severity is the sum of the magnitudes of all N detected surge events. am. Next, surge count N and surge severity cumulative value is checked to see if the shutdown condition for compressor 404 is satisfied. Surge count N is the shutdown surge count limit greater than or equal to or cumulative surge severity A shutdown surge severity limit greater than or equal to , control system 400 initiates a shutdown, and compressor 404 is locked out. If the conditions for shutdown described above are not met, a fault check is performed using thresholds lower than those used in the shutdown decision. Surge count N is the fault surge count limit greater than or equal to or cumulative surge severity A fault surge severity limit greater than or equal to , the system 400 increases the surge speed control margin of the dynamic compressor 404 as indicated by the control margin shift 1008 of the operating map 1000 shown in FIG. 11 . The surge speed control margin can be increased by a fixed amount, by a fixed percentage or by a variable amount. After the surge speed control margin is increased, a surge fault is issued to the controller 410. In some embodiments, the surge fault is an alarm issued to a separate system controller (not shown in FIG. 6 ) of the HVAC system of which the dynamic compressor 404 is a part. If the above fault conditions are not met, an alarm limit check is performed using thresholds lower than those used in the fault check. Surge count N is the alarm count limit greater than or equal to or cumulative surge severity A. Alarm surge severity limit greater than or equal to , the control system 400 issues a surge warning to the controller 410. In some embodiments, a surge warning is an alarm issued to a separate system controller of the HVAC system. Moreover, when a surge event is detected, the speed S of the dynamic compressor 404 is measured and the predicted surge speed and charge margin compared to the sum of Surge speed at which speed S is predicted and charge margin greater than the sum of , the surge speed control margin is increased. When this occurs, a low charge warning is issued to the controller 410 indicating that the system may require additional work fluid (eg, refrigerant). In some embodiments, the low charge warning is an alarm issued to a separate system controller (not shown in FIG. 6 ) of the HVAC system of which dynamic compressor 404 is a part. Other embodiments may perform the above comparisons in reverse order. That is, an alarm limit check may be performed first, a fault check second, and a shutdown check performed last. In such embodiments, if the alarm limit check determines not to issue a surge warning, comparisons can be stopped because the thresholds for the fault check and shutdown check are greater than the threshold for the alarm limit check. , these are lower alarm limit thresholds ( ) cannot be exceeded unless it is exceeded.

In some embodiments, when a surge event is detected, an unloading device is activated as a protective measure to unload the compressor to reduce the severity of the surge. In an exemplary embodiment, the unloading device is a load balance valve, and the time before returning the load on the compressor 404 Reduce the load on the compressor 404 for a minute.

The technical advantages of the methods and systems described herein are: (a) continuous monitoring of the number of surge events and surge severity from the perspective of a compressor in an HVAC system, (b) surge events and surge severity to the maximum number of surges the compressor can handle in the HVAC system, and (c) comparing the compressor speed during surge events to the expected surge speed at the current pressure ratio.

When introducing elements of this disclosure or its embodiment(s), the articles ("a", "an") and the definite articles ("the", "said") indicate that there is one or more of the elements. It is used with the intention to mean. Terms such as 'comprising', 'comprising', 'containing', and 'having' are used with the intention of inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a specific orientation (eg, 'upper', 'lower', 'side', etc.) is for convenience of description and does not limit the orientation of the described item to any specific direction. no.

As various changes could be made in the foregoing configurations and methods without departing from the spirit of the present disclosure, all matter contained in the foregoing description and shown in the accompanying drawing(s) should be interpreted in an illustrative and non-limiting sense. something to do.

Claims (40)

As a system,
dynamic compressor,
a variable frequency drive (VFD), and
Including a controller,
The dynamic compressor,
a motor having a driveshaft rotatably supported within the dynamic compressor; and
a compression mechanism coupled to the drive shaft and operable to compress a working fluid upon rotation of the drive shaft;
The variable frequency driver includes a sensor configured to sense a current provided to the motor,
The controller is connected to the motor, the controller includes a processor and a memory,
The memory operates the motor using the VFD to compress the working fluid, receives signals representing current from the VFD to the motor, and the received signal represents current from the VFD to the motor. storing instructions that program the processor to determine when a surge event has occurred based at least in part on
system. According to claim 1,
wherein the memory determines that the surge event has occurred by determining a difference between a previous current and a present current based on the received signals representing current from the VFD to the motor. storing additional instructions for programming the processor;
system. According to claim 2,
The memory performs the previous operation by averaging a plurality of signals representative of the current from the VFD to the motor received by the processor prior to receiving a signal representative of the current current from the VFD to the motor from the VFD. storing additional instructions for programming the processor to determine the current of
system. According to claim 2,
wherein the memory stores additional instructions that program the processor to determine that the surge event has occurred when the difference exceeds a surge threshold;
system. According to claim 4,
The surge threshold is a variable threshold,
system. According to claim 5,
Further comprising a speed sensor configured to detect a speed of the motor;
wherein the memory stores additional instructions that program the processor to determine the surge threshold based at least in part on the detected speed of the motor when a signal indicative of the current current is received.
system. According to claim 2,
wherein the memory stores additional instructions that program the processor to determine the magnitude of the surge based on the difference between the previous current and the current current.
system. According to claim 7,
wherein the memory stores additional instructions that program the processor to store an indication of the occurrence of the surge event and the determined magnitude of the surge to the memory;
system. According to claim 1,
The dynamic compressor is a centrifugal compressor, and the compression mechanism is an impeller.
system. According to claim 9,
The system is an HVAC system, the processing fluid is a refrigerant,
system. A controller for a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor, comprising:
processor, and
contains memory;
The memory operates the motor to compress the working fluid, receives signals representative of a current supplied to the motor for operating the motor, and transmits at least to the received signals representative of the current supplied to the motor. storing instructions that program the processor to determine based in part on when a surge event has occurred;
controller. According to claim 11,
The memory stores additional instructions that program the processor to determine that the surge event has occurred by determining a difference between a previous current and a current current based on the received signals representative of the current provided to the motor. doing,
controller. According to claim 12,
The memory is configured to determine the previous current by averaging a plurality of signals representative of the current provided to the motor received by the processor prior to receiving the signal representative of the current provided to the motor. storing additional instructions to program
controller. According to claim 12,
wherein the memory stores additional instructions that program the processor to determine that the surge event has occurred when the difference exceeds a surge threshold.
controller. According to claim 14,
The surge threshold is a variable threshold,
wherein the memory stores additional instructions that program the processor to determine the surge threshold based at least in part on a detected speed of the motor when a signal indicative of the current current is received.
controller. According to claim 12,
The memory may include the processor to determine a magnitude of the surge based on the difference between the previous current and the current current and to store an indicator of occurrence of the surge event and the determined magnitude of the surge in the memory. storing additional instructions to program;
controller. A method for detecting the occurrence of a surge event in a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor, comprising:
Compressing the processing fluid by operating the motor;
receiving signals representative of the current provided to the motor to operate the motor; and
determining when a surge event has occurred based only on the received signals indicative of the current provided to the motor and a surge threshold.
method. According to claim 17,
The step of determining when the surge event occurred,
determining a difference between a previous current and a current current based on the received signals representative of the current provided to the motor; and
determining that the surge event has occurred when the difference exceeds the surge threshold.
method. According to claim 18,
The step of determining the previous current,
averaging a plurality of signals representative of the current provided to the motor received by the processor prior to receiving a signal representative of the current provided to the motor.
method. According to claim 18,
The surge threshold is a variable threshold,
The step of determining when the surge event occurred,
determining the surge threshold based at least in part on the detected speed of the motor when the signal indicative of the current current is received.
method. As a system,
a dynamic compressor and controller;
The dynamic compressor,
A motor having a drive shaft rotatably supported within the dynamic compressor, and
a compression mechanism coupled to the drive shaft and operable to compress a working fluid upon rotation of the drive shaft;
The controller is connected to the motor, the controller includes a processor and a memory,
The memory operates the motor to compress the fluid at a motor speed greater than the predicted minimum surge speed plus a control margin, and determines when surge events have occurred. and storing in the memory an indicator of each surge event that the processor determines has occurred and programming the processor to determine whether or not to take a protective action when the processor determines that a surge event has occurred. to save,
system. According to claim 21,
The protective action comprises generating an alert,
system. The method of claim 22,
The memory further directs the processor to determine to raise an occurrence alert as the alert when an indicator indicates that the number of surge events stored in the memory is greater than or equal to an occurrence alarm limit. storing additional instructions to program;
system. According to claim 23,
wherein the memory programs the processor to determine to generate a fault alert as the alert when an indicator indicates that the number of surge events stored in the memory is greater than or equal to a fault limit. storing additional instructions, wherein the failure limit is greater than the generated alarm limit;
system. According to claim 24,
wherein the memory stores additional instructions that program the processor to increase the adjustment margin whenever the processor determines to generate the failure notification.
system. The method of claim 22,
the indicator of each surge event includes an indicator of the magnitude of the surge event;
The memory further instructions to program the processor to generate a severity alert as the alert when the sum of the magnitudes of the determined surge events stored in the memory is greater than or equal to a severity alarm limit. to save them,
system. The method of claim 26,
The memory further programs the processor to determine to generate a fault notification as the notification when the sum of the magnitudes of the determined surge events stored in the memory is greater than or equal to a severity fault limit. storing instructions, wherein the severe failure limit is greater than the severe alarm limit;
system. The method of claim 27,
wherein the memory stores additional instructions that program the processor to increase the adjustment margin whenever the processor determines to generate the failure notification.
system. The method of claim 22,
The system is an HVAC system,
The processing liquid is a refrigerant,
The memory determines to generate the notification when a speed of the motor when the surge event is determined to have occurred exceeds a sum of the predicted minimum surge speed, the adjustment margin, and a charge margin; and storing additional instructions for programming the processor to increase the adjustment margin when the processor determines to generate the alert;
system. The method of claim 22,
The notification includes a warning signal transmitted to a system controller located remotely,
system. According to claim 21,
the protective action includes stopping the motor;
the indicator of each surge event includes an indicator of the magnitude of the surge event;
The memory is configured such that the number of surge events the processor determines to have occurred is greater than or equal to an occurrence shutdown threshold, or the sum of the magnitudes of the determined surge events stored in the memory is a cumulative shutdown threshold. storing additional instructions that program the processor to determine to stop the motor when greater than or equal to (accumulation shutdown threshold);
system. According to claim 21,
The system further comprises an unloading device;
Wherein the protective action comprises activating the unloading device to unload the compressor to reduce the severity of the determined surge event.
system. A controller for a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor, comprising:
includes a processor and memory;
The memory compresses the fluid at a motor speed greater than the minimum surge speed predicted by operating the motor plus an adjustment margin, determines when surge events have occurred, and determines when surge events have occurred, and each of the surge events determined by the processor to have occurred. storing an indicator of a surge event in the memory and programming the processor to determine whether or not to take protective action when the processor determines that a surge event has occurred;
controller. 34. The method of claim 33,
The memory generates an occurrence notification when the number of surge events with identifiers stored in the memory is greater than or equal to the occurrence alarm limit, and the number of surge events with identifiers stored in the memory exceeds the failure limit. greater than or equal to - the failure limit is greater than the occurrence alarm limit - generating a failure notification, increasing the adjustment margin each time the processor decides to generate the failure notification and the processor is deemed to have occurred instructions that program the processor to determine whether or not to take protective action when the processor determines that a surge event has occurred, by stopping the motor when the determined number of surge events is greater than or equal to an occurrence shutdown threshold to save them,
controller. 34. The method of claim 33,
the indicator of each surge event includes an identifier of the magnitude of the surge event;
The memory generates a severe notification when the sum of the determined magnitudes of surge events stored in the memory is greater than or equal to the Severe Alert Limit, and the sum of the determined magnitudes of surge events stored in the memory is greater than or equal to the Severe Failure Limit greater than or equal to - the severe failure limit is greater than the severe alarm limit - generating a failure notification, increasing the adjustment margin each time the processor decides to generate the failure notification and the processor to determine whether or not to take a protective action when the processor determines that a surge event has occurred, by stopping the motor when the sum of the magnitudes of the determined surge events stored is greater than or equal to a cumulative shutdown threshold; storing additional instructions to program
controller. 34. The method of claim 33,
the dynamic compressor is part of an HVAC system;
The processing liquid is a refrigerant,
The memory determines to generate a charge alert when the speed of the motor when it is determined that the surge event has occurred exceeds the sum of the predicted minimum surge speed, the control margin, and the charge margin, storing additional instructions for programming the processor to determine whether or not to take protective action when the processor determines that a surge event has occurred;
controller. A method for controlling a dynamic compressor comprising a motor and a compression mechanism coupled to the motor and operable to compress a working fluid upon operation of the motor, comprising:
operating the motor to compress the working fluid at a motor speed greater than the sum of the predicted minimum surge speed and a control margin;
determining when surge events have occurred;
storing an indicator of each surge event that the processor determines has occurred; and
determining whether or not to take protective action when the processor determines that a surge event has occurred.
method. 38. The method of claim 37,
The step of determining whether or not to take protective action when the processor determines that a surge event has occurred,
Generating an occurrence notification when the number of surge events whose identifiers are stored in the memory is greater than or equal to an occurrence alert limit;
generating a failure notification when the number of surge events whose identifiers are stored in the memory is greater than or equal to a failure limit, wherein the failure limit is greater than the occurrence alarm limit;
increasing the adjustment margin whenever the processor determines to generate the failure notification; and
stopping the motor when the number of surge events determined by the processor to have occurred is greater than or equal to an occurrence shutdown threshold;
method. 38. The method of claim 37,
The step of determining whether or not to take protective action when the processor determines that a surge event has occurred,
generating a severe alert when the sum of the magnitudes of the determined surge events stored in the memory is greater than or equal to a severe alert limit;
generating a fault notification when the sum of the determined magnitudes of the surge events stored in the memory is greater than or equal to a severe fault limit, wherein the severe fault limit is greater than the severe alarm limit;
increasing the adjustment margin whenever the processor determines to generate the failure notification; and
stopping the motor when the sum of the magnitudes of the determined surge events stored in the memory is greater than or equal to a cumulative shutdown threshold.
method. 38. The method of claim 37,
the dynamic compressor is part of an HVAC system;
The processing liquid is a refrigerant,
The step of determining whether or not to take protective action when the processor determines that a surge event has occurred,
Determining to generate a charge notification when the speed of the motor when it is determined that the surge event has occurred exceeds the sum of the predicted minimum surge speed, the control margin, and the charge margin,
method.