US20110179644A1 - System for protecting bearings and seals of refrigerant compressor - Google Patents
System for protecting bearings and seals of refrigerant compressor Download PDFInfo
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- US20110179644A1 US20110179644A1 US13/065,977 US201113065977A US2011179644A1 US 20110179644 A1 US20110179644 A1 US 20110179644A1 US 201113065977 A US201113065977 A US 201113065977A US 2011179644 A1 US2011179644 A1 US 2011179644A1
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- housing
- high frequency
- common mode
- rotor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D25/00—Pumping installations or systems
- F04D25/02—Units comprising pumps and their driving means
- F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
- F04D25/0606—Units comprising pumps and their driving means the pump being electrically driven the electric motor being specially adapted for integration in the pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/02—Surge control
- F04D27/0292—Stop safety or alarm devices, e.g. stop-and-go control; Disposition of check-valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
- F04D29/056—Bearings
- F04D29/059—Roller bearings
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49229—Prime mover or fluid pump making
- Y10T29/49236—Fluid pump or compressor making
- Y10T29/49238—Repairing, converting, servicing or salvaging
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Motor Or Generator Frames (AREA)
Abstract
To protect the bearings, lubricant and seals of a refrigerant compressor, the compressor includes one or more inductors for mitigating a high frequency common mode current that produces a high frequency shaft voltage. Each inductor is a ring of magnetic material encircling three insulated cables that convey three-phase power from an adjustable frequency drive to the compressor's motor. Without the inductors, the high frequency shaft voltage can become damagingly high due to the length of a cast iron housing that can be particularly long if the housing contains both a motor and several centrifugal impellers. The high frequency shaft voltage is just one component of a composite adverse shaft voltage. Another component, known as an operationally induced shaft voltage, can be reduced by a grounding contact, so instead of using just an inductor or just a contact, both can be used to provide a total solution to the problem.
Description
- 1. Field of the Invention
- The subject invention generally pertains to centrifugal compressors, screw compressors and other types of compressors of hermetically sealed refrigerant systems and more specifically to a means for protecting the motor bearings and seals of such compressors.
- 2. Description of Related Art
- For years, it has been known that adverse shaft voltage can develop between the shaft and housing of electric motors. When the voltage discharges with sufficient energy across a bearing that supports the shaft, the resulting current can damage the bearing through electrical arcing and/or by degrading the bearing's lubricant.
- The shaft voltage can actually be a combination of voltages originating from different sources. It can be electrostatically generated within the motor, or the voltage can arise from imbalanced ampere-turns in the stator or from stator or rotor asymmetries. In cases where the motor is driven by an AFD (adjustable frequency drive) with high speed power switching devices (e.g., insulated gate bipolar transistors), the rapid switching rate of the power switching devices can generate a high frequency common mode voltage that can ultimately lead to a damaging component of the shaft voltage.
- Attempts at solving the shaft voltage problem have involved various means such as shaft-grounding brushes, electrically insulated bearings, ceramic bearings, low impedance lubricant, common mode inductors or line filters applied to the motor's AFD.
- Although such solutions may be effective for a typical motor driven by an AFD, centrifugal refrigerant compressors do not fit this simple model. Centrifugal refrigerant compressors are unique in that the motor and the compressor share a common housing. With a shared common housing, some mixing of the lubricant and the refrigerant can occur, which can alter the dielectric and/or other properties of the lubricant. Also, various properties of the housing and even the quantity and location of the impellers within the housing seem to have an effect on the induced shaft voltage.
- Since centrifugal refrigerant compressors do not fit the typical inverter/motor model, it has been painfully discovered that previous shaft voltage mitigating solutions are not always successful when applied to refrigerant-based systems. For centrifugal refrigerant compressors, solutions that have worked in the past are often found to be unsuccessful today, which suggests that something has changed.
- Identifying which particular change or changes are making present shaft voltage problems more difficult to correct is very challenging. Some of the variables may include new refrigerants, new lubricants, new bearings, different refrigerant seals, and the style of the compressor housing as it relates to the quantity and layout of the compressor's impellers.
- To fully correct the shaft voltage problem, a need exists for a total solution or a set of solutions that can be successfully applied to centrifugal refrigerant compressors of various designs and configurations.
- It is an object of the invention to protect the bearings, seals, and/or the lubricant of a refrigerant compressor by mitigating a composite adverse shaft voltage that develops between the shaft and the compressor's housing.
- Another object of some embodiments is to mitigate the composite adverse shaft voltage by reducing the amplitude and/or frequency of a high frequency common mode current that influences the composite adverse shaft voltage.
- Another object of some embodiments is to reduce the frequency of the high frequency common mode current to a lower, non-damaging level (preferably less than 500 kHz) by installing an inductor ring of magnetic material that encircles three insulated conductors (forming an inductor) that convey three-phase electrical power from an AFD to a compressor system.
- Another object of some embodiments is to minimize the damaging effects of a composite adverse shaft voltage by installing both a grounding brush device and an inductor in an existing functional compressor system, wherein the grounding brush device reduces or drains off an operationally induced shaft charge, reducing voltage, and the inductor mitigates the high frequency common mode current.
- Another object of some embodiments is to reduce the frequency and/or amplitude of the high frequency common mode current flowing in a compressor system that includes a cast iron housing, steel piping, and a ground return path conductor, wherein the material of the steel piping is more electrically conductive than the cast iron material of the housing but is less electrically conductive than the material of the ground return path conductor.
- Another object of some embodiments is to strategically position the point at which the ground return path conductor connects to the housing of the compressor system to minimize the adverse effects of high frequency common mode currents.
- Another object of some embodiments is to use a rolling element bearing and a hydrodynamic bearing to support a shaft within a motor housing, and to connect the ground return path conductor to the housing at point that minimizes internal voltage to the rolling element bearing, thereby protecting the rolling element bearing, which is particularly susceptible to being damaged by electrical discharge.
- Another object of some embodiments is to add a number of inductors to a compressor that includes a number of impellers, wherein the number of inductors is at least as great as the number of impellers.
- Another object of some embodiments is to prolong the life of a lubricant that might be diluted by refrigerant.
- Another object of some embodiments is to mitigate a composite adverse voltage by reducing the frequency and/or the amplitude of just certain components of the composite adverse voltage.
- Another object of some embodiments is to retrofit an existing functional compressor with a grounding brush device by replacing a sight glass of the compressor with the grounding brush device.
- Another object of some embodiments is to retrofit an existing functional compressor with a plurality of inductors.
- One or more of these and/or other objects of the invention are provided by a refrigerant compressor system that includes an inductor comprising a ring of magnetic material (a choke) encircling three insulated conductors, wherein the conductors provide the compressor with three-phase electrical power from an adjustable frequency drive that includes a plurality of power switching devices.
- The present invention provides a refrigerant system including a conductive housing made of a conductive material, a refrigerant disposed within the conductive housing, a motor, a compressing element, and an adjustable frequency drive. The conductive housing includes a motor housing and a compressor housing, and the motor includes a rotor, a shaft extending from the rotor, a stator winding disposed within the motor housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the motor housing. The compressing element is disposed within the compressor housing and is coupled to the rotor such that rotation of the rotor motivates the compressing element to compress the refrigerant. The adjustable frequency drive provides the stator winding with three-phase electrical power to rotate the rotor and three conductors electrically coupling the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding. The system also includes an inductor, a refrigerant loop, a common mode current loop and a loop of electrical continuity. The inductor is formed of a ring of magnetic material encircling the three conductors. The refrigerant loop includes the conductive housing, a first heat exchanger, an expansion device, and a second heat exchanger, wherein the compressing element forces the refrigerant to circulate through the refrigerant loop. The common mode current loop includes the adjustable frequency drive, the three conductors, the stator winding, and a capacitive coupling between the compressing element and the conductive housing. The loop of electrical continuity includes the conductive housing, the first heat exchanger, the second heat exchanger, a discharge line extending between the conductive housing and the first heat exchanger, a suction line extending between conductive housing and the second heat exchanger, and an expansion line extending between the first heat exchanger and the second heat exchanger.
- The invention may also include a ground return path conductor extending between the conductive housing and the adjustable frequency drive and made of a material that has greater electrical conductivity than the conductive material, or a grounding contact device supported by the conductive housing and operably contacting the shaft and providing an electrical path between the conductive housing and the shaft.
- The present invention also provides a compressor system including a conductive housing, a refrigerant disposed within the conductive housing, a motor, at least one compressing element, an adjustable frequency drive, and a plurality of inductors. The conductive housing is made of a conductive material and includes a motor housing and a compressor housing. The motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the motor housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the motor housing. The compressing element is disposed within the compressor housing and is coupled to the rotor such that rotation of the rotor motivates the compressing element to compress the refrigerant wherein a capacitance is formed between the compressing element and the conductive housing. The adjustable frequency drive provides the stator winding with three-phase electrical power to rotate the rotor and three conductors electrically couple the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding. The plurality of inductors are arranged in an installed position encircling the three conductors. Each inductor is formed from a ring of magnetic material. A high frequency common mode voltage exists between the conductive housing and the stator winding and the high frequency common mode voltage drives a high frequency common mode current through the conductive housing. The plurality of inductors is sufficient to reduce the common mode current.
- The present invention further provides a compressor system including a conductive housing, a refrigerant disposed within the conductive housing, a motor, at least one compressing element, an adjustable frequency drive, an inductor, and a grounding contact device. The conductive housing is made of a conductive material and includes a motor housing and a compressor housing. The motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the motor housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the motor housing. The compressing element is disposed within the compressor housing and is coupled to the rotor such that rotation of the rotor motivates the compressing element to compress the refrigerant wherein a capacitance is formed between the compressing element and the conductive housing. The adjustable frequency drive provides the stator winding with three-phase electrical power to rotate the rotor and three conductors electrically couple the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding. The inductor may be formed from a ring of magnetic material encircling the three conductors, and the grounding contact device is supported by the motor housing and is in electrical contact with the shaft. The compressor system may also include at least one compressing element and a number of inductors wherein the number of inductors is sufficient to create an inductance reducing a common mode current.
- The present invention further provides a compressor system including a conductive housing, a refrigerant disposed within the conductive housing, a motor, at least one compressing element, an adjustable frequency drive, and an inductor. The conductive housing is made of a conductive material and includes a motor housing and a compressor housing. The motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the motor housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the motor housing. The compressing element is disposed within the compressor housing and is coupled to the rotor such that rotation of the rotor motivates the compressing element to compress the refrigerant wherein a capacitance is formed between the compressing element and the conductive housing. The adjustable frequency drive with a plurality of switching devices that provide the stator winding with three-phase electrical power to rotate the rotor and the shaft at various speeds including a certain rated speed and torque. Three conductors electrically couple the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding and upon doing so the conductive housing is subjected to a composite adverse voltage that is comprised of a plurality of component voltages including a high frequency shaft voltage and an operationally induced shaft voltage. A high frequency common mode voltage is caused by a switching operation of the plurality of switching devices and exists between the conductive housing and the stator winding, and the high frequency common mode voltage drives a high frequency common mode current through the conductive housing. The high frequency common mode current passing through the conductive housing creates a high frequency internal voltage, the high frequency internal voltage provides the high frequency shaft voltage between the conductive housing and the shaft; and the operationally induced shaft voltage exists between the conductive housing and the shaft and is influenced by at least one of an imbalanced ampere-turns of the stator winding, a stator winding asymmetry, a rotor asymmetry, and an electrostatic charge due to operation of the compressor system. The inductor includes a ring of magnetic material and is in an installed position encircling the three conductors. The adjustable frequency drive can power the stator winding to rotate the rotor at the certain rated speed and torque even if the inductor were omitted such that at the certain rated speed and torque the high frequency common mode current has a frequency that is lower by a certain percentage when the inductor is in the installed position than if the inductor were omitted, and the certain percentage is such that the inductor has a greater effect on the high frequency common mode current than on the high frequency common mode voltage, and the inductor has a greater effect on the high frequency common mode current than on the operationally induced shaft voltage, the certain percentage is sufficient to appreciable mitigate the composite adverse voltage.
- The present invention yet further provides a method of retrofitting a compressor system. The compressor system includes a housing; a sight glass supported by the housing in an aperture; a motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the housing; a compressing element disposed within the housing and being coupled to the rotor such that rotation of the rotor motivates the compressing element to compress a refrigerant; an adjustable frequency drive that provides the stator winding with three-phase electrical power to rotate the rotor; and three conductors electrically coupling the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding. The method includes the steps of removing the sight glass from the aperture; and inserting a grounding contact device into the aperture such that the grounding contact device is in electrical contact with the shaft.
- The present invention still further provides a method of retrofitting a functional compressor system. The functional compressor system includes a housing; a motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the housing; a compressing element disposed within the housing and being coupled to the rotor such that rotation of the rotor motivates the compressing element to compress a refrigerant; an adjustable frequency drive that provides the stator winding with three-phase electrical power to rotate the rotor; and three conductors electrically coupling the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding. The method includes the steps of temporarily disabling the functional compressor system; temporarily disconnecting the three conductors; inserting the three conductors through an annular inductor; reconnecting the three conductors; and restoring operation to the functional compressor system. The method may also include the steps of operating the functional compressor system without the annular inductor; prior to temporarily disconnecting the three conductors, generating a first high frequency common mode voltage that drives a first high frequency common mode current through the housing; and after reconnecting the three conductors and restoring operation to the functional compressor system, generating a second high frequency common mode voltage that drives a second high frequency common mode current through the housing, wherein a voltage ratio of the first high frequency common mode voltage to the second high frequency common mode voltage is less than a current ratio of the first high frequency common mode current to the second high frequency common mode current.
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FIG. 1 is a schematically illustrated refrigerant circuit with a cross-sectional view of a compressor system powered by a schematically illustrated AFD. -
FIG. 2 is a schematic view of the system ofFIG. 1 . -
FIG. 3 is a schematic view similar toFIG. 2 but with a grounding contact device and a plurality of inductors omitted. -
FIG. 4 is a view similar toFIG. 1 but showing a method of installing a plurality of inductor. -
FIG. 5 is a view similar toFIG. 4 but showing another method of installing a plurality of inductor. -
FIG. 6 is a view similar toFIGS. 1 , 4 and 5 but showing a sight glass being replaced by a grounding brush device. - A
refrigerant system 10, shown inFIG. 1 , comprises acondenser 12, anexpansion device 14, anevaporator 16, and acompressor system 36 driven at varying speed by an AFD 18 (adjustable frequency drive). For the illustrated embodiment,compressor system 10 comprises two centrifugal impellers (afirst stage impeller 20 and a second stage impeller 22) driven by amotor 24, whereinmotor 24 includes arotor 26, ashaft 28 extending fromrotor 26,stator windings 30, and at least one rolling element bearing 32 that helpssupport shaft 28 within acast iron housing 34.Compressor system 36 includes one ormore inductors 38 and/or a grounding contact device 40 (typically a brush) to help protectbearing 32 against a composite adverse shaft voltage. The composite adverse shaft voltage and its various components will be explained after a more detailed description ofrefrigerant system 10 andcompressor system 36. -
Refrigerant system 10 contains a refrigerant 42 (e.g., R123, R134a, R410, R410a, R22, etc.) thatcompressor system 36 forces from asuction line 44 to adischarge line 46. In the most basic form ofsystem 10, refrigerant discharged toline 46 flows generally sequentially through a first heat exchanger such ascondenser 12 for releasing heat to a heat sink 48 (e.g., via air cooled fin heat exchanger, evaporative cooling tower, a water cooled shell-and-tube heat exchanger, etc.), through anexpansion line 50 for cooling the refrigerant by expansion, and through a second heat exchanger such as evaporator 16 (e.g., a chilled water shell-and-tube heat exchanger) where refrigerant therein vaporizes upon absorbing heat from acooling load 52. Fromevaporator 16,suction line 44 returns vaporized refrigerant back tocompressor system 36 to repeat the cycle. Numerous variations ofsystem 10, including more or less stages of compression and the use of economizer circuits, are well known to those of ordinary skill in the art and are well within the scope of the invention. - Although the actual structure of
compressor system 36 may vary, the illustrated embodiment hasshaft 28 supporting bothrotor 26 ofmotor 24 and at least one compressor element. The term, “compressor element” refers to any component that can be driven to compress a gas. Examples of a compressor element include, but are not limited to,centrifugal impellers rotor 26 andimpellers rotor 26 and the impellers be supported by two separate shafts that are coupled to each other by way of gears or some other appropriate coupling. - For the direct drive example of
FIG. 1 , bearing 32 supports one end ofshaft 28, and asecond bearing 54supports shaft 28 at an intermediate point so thatshaft 28 can supportimpellers Bearing 32 can be a rolling element duplex bearing for providingshaft 28 with both axial and radial support, while bearing 54 can be a hydrodynamic bearing solely for providing radial support. Anoil pump 56 can be used to circulate alubricant 58 throughbearings Rotor 26, which is situated betweenbearings stator windings 30 that are supported by aconductive housing 34 typically formed of cast iron but also formable from other conductive materials such as, for example, steel. The term, “stator windings” refers to a stator core plus the actual coil of wires associated with the core. - To drive
compressor system 36 at various speeds, threeinsulated conductors 60electrically couple AFD 18 tostator windings 30. One example ofAFD 18 is a “LiquiFlo 2.0 AC Drive” manufactured by Reliance Electric, which is part of Rockwell Automation of Milwaukee, Wis. with further headquarters in Greenville, S.C.AFD 18 includes aconverter section 62 with a plurality ofpower switching devices 64 for converting an incoming 3-phaseAC supply voltage 66 to a DC voltage.AFD 18 also includes aninverter section 68 electrically coupled toconverter section 62.Inverter section 68 comprises a plurality ofpower switching devices 70 for converting the DC voltage to a variable frequency 3-phaseelectrical power 72 thatconductors 60 feed tostator windings 30. Examples ofpower switching devices power 72 is generally less than a few hundred hertz so as to rotaterotor 26 at a reasonable speed withinhousing 34. -
Cast iron housing 34 comprises a castiron motor housing 74 and a castiron compressor housing 76 that can be bolted or otherwise connected at ahousing joint 78. The term, “cast iron’ refers to an iron-based material containing at least 2% carbon.Housings Compressor housing 76, for instance, might be comprised of afirst stage housing 76 a containingimpeller 20 and asecond stage housing 76b containing impeller 22.Motor housing 74 generally containsrotor 26 and stator windings 30. -
Refrigerant 42 exists withinmotor housing 74 as well as incompressor housing 76, thuslubricant 58 inmotor housing 74 can be contaminated with at least a trace ofrefrigerant 42, and refrigerant 42 incompressor housing 76 may contain at least a trace oflubricant 58. A trace amount of refrigerant can alter the dielectric and/or other properties oflubricant 58, so the contamination might be a factor that alters the effect that the composite adverse voltage has on the lifespan of bearing 32 and/orlubricant 58. - The composite adverse voltage can best be understood with reference to the schematic diagrams of
FIGS. 2 and 3 .FIG. 2 corresponds toFIG. 1 , andFIG. 3 is similar toFIG. 2 but withinductor 38 and groundingbrush device 40 omitted. To help explain the composite adverse voltage and related phenomena, some definitions are provided as follows. - High frequency common mode voltage refers to the component of voltage present at all three
motor winding terminals 80 relative to aground 82. The high frequency common mode voltage is not the primary component of the three-phase electrical power that drivesrotor 26 at a few hundred hertz, but rather the high frequency common mode voltage is caused by the rapid switching rates or high dv/dt of the power switching devices withinAFD 18. The rapid switching rates can generate frequencies in the range of 500 kHz to perhaps as high as 15 MHz. The term, “high frequency” used herein and throughout refers to at least 100 kHz. - High frequency common mode current refers to the electrical current flowing throughout
housing 34 due to the high frequency common mode voltage and a winding-to-housing capacitance 84 that naturally exists betweenhousing 34 and stator windings 30. Although common mode currents can have components across a broad frequency range, high frequency common mode current specifically refers to components that are at frequencies of at least 100 kHz. A dashedline 86 ofFIG. 2 represents high frequency common mode current flowing throughmotor housing 74 andcompressor housing 76. Iflines housing 34, some high frequency common mode current might even flow throughdischarge line 46 orsuction line 44. In some cases,lines housing 34. High frequency common mode current can also flow along a common modecurrent loop 88 comprisingAFD 18, the threeinsulated conductors 60,stator windings 30,capacitive coupling 84, and a groundreturn path conductor 90 extending betweenhousing 34 andAFD 18. To minimize the voltage potential between apoint 92 onhousing 34 and asecond point 94 onAFD 18,conductor 90 can be made of a material, such as copper, that has an electrical conductivity that is greater than that of the cast iron material ofhousing 34. The copper of groundreturn path conductor 90 might also have an electrical conductivity that is greater than the mild steel oflines path conductor 90 can be made of steel or other electrically conductive materials. In cases whereAFD 18 is mounted directly tohousing 34, ground returnpath conductor 90 can be comprised of brackets, an electrical enclosure and/or fasteners that facilitate attachingAFD 18 tohousing 34. - High frequency internal voltage, generally denoted by
numeral 96, refers to voltage gradients created by high frequency common mode current flowing throughhousing 34. Due to theinherent inductance 98 andresistance 100 ofhousing 34, the high frequency internal voltage can vary along the length ofhousing 34 and can be affected by various physical characteristics ofrefrigerant system 10. Some examples of such physical characteristics include, but are not limited to, the overall length ofhousing 34, the number of impellers, the location ofimpellers motor 24, the mass and thickness ofhousing 34, and various joints such as joint 78. A system loop ofelectrical continuity 102 might also affect the voltage gradients of the high frequency internal voltage, wherein the system loop ofelectrical continuity 102 might comprise various electrically conductive components such ascast iron housing 34,discharge line 46,condenser 16,expansion line 50,evaporator 16, andsuction line 44. - High frequency shaft voltage is a voltage component that occurs at frequencies of at least 100 kHz and is due to a voltage differential between
shaft 28 and the high frequency internal voltage. High frequency shaft voltage can exist across bearing 32, e.g., between apoint 104 onshaft 28 and anearby point 106 onhousing 74. High frequency common mode current flowing throughouthousing 34 creates high frequency internal voltage gradients that vary in amplitude and location, thus high frequency shaft voltage of varying amplitude may also develop at bearing 54 and at alabyrinth seal compressor system 36. - Operationally induced shaft voltage, schematically represented by a
line 112, is another voltage component that can exist across bearing 32, e.g., betweenpoint 104 onshaft 28 and anearby point 114 onhousing 34. Operationally induced shaft voltage occurs at frequencies that are substantially less than 100 kHz and can include static DC voltage. Operationally induced shaft voltage might develop due to various known or unknown reasons such as, for example, stator or rotor asymmetries, imbalanced ampere-turns in the stator, stator to rotor capacitance, or static charge generated by rotating members withinhousing 34. - Composite adverse shaft voltage is a total voltage that can exist across bearing 32 (e.g., between
points 104 and 106) and can be a combination of component voltages such as the high frequency shaft voltage and the operationally induced shaft voltage. The high frequency common mode voltage, the high frequency common mode current, and the high frequency internal voltage might also influence the composite adverse shaft voltage's severity or its damaging impact on bearing 32,lubricant 58,seal 108, bearing 54, and other components ofcompressor system 36. The actual severity can be difficult to quantify because the potentially damaging impact can be a function of voltage amplitude, frequency, and total electrical discharge energy. In some cases, the composite adverse voltage across bearing 32 can lead to a dielectric breakdown oflubricant 58, and the resulting electrical discharge or current through bearing 32 can degrade the lubricant and/or pit the bearing's inner and outer races. - This problem can be addressed by mitigating one or more components or influencing factors of the composite adverse shaft voltage. In some embodiments, for example, the operationally induced shaft voltage can be reduced by adding grounding
brush device 40 tomotor housing 74.Brush 40 provides an electrically conductive path through which the operationally induced shaft voltage and can discharge directly into anendplate 116 ofmotor housing 74, whereby the current driven by the operationally induced shaft voltage can bypassbearing 32. Although groundingbrush device 40 can be of various designs, in a currently preferred embodiment,device 40 comprises atubular housing 118 that attaches toendplate 116 and an electricallyconductive wire brush 120 that brushes againstshaft 28 as the shaft rotates. Electrical current can flow from the end ofshaft 28, throughbrush 120, throughtubular housing 118, and intoendplate 116 ofmotor housing 74. - Even if grounding
brush device 40 can electrically ground the end ofshaft 28, a high frequency shaft voltage might still exist betweenshaft 28 and various points of housing 34 (e.g., at bearing 32, bearing 54, or seal 108) because the high frequency common mode current 86 creates a range of voltage gradients (high frequency internal voltage) throughouthousing 34. Thus, the high frequency shaft voltage, which is a component of the composite adverse shaft voltage, might still cause damage at some points alongshaft 28 if groundingbrush device 40 is the only solution being applied to address the problem. - To help prevent the high frequency shaft voltage from damaging
bearing 32, ground returnpath conductor 90 might be connected tomotor housing 74 at a point that is as close as possible to bearing 32. Doing so, however, would place ground return path conductor 90 a substantial distance from bearing 54 andseal 108, which could increase the amplitude of the high frequency shaft voltage at those locations, and thus create potential voltage discharge problems for bearing 54 andseal 108, especially ifhousing 34 is particularly long. As a compromise,connection point 92 should be at an optimum axial location that is best forbearings housing 34, parallel to shaft 28), such an optimum location is between bearing 32 andseal 108, between bearing 32 andimpeller 20, and preferably betweenbearings - To further address the voltage discharge problem, the composite adverse shaft voltage can be effectively mitigated by reducing the amplitude or frequency of the high frequency shaft voltage, which can be accomplished by reducing the amplitude or frequency of the high frequency common mode current. It has been found that the amplitude and particularly the frequency of the high frequency common mode current can be reduced by adding inductance to common mode
current loop 88. Such inductance can be added by installing one ofmore inductor 38, each of which can comprise a ring of magnetic material, so thatinductor 38 encircle the threeinsulated conductors 60 but do not encircle ground returnpath conductor 90. Examples of magnet materials might include, but are not limited to, pure or various combinations of ferrite, iron oxide ceramic, manganese-zinc, nickel-zinc, etc. - The style and quantity of
inductor 38 might depend on the style and size ofcompressor system 36 andrefrigerant system 10. In some embodiments,inductor 38 is a Magnetec model number M-116 or M-117 (Magnetec GmbH of Langenselbold, Germany). The quantity and/or size ofinductor 38 should be such that one ormore inductor 38 provide sufficient inductance to reduce the magnitude and/or frequency of the common mode currents to a non-damaging level. Positive results have been achieved when the quantity ofinductor 38 are equal to or greater than the quantity of compressing elements or impellers incompressor housing 76. Sinceinductor 38 encircle insulatedconductors 60 and are not actually wired to them,compressor system 36 is functional regardless of whetherinductor 38 are installed (FIG. 2 ) or omitted (FIG. 3 ). -
FIG. 4 illustrates a method of retrofitting an existingfunctional compressor system 36 withinductor 38. The retrofitting steps could be as follows: temporarily disablingcompressor system 36 by de-energizing it, temporarily disconnecting the threeinsulated conductors 60 as indicated byarrow 122, inserting the three insulated conductors throughinductor 38 as indicated byarrow 124, reconnecting the threeinsulated conductors 60 as indicated byarrow 126, and restoring operation tocompressor system 36 by energizing it throughAFD 18. - In some cases, the installation of
inductor 38 reduces the frequency of the high frequency common mode current such that inductor 38 (for a given or certain rated speed and torque) has a greater effect (amplitude or frequency reduction) on the high frequency common mode current than on the high frequency common mode voltage, andinductor 38 has a greater effect on the high frequency common mode current than on the operationally induced shaft voltage. In other words, prior to installinginductor 38,compressor system 36 generates a first high frequency common mode voltage that drives a first high frequency common mode current throughhousing 34; and after installinginductor 38,compressor system 36 generates a second high frequency common mode voltage that drives a second high frequency common mode current throughhousing 34, wherein a voltage ratio of the first high frequency common mode voltage to the second high frequency common mode voltage is less than a current ratio of the first high frequency common mode current to the second high frequency common mode current. In some cases, the first high frequency common mode voltage is at a first frequency, the second high frequency common mode voltage is at a second frequency, the first high frequency common mode current is at a third frequency, the second high frequency common mode current is at a fourth frequency, and a first ratio of the first frequency to the second frequency may not be the same as a second ratio of the third frequency to the fourth frequency.Inductor 38 preferably reduces the frequency of the high frequency common mode current to less then 500 kHz. - It is well within the scope of the invention to retrofit
compressor system 36 without having to disconnectconductors 60.FIG. 5 , for instance, shows asplit inductor 38′ formed from a ring of magnetic material that can be open and closed to facilitate its installation. In this case, the retrofitting steps could be as follows: selectinginductor 38′ that is selectively configurable to an open position and a closed position; whileinductor 38′ is in the open position, positioninginductor 38′ adjacent to the threeinsulated conductors 60 as indicated byarrow 128; reconfiguringinductor 38′ to the closed position, as indicated byarrow 130, so thatinductor 38′ encircles the threeinsulated conductors 60; and clamping the two halves ofinductor 38′ together (via a hose clamp, tape, wire, clasp, fastener, etc.) so thatinductor 38′ is held in the closed position. -
FIG. 6 illustrates a method of retrofitting an existingfunctional compressor system 36 with grounding contact device such as groundingbrush device 40. The retrofitting steps could be as follows: unscrewing or otherwise removing an existingsight glass 132 from an aperture 138 inendplate 116 ofmotor housing 74, as indicated by arrow 134; and adding groundingbrush device 40 to the aperture 138 in thehousing 74, as indicated by arrow 136, such that groundingbrush device 40 is in electrical contact withshaft 28. In some cases, groundingbrush device 40 can be screwed into a threaded hole 138 from whichsight glass 132 was removed. - Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art; therefore, the scope of the invention is to be determined by reference to the following claims.
Claims (48)
1. (canceled)
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38. (canceled)
39. A method of retrofitting a compressor system, wherein the compressor system comprises a housing; a sight glass supported by the housing in an aperture; a motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the housing; a compressing element disposed within the housing and being coupled to the rotor such that rotation of the rotor motivates the compressing element to compress a refrigerant; an adjustable frequency drive that provides the stator winding with three-phase electrical power to rotate the rotor; and three conductors electrically coupling the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding; the method comprising:
removing the sight glass from the aperture; and
inserting a grounding contact device into the aperture such that the grounding contact device is in electrical contact with the shaft.
40. The method of claim 39 , further comprising encircling the three conductors with an inductor made of a magnetic material.
41. The method of claim 39 wherein the compressor system includes a ground return path conductor extending between the adjustable frequency drive and the housing, the ground return path conductor is made of an electrically conductive material that has greater electrical conductivity than an iron-based material of which the housing is made, the method further comprising encircling the three conductors with an inductor made of a magnetic material while leaving the ground return path conductor lie outside the inductor, whereby the inductor does not encircle the ground return path conductor.
42. A method of retrofitting a functional compressor system, wherein the functional compressor system comprises a housing; a motor that includes a rotor, a shaft extending from the rotor, a stator winding disposed within the housing in proximity with the rotor, and a bearing supporting the shaft and the rotor within the housing; a compressing element disposed within the housing and being coupled to the rotor such that rotation of the rotor motivates the compressing element to compress a refrigerant; an adjustable frequency drive that provides the stator winding with three-phase electrical power to rotate the rotor; and three conductors electrically coupling the adjustable frequency drive to the stator winding such that the three conductors can convey the three-phase electrical power to the stator winding; the method comprising:
temporarily disabling the functional compressor system;
temporarily disconnecting the three conductors;
inserting the three conductors through an annular inductor;
reconnecting the three conductors; and
restoring operation to the functional compressor system.
43. The method of claim 42 , further comprising:
operating the functional compressor system without the annular inductor;
prior to temporarily disconnecting the three conductors, generating a first high frequency common mode voltage that drives a first high frequency common mode current through the housing; and
after reconnecting the three conductors and restoring operation to the functional compressor system, generating a second high frequency common mode voltage that drives a second high frequency common mode current through the housing, wherein a voltage ratio of the first high frequency common mode voltage to the second high frequency common mode voltage may not be the same as a current ratio of the first high frequency common mode current to the second high frequency common mode current.
44. The method of claim 42 , further comprising:
prior to temporarily disconnecting the three conductors, operating the functional compressor system without the annular inductor and generating a first high frequency common mode voltage that drives a first high frequency common mode current through the housing; and
after reconnecting the three conductors and restoring operation to the functional compressor system, operating the functional compressor system with the annular inductor and generating a second high frequency common mode voltage that drives a second high frequency common mode current through the housing, wherein:
a) the first high frequency common mode voltage is at a first frequency,
b) the second high frequency common mode voltage is at a second frequency,
c) the first high frequency common mode current is at a third frequency,
d) the second high frequency common mode current is at a fourth frequency, and
e) a first ratio of the first frequency to the second frequency may not be the same as a second ratio of the third frequency to the fourth frequency.
45. The method of claim 42 wherein the compressor system includes a ground return path conductor extending between the adjustable frequency drive and the housing, the ground return path conductor is made of an electrically conductive material that has greater electrical conductivity than an iron-based material of which the housing is made, the method further comprising leaving the ground return path conductor lying outside the annular inductor, whereby the annular inductor does not encircle the ground return path conductor.
46. The method of claim 42 wherein the inserting step comprises the further steps of: selecting the annular inductor from a ring of magnetic material that is selectively configurable to an open position and a closed position; positioning the ring of magnetic material adjacent to the three conductors while the ring of magnetic material is in the open position; and reconfiguring the ring of magnetic material to the closed position so that the ring of magnetic material encircles the three conductors, thereby installing the annular inductor.
47. The method of claim 46 further including the steps of: removing a sight glass from an aperture in the housing; and adding a grounding contact device to the aperture such that the grounding contact device is in electrical contact with the shaft.
48. The method of claim 46 wherein the inductor selecting step includes forming the inductor from a number of inductors such that the number of inductors is sufficient to reduce the common mode current.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US13/065,977 US20110179644A1 (en) | 2007-01-05 | 2011-04-04 | System for protecting bearings and seals of refrigerant compressor |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US11/650,279 US7922467B2 (en) | 2007-01-05 | 2007-01-05 | System for protecting bearings and seals of a refrigerant compressor |
US13/065,977 US20110179644A1 (en) | 2007-01-05 | 2011-04-04 | System for protecting bearings and seals of refrigerant compressor |
Related Parent Applications (1)
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US11/650,279 Division US7922467B2 (en) | 2007-01-05 | 2007-01-05 | System for protecting bearings and seals of a refrigerant compressor |
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US20110179644A1 true US20110179644A1 (en) | 2011-07-28 |
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US11/650,279 Active 2030-02-10 US7922467B2 (en) | 2007-01-05 | 2007-01-05 | System for protecting bearings and seals of a refrigerant compressor |
US13/065,977 Abandoned US20110179644A1 (en) | 2007-01-05 | 2011-04-04 | System for protecting bearings and seals of refrigerant compressor |
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US11/650,279 Active 2030-02-10 US7922467B2 (en) | 2007-01-05 | 2007-01-05 | System for protecting bearings and seals of a refrigerant compressor |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3578822A4 (en) * | 2017-01-31 | 2020-10-28 | Hitachi Industrial Equipment Systems Co., Ltd. | Scroll compressor |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5433987B2 (en) * | 2008-06-13 | 2014-03-05 | ダイキン工業株式会社 | Refrigeration equipment |
JP5192440B2 (en) * | 2009-05-15 | 2013-05-08 | 株式会社神戸製鋼所 | Motor and compressor provided with the same |
DE112010004398A5 (en) * | 2009-11-12 | 2013-03-21 | Conti Temic Microelectronic Gmbh | CONTROL UNIT FOR AN ELECTRIC DRIVE DEVICE AND ELECTRIC DRIVING DEVICE WITH SUCH A CONTROL GEAR |
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US10008909B2 (en) * | 2015-04-24 | 2018-06-26 | Asmo Co., Ltd. | Motor driving control device for vehicle |
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CN109952440A (en) * | 2016-08-25 | 2019-06-28 | 丹佛斯公司 | Coolant compressor |
US20180274527A1 (en) * | 2017-03-24 | 2018-09-27 | Johnson Controls Technology Company | Labyrinth seals for compressor |
DE102017007857A1 (en) * | 2017-08-23 | 2019-02-28 | Deckel Maho Pfronten Gmbh | Spindle device for use on a numerically controlled machine tool |
JP2019180194A (en) * | 2018-03-30 | 2019-10-17 | 日本電産サーボ株式会社 | motor |
JP2019180139A (en) * | 2018-03-30 | 2019-10-17 | 日本電産サーボ株式会社 | motor |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4375612A (en) * | 1979-09-12 | 1983-03-01 | Borg-Warner Corporation | Controlled regenerative d-c power supply |
US5553997A (en) * | 1994-11-28 | 1996-09-10 | American Standard Inc. | Control method and apparatus for a centrifugal chiller using a variable speed impeller motor drive |
US5646498A (en) * | 1995-08-07 | 1997-07-08 | Eaton Corporation | Conducted emission radiation suppression in inverter drives |
US5990654A (en) * | 1998-01-21 | 1999-11-23 | Allen-Bradley Company, Llc | Apparatus for eliminating motor voltage reflections and reducing EMI currents |
US6028405A (en) * | 1998-01-14 | 2000-02-22 | Yaskawa Electric America, Inc. | Variable frequency drive noise attenuation circuit |
US6068457A (en) * | 1998-12-03 | 2000-05-30 | American Standard Inc. | Lobed pinion drive shaft for refrigeration compressor |
US6116046A (en) * | 1999-03-05 | 2000-09-12 | American Standard Inc. | Refrigeration chiller with assured start-up lubricant supply |
US6167713B1 (en) * | 1999-03-12 | 2001-01-02 | American Standard Inc. | Falling film evaporator having two-phase distribution system |
US6208098B1 (en) * | 1998-03-02 | 2001-03-27 | Yaskawa Electric America, Inc. | Variable frequency drive noise attenuation circuit |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3122894A (en) * | 1962-07-05 | 1964-03-03 | American Radiator & Standard | Hermetic motor cooling by direct expansion of system refrigerant into motor |
US6670733B2 (en) * | 2001-09-27 | 2003-12-30 | Reliance Electric Technologies, Llc | System and method of reducing bearing voltage |
US7173832B2 (en) * | 2002-04-15 | 2007-02-06 | Jialin Wu | Multifunction power convertor |
US6987338B1 (en) * | 2003-12-29 | 2006-01-17 | Lavasser Leonard J | Ground strap for a motor having a plastic housing |
-
2007
- 2007-01-05 US US11/650,279 patent/US7922467B2/en active Active
-
2011
- 2011-04-04 US US13/065,977 patent/US20110179644A1/en not_active Abandoned
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4375612A (en) * | 1979-09-12 | 1983-03-01 | Borg-Warner Corporation | Controlled regenerative d-c power supply |
US5553997A (en) * | 1994-11-28 | 1996-09-10 | American Standard Inc. | Control method and apparatus for a centrifugal chiller using a variable speed impeller motor drive |
US5646498A (en) * | 1995-08-07 | 1997-07-08 | Eaton Corporation | Conducted emission radiation suppression in inverter drives |
US6028405A (en) * | 1998-01-14 | 2000-02-22 | Yaskawa Electric America, Inc. | Variable frequency drive noise attenuation circuit |
US5990654A (en) * | 1998-01-21 | 1999-11-23 | Allen-Bradley Company, Llc | Apparatus for eliminating motor voltage reflections and reducing EMI currents |
US6208098B1 (en) * | 1998-03-02 | 2001-03-27 | Yaskawa Electric America, Inc. | Variable frequency drive noise attenuation circuit |
US6068457A (en) * | 1998-12-03 | 2000-05-30 | American Standard Inc. | Lobed pinion drive shaft for refrigeration compressor |
US6116046A (en) * | 1999-03-05 | 2000-09-12 | American Standard Inc. | Refrigeration chiller with assured start-up lubricant supply |
US6167713B1 (en) * | 1999-03-12 | 2001-01-02 | American Standard Inc. | Falling film evaporator having two-phase distribution system |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3578822A4 (en) * | 2017-01-31 | 2020-10-28 | Hitachi Industrial Equipment Systems Co., Ltd. | Scroll compressor |
US11469643B2 (en) | 2017-01-31 | 2022-10-11 | Hitachi Industrial Equipment Systems Co., Ltd. | Scroll compressor having axial fan and discharge brush |
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US20080166246A1 (en) | 2008-07-10 |
US7922467B2 (en) | 2011-04-12 |
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