An enhanced API 546

IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS The third edition of this common performance standard for large synchronous machines © FOTOSEARCH BY BILL LOCKLEY, MARK CHISHOLM, TRAVIS GRIFFITH, GABE D’ALLEVA, & BARRY WOOD HE STANDARD AMERICAN PETRO- of all aspects of a synchronous machine When compared leum Institute (API) 546 third edition was with earlier editions, this edition has various enhancements written by and for users, consultants, and designed to make it easier to purchase or specify a more manufacturers to provide a common perform- durable machine It has new requirements in some areas ance standard for large synchronous machines The standard is such as excitation systems, frame vibration, and insulation designed as a stand-alone document listing the requirements tests, as well as improved sections concerning dynamic analysis T and thermally induced vibration changes To reduce the risk 12 Digital Object Identifier 10.1109/MIAS.2010.938394 of confusion, it should be used with the supplied data sheets 1077-2618/10/$26.00©2010 IEEE Durability of Synchronous Machines Large synchronous motors and generators are often the most important pieces of electrical machinery in large process plants such as refineries, compressor stations, chemical plants, and other process facilities API Standard 546 third edition [1] has been written to assist users, consultants, and manufacturers of these large synchronous machines Users and consultants can use it to specify a high-quality machine and more easily compare proposals, while manufacturers have a standard specification that will make their proposals easier to produce As part of the revision process while developing this third edition, the working group looked at issues that had been concerning users regarding the durability of the machines and attempted to address these issues We believe that the changes have made the document better at defining what is needed for a durable cost-effective machine The standard uses data sheets to define particular requirements and equipment offerings It is essential that users fill in these data sheets so that manufacturers know exactly what is required of their product There are separate data sheets for motors and generators as well as for North American and international practices and standards To assist users in filling out the data sheets, the data sheet guides have been updated Why Use Synchronous Machines? Generally, a power supply needs to run at a fixed predetermined frequency (typically 50 or 60 Hz) This requirement dictates the use of synchronous generators or at least induction generators with frequency converters For motor applications, a more comprehensive evaluation may be required to determine the most appropriate solution Some of the factors are summarized in Table In addition to these factors, there are other softer, less readily quantifiable issues that a user may be concerned about, e.g., excitation systems, control systems, and reliability These factors have been more thoroughly addressed in the latest edition of the standard History of the Standard In 1986, at the completion of the document for the second edition of API Standard 541, Form-Wound Squirrel-Cage Induction Motors 250 hp and Larger, participants concluded that a similar standard was needed to address synchronous machines A task force was formed from the mutual APIPetroleum and Chemical Industry Committee motor resource group The task force included representation from process industry members and large machine manufacturers The first edition of API Standard 546, Form-Wound Brushless Synchronous Motors, was published in June 1990 Despite the similarity of participation in the 541 and 546 groups, substantive differences existed between the two documents irrespective of the technological differences The 541 task force was then reconstituted to review and update the induction motor standard, resulting in the printing of the third edition in 1995 As before, work on the TABLE SYNCHRONOUS AND INDUCTION MOTOR COMPARISON Capital cost Power consumption and efficiency Power factor Starting current Accelerating torque margin Pulsating/oscillating torque during starting Current pulsations for nonsteadystate loads such as reciprocating compressors Rotor inertia (application dependent) Suitability for adjustable speed drive Two-pole applications Lead-time Ride-through supply interruptions Induction Advantage Synchronous Advantage IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS Factor 13 IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS A slow speed rotor (Photo courtesy of General Electric.) 14 second edition of 546 started immediately after completion of 541 To keep within the American National Standards Institute mandated reissue/reaffirm schedule, the task force labored on an expedited basis to issue the standard in June 1997 Important changes were the inclusion of generators (elevated from parenthetical statements at the end of paragraphs) and establishment of a power rating, so the title was changed to Brushless Synchronous Machines—500 kVA and Larger Generator data sheets were added, but the substantive differences still existed As before, the 541 group revised and published its fourth edition in 2004 The API Subcommittee on Electrical Equipment (SOEE) also directed that the substantive differences be resolved, and a mutual list of electrical standard paragraphs be developed where commonalities existed, i.e., insulation systems and mechanical design features API also inserted a new group in the schedule to address the needs for intermediate-sized induction machines, and API 547, General-Purpose Form-Wound Squirrel Cage Induction Motors— 250 hp and Larger, was introduced in 2005 At the API 2005 Spring Refining Meeting, the present 546 task force was formed and the review cycle initiated Improvements are herein detailed API members recognize the distinctive nature, severe duty, and special operating demands for electric machines within their process industry The API series of electrical standards are continuously evolved to address those concerns and communicate specific requirements to various internal and external engineering organizations Importantly, they establish minimum design, performance, and testing criteria for manufacturers This also serves to generate A higher speed rotor (Photo courtesy of General Electric.) common technical understanding and standardize machines to improve operating reliability and reduce cost Significant changes have occurred in both the process and manufacturing industries It is common for large machine manufacturers to offer both induction and synchronous equipment, so the harmonization in language between the 541– 547 induction and the 546-type synchronous machines remained an important issue Users’ needs have also changed with heightened attention toward accomplishing generalpurpose requirements without having to procure specialpurpose machines Improvements in materials, design, and construction of machines, as well as changes in codes, regulations, other standards, and implementation of internationally based mandates [i.e., International Electrotechnical Commission (IEC) and International Organization for Standardization] have spurred equal development within API 546 Typical synchronous machine rotors are shown in Figure (slow speed machine) and Figure (higher speed machine) Contents of the Standard Some areas where the third edition has been significantly changed from its predecessor are given in the subsequent sections Mechanical Requirements As noted in the “History of the Standard” section, multiple interests affect the writing and consensus of any document API 541 and 546 have traditionally reflected the input and experience of electrical engineers Within the API’s Committee on Refining Equipment (parent of the SOEE) is another interest group: the Subcommittee on Mechanical Equipment (SOME) These equally skilled group of engineers have concerns usually related to the driven equipment, such as pumps, compressors, and other nonelectrical rotating devices Through past balloting procedures, SOME members had comments and desired to insert the API 600 (mechanical series) experience They saw a need to generate a common rotational dynamics approach across all API machines A small team of SOME members assembled and recommended mechanical changes, which were considered and implemented where appropriate by the 546 task force Many of the dynamic analysis requirements suggested by the SOME group were adopted, such as the requirement to update the dynamic model if the test results varied from prediction by more than 5% and the methods for handling nonmassive foundations The requirements for dynamic analyses are now more clearly defined However, the prime requirements for achieving satisfactory vibration performance and verifying separation margin from rotor and support system critical speeds were maintained as being performance on the test stand rather than by analysis The bearing housing and shaft vibration limit figures [Figures 4.1(a) and (b) and 4.2(a) and (b) in API 546] have been updated to include both U.S customary and metric units and to make them more readable Also, the figures for the shaft vibration limits have been updated to make them more consistent with the vibration limit equations In this context, the allowable shaft vibration has been slightly reduced for higher speed machines so that a 3,600 r/min machine now has a maximum unfiltered peak-to-peak vibration displacement of 46 lm (1.83 mil) versus the previous 51 lm (2.0 mil) Otherwise, the vibration limits remain the same as in the 546 second edition n Excitation System Partial-Discharge Monitors Partial-discharge (PD) monitoring systems are becoming more common on higher voltage fixed-speed machines to assist in predicting and avoiding stator winding insulation problems The standard now lists this equipment as an option and gives requirements for the PD sensors, including internal wiring, terminal boxes, output terminals, and output devices Insulation Quality One concern with higher voltage (typically more than 4,160 V) machines in general is the possibility of voids in the stator insulation, especially with the coils that are near to full-line voltage Internal insulation voids tend to cause excessive PD across the voids in these stator coils, which may eventually lead to a winding failure The standard has sections listing optional tests and inspection to reduce the possibility of PD-induced failures in service n n n n TEWAC Heat Exchanger Thermal Test There have been cases in the field where totally enclosed water-to-air-cooled (TEWAC) machines have not been able to provide full power output because the water-to-air heat exchanger has not been capable of dissipating the heat generated by the machine, even though the machine losses were per design To ensure that the heat exchangers are adequate to handle the heat generated with the specified cooling water conditions and flow, an optional “Heat Exchanger Performance Verification Test” has been included in the document This minimum 4-h test requires the cooling water flow and temperature to be maintained as close as practical to rated conditions while the machine is operating in the factory at rated temperature With rated cooling water conditions, the air out of the heat exchanger into the motor shall not exceed the specified level, usually 40 °C When practical, this may be performed as part of the complete test Alternatively, the user and manufacturer may jointly develop an alternative test if the specified test is impractical Data Sheets and Data Sheet Guide API 546 third edition is an improved and comprehensive synchronous machine specification that reflects current user performance requirements for highly engineered machines The specification of high-performance machines requires IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS An area where some users’ experience indicated that synchronous motors had issues with reliability was the excitation system, including the power supply to the exciter and the field application package, plus the stationary and rotating portions of the exciter The working group looked at the areas where problems had been reported and developed requirements for those parts of the excitation system Some of the issues addressed were the following: n Ride-Through of Dips or Spikes in the Power and Control Supply Voltage: This was addressed by requiring a constant voltage transformer, phase-controlled rectifier, or other means to maintain at least 95% nominal exciter input voltage for s for a 50% voltage dip and by requiring input surge protection n Failures of Rotating Electronics: A 48-h burn-in is now required, plus an overvoltage protection circuit, a diode voltage rating of at least 1,200 V, and a 125 °C limit on worst case junction temperature Diode failure detection is listed as an option for fixed-speed applications Device test and rotor monitoring systems are also options n Stationary and Rotating Winding Failures: The windings are now required to be capable of withstanding spikes from the solid-state switching, plus common mode voltages, and to be braced adequately for centrifugal forces when applicable n Field Application and Control Problems: The criteria for field application of a motor (speed, current, time, etc.) are not specified; however, the method must be jointly agreed between the user and manufacturer In addition, wiring methods in the control panel are specified to improve reliability and avoid interference between systems n Field Discharge Resistor Capabilities: Bracing and thermal requirements are specified, plus a requirement that the resistor be waterproof We believe the requirements introduced will improve performance in these areas and make synchronous motors more reliable for users When specified, during winding and coil impregnation, two extra sacrificial coils shall be made and impregnated along with the rest of the winding, and after surge tests at higher than standard levels, they are cut into segments and inspected Any visible voids would be cause for further discussion The finally completed stator may have a “Power Factor Tip-Up Test” specified to be performed along with the other insulation tests This test looks at the change in insulation power factor from a relatively low voltage to a voltage at approximately operating voltage A greater than expected increase is a possible indication of excessive voids IEEE Standard 286 [2] or IEC Standard 60894 [3] is called up to provide the requirements of this test An off-line PD test may be specified This test determines the PD performance of the winding for each phase IEEE Standard 1434 [4] or IEC TS 60034-27 [5] are used as the basis for this test Each manufacturer’s insulation system behaves slightly different and has variable levels of acceptable performance under some of these tests Therefore, there are not yet hard and fast rules indicating what void size, tip-up figures, or PD measurements are acceptable The acceptance criteria should be discussed and agreed upon between the user and manufacturer before the tests are done Not all the earlier tests have strict “Pass/Fail” criteria; however, the API task force concluded that the tests were still useful in many cases Different manufacturers may see a wide variation of results in some tests for insulation systems, which perform equally well In many cases, the tests provide useful data to compare with results from other machines from the same manufacturer In future, we expect that better defined acceptance criteria will be developed 15 TABLE DATA SHEET LAYOUT IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS Section Headings 16 Motor Data Sheets Generator Data Sheets General General Lubrication system Lubrication system Special conditions Special conditions Main conduit box Main conduit box Accessories Accessories Controls Controls Driver equipment information Driver equipment information Miscellaneous Miscellaneous Motor data—first section Generator data—first section 10 Motor data—second section Generator data—second section 11 Stator and rotor winding repair data Stator and rotor winding repair data 12 Analysis, shop inspection, and tests Analysis, shop inspection, and tests significant user information The standard requires completed data sheets and identifies 127 bulleted paragraphs (), where a decision or additional information is required by the user An API 546 machine cannot be built without a data sheet The basis of the standard is for the manufacturer to design and build an engineered machine to meet the exact requirements of the end user as defined by the 11-page data sheet An incomplete data sheet, incorrect information on a data sheet, or worst of all no data sheet may result in an inadequate or incompatible machine design requiring costly modification or redesign The API 546 third edition data sheets and supporting data sheet guides have been extensively revised and updated There are separate multipage sheets for motors and generators with further subdivisions between North American and international practices The data sheet changes include: layout and format revisions, changes to technical content, and user-selected inspection and tests The new data sheets are structured with the sections as shown in Table The changes made in the data sheet format include the following: n The data sheet layout is changed from a word processor-based format to a spreadsheet format n An improved method of selecting and deselecting data sheet items with a single keystroke is included n Color-coded line items to distinguish between usercompleted and manufacturer-completed line items are included n API 546 paragraph references are shown adjacent to applicable line items for easy reference n Metric unit motor and generator data sheets were added to the customary English unit motor and generator data sheets n Bold-type on data sheet line items are used to identify typical standard default selection n Required minimum factory tests and meetings are preselected on the data sheet testing section There is more space for user notes and additional technical requirements n The number of data sheet pages increased from ten to 11 The following are basic descriptions of the contents of each of the data sheet sections mentioned in Table The General section covers basic machine ratings, site data, enclosure types, machine mounting, electrical supply system, and bearing information Some of the significant data sheet technical changes in the General section include: n added a maximum sound pressure level requirement of 85 dBA or other user-specified sound level n explosion protection “Ex”-labeled machines and thirdparty certification added on metric data sheets n adjustable speed drive (ASD) section added on motor data sheets n TEWAC heat exchanger section was moved from the Accessories section to under the TEWAC enclosure section n Weather protected, Type II (WP II) filter information was moved from the Accessories section to under the WP II enclosure section The Lubrication System section describes the type of lubrication, method, and supply source of the machine lubrication A data sheet change in the Lubrication System section includes: n deleted external lubrication pump skid-related line items from the Lubrication System section, since machine manufacturer normally does not provide an external skid with lubrication pumps The Special Conditions section lists options for the user to select one piece shaft forging, special vibration requirements, cost data for efficiency evaluation factor determination, local code requirements, special overspeed requirement, and any user-identified external forces on machine enclosure that may affect performance A data sheet change in the Special Conditions section includes: n for loads such as reciprocating compressors where the torque requirements vary through a revolution of the motor, a line item option was added for the manufacturer to supply current variation information, calculated efficiencies, and efficiency calculation method on motor data sheets The Generator and Motor Data—Second section provides areas where the manufacturer provides bearing dimensions data, machine parameters, and preliminary parameters to be supplied with the proposal One of the changes to the Generator and Motor Data—Second section is the addition of a new subsection for the user to select an option for the manufacturer to supply preliminary parameters with the proposal for user system studies The Stator and Rotor Winding Repair Data section lists the stator coil details and rotor winding information to be provided by the manufacturer, after the order is placed for use, in the event future repairs are required The Analysis, Shop Inspection, and Tests section provides a broad list of factory tests that can be selected as required by the user to be witnessed or observed Here, the data sheet guide can be very useful to determine which optional factory tests should be selected The required coordination meeting, optional design review meeting, and a factory inspection option are listed for the user to consider Some of the significant data sheet technical changes in the Analysis, Shop Inspection, and Tests section include new line items for the user to select the following: n manufacturer-supported coordination meeting; the standard lists 12 suggested discussion and review items for this meeting n submittal of test procedures six weeks before scheduled factory tests; although this option is in the body of the API 546 second edition, it was not listed as a data sheet option n sacrificial coils cut into segments for insulation inspection for voids and to check groundwall insulation thickness n PD test at the factory to establish a baseline for future PD tests and insulation condition n dynamic balance of rotors on machines 600 r/min and above n bearing dimensional checks after factory tests n tests for torque pulsations during starting on machines other than four and six poles n ultrasonic inspection of shaft forging n burn-in testing of rotor electronic components n TEWAC heat exchanger performance tests Clearly, there is a significant amount of information that must be evaluated to specify an API 546 machine The data sheets list all the API 546 options and topics where additional information must be provided A detailed review of the data sheets can give the user the opportunity to consider each of the 127 bulleted items for a comprehensive specification The Appendix D—Motor Data Sheet Guide and Appendix E—Generator Data Sheet Guide given in API 546 provide instructions on how to complete the motor and generator data sheets Instructions for every topic in every section of the data sheets are given The guide was prepared by selected members of the working group to provide clear, concise, and easy to understand instructions on how to fill in the data sheets These instructions are in effect a tutorial n IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS new line items added for a one-piece shaft forging option, user-supplied list of applicable local codes, and unusual overspeed requirements The Main Conduit Box section provides line items for the user to specify power supply feeder information and a listing of manufacturer-installed accessories The Accessories section contains the user-specified machine space heater information, temperature detectors, vibration detectors, monitors for equipment health monitoring, and power supply details for auxiliary mounted fans Some of the specific changes in the Accessories section include: n A new “Monitors and Devices” subsection was added, listing new individual line items for shaft grounding brush replacement monitor, test device for rotating electronic components, rotating diode failure detection, and online rotor monitoring system n Under the “Exciter Power Supply” subsection, permanent magnet generators were added to the existing constant voltage transformer and phase-controlled rectifier power supply options n A new subsection titled “Auxiliary Equipment Enclosures” was added for the user to select enclosure location on the machine and conduit/cable entry location n An option for PD detectors was added n A new subsection for separately powered fans was added for the user to specify quantities, power supply, location, and enclosure type for nonshaft-driven auxiliary fans The Controls section lists the user-selected excitation power source as well as external controls panel and panelmounted devices to be provided by the manufacturer In addition, the generator data sheets list excitation, type description, response information, and ceiling voltage information to be provided by the manufacturer after the order placement The Driver (generator) or Driven (motor) Equipment Information section lists line items where the user or manufacturer provides mechanical load information descriptions and data for motor loads and generator drivers The Miscellaneous section is for the user to select paint requirements, technical documentation and certifications, instruction manuals, shipment information, and any special identification or nameplates The Miscellaneous section changes include new line items for the user to specify: n quantities and format for drawings, literature, and test documentation n the vendor to supply itemized pricing for optional tests n special shipping of bearings n outdoor storage for more than six months n equipment to be mounted on skid for shipment n whether any machine piping must be factory assembled before shipment The Generator and Motor Data—First section lists line items for the manufacturer to provide nameplate data, efficiency, exciter data, and rotor construction-type information with the proposal It also lists options for the user to select whether guaranteed efficiencies are required Some of the changes to the Generator and Motor Data—First section include: n added line item options for selecting guaranteed efficiencies and results of the unbalance response analysis if specified on both generator and motor data sheets n 17 Resultant Vector: 0.73 mil at 10° to assist with interpretation of acceptable vector shifts and a possible option to further check stability The polar plots shown in Figures and are taken from the document and illustrate typical acceptable and unacceptable thermal vector shift situations, respectively 90° Hot Vector: 1.13 mil at 70° Operation on ASDs 180° 0.8 mil 1.6 mil 0° Cold Vector: 0.93 mil at 110° 270° Example of an acceptable thermally induced vibration change on electrical and mechanical design, which provides guidance to both the infrequent user and expert user on selecting data sheet accessory options and when to select specific machine tests IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS Thermal Stability Explanation 18 A requirement that has been included in the testing section of the previous edition and kept in the latest edition is for the thermal stability of the machine to be proven This is achieved by comparing the vibration levels of a cold machine with one at full operating temperature If the rotor develops a bow (or thermal growth causes components to expand unevenly) as its temperature changes with load, then the vibration of the shaft in its bearings will change The requirements of the standard have not changed from the previous maximum permitted vector shift being 50% of the allowable running speed vibration, but the acceptance criteria have been difficult to interpret The explanatory notes from the API 541 Induction Motor Standard were adapted and included as an Appendix to API 546 Motors on ASDs have some extra issues that must be addressed Depending on the application and the drive selected, these may include: n conductor heating caused by the harmonic currents n extra electrical stresses on the winding insulation caused by high rate of change of voltage (dV/dT) and displaced neutrals n operation at different speeds exciting mechanical resonances n extra torsional oscillations caused by the harmonics in the waveform The standard has requirements listed in various sections to address these issues Frame Vibration Some recent situations have arisen where portions of a machine frame had unacceptably high levels of vibration, while the shaft vibration and the bearing housing vibration were well within the required limits These situations were due to frame resonances being excited by some normally occurring force, which would not be a concern if the resonance were not present The standard now imposes limits on frame vibrations At shaft height, the vibration of any loaded structural member of the frame shall not exceed two times the permitted bearing housing vibration For designs that not have structural members in this area, the manufacturer and user should agree on criteria before the tests There has not yet been extensive data available on these frame vibrations and the effects, but based on recent experience and available measurements, the task force concluded that these figures were reasonable However, future revisions of the standard may have changes in this area as more test data is acquired Other Revisions 90° Resultant Vector: 1.46 mil at 150° 180° 0.8 mil Hot Vector: 1.2 mil at 120° 1.6 mil 0° Cold Vector: 0.93 mil at 45° 270° Example of an unacceptable thermally induced vibration change Other changes of note include: n deleted reference to “special purpose” machines n modifications to better address two-pole supersynchronous machines n expanded to cover “other industrial applications” n caution given for service factor above 1.0 n “step balance” clarified to better address synchronous rotor construction n minimum service life of 25 years before an in-service failure and at least five years of uninterrupted continuous operation (from 20 years minimum with three years continuous) n voltage rating changed to bus rating for 1.0-pF machines, i.e., 4.16 kV versus kV and 13.8 kV versus 13.2 kV n addition of noise limit—maximum sound pressure level of the machine shall not exceed 85 dBA at any location at a reference distance of m (3 ft) n the addition of optional tests performed to determine pulsating torques in accordance with IEEE 1255 [6] n n n default to TEWAC or totally enclosed air-to-air cooled (TEAAC) on machines kV and above fault withstand or rupture disc required as standard for the main terminal box; there are no known common standards or tests for the adequacy of these rupture discs; however, it was felt that this was a useful start extensive rewrites to reflect current application of the technology Conclusions Synchronous machines are vital components of most process industry systems The third edition of API 546 on synchronous machines has been written by and for a group of experienced users, consultants, and manufacturers It has many enhancements in the areas where there have been concerns in the past, so that the electrical and mechanical performance and durability are improved as well as the purchasing process made easier Acknowledgments The authors gratefully acknowledge the work done by the following members of the working group: Paul Anderson, Dennis Bogh, Mark Chisholm, Gabe D’Alleva, Gary Donner, Donald Dunn, Dan Eaton, Mark Fanslow, Travis Griffith, Mike Henry, Royce King, Horst Kuemmlee, Scott Lambie, Bill Lockley, Stefan Palmgren, Jerry Pittman, David Rains, John Rama, Rubem Ribeiro, Richard Romero, Mark Saldana, Tim Trumbo, Barry Wood, and Craig Wylie References [1] Brushless Synchronous Machines—500 kVA and Larger, API Standard 546, 2008 [2] IEEE Recommended Practice for Measurement of Power Factor Tip-Up of Electric Machinery Stator Coil Insulation, IEEE Standard 286, 2000 [3] Guide for a Test Procedure for the Measurement of Loss Tangent of Coils and Bars for Machine Windings, IEC 60894 [4] IEEE Trial-Use Guide to the Measurement of Partial Discharges in Rotating Machinery, IEEE 1434 [5] Rotating Electrical Machines Off Line Partial Discharge Measurement on the Stator Winding Insulation of Rotating Electrical Machines, IEC TS 60034-27 [6] IEEE Guide for the Evaluation of Torque Pulsations During Starting of Synchronous Motors, IEEE 1255 Bill Lockley (lockley@ieee.org) is with Lockley Engineering in Calgary, Alberta, Canada Mark Chisholm is with General Electric in Pittsburgh, Pennsylvania Travis Griffith is with GE Oil & Gas in Houston, Texas Gabe D’Alleva is with ExxonMobil in Fairfax, Virginia Barry Wood is with Chevron in Richmond, California Lockley and Wood are Fellows of the IEEE Chisholm, Griffith, and D’Alleva are Senior Members of the IEEE This article first appeared as “API 546 3rd Edition— Making Synchronous Machines Better” at the 2008 Petroleum and Chemical Industry Conference IEEE INDUSTRY APPLICATIONS MAGAZINE  NOV j DEC 2010  WWW.IEEE.ORG/IAS How to Use the Standard API 546 permits a wide range of options while still requiring a reliable machine It can be used as such to specify a synchronous motor or generator Alternatively, it can be used with a corporate overlay that lists areas where the particular user wants something different from what is listed in the standard It is also possible to just call up certain sections of API 546 and incorporate them into a corporate standard However, this can cause confusion as the corporate documents written this way often have unexpected conflicting requirements The different sections of API 546 are often interrelated to provide requirements for the complete machine For these reasons, using only part of API 546 is discouraged Once the decision to purchase a synchronous motor or generator has been made, the following are the recommended ways to use the API 546 standard: 1) Decide What Is Needed: There are many choices to be made when buying a large synchronous machine These include power, speed, voltage, power factor, enclosure type, cooling method, surge protection, starting requirements, and many other issues 2) Fill Out the Data Sheets: It is essential to fill out the purchaser’s sections of the relevant data sheets so that the bidders know exactly what will be required of them and will not have to make assumptions or come back with questions during the bid preparation In addition to the major items mentioned earlier, the questions cover the site conditions, the load and starting requirements, excitation requirements, lubrication, efficiency cost factors, design reviews, data exchange, and testing To help navigate the data sheets, the data sheet guides give advice to assist with completion of the machine requirements 3) Evaluate the Manufacturers’ Responses: For both competitive and single-source proposals, the manufacturers’ responses must be evaluated carefully to ensure that they meet the requirements of the application Sometimes, a manufacturer will propose an alternative to what is specified, and this should be carefully evaluated In most cases, there will be some clarification questions required before decisions can be made 4) Maintain Communication with the Manufacturer: After the purchase decision has been made, there will still be some questions that arise as detailed engineering is carried out by both parties Clear communications are necessary to ensure that the final product does what is required of it 5) Test the Machine Thoroughly: Generally, we have found that it helps to perform as much testing as possible in the factory This consistently has been shown to reduce the problems that occur during and after startup, and it is almost always faster and cheaper to solve a problem in the factory than on-site 6) Install, Start, and Run Correctly: The machine should generally be installed on a solid, flat mounting base with proper shimming and alignment by those skilled in the craft The lubrication system should be flushed and tested to ensure that a consistent supply of clean oil reaches the bearings All the standard prestart tests, such as insulation resistance, should be performed and the motor protection system calibrated to ensure the motor is protected After startup, the machine should be maintained in accordance with the manufacturer’s instructions, not allowed to overheat and not subjected to an excessive frequency of starts (in the case of a motor) 19 ... process facilities API Standard 546 third edition [1] has been written to assist users, consultants, and manufacturers of these large synchronous machines Users and consultants can use it to specify... Electric.) common technical understanding and standardize machines to improve operating reliability and reduce cost Significant changes have occurred in both the process and manufacturing industries It... performance and verifying separation margin from rotor and support system critical speeds were maintained as being performance on the test stand rather than by analysis The bearing housing and shaft