A comparison between IEEE 841, API 541, AND API 547.

B Y J O H N M A L I N O W S K I , G A B E F . D ’ A L L E V A ,

& M A R K M . H O D O W A N E C

ANY MOTOR USERS MAY BE CONFUSED

when it comes to calling out the appropriate stan-

dard or specification for their applications. Some

standards are better suited to certain applications

than others. By thoroughly understanding what each specification

was developed for, the most appropriate standard can be chosen. This

article discusses the IEEE 841-2001, API 541 4th edition, and API

547 standards and provides guidance as to the applicability of each.

History

IEEE 841, API 541, and API 547 are all ac induction motor stan-

dards developed by the petrochemical industry. Nonetheless, they

have been adopted by other process industries that also require

motors with high levels of reliability. A working group consisting

of motor end-users, consultants, and suppliers initially developed

API 541 approximately 20 years ago. The standard is meant to

provide an ac induction motor with increased reliability and value.

Throughout 541’s life, each revision has added changes to promote

increased reliability, safety and ease of use. API 541 finished its

fourth revision in the fall of 2003 and was released in 2004.

IEEE 841 was completed in September 1985 with a similar

working group as the API standard. Initially the requirement for

IEEE 841 was to produce a recommended practice (RP) so motor

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manufacturers could build a low-voltage (460 or 575 V)totally enclosed fan-cooled (TEFC) ac induction motor thatcould be made available from stock for easy procurement.In 1990, the RP was revised and made into a standard. Thestandard’s latest version is IEEE 841-2001, which has beenwidely adopted into many other process industries, butmost heartily endorsed by the pulp and paper industry.

During the ballot process for the fourth revision ofAPI 541, great efforts were made to simplify the stan-dard. In the process of doing this, the standard defaultswere made to reflect appropriate choices for the largest,most critical machines. During the balloting process, itwas realized that a standard did not exist for general-pur-pose, noncritical service machines in the 250–3,000-hpranges. These machines are commonly found in thepetrochemical industry. A working group was chartered

to address the needs of these machines, and the standardnumber for this was API 547. This standard coversmedium horsepower motors (250–3,000 hp) that spanbetween IEEE 841 and API 541. Motors of this size arelikely to be of a more standard construction and mightbe made available for delivery from a manufacturer ordistributor’s inventory. API 547 was completed, and thefirst edition was issued in January 2005.

Obviously, there is much overlap between the threestandards. That is the unfortunate outcome when variouschoices/options exist for a machine that goes into a partic-ular application. With appropriate exceptions taken, aswell as options selected, it is possible to make any one ofthe specifications “valid.” However, one specification maybe more appropriate than another. This article will helpidentify which of the three standards are most appropriatefor a particular application.

IEEE 841 Motor RequirementsThe IEEE 841 motor is intended to be a standardizedproduct available from stock (from motor manufactur-ers and motor distributors) and is produced by severalmanufacturers. The purpose of having such a specifica-tion is to establish a recognized baseline standard forpetroleum and chemical industry severe duty motors.Prior to this standard being in place, manufacturershad total latitude on what they deemed to be sufficientfor a “severe duty” motor. IEEE 841 put all manufac-turers on an even playing field and simplified procure-ment activities from the end-user side.

IEEE 841 motors must satisfy the following:■ severe duty for petroleum and chemical industry■ enclosure limited to TEFC and totally enclosed non-

ventilated (TENV) construction■ a NEMA frame size of 143T and larger, up through

500-hp rating■ voltages to 4,000 V■ horizontal and vertical motors■ antifriction bearing only■ bearing reliability by specifying temperature and

vibration limits as well as bearing life requirements■ IP details of protection: IP54/IP55■ sound limit: 90 dBA sound power■ corrosion-resistance tested per ASTM B117-97

TABLE 1. FEATURES OF EACH STANDARD.

IEEE 841 API 547 API 541

•Petroleum and chemical industry •Petroleum and chemical industry •Petroleum and chemical industry

•Severe duty •Severe duty •Critical duty

•General purpose service (spared) •General purpose service (spared) •Special purpose service(unspared)

•Induction generators

•Severely corrosive •High inertia loads atmospheres •Adjustable speed drives

•Antifriction bearings •Sleeve bearings •Sleeve bearings•TEFC •TEFC and WPII •All enclosures

•Horizontal & Vertical •Horizontal •Horizontal and vertical

TABLE 2. APPLICATION GUIDELINESFOR EACH STANDARD.

Application IEEE 841 API 547 API 541

Coupled loads Y Y Y

Belted loads Y N N

Axial Thrust Loads Y N Y

Centrifugal Y Y Ycompressors

Reciprocating U U Ycompressors

Centrifugal pumps Y Y Y

Vertical turbine Y N Ypumps

Fans & blowers Y Y Y

Induction generator N N Y

Division 2 (Zone 2) U Y Y

Adjustable speed U U Y(ASD)

Y = Suitable for application

N = Not suitable for application

U = Unusual condition − specify on data sheet

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APPENDIX A-1. DETAILED COMPARISON OF IEEE 841, API 541, AND API 547.

Standard IEEE 841-2001 API 547 API 541 rev 4

Title IEEE Standard for Petroleum General Purpose Form-Wound Form-Wound Squirrel Cageand Chemical Industry Squirrel Cage Induction Motors – Induction Motors – 500 hp—Severe Duty TEFC Sqirrel- 250 hp and Larger and LargerCage Induction Motors upto and Including Cage- Induction Motors – up to andIncluding 370 kW (500 hp)

Induction Generator No No YesApplication

Design Standards ANSI, NEMA, IEEE ANSI, NEMA, IEEE, IEC, ISO ANSI, NEMA, IEEE, IEC, ISO

Power Range 0.75 − 370 kW (1 − 500 hp) 2P TEFC 185–600 kW 370 kW − up (500 hp − up)(250–800 hp)

2P − WP II 185–930 kW (1250 hp)

4-6-8 pole 185 − 1500 kWTEFC or (250 − 3000 hp)WPII

Rating • Continuous duty • Continuous duty • Continuous duty• Size for 1.0 SF, with 1.15 • Size for 1.0 SF • Size for 1.0 SFSF on nameplate

Voltage Ratings 50 Hz 60 Hz 50 Hz 60 Hz 50 Hz 60 Hz

Not specified 200 3,000 2,300 3,000 2,300

230 3,300 4,000 3,300 4,000

460 6,000 6,000 6,600

575 6,600 6,600 13,200

2,300 10,000

4,000 11,000

Speed (poles) 2, 4, 6 & 8 pole 2, 4, 6 & 8 pole All poles

Efficiency • EPAct + 1 NEMA range •Manufacturer’s standard •Manufacturer’s standard (most manufacturers •Specified on data sheet •Specified on data sheetbuild to NEMAPremiumTM efficiency)

Rotor Cage • Copper, aluminum or • Copper or aluminum • Fabricated copper-barMaterial respective alloys (Typically >1000 hp fabricated-bar • Optional–cast or

die cast aluminum) ≤1000 hp fabricated or die fabricated aluminum cast cage cage

Winding Type • Random wound • Form wound • Form wound• Form wound

Winding Insulation • Minimum Class F • Minimum Class F • Minimum Class F• Random wound • Form wound • Form woundCoils to have phase • Epoxy base VPI • Epoxy base VPIinsulation in addition to • Corona suppressant • Corona suppressant varnish for each group of materials for windings operating materials for windings random windings at 6000 volt or greater operating at 6000 volt or • Form wound • Stator windings to have greaterVPI for 2300/4000 volt sealed system capable of • Stator windings to have designs NEMA MG 1-20 sealed sealed system capable of • Sealed system capable winding conformance test NEMA MG 1-20 sealed of withstanding immersion winding conformance test test

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APPENDIX A-2. DETAILED COMPARISON OF IEEE 841, API 541, AND API 547.

Standard IEEE 841-2001 API 547 API 541 rev 4

Enclosure Type or NEMA IP NEMA IP NEMA IP

IEC Details of Protection TEFC TENV IP54 < NEMA WP II IPW24 IC01 DGP IP22 ICO1320 TEFC IP44-54 IC411 WP I IP23 IC01

frame IP55 WP II IPW24 IC01

≥ 320 frame TEFC IP44-54 IC411TEPV IP44 IC31/37

TEWAC IP44-54 IC81W

TEAAC IP44-54

IC611/IC616

Frame Sizes Per NEMA MG 1-1998, Manufacturer’s standard Manufacturer’s standardPart 13

Frame and Endplate Cast iron Cast iron or Cast iron or fabricated Material fabricated steel steel

Terminal Box ≤600V and Cast iron Cast iron, nodular iron, cast Cast iron, nodular iron, ≤445T frame steel, cast aluminum, steel cast steel, cast

plate, aluminum plate aluminum, steel plate,aluminum plate

>600V and Cast iron, >445T frame cast steel or

steel plate

Bearings • Antifriction • Hydrodynamic (i.e., • Hydrodynamic (i.e.,sleeve and tilting pad) sleeve and tilting pad)standard standard • Anti-friction optional • Anti-friction optional

Power Supply Variation Not exceeding: Not exceeding: Not exceeding:• ±10% voltage with • ±10% voltage with • ±10% voltage withrated frequency rated frequency rated frequency• ±5% frequency with • ±5% frequency with • ±5% frequency withrated voltage rated voltage rated voltage• Combination of voltage • Combination of voltage • Combination of voltageand frequency of 10% and frequency of 10% and frequency of 10% provided frequency ≤5% provided frequency ≤5% • ≤1% voltage imbalance• ≤1% voltage imbalance • ≤1% voltage imbalance

Design and Starting • Design B • Design B • All designs (A, B, C & D)• Torque/current and • Torque/current and • Torque/current and starting per NEMA MG starting per NEMA MG starting per NEMA MG 1-1998, Part 12 or Part 20 1-1998, Part 12 or Part 20 1-1998, Part 20 or IECwith 90% of rated voltage with 80% of rated voltage 60034-1 with 80%• Two consecutive starts • Two consecutive starts of rated voltagewith the first start at with the first start at • Two consecutive startsambient temperature ambient temperature with first start at ambient• One start with motor at • One start with motor at temperature with motoroperating temperature operating temperature coasting to rest

• Three consecutive starts with motor coasting to rest and idle for 20 minutes• Three evenly spacedstarts over first hour

Design Minimum Number Not specified Minimum 5,000 Minimum 5,000of Full-voltage Starts

Safe Stall Time NEMA MG 1, not less than NEMA MG 1, not less 150% of, or 5 seconds 12 seconds total than 12 seconds total more than, time required

to accelerate the load

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APPENDIX A-3. DETAILED COMPARISON OF IEEE 841, API 541 AND API 547.

Standard IEEE 841-2001 API 547 API 541 rev 4

Vibration Levels • Radial - Unfiltered 2.03 • 0.10 in/s (filtered and • 2 / 4 / 6 pole 0.10 in/smm/s peak for 2,4,6 pole; unfiltered) 8 pole 0.08 in/s, 10 pole 0.061.52 mm/s for 8 pole in/s, 12 pole 0.05 in/s, 14 pole• Axial - Unfiltered 1.52 0.043 in/s, etc (unfiltered)mm/s • Shaft vibration 1.5 mils• Filtered - 1.27 mm/s (unfiltered) displacement forpeak at 2n (twice speed) 2 and higher pole motorsor 2f (twice frequency)

Airborne Sound ≤90 dBA sound power ≤85 dBA sound pressure ≤85 dBA sound pressure

Temperature Rise ≤80 ◦C by winding Not to exceed Class B Not to exceed Class Bresistance insulation listed sinsulation listed

temperature temperatures

Routine Factory Tests a) No load current, power, a) No load current a. No load current and speed measurement measurement

b) Determination of b. Determination by locked-rotor current calculation of locked-

rotor currentb) High-potential c) High-potential tests of c. High-potential tests of

stator windings, space stator windings, spaceheaters and RTDs heaters and RTDsd) Insulation resistance d. Insulation resistance (IR)(IR) test by megohmmeter test by megohmmeter andand polarization index polarization index (PI)(PI) per IEEE 43 per IEEE 43

c) Winding resistance e) Measurement of e. Measurement of statorstator resistance resistance

d) Mechanical vibration f) Measurement of f. Measurement of vibrationvibrationg) Test of bearing g. Test of bearing insulationinsulationh) Test of bearing h. Test of bearing temperature rise temperature rise

i. Inspection of bearingand oil supplyj. Measurement of rotor air gapk. Measurement of shaft voltage and current

i) Surge comparison test l. Surge comparison test

Special (Optional) None specified a. Complete test a. Complete test Factory Tests b. Unbalanced response b. Unbalanced response

c. Rated rotor c. Rated rotor temperaturetemperature vibration testvibration testd. Sealed winding d. Sealed windingconformance conformance

e. Stator core testf. Surge test of sample motor coilg. Power factor tip-uph. Bearing housing natural frequency test

Winding Temperature None identified Stator RTDs required Stator RTDs requiredDetectors

Space Heaters Optional Required Optional

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■ minimum efficiency specified for all ratings coveredby specification

■ routine factory tests identified■ test information supplied with the motor (i.e., each

motor has a “birth certificate” attached to it)■ standardized design (data sheet not as important)■ intended to be a standard product that can be

stocked.

API 541 Motor RequirementsAPI 541 is the premier large induction motor stan-dard. It has rigorous specifications but requires muchmotor knowledge from the user to be used successful-ly. There are many decisions (i.e., specification ofoptions) within the specification that must be made.Proper utilization of this specification requires thatthe data sheets be correctly filled out. Regrettably, thedata sheets are often incomplete and/or inaccurate.Unfortunately, many users and original equipmentmanufacturers (OEMs) fail to recognize the impor-tance of the data sheets.

API 541 motors must satisfy the following:■ minimum requirements for form-wound squirrel-

cage induction motors 500 hp and larger for use inthe petroleum industry

■ use in “critical service” machines■ enclosure not specified (WPII, open, TEWAC, etc.

all are acceptable)■ horizontal and vertical motors■ IP level of protection: IP55 (bearings only)■ sleeve bearing standard, but antifriction bearing

option■ bearing reliability specifying temperature and vibra-

tion limits as well as bearing life requirements■ corrosion-resistant components specified but their

testing method is not■ minimum design and construction guidelines

defined for manufacturer■ sound pressure limit of 85 dBA ■ comprehensive routine and special (optional) factory

tests identified■ data sheets must be filled out to properly specify the

motor

API 547 Motor RequirementsAPI 547 is a simpler version of API 541, but it will nothave significantly relaxed performance requirements. Ifany exceptions to API 547 are taken, the user is encour-aged to use API 541 for more detailed technical guid-ance. In this regard, API 547 is similar to IEEE 841; themotor is standardized to a high enough degree such thatit can be available from stock. This is not possible withAPI 541 because of its highly customized nature.

API 541 motors must satisfy the following:■ requirements for form-wound squirrel-cage induc-

tion motors for general use in petroleum, chemical,and other industrial severe-duty applications

■ cover motors from 250–3,000 hp■ enclosures are limited to WPII and TEFC■ horizontal motors only■ IP level of protection: IP55 (bearings only)

■ sleeve bearing standard but antifriction bearingsoptional

■ bearing reliability by specifying temperature andvibration limits as well as bearing life requirements

■ corrosion-resistant components specified but theirtesting method is not

■ minimum design and construction guidelines aredefined for manufacturer

■ sound pressure limit of 85 dBA ■ routine and special (optional) factory tests

identified■ data sheets are optional but should be filled out to

specify the motor but are not as detailed as the datasheets in API 541.

All three standards target increased reliability,although they accomplish it in different ways. Obviously,the scope of these standards can be extended, but caremust be taken to avoid unintentional exceptions orincompatible requirements.

Data SheetsIEEE 841 provides an optional one-page data sheet to beused if the end-user is specifying a motor for unusual ser-vice conditions. Manufacturers rarely see these used.Most IEEE 841 sales come from motors available frominventory made to comply with the standard’s specifica-tions with few differentiators from manufacturer-to-manufacturer. These differentiators are items notspecified clearly in the standard but often expected byend-users such as shaft labyrinth seals on each end, ter-minal lead lugs, and NEMA Premium efficiency levels.Some companies specify IEEE 841 on motors larger than500 hp to obtain a robust severe-duty motor design withless complexity and cost than API 541.

An API 541 motor cannot be built without a datasheet. The entire concept of the standard is for the manu-facturer to design and build a special motor to meet theexact requirements of the end-user as defined by the six pages of data sheets. When the end-user or OEM doesnot fill out data sheets, the motor manufacturer mustmake some assumptions as to what is required. Discussionover construction, requirements, and final configuration iscommon during commercial negotiations. Because of thecritical nature of many API 541 motors, particularly inhigher outputs, witness tests at the manufacturer’s testlaboratory are common.

API 547 is a more standard motor design for general-purpose applications. A data sheet is provided for specialconditions, however it is not required to build the motor.

Motors are often supplied with equipment to end-users. When OEMs work with manufacturers onmotors for their equipment, they request that themotors be constructed per IEEE 841 or API 541. Datasheets are often not supplied by OEMs. If the end-userrequires a motor built to API 541, he or she will needto work with the OEM and help complete the datasheet. IEEE 841 motors are much more standard andcan be supplied when the data sheet is not filled outas long as basic information (speed, voltage, rating,etc.) is available.

APPENDIX A-4. DETAILED COMPARISON OF IEEE 841, API 541, AND API 547.

Standard IEEE 841-2001 API 547 API 541 rev 4

Service • Full voltage across- • Full voltage across-the-line • User specified on Conditions the-line starting starting data sheet

• Temp range −25 ◦C • Temp range −25 ◦C toto +40 ◦C +40 ◦C• Altitude ≤ 1000 m • Altitude ≤ 1000 mabove sea level above sea level• Indoor or outdoor • Indoor or outdoor• Severe duty • Severe duty

– Humid – Humid– Chemical (corrosive) – Chemical (corrosive)– Salty atmospheres – Salty atmospheres

• Minimum L-10 bearing • Horizontal mountinglife specified as 26,280 • Sinusoidal input power • Sleeve bearing hours • Sleeve bearing temperature ≤93 ◦C• Bearing temperature temperature ≤93 ◦C • 20 year service liferise (coupled) ≤ 45 ◦C • Class 1, Div. 2 or Zone • 3 year (50 ◦C for 2 pole) 2 location uninterrupted service

Unusual Service Exposure to: Exposure to: • User specified on Conditions • Flammable or explosive • Combustible, explosive, data sheet

gasses abrasive, conductive dust• Combustible, explosive, • Dirty operating conditions abrasive, conductive dust where accumulation of dirt • Lint or dirty atmospheres will interfere with normal that interfere with ventilationventilation • Nuclear radiation• Nuclear radiation • Abnormal external shock, • Abnormal external shock, vibrations, or mechanical loadsvibrations, or mechanical • Altitudes >1000 mloads • Temperatures outside of • Altitudes >1000 m −25 ◦C to +40 ◦C• Temperatures outside of • Abnormal axial or side −25 ◦C to +40 ◦C thrust on shaft• Abnormal axial or side • AC supply outside of thrust on shaft NEMA MG 1 limits• AC supply outside of • Supply voltage NEMA MG 1 limits unbalance >1%• Supply voltage • Operating speeds other unbalance >1% than rated• Operating speeds other • Operation from solid-state than rated device for adjustable speed • Operation from solid- applicationstate device for adjustable • Load inertia greater than speed application NEMA MG 1-1998, Section • Load inertia greater 12.55 (Note: 2 pole motors than NEMA MG 1-1998, ≤ 1⁄2 NEMA MG 1 inertia)Section 12.55 • Reciprocating or positive

displacement loads

Motor Data • 1 page • 3 pages • 6 pagesSheet • Completion by user is • Completion by user is • Completion by

optional optional (but recommended) user is required

Certification to • Self-certification • Self-certification • Self-certificationStandard • API Monogram Program

certification (optional)

Availability • Commonly stocked as • Built to order (Expect • Built to order1–250 hp 2, 4 & 6p 460v common ratings will be and 575v stocked)

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Use with Adjustable Speed DrivesIEEE 841-2001 allows for the motor to be operated froman adjustable speed drive (ASD) as an unusual servicecondition. The user is instructed to contact the motormanufacturer to determine suitability for the requiredspeed range. NEMA MG 1, Part 30 is referenced. Con-cerns specified in Part 5.3 of the standard deal with heat-ing issues, insufficient acceleration torque, noise, torquepulsations, winding failures due to high amplitude voltagespikes (dv/dt) from the drive’s output voltage.

Additionally, the user is cautioned regarding opera-tion of the motor above allowable temperatures for Divi-sion 2 hazardous (classified) areas. IEEE 1349-2001,Guide for the Application of Electric Motors in Class I, Divi-sion 2 Hazardous (Classified) Locations, should be consult-ed for application guidelines.

Most manufacturers building IEEE 841 motors providea motor with an insulation system that will allow opera-tion on an ASD. Constant torque speed range may be lim-ited depending on the motor rating. Variable torqueapplications are generally not a problem. Voltage spikesare often addressed by referring the user to limit the spikesto levels defined by NEMA MG 1 Part 31.4.4.2 withstandpeak voltage capability.

In API 541, each item dealing with an ASD is identifiedwith a diamond symbol in the margin. Unlike IEEE 841,API 541 requires the motor to operate below an 80 °C temperature rise at any speed with a variable torqueload. Also, with these larger motors, critical speeds must beevaluated when used with an ASD as some larger motors mayhave a flexible shaft. A flexible shaft machine is a machinethat has its first lateral critical speed below the nominal oper-ating speed. Continuous operation at a critical speed must beavoided. Because API 541 relies heavily on a complete set ofdata sheets, the user can document complete drive and appli-cation details. This allows the manufacturer to design andbuild a motor that will produce desired performance.

Use of Standards by ApplicationDespite being developed by two separate organizations,the American Petroleum Institute (API) and the IEEEPetroleum and Chemical Industry Technical Committee(PCIC), all three standards were developed by end-usersin the petroleum and chemical industry. IEEE 841 hasfound wide use in other process industries where a reli-able and well-protected NEMA-size motor is required,such as in the pulp and paper industry.

Table 1 provides basic features and some guidance onthe use of each standard. Table 2 provides typical applica-tions for each standard. The end-user is responsible fordetermining which of the three standards is most appro-priate for his specific application.

Certification to StandardEach manufacturer is responsible for designing and man-ufacturing their motor to each applicable standard (IEEE841, API 547 or API 541). No outside agency is requiredto certify the compliance of these motors to the standard.The way the standards are interpreted, features offeredmay vary slightly from manufacturer-to-manufacturer.

API plans to offer a Monogram Program to certifymotors that are made in compliance to their standardand, further, that the plant producing them has ade-quate quality processes in place. In order to meet therequirements of the API Monogram Program, a facilitylicensed under API/IP Standards must not only meetthe onsite audit requirements of API Spec Q1, butmust also demonstrate, through a series of qualifica-tion tests audited by an API auditor-witness, that theproduct meets all the performance criteria specified bythe standard.

ConclusionAll three standards provide specific and verifiablerequirement that enable a user to purchase ac inductionmotors for most applications that will yield increasedreliability over standard or severe duty motors. Wherethese standards are used to specify larger motors suited tospecific applications, additional application data must beshared between the end-user and manufacturer. IEEE841 provides the means to specify a very high qualitymotor, usually available off the shelf. API 541 motors areoften applied to critical applications that would have alarge cost impact or shut down a facility if they were tofail. API 547 completes the spectrum between these twowidely accepted standards. See Appendix A for a detailedcomparison between the three standards.

References[1] Motors and Generators, NEMA MG 1-1998 and 1-2003.[2] IEEE Standard for Petroleum and Chemical Industry—Severe Duty Totally

Enclosed Fan-Cooled (TEFC) Squirrel Cage induction Motors—Up to andincluding 370 kW (500 hp), IEEE 841-2001.

[3] Form-Wound Squirrel Cage Induction Motors—Larger than 500 Horsepower,ANSI/API 541, Fourth ed.

[4] General-Purpose Squirrel Cage Induction Motors—250 Horsepower and Larger,ANSI/ API STD 547, First ed.

[5] National Electrical Code, NFPA 70-2002.[6] IEEE Guide for the Application of Electric Motors in Class I, Division 2

Hazardous (Classified) Locations, IEEE 1349-2001.[7] R.L. Doughty and A.H. Bonnett, “Introduction to IEEE 841-2001,

IEEE Standard for Petroleum and Chemical Industry—Severe DutyTotally Enclosed Fan-Cooled (TEFC) Squirrel Cage InductionMotors—Up to and Including 370 kW (500 HP),” in IEEE PCICConf. Rec., 2001, pp. 45–52.

[8] M. Hodowanec, M. Costello, B. Lockley, J. Rama, and T. Griffith,“Introduction to API Standard 541, 4th Edition—Form-WoundSquirrel Cage Induction Motors—Larger than 500 Horsepower” inIEEE PCIC Conf. Rec., 2003, pp. 311–319.

[9] L.K. Padden, R. Bried, and J. Dymond, “IEEE 1349-2001 guide forthe application of electric motors in Class I Division 2 hazardous (clas-sified) locations,” in IEEE PCIC Conf. Rec., 2003 pp. 59–69.

John Malinowski (jmalinowski@baldor.com) is with BaldorElectric Company in Fort Smith, Arkansas. Gabe F. D’Allevais with ExxonMobil Research and Engineering in Fairfax, Vir-ginia. Mark M. Hodowanec is with Siemens Energy & Automa-tion in Norwood, Ohio. Malinowski and Hodowanec are SeniorMembers of the IEEE. This article first appeared in its originalform at the 2004 IEEE/IAS Petroleum and Chemical IndustryTechnical Committee Conferece.