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SYNCHRONIZERThe ABC’s of ‘P’ Type Motors200 -SYN- 97
INTRODUCTIONIntroduction to‘P’Type Motor ProtectionThe objective of this handbook is to provide a thorough and concise source of information concerning ‘p’type motors manufactured at Electric Machinery (EM). A ‘p’ type motor is a motor specifically designedto support and accommodate the proper form of ‘p’ type protection, so it can safely operate in a givenhazardous gas environment.‘P’ type protection was developed to prevent the ingress of a potentially explosive atmosphere into theenclosure of an electric motor or generator. The primary objective for implementing this type of protectionwas to create a machine that can be operated in a potentially hazardous gas environment and satisfy theapplicable international standards; specifically, IEC (International Electrotechnical Commission) or EN(Euronorm) Standards. Once these standards are met, EM can have the motor tested and certified by anAuthorized Test Institution if desired by the customer. Although this handbook focuses on internationalstandards, comparisons are made between both international and national standards.After extensive research and development, several design modifications and additions were required inorder to implement ‘p’ type protection. Some of these changes included special electrical and mechanicalcontrol equipment, enclosure design, and shaft seals. Electric Machinery has manufactured, tested andsold a wide range of electric motor designs equipped with ‘p’ type protection that have met thecertification requirements to ensure safe operation in the field. The horsepower rating of these machinescan range from 500 hp - 25,000 hp, for induction motors, and 500 hp - 60,000 hp, for synchronous motors,with speed ratings of 200 rpm - 3600 rpm.Cover photo: 'P' type induction motor rated 2950 HP, 6000 V, 880 RPM, 8 Pole, 60 Hz, 3-phase; Compressorapplication; Zone 1 hazardous area2Third EditionCopyright August 1997
CONTENTSsectionpage1.0 What is ‘P’ Type Motor Protection? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.0 Characteristics of ‘P’ Type Motor Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.1 Ex p Protection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 Pressurization Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2.1 Leakage Compensation (LC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2.2 Continuous Circulation (CC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3 Purge Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 Purge Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5 Ex p Motor Protection Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5.1 Classification of CCF Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.0 LCA and LCF Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83.1 LCA System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.1.1 Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.1.1.1 Purge Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.1.1.2 Pressurization Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.1.2 Control Unit (CU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.1.3 Protection Unit (PU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.1.4 Air Control Unit (ACU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.1.5 Purge Air Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.2 LCF System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.2.1 Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2.2 Component Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.0 Testing for ‘P’ Type Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.1 Test Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.2 Over-pressure Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.3 Purge Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3.1 Test Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3.2 Test Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.4 Running Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5 Temperature Rise Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.1 Heat Run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.2 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.3 Temperature Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.3.1 External . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.5.3.2 Internal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145.0 Enclosure Designs for ‘P’ Type Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.1 TEFV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.2 TEAAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.3 TEWAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.0 Applicable Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.1 International Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.1.1 Zone 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.1.2 Zone 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.1.3 Zone 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.2 National Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.3 Comparison of IEC and NEC Requirements for ‘P’ Type Motors . . . . . . . . . . . . . . . . . . . . . . . 19Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20A. Temperature Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20B. Classification of Hazardous Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20C. Methods of Explosion Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22D. Degree of Protection (IP Code) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23E. Degree of Cooling (IC Code) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23F. Comparisons of Standards Between Major Countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25G. Authorized Test Institutions in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27The Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283
PROTECTION1.0 What is‘P’Type Motor Protection ?‘P’ type protection is a recognized protectionconcept for rotating electric machines operating ina potentially explosive environment, where therisk of a fire or an explosion is prominent withflammable gas present in the vicinity of an electricmotor. Furthermore, totally enclosed motors shallhave no external surface with an operatingtemperature in excess of the ignition temperatureof the flammable gas (see Appendix A). ‘P’ typeprotection prevents any flammable gas fromentering the enclosure by purging and pressurizingthe motor enclosure. IEC refers to this type ofprotection as “Ex p.”4In applying this type of protection, the purgesequence must be initiated before the motor isenergized. First, a pressurization technique mustcreate a positive pressure—a pressure within themotor enclosure that is slightly higher than theoutside atmospheric pressure. Next, a purgemedium, usually clean dry air, must circulatethrough the motor enclosure so that anyflammable gas trapped inside will be diluted andforced out of the enclosure. Once the purgesequence is completed, the motor can beenergized. The pressurization technique mustmaintain positive pressure during operation soany leakage from the enclosure will be of clean airgetting out, rather than flammable gas getting in.This inevitable leakage of clean air may beminimized by using a motor enclosure that is asnear airtight as possible.
2.1 Ex p Protection MethodsIn general, when considering Ex p protectionfor an enclosed electrical apparatus (see Figure 2.1),two principle questions are usually addressed:i) Is flammable gas released or used within theenclosure?ii) Are people needed to enter or open theenclosure while the device is operating?air leakageoutletvalvepurgeair outELAPECTRPA ICRA ALTUSapparatusenclosureclean airsupplyenclosureseamsFigure 2.1 Typical model of a ‘p’ type electrical apparatus.The pressurization technique that will be used toachieve the desired protection is determined fromthe answers to these questions. For the motors andgenerators manufactured at Dresser-Rand/ElectricMachinery Division, “no” flammable gas is releasedwithin a machine enclosure, and “no” people needto open or enter an enclosure while a machine isoperating. Therefore, pressurization is bestachieved by using either the leakage compensation(LC) or the continuous circulation (CC) technique.When one of these two techniques is combined witha specific purge method, it will create an Ex pprotection system. The following sub sections willdescribe and compare the two pressurizationtechniques and the different purge methods.2.2 Pressurization TechniquesThe pressurization technique shall provide theminimum required pressure of 0.5 mbar (0.2 in. ofH2O)1 which should be achieved with the lowestpossible flow of purge medium. Therefore, thenormal working pressure is higher than 0.5 mbar.The motor enclosure must be able to withstand apressure of 1.5 times1 the normal workingpressure.2.2.1 Leakage Compensation (LC)Before the start of a purge sequence, theleakage compensation method will supply anample amount of purge medium to create an overpressure and effectively purge the motorenclosure. Once purge sequence is completed, theoutlet valve is automatically closed and theleakage compensation method will supply onlyenough clean air to compensate for any leakage,and to maintain the positive pressure inside themotor enclosure (refer to Figure 2.1).2.2.2 Continuous Circulation (CC)Before, during and after the purge sequence, acontinuous supply of clean dry air will circulatethrough the motor enclosure. The enclosurepressure is maintained by the back pressurecreated from the air outlet assembly. Thistechnique is typically used on large motorenclosures where the leakage is normally higher.2.3 Purge MethodsIn general, the purge sequence shall initiallypurge the motor with at least 5 times the volume ofthe free space in the enclosure and associatedducts.1 However, if the enclosure arrangement islarge or complex, more volume exchanges may beneeded. The time needed to purge the motor isproportional to the size of the enclosure. Typically,the purge times range from 15-30 minutes. Thereare basically three different types of purge methods: Compressed air (A) Fan air (F) Inert gas (
motor enclosure that is slightly higher than the outside atmospheric pressure. Next, a purge medium, usually clean dry air, must circulate through the motor enclosure so that any flammable gas trapped inside will be diluted and forced out of the enclosure. Once the purge sequence is completed, the motor can be energized. The pressurization technique must
