How To Test A Power Switch On A Power Supply

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1 transfer switches Soft load Innovative, reliable, integrated solution

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3 Built with years of experience Powered with innovation Delivered with reliability A history of experience, innovation and reliability As a premier industrial manufacturer, Eaton s Electrical Sector is one of the world s leading suppliers of electrical control products and power distribution equipment with yearly sales of over $2.5 billion. Eaton s electrical products include a complete line of low and medium voltage assemblies from substations, switchgear and panelboards, to loadcenters, transformers and safety switches. These products are used wherever there is a demand for electrical power in residences, high-rise apartment and office buildings, commercial sites, hospitals and factories. Built with experience For over a century, Eaton has focused on providing quality power-centric products and services. In today s business environment, customers like you are driving our transformation from a leading global electrical components provider into a customer-centric solutions partner who understands your business. We do this through in-depth collaboration with customers and subject matter experts studying the issues inherent to the electrical power distribution and control systems. Eaton is one of the pioneering electrical manufacturers and has been focused on providing reliable backup power systems with transfer switch equipment for over 75 years. Powered with innovation Eaton continues to meet changing industry needs by providing a broad range of automatic transfer switches. These switches may be grouped into a basic, enhanced or premium set of features that will meet your application requirements. Eaton has used industry-leading breaker-based designs for years and now has a line of contactor-based designs. These designs can be matched to a family of automatic transfer switch controllers that will meet your specific needs. Identify your application, define your needs, and select the solution from Eaton. Delivered with reliability Power outages due to bad weather or utility failure have grown increasingly costly and more disruptive to businesses and homeowners. A backup power system will keep your computers, security system, heating or refrigeration system, cash registers, home health care equipment, or any system that uses electric power energized and operational. The demands for reliability have increased. Eaton meets those expectations by the stringent ULT 1008-listed automatic transfer switches with a world-class product delivery system. Eaton will provide the individual transfer switch built to exacting standards or supply the same transfer switch in an integrated lineup with other Eaton gear. For startup service, application support and emergency support, call Eaton Electrical Services & Systems at EATON CORPORATION transfer switches 3

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5 transfer switches Switch type overview and standards Solutions overview Eaton s automatic transfer switches are designed to provide you with a full offering of transfer switches to solve your industry and application needs. Eaton offers the industry s most complete line of MagnumE-based, contactorbased and breaker-based transfer switches. This wide range of selections enables you to identify your application needs and the benefits you expect to realize, and then choose the solution best for you. The cornerstone of these offerings is the proven design experience and reliability built into all Eaton transfer switches. Basic solution The basic solution offers a transfer switch that meets the most basic and cost-effective requirements for an automatic, manual or non-automatic transfer switch. This solution set allows you to choose from either a contactorbased or a breaker-based design and match that power-switching device with our basic transfer switch controller. Enhanced solution The enhanced solution meets all of the basic automatic transfer switch needs. In addition to meeting the most basic transfer switch requirement, the enhanced solution allows for optimal control and improved flexibility. This solution set allows you to choose from either a contactor-based or a breaker-based design. Premium solution The premium solution is offered for those applications requiring continuity of power during the transfer and routine test. This solution set offers both contactor-based and breakerbased designs with drawout capability. Switch types available Delayed transition Soft load Soft load bypass isolation Magnum Transfer Switch Standards UL 1008 UL 891 A UL 489 CSAT NECT Articles 517, 700, 701, 702 NFPAT 110 NFPA 99 EGSA 100S NEMAT ICS10 Standard for safety for automatic transfer switches up to 3200A Standard for switchboards carrying up to 100 ka at 5000A Standard for circuit breakers and molded case switches Canadian transfer switch standard Code sections for applicable switch equipment Source 2 and standby power systems Health care facilities Standard for transfer switches Standard for transfer switch equipment UBCT Uniform Building Code for Seismic Zone 4 ISOT 9000 International Organization for Standardization CBC California Building Code IBC International Building Code BOCAT Building Officials Code Administrators A 4000 and 5000A available as UL 891 only. EATON CORPORATION transfer switches 5

6 Make the right decision: Identify your application Define your needs Determine your right solution Select Eaton ATS Solution Guide: Highlighting Magnum-Based Designs A Eaton Solution Customer Benefits Key Features Agriculture Premium solution Greater reliability to avoid lost revenue and production time Continuity of power through synchronization of sources Soft load ramping 30 cycle, 85 ka short-time ratings Continuity of power during retransfer Lower energy costs realized through managing demand charges No power interruption during switch inspection or testing Integral overcurrent protection available Drawout design Critical load transfer applications Maximum control and ultimate flexibility Maximum investment Greater reliability to avoid lost revenue and production time Safe preventative maintenance without power interruption No power interruption during switch inspection or testing Greater reliability to avoid lost revenue and production time Safe preventative maintenance without power interruption No power interruption during switch inspection or testing 30 cycle, 85 ka short-time ratings Integral overcurrent protection available Integrated service entrance solution Interchangeable bypass and switch devices Drawout design Interchangeable bypass and switch devices Drawout design standard Front access standard Dual ATS Enhanced solution Momentary loss of power acceptable during retransfer Optimal control and improved flexibility Moderate investment Basic solution Momentary loss of power acceptable during retransfer Least critical load transfer applications Basic control and flexibility Greater reliability to avoid lost revenue and production time Lower energy costs realized from managing demand charges No power interruption during generator set testing Greater reliability to avoid lost revenue and production time Lower energy costs realized from managing demand charges No power interruption during generator set testing Ability to transfer large motor or inductive loads Allows loads to re-energize after transfer at normal inrush currents Avoid higher starting currents which increase energy costs Ability to transfer large motor or inductive loads Allows loads to re-energize after transfer at normal inrush currents Avoid higher starting currents which increase energy costs Ability to transfer large motor or inductive loads Allows loads to re-energize after transfer at normal inrush currents Avoid higher starting currents which increase energy costs Simplest of transfer switching solution Safe manual transfer under load Most simple operation Most cost-effective Application flexibility Permits safe and convenient non-auto transfer under load 30 cycle, 85 ka short-time ratings Integral overcurrent protection available Integrated service entrance solution Drawout design available Paralleled in less than 100 ms Programmable field settings Communication capability 30 cycle, 85 ka short-time ratings on power circuit breaker Integral overcurrent protection available Integrated service entrance solution Multi-tap transformer voltage selection available Easily adjustable time delays for the neutral position 30 cycle, 85 ka short-time ratings on power circuit breaker Integral overcurrent protection available Integrated service entrance solution Drawout design available Equal withstand, interrupting and closing ratings Integral overcurrent protection available Integrated service entrance solution Most compact offering Multi-tap transformer voltage selection available Minimum investment Special solution Continuity of power for UPS applications Required UPS bypass signal prevents unauthorized bypass High interrupting ratings Reliable, manually initiated electrical operation A Emphasis in yellow bars. Permits safe and convenient manual transfer under load Most cost-effective manual transfer 30 cycle, 85 ka short-time ratings on power circuit breaker Integral overcurrent protection available Drawout design available Equal withstand, interrupting and closing ratings Integral overcurrent protection available Deadfront design ( A) ( A) 6 EATON CORPORATION transfer switches

7 Commercial Industrial Utilities Institutions Government Communications Data Center Soft load ( A) Soft load ( A) Soft load ( A) Soft load ( A) Soft load ( A) ( A) ( A) ( A) ( A) ( A) ( A) ( A) Delayed transition ( A) Delayed transition Delayed transition ( A) Delayed transition Delayed transition ( A) Delayed transition Delayed transition ( A) Delayed transition Delayed transition ( A) Delayed transition ( A) Non-auto Manual or non-auto ( A) ( A) Non-auto Manual or non-auto ( A) ( A) ( A) ( A) Maintenance bypass ( A) Maintenance bypass ( A) Maintenance bypass ( A) Maintenance bypass ( A) Maintenance bypass ( A) Maintenance bypass ( A) Maintenance bypass ( A) EATON CORPORATION transfer switches 7

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9 transfer switches Switch type open transition Magnum Fixed Mounted Through-the-Door Design Product description Eaton Magnum transfer switches feature the Eaton Magnum power switch and power breaker, covering application ranges from 200A to 5000A. The Magnum design can be used for automatic and non-automatic applications. The Magnum design is available in both fixed mounted and drawout type construction. Enclosures meet all current applicable NEMA and UL standards for conduit entry, cable bending, gutter space and shielding of live components. Electrical ratings A Two-, three- or four-pole Automatic Non-automatic 100% rated UL 1008 Up to 3200A UL and 5000A Commercial design highlights NEMA 1 and NEMA 3R Fixed mounted Drawout type design Magnum power switches Fastest switching times available (<3 cycles) Features Highest withstand capability Stored energy switching device Ability to test power switching devices in test position Interchangeable power switching devices Safe to transfer manually under full load Contact wear indication Optional service entrance rated switches Optional front access Features ATC-600 controller Multi-tap voltage selection transformer Optional communication capability Transfer Switch Withstand, Interrupting and Closing Ratings Systems Coordination Information Transfer Switch Ampere Rating Rating When Used with Upstream Circuit Breaker 3-Cycle 600V (ka) Ratings Used for Coordination with Upstream Breakers with Short-Time Rating 30-Cycle 600V (ka) Note: Tested in accordance with UL Eaton s Drawout Magnum Transfer Switch will coordinate with a power switching device short-time rating. Contact factory for details. Dimensions in Inches (mm) NEMA 1 Fixed Mount Ampere Rating No. of Poles Height Width Depth ABC Weight in lbs (kg) D or (2286.0) (812.8) (1219.2) 1050 (476.7) (2286.0) (812.8) (1219.2) 1250 (567.5) or (2286.0) (1117.6) (1219.2) 1900 (862.6) (2286.0) (1117.6) (1219.2) 2000 (908.0) E E E E E A Drawout NEMA 1 depth is 60 inches ( mm). B Drawout NEMA 3R depth is 75 inches ( mm). C Fixed mounted NEMA 3R depth is 63 inches ( mm). D Contact factory for drawout and NEMA 3R weights. E Consult factory for dimensions and weight. Note: For NEMA 3R and for drawout, add inches (381.0 mm) to depth. EATON CORPORATION transfer switches 9

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11 transfer switches Switch type closed transition Product description The automatic closed transition power case breaker-based transfer switch is the most basic design that will provide a fully functioning automatic transfer switch. An automatic closed transition transfer switch may be used for those applications where emergency backup power is required, but a momentary loss of power is not acceptable on the retransfer from emergency to normal. Electrical ratings A Up to 600V Two-, three- or four-pole NEMA 1, 3R 100% rated UL 1008 Commercial design highlights High withstand and closing ratings Fixed mounted or drawout design Features Standard features Voltage and frequency sensing Multiple field programmable time delays Switch position indication Source availability indication Source 1 and 2 auxiliary contacts Mimic diagram Programmable plant exerciser Safe manual operation under full load with electrical pushbuttons System test pushbutton Optional features Load shed from emergency Two- or four-position test switch Multi-meter options available Selectable automatic or non-automatic operation Space heaters Load sequencing contacts Surge suppression Remote communications Magnum Closed Transition Design Transfer Switch Withstand, Interrupting and Closing Ratings Systems Coordination Information Transfer Switch Ampere Rating Rating When Used with Upstream Circuit Breaker 3-Cycle 600V (ka) Ratings Used for Coordination with Upstream Breakers with Short-Time Rating 30-Cycle 600V (ka) Dimensions in Inches (mm) NEMA 1 Fixed Mount Ampere Rating No. of Poles Height Width Depth ABC Weight in lbs (kg) D or (2286.0) (812.8) (1219.2) 1050 (476.7) (2286.0) (812.8) (1219.2) 1250 (567.5) or (2286.0) (1117.6) (1219.2) 1900 (862.6) (2286.0) (1117.6) (1219.2) 2000 (908.0) E E E E E A Drawout NEMA 1 depth is 60 inches ( mm). B Drawout NEMA 3R depth is 75 inches ( mm). C Fixed mounted NEMA 3R depth is 63 inches ( mm). D Contact factory for drawout and NEMA 3R weights. E Consult factory for dimensions and weight. Note: For NEMA 3R and for drawout, add inches (381.0 mm) to depth. Note: Tested in accordance with UL Eaton s Drawout Magnum Transfer Switch will coordinate with a power switching device short-time rating. Contact factory for details. EATON CORPORATION transfer switches 11

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13 transfer switches Switch type delayed transition Product description The automatic delayed transition contactor-based transfer switch is the most basic design that will provide a fully functioning automatic transfer switch. An automatic delayed transition transfer switch may be used for those applications where emergency backup power is required but a momentary loss of power is not acceptable on the retransfer from emergency to normal. Electrical ratings A Up to 600V Two-, three- or four-pole NEMA 1, 3R 100% rated Commercial design highlights UL 1008 three-position contactor High withstand and closing ratings Compact design Features Standard features Voltage and frequency sensing Multiple field programmable time delays Switch position indication Source availability indication Source 1 and 2 auxiliary contacts Mimic diagram Programmable plant exerciser Safe manual operation under full load with electrical pushbuttons System test pushbutton Optional features Load shed from emergency Two- or four-position test switch Multi-meter options available Selectable automatic or non-automatic operation Space heaters Load sequencing contacts Surge suppression Remote communications Magnum Transfer Switch in NEMA 1 Enclosure Transfer Switch Withstand, Interrupting and Closing Ratings Systems Coordination Information Transfer Switch Ampere Rating Rating When Used with Upstream Circuit Breaker 3-Cycle 600V (ka) Ratings Used for Coordination with Upstream Breakers with Short-Time Rating 30-Cycle 600V (ka) Dimensions in Inches (mm) NEMA 1 Fixed Mount Ampere Rating No. of Poles Height Width Depth ABC Weight in lbs (kg) D or (2286.0) (812.8) (1219.2) 1050 (476.7) (2286.0) (812.8) (1219.2) 1250 (567.5) or (2286.0) (1117.6) (1219.2) 1900 (862.6) (2286.0) (1117.6) (1219.2) 2000 (908.0) E E E E E A Drawout NEMA 1 depth is 60 inches ( mm). B Drawout NEMA 3R depth is 75 inches ( mm). C Fixed mounted NEMA 3R depth is 63 inches ( mm). D Contact factory for drawout and NEMA 3R weights. E Consult factory for dimensions and weight. Note: For NEMA 3R and for drawout, add inches (381.0 mm) to depth. Note: Tested in accordance with UL Eaton s Drawout Magnum Transfer Switch will coordinate with a power switching device short time rating. Contact factory for details. EATON CORPORATION transfer switches 13

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15 transfer switches Switch type bypass isolation B Source 1 Isolated G Source 1 Position A Source 1 Available Incoming Source 1 Ats Source 1 Source 1 Bypass 1 3 Load Source 1 Bypass B Source 2 Isolated R Source 2 Position A Source 2 Available Ats Source 2 Source 2 Bypass 2 4 Incoming Source 2 Source 2 Bypass Magnum Bypass Isolation Schematic Magnum Bypass Isolation Front View Transfer Switch Withstand, Interrupting and Closing Ratings Systems Coordination Information Transfer Switch Ampere Rating Dimensions in Inches (mm) NEMA 1 Drawout Design Ampere Rating Rating When Used with Upstream Circuit Breaker 3-Cycle 600V (ka) No. of Poles Height Width Depth Weight in lbs (kg) or (2286.0) (1625.6) (1524.0) 3100 (1407.4) (2286.0) (1625.6) (1524.0) 3700 (1679.8) or (2286.0) (1625.6) (1524.0) 4700 (2133.8) (2286.0) (1625.6) (1524.0) 5500 (2497.0) A Consult factory for dimensions and weight. Note: For NEMA 3R, add inches (381.0 mm) to depth. Ratings Used for Coordination with Upstream Breakers with Short-Time Rating 30-Cycle 600V (ka) Note: Tested in accordance with UL Eaton s Drawout Magnum Transfer Switch will coordinate with a power switching device short-time rating. Contact factory for details. Product description A bypass isolation transfer switch may be used to provide emergency power to life safety and other critical loads where maintenance of the main transfer switch, without interruption of power to the load, is either desirable or required. The Magnum bypass section is properly interlocked to prevent simultaneous connection to both sources, but does not prevent using the bypass section as a manual transfer switch in an emergency. Electrical ratings A Up to 600V Two-, three- or four-pole NEMA 1 and 3R enclosures UL 1008 Commercial design highlights Drawout type design High withstand rating Service entrance ratings available Features Standard features Reliable microprocessor logic Designed to safely withstand fault currents Eliminates need for complex interlocks Most versatile bypass isolation transfer switch available Eaton drawout cassette design Overcurrent protection available No service interruption when bypassing to the same source Drawout capabilities on both ATS and bypass portions Compact design Ability to test power switching elements during drawout process Power switching devices completely interchangeable between ATS and bypass portions Optional features Front access cubicle Dual ATS technology Load shed from emergency EATON CORPORATION transfer switches 15

16 transfer switches Switch type closed transition soft load Magnum Soft Load Front View Transfer Switch Withstand, Interupting and Closing Ratings Systems Coordination Information Transfer Switch Ampere Rating Rating When Used with Upstream Circuit Breaker 3-Cycle 600V (ka) Ratings Used for Coordination with Upstream Breakers with Short-Time Rating 30-Cycle 600V (ka) Note: Tested in accordance with UL Eaton s Drawout Magnum Transfer Switch will coordinate with a power switching device short-time rating. Contact factory for details. Product description soft load switches are the ideal solution for the power availability, energy management and generator set testing applications. Eaton s closed transition soft load transfer switches are designed to avoid the interruption of electricity supply when both sources of power are available. This is accomplished by synchronizing the two available sources through the active control of the generator set voltage and frequency, followed by a make-before-break transfer operation. Eaton s closed transition soft load switch uses an integrated microprocessorbased power controller to make active paralleling of two power sources possible. It manages the speed governor and voltage regulator of the generator set to bring the two sources into synchronization. Electrical ratings A Up to 600V Three- or four-pole NEMA 1, 3R Commercial design highlights Drawout breakers Service entrance rated switches available Features Standard features UL 1008 and UL 891 listed Free-standing Fixed and drawout Magnum DS insulated case switches High withstand rating Full 30-cycle short-time withstand capability Advanced, integrated, microprocessor control Integrated front panel display PC and front panel configurable ATS functions Engine and generator monitoring, protection and control Load management Automatic base load/peak shaving Import/export power control Multiple level password for secured access to critical parameters Automatic start/stop control (diesel and gas engines) Event logging Communications ready Optional features Optional service entrance ratings Optional intertie protective relay to comply with IEEE P.1547 Available utility grade metering Transient Voltage Surge Suppression (TVSS) 16 EATON CORPORATION transfer switches

17 ATC-5000 integrated microprocessor controller product description The integrated logic controller is a microprocessor-based generator set control and management package. ATC-5000 provides a userfriendly interface, allowing operators to easily view system status, view and reset alarms, display metered values and modify device set points. Magnum Soft Load with ATC-5000 Controller and Door Controls Features Integrated LED display Automatic transfer switch logic True rms sensing Frequency and voltage bias outputs for the generator sets Protective relays Device 25A synchronizer Device 59/27 over/ undervoltage for generator set and utility tie Device 81 over/ underfrequency for generator set and utility tie Device 78 phase/vector shift for the utility tie Device 32/32R overload/ reverse power for the generator set Device 46 load imbalance for the generator set Device 50/51 overcurrent for the generator set Load management Automatic base load/peak shaving Import/export power control Automatic start/stop sequencing for gas and diesel engines Load dependent start/stop Real power/pf control Counters for kwh, engine starts, operating hours and maintenance call Freely configurable discrete and analog alarm inputs Freely configurable relay and analog outputs Language manager Event logging PC and front panel configurable Multi-level password protection Battery voltage monitoring CANbus communication EATON CORPORATION transfer switches 17

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19 transfer switches Service entrance With Eaton s service entrance rated transfer switches, installation can be made directly at the point of service entrance while simultaneously eliminating the need for separate upstream fault protection and their respective power interconnections. Features UL 1008 service entrance listed transfer switch Service disconnect both off capability Integral overcurrent protection Lockout (when in disconnected position only) Indication of service disconnect Integrated design Disconnecting neutral assembly Ground fault protection capability all ratings (required by code on ratings 480V and 1000A or higher) Keyed service entrance switch Service Entrance Rated Magnum Power Breaker Transfer Switch Front View Magnum Service Entrance Conventional approach Automatic transfer switch Separate generator breaker Separate generator breaker enclosure Separate service entrance disconnect Separate service entrance disconnect enclosure Power cable/bus interconnections Installation of the separate components Additional space requirement Added maintenance UL 891 compliance Service Entrance Label Magnum Breaker supplied with standard Digitrip 520 for overcurrent protection. Utility Service G Generator Breaker Service Disconnect ATS Load Conventional Approach Eaton approach Utility Service Eaton s approach uses a breaker-based automatic transfer switch that is easily Single enclosure applied to service entrance Service Disconnect applications by adding an Reduced power cable/bus overcurrent trip to the switch interconnections G and then including the service Generator Reduced ATSspace requirements Breaker UL 1008 compliance entrance option. This means that the combined service entrance rated ATS is installed directly at the point of service entrance. Transfer switch with service entrance rating Load Conventional Approach Utility Service G Generator Breaker Service Disconnect Load Eaton Approach ATS EATON CORPORATION transfer switches 19

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21 transfer switches Magnum drawout switch features Power Panel Performs power transfer between Source 1 and Source 2 utilizing Magnum Power Case Switches or Circuit Breakers Electrical Operator Pushbutton Side-to-Side Ledge Contact Wear Inspection Area (Ledge Not Visible Under Contacts) Contact Wear Indicator Contacts Closed and in Good Condition Contact Wear Indicator Contacts Closed and Wear is Indicated Side-to-Side Ledge Contact Wear Inspection Area (Ledge Now Becoming Visible Under Contacts) Magnum Drawout Design Product description Eaton s drawout Magnum switch should be considered for any system requiring either greater redundancy, easier maintainability, or where true selective coordination is desired. Eaton s drawout Magnum switch provides the capability to isolate either of the two power sources (normal or emergency) and its associated logic, while maintaining power to the load. The switches are interchangeable. Selective coordination is available with optional integral overcurrent protection capability. Electrical ratings A UL 489 and UL 1008 Commercial design highlights Drawout design available on: Automatic open transition Automatic closed transition Non-automatic (standard) Soft load (standard) Features ka standard withstand ratings 30-cycle extended withstand rating Five-cycle closing speed Totally enclosed contact assembly Fixed mount and drawout designs available EATON CORPORATION transfer switches 21

22 transfer switches Ordering information Magnum Bypass, Automatic and Non-Automatic Transfer Switches A Catalog Numbering System The catalog number ATVIMGB33200XRU describes an ATS with the switching devices mounted vertically in the enclosure. The intelligence, represented by the ATC-600 is a microprocessor-based logic package. The Magnum breaker is used as the switching device and is a three-pole molded case breaker for each source. The continuous current rating of this equipment is 3200A and is applicable at 480/277 Vac, 60 Hz. The transfer switch equipment is enclosed in a NEMA 3R enclosure and is listed for Underwriters Laboratories (UL) and Canadian Standards Association (CSA) applications. AT V I MG B X R U Type AT = Automatic CT = Closed transition BI = Bypass transition CB = Closed transition bypass isolation NT = Non-auto Orientation V = Vertical Logic C = ATC-5000 I = ATC-600 (open transition) I = ATC-800 (closed transition) Frame Size (Amperes) MG = Magnum DS Switch A = Fixed mount, power case switch (PCS) both B = Fixed mount, power case circuit breaker (PCB) both C = Fixed mount, PCB normal, PCS emergency D = Fixed mount, PCS normal, PCB emergency E = Drawout, PCS both F = Drawout, PCB both G = Drawout, PCB normal, PCS emergency H = Drawout, PCS normal, PCB emergency Number of Poles 2 = Two-pole 3 = Three-pole 4 = Four-pole Amperes 0200 = 200A 0300 = 300A 0400 = 400A 0600 = 600A 0800 = 800A 1000 = 1000A 1200 = 1200A 1600 = 1600A 2000 = 2000A 2500 = 2500A 3200 = 3200A 4000 = 4000A 5000 = 5000A Voltage A = 120V 60 Hz Three-phase Three-wire B = 208/120V 60 Hz Three-phase Four-wire E = 600V 60 Hz Three-phase Three-wire E = 600V 60 Hz Three-phase Four-wire G = 220/127V 50 Hz Three-phase Four-wire G = 220/110V 50/60 Hz Single-phase Three-wire H = 380/220V 50 Hz Three-phase Four-wire K = 600V 50 Hz Three-phase Four-wire M = 230V 50 Hz Three-phase Three-wire M = 230V 50 Hz Single-phase Three-wire N = 401/230V 50 Hz Three-phase Four-wire O = 415/240V 50 Hz Three-phase Four-wire W = 240/120V 60 Hz Single-phase Three-wire W = 240V 60 Hz Three-phase Three-wire W = 240/120V 60 Hz Three-phase Four-wire, hi-leg W = 230/115V 60 Hz Single-phase Three-wire X = 480V 60 Hz Three-phase Three-wire X = 480/277V 60 Hz Three-phase Four-wire X = 480/240V 50 Hz Single-phase Two-wire X = 346/220V 50 Hz Three-phase Four-wire Enclosure S = NEMA 1 R = NEMA 3R T = Throughthe-door design Certification U = UL listed R = UL recognized X = No listing 22 EATON CORPORATION transfer switches