Factors to Consider in the selection and application of Automatic Transfer Switches 

• Automatic Transfer Switch
• Controller Features
• Bypass Isolation Switch Features
• Closed Transition Transfer Switches
• ASCO Services

Automatic Transfer Switch
Feature	Customer Benefits
Single Operator	Provides inherent double-throw operation. The same operator opens one set of contacts while closing the other set. Ensures positive locking and high contact pressure.
Solenoid Operator Design	Simple, proven operator. Less moving parts result in higher reliability. Repeatably fast operation.
Same Operator 30-4000 amp, ATS, CTS and DTS	Provides uniformity of design across entire product line and simplifies maintenance for owner.
Non-fused Operator	A transfer switch is an emergency device. A fused device intentionally renders the switch inoperable is undesirable and defeats the purpose of a transfer switch.
Contacts designed and manufactured specifically for transfer switch duty	Silver alloy main contacts (highly conductive) and arcing contacts (resistant to heat) designed for specific purpose.
Contacts designed by ATS manufacturer	Does not use components or parts designed for other electrical applications and not dependent other component manufacturer for supply.
3 Cycle WCR on all bypass-isolation switches as well as all transfer switches rated 260 amps and above. 1-1/2 Cycle WCR on transfer switches rated below 260 amps.	3 Cycle WCR provides UL 1008 listing with "any breaker", as does 1-1/2 Cycle on low amperage switches. Allows consultant to specify switch with any manufacturer's circuit breaker.
Short time withstand current ratings on all switches 800 amps and above.	Short time ratings enable protective circuit breaker selective coordination schemes, allowing upstream breaker trips to be set for delays of up to 30 cycles.
Low current arc quenching capabilities	Wide arc gaps assure arc is quenched even at low current levels, eliminating "lazy arc."
Easy to inspect, maintain and replace contacts and coils	Simplifies inspection and maintenance. Ensures minimum downtime on essential and critical loads.
Segmented contacts on switches 800 amps and larger	Assures adequate contact surface and pressure through multiple, spring-loaded contacts.
Manufactures complete line 30-4000 amp	Coordinated design; Engineering, design, manufacturing, and service responsibility under control of one manufacturer.
National Service Support	National Service Centers are staffed and equipped for deployment 7 x 24 x 365. Service vans are stocked with parts and not dependant upon supply from other manufacturers.
Repeatably fast transfer operation	Allows use of in-phase and closed transition transfer; restores power to critical loads quickly; avoids drop-out of motor starters on hot-to-hot transfer.
Overlapping Neutral	Provides isolation of neutral for proper ground fault detection; eliminates voltage transients caused by neutral interruption; eliminates arcing damage on neutral contact; Overlapping neutral pole is fully rated for continuous and WCR currents
Service Handle	Allows slow switch operation for maintenance and adjustment.
Optional External Load-Break UL Approved QMQB Operator	Provides manual operation under load (without opening door).

Controller Features
Feature	Customer Benefits
Serviceability and maintenance	Safety and ease of trouble-shooting
Standard microprocessor control panel with LCD Screen	State of the art technology; Integrated features ensure proper operation under all conditions.
Frequency sensing on emergency, standard	Protects against bogging down generator which has not come up to speed.
Touch pad programming for features and settings	Provides accurate field adjustability of time delays and voltage settings, without the use of special tools, meters, or power supplies.
Surge and transient protection Compliance with (EN 55011:1991), (EN 50082-2:1995), (EN 61000-4-2:1995), (ENV 50140:1993), (EN 61000-4-4:1995), (EN 61000-4-5:1995), (EN 61000-4-6:1996), (EN 61000-4-11:1994)	Protects against electromagnetic pulses or electrical transients on power or serial lines.
Event log with statistical and diagnostic screens	Event log displays up to 99 events. Assists in troubleshooting and testing.
Automatic engine exerciser	Standard load/no load exerciser timer with seven independant programmable test schedules
In-phase monitor, built-in, standard	Eliminates excessive motor inrush, without the need for a neutral, or "off" position.
Serial communications capability with plug-in card	Provides owner with the ability to control and monitor ATSs form a local area network or through the internet from anywhere in the world.

Bypass-Isolation Switch Features
Feature	Customer Benefits
No Load Break Bypass	Provides ability to test and maintain without disturbing load; eliminates need for load disconnect contact.
Allows simple and secure operation	Allows safe operation.
Permanently mounted bypass handle	Eliminates need for locating "loose" handle and inserting into opening.
Bypass switch accessible	Allows inspection of bypass contacts.
Available through 4000 Amp	Ensures uniform design concept by one manufacturer over entire range.
Silver-plated copper bus	Maximizes conductivity and minimizes heating when compared to tin plated aluminum bus.
Mechanical and electrical position indicators for bypass and transfer switch	Provides user with clear indication of bypass and transfer switch status.

Closed Transition Transfer Switch Features
Feature	Customer Benefits
Closed Transition Transfer (CTTS)	Allows transfer of load between acceptable power sources without interruption of power to the load: typical overlap time does not exceed 100ms.
0.2 Hz Frequency differential and 5 degree window	Can be applied to any engine generator equipped with an isochronous governor.
Default to Inphase Operation	Separate inphase monitor ensures transfer of motor load will occur without excessive inrush currents even in open transition mode; alternate method requires less reliable "off" position transfer.
Soft Loading Option	Allows ramping of load to generator and control operation using graphical user interface with user friendly pull-down menus. CTTS can be field upgraded for soft load operation.

ASCO Services
Feature	Customer Benefits
ASI / Factory Trained Service	Provides timely, knowledgeable field service; Ability to furnish maintenance contracts.
Proven Field Record Over 70 Years	Stable and dependable company to provide 7x24 field service from over 120 ASI service personnel and over 500 Emerson associates.