| Alternate Power
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Also called back-up and critical power. If there is a normal power source failure, emergency power can be supplied as an additional source from the utility or an on site generation, from an engine-generator set for example.
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| Alternative System
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On-site power generation assets installed as a back-up to the normal source or as a way to reduce energy bills. Surplus generating capacity allows for power to be supplied back to the utility grid (Cogeneration). For cogeneration to take place, the on-site asset must run in parallel with the utility source.
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| ANSI
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American National Standards Institute
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| Arcing
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The effect generated when electrical current bridges the air gap between two contacts or conductors
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| Automatically Operated
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Mechanisms that do not require the intervention of operating personnel.
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| Automatic Transfer Switch (ATS)
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The ATS includes sensing circuits to detect when a power failure occurs, and triggers logic to start the engine when the emergency power source is an engine generator. When the generator reaches the proper voltage and frequency, the switch automatically transfer load circuits from the normal source to the emergency source. When the normal source is restored, the switch re-transfers the load circuits back to the normal source.
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| Back-up Power
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See Emergency Power
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| Basic Transfer Switch
| A design for use with customer furnished controls. Similar to an automatic transfer switch except intelligence and supervisory circuits are omitted. |
| Circuit Breaker Type Switch
| Transfer switches known as the circuit breaker type use specially designed switching devices that are typically molded /insulated case switches. A molded case switch is like a molded case circuit breaker without magnetic or thermal trip elements and does not trip on overload or faults. Used when a compact, high capacity disconnect is needed, and is held to a more rigorous testing standard than the contactor type. |
| Closed Transition
| Power is maintained to the load throughout the transfer process to the second power source. (Make before Break) |
| Contactor Type Transfer Switch
| Transfer switches that use a contactor type design. The contactor type switches do not use motor starting/lighting type contactors. In fact, contactor type transfer switches used circuit breaker design contacts, arc chutes and arcing horns. |
| Continuous Current
| The amount of current a device can carry constantly at 60 cycles without exceeding the temperature rise, according to ANSI charts. |
| Drawout
| A type of circuit breaker that can be moved into or out of its structure without unbolting, often on a racking mechanism. |
| Electrically Operated
| A version of the manually operated mechanism, but is electrically operated. Operating personnel must be present to initiate the operation. |
| Electrically Operated Non-automatic Transfer Switch
| Similar to the manually operated version except that an electrical operation feature is added to the switch. The switch electrically transfers power when a pushbutton, generally mounted on the enclosure, is activated. Can also be operated manually. |
| Emergency Power
| Also called alternate, back-up and critical power. If there is a normal power source failure, emergency power can be supplied as an additional source from the utility or an on site generation, from an engine-generator set for example. |
| Emergency System
| A system legally required and classified by government jurisdiction. Applies when loss of the normal power source would be a hazard to safety or human life. Intended to automatically supply illumination and/or power to designated areas and equipment. Characterized by a transfer time of less than 10 seconds. (Hotels, Sports Arena's, Health Care) |
| Interrupting rating
| Also “Ampere Interrupting Capacity (AIC), a rating of the a mount of current that a protective device can safely interrupt. |
| IQ Transfer
| A programmable microprocessor based monitoring device designed specifically to use with transfer switches. |
| Legally Required Standby System
| A system legally required and classified by government jurisdiction. These systems are intended to automatically supply power to selected loads, other than those already classified as emergency. Transfer time from the normal source to the emergency source cannot exceed 60 seconds. (Refrigeration, Communications, Smoke removal, Sewage disposal, Industrial processes) |
| Logic Panels
| Provides the intelligence/supervisory logic circuits necessary for the switch and related circuit operations. There are three forms; Electromechanical Relay, Solid State, Microprocessor-based. |
| Manually Operated
| Mechanisms requiring operating personnel to perform a function by hand. |
| Manually Operated Non-automatic Transfer switch
| Provide all the mechanics to effect the transfer from source to source. The actual transfer or power, however, is accomplished by true hand operation of the transfer switch. |
| Manual Transfer Switch
| Transferring from the normal to the back-up power source is done with a manually operated device. Operating personnel are readily available and the load is not of a critical nature requiring immediate restoration. Also called a Non-Automatic transfer switch. |
| Non-automatic Transfer Switch
| See Manual Transfer Switch |
| Normal Power
| The power source used every day in non-emergency situations. Also called the preferred source |
| On-site Generation
| Power is produced by the user, typically from an engine-generator set (genset), located in their facility. |
| Open Transition
| Power is removed from the load before the transfer to the second power source. (Break before Make) |
| Optional Standby System
| Intended to protect public or private property or facilities, where life and safety do not depend on the system's performance. Generally, on-site generated power is supplied to selected loads automatically or manually. There is no time limit associated with the transfer. (Commercial buildings, Farms, Residences) |
| Preferred Source
| See Normal Power |
| Service Entrance Equipment
| Equipment located at the point where power from the utility first enters a facility. |
| Standby Power
| A power source other than that used everyday. Usually refers to a power used with optional or alternative systems. |
| Step-Down Transformer
| A device used to change a voltage level to a lower voltage level. |
| Stored Energy
| A mechanism used to overcome inherent forces opposed to the insulated switch (circuit breaker) closing process, which stores energy until it is needed to help open the breaker. |
| Transfer Switch
| A critical component of any emergency or standby power system. When the normal (preferred) source of power is lost, the transfer switch transfers from the normal source of power to the emergency (Alternate) source of power. Operation of the transfer switch from normal to emergency and back to normal can be a manual type operation or an automatic type operation. |
| Transformer Panel
| Provides operating voltage to power the switch's motors, coils, logic, etc. |
| Trip Unit
| Device that trips the operating mechanism in case of a short circuit or overload condition. |
| Twin Stored Energy
| This type of mechanism utilizes insulated case switches with true two step stored energy mechanisms as the switching devices. The stored energy provides the mechanical motion to open and close the two sets of main contacts. |
