ANSI / NEMA Device Numbers (RTO Commonly Used)
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- Stopping Device
- A control device used primarily to shut down equipment and hold it out of operation.
- (This device may be manually or electrically actuated, but excludes the function of electrical lockout [see device function 86] on abnormal conditions.)
- Over-Speed Device
- Usually a direct-connected speed switch which functions on machine over speed.
- Directional Power Relay
- A device that functions on a desired value of power flow in a given direction or upon reverse power resulting from arc back in the anode or cathode circuits of a power rectifier.
- Bearing Protective Device
- A device that functions on excessive bearing temperature, or on another abnormal mechanical conditions associated with the bearing, such as undue wear, which may eventually result in excessive bearing temperature.
- Field Relay
- A relay that functions on a given or abnormally low value or failure of a machine field current, or on excessive value of the reactive component of armature current in an AC machine indicating abnormally low field excitation.
- Field Circuit Breaker
- A device that functions to apply or remove the field excitation of a machine.
- Manual Transfer or Selector Device
- A manually operated device that transfers the control circuits in order to modify the plan of operation of the switching equipment or of some of the devices.
- Machine or Transformer Thermal Relay
- A relay that functions when the temperature of a machine armature or other load carrying winding or element of a machine or the temperature of a power rectifier or power transformer (including a power rectifier transformer) exceeds a predetermined value.
- Instantaneous Over-Current or Rate-of-Rise Relay
- A relay that functions instantaneously on an excessive value of current or on an excessive rate of current rise, thus indicating a fault in the apparatus or circuit being protected.
- AC Time Over-Current Relay
- A relay with either a definite or inverse time characteristic that functions when the current in an AC circuit exceed a predetermined value.
- AC Circuit Breaker
- A device that is used to close and interrupt an AC power circuit under normal conditions or to interrupt this circuit under fault of emergency conditions.
- Over-Voltage Relay
- A relay that functions on a given value of over-voltage.
- Pressure Switch
- A relay that operates on given values of liquid or gas pressure or on given rates of change of these values.
- The assembly of fluid, electrical, or mechanical control equipment used for regulating the flow of water, steam, or other medium to the prime mover for such purposes as starting, stopping or holding speed or load.
- AC Reclosing Relay
- A relay that controls the automatic reclosing and locking out of an AC circuit interrupter.
- Locking-Out Relay
- An electrically operated hand, or electrically reset relay or device that functions to shut down or hold an equipment out of service, or both, upon the occurrence of abnormal conditions.
- Differential Protective Relay
- A protective relay that functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities.
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