Eaton Digitrip RMS Series Instructional Leaflet

Also see for Cutler-Hammer Digitrip RMS 510: Instructions Instructions Instruction leaflet

The breaker tripping system requires a PT Module to providepower and energy monitoring functions via a communica-tions network (Figure 4). A power relay module is also in-cluded to provide power for the communication function andrelay outputs for alarming (Figure 5). Refer to I.L. 29C891 formore detailed information on Digitrip OPTIM 1050 Trip Units.5.0 Principle of Operation5.1 GeneralThe circuit breaker is tripped on overload and short circuitconditions by combined action of three components:1. The sensors which determine the current level.2. The Trip Assembly, which contains the Trip Unit and pro-vides a tripping signal when pre-determined time-currentlevels are reached.3. The actuator which actually trips the circuit breaker.Schematically, this is represented in Figure 6. This arrange-ment provides a very flexible system covering a wide rangeof tripping characteristics as illustrated by the time-currentcurves referenced in Section 8.2 of this instruction book.Not only is the Trip Unit adjustable or programmable, but thevariety of sensors and rating plugs provides a wide range ofcurrent ratings.The automatic overload and short circuit tripping character-istics for a specific circuit breaker are determined by theratings of the installed current sensors, rating plugs, andthe selected functional protection settings. Specific settinginstructions are provided in the applicable trip unit instructionleaflet referenced in Section 8.1.When the time-current conditions exceed the functionalprotection settings, the Trip Unit supplies a trip signal to theactuator. Thus all tripping functions are performed by second-ary control circuitry, with no mechanical or direct magneticaction between the primary current and the mechanical trip-ping parts of the breaker and with no external control powerrequired.5.2 Digitrip Trip assemblyThe basic Digitrip Trip Assembly, as shown in Figures 4 and5, includes the following which could vary slightly dependingupon the exact model of the Digitrip Trip Unit installed:1. Digitrip Mounting Assembly2. Digitrip Trip Unit3. Rating Plug4. Auxiliary Current Transformer Assembly (3 or 4 currenttransformers depending upon whether or not ground faultprotection is included)5. Stab-in Edge Connector for Trip Unit6. Terminal Block equipped with Test Plug Receptacles foruse with Portable Test Kit7. Power/Relay Module (provided on all models except theDigitrip RMS 510)8. Potential Transformer Module with Dielectric DisconnectPlug (Digitrip RMS 810 and 910, Digitrip OPTIM 1050 only)As shown in Figures 1 and 4, the Digitrip Trip Unit assemblymounts on the top front of the circuit breaker. CauTIONThE aCTuaTOr COIl has a pOlarITy markINg ON ThEpOsITIVE lEaD whICh musT BE OBsErVED. OThErwIsE ThEBrEakEr wIll NOT haVE OVErlOaD Or faulT prOTECTIONwhICh COulD rEsulT IN BODIly INJury aND/Or sErIOusEQuIpmENT DamagE.5.3 Trip actuatorThe trip actuator receives a tripping pulse from the DigitripTrip Assembly, and produces a mechanical force to trip thebreaker. Refer to Figure 3-11 in I.B. 694C694 for location anddetails. The actuator is made up of a permanent magnet, adisc held by the magnet, a rod acted on by a spring, a leverfor tripping the breaker, and a lever for mechanically reset-ting the actuator. The magnet cannot pull and reset the discagainst the force of the spring acting on the rod, but canovercome the spring force when the disc is in contact withthe magnet pole piece.A tripping pulse from the Digitrip Trip Assembly counteractsthe effect of the permanent magnet, allowing the spring toseparate the disc from the magnet pole piece and move therod to actuate the trip shaft lever. The trip shaft lever thenrotates the trip shaft and trips the breaker.Effective July 2010 Instructional Leaflet IL8700C39-0412 eaTOn CORPORaTIOn www.eaton.com