power distribution - Siemens

Motor Control CentersIncoming Cable Space, Wiring Troughs, Wiring TerminationsThe National Electrical Code establishesvery specific guidelines for minimumcable bending space within motor controlcenters. Figures 1 through 5 belowdescribe the most commonarrangements for terminating mainincoming power cables in the MCC.Consult Siemens for incoming linecompartment braced for 100,000amperes symmetrical, short circuit.Incoming Cable SpaceDescription ofTop or BottomIncoming ServiceIncoming Section≤ 350 kcmilTwo per Phase≤ 600 kcmil One orTwo per Phase≤ 600 kcmil Three orFour per Phase750 kcmil One orTwo per Phase350 kcmil One orTwo per Phase≤ 600 kcmil One orTwo per Phase≤ 750 kcmil, up to eight per phase≤ 500 kcmil One or Two per Phase≤ 750 kcmil One per Phase toMain Breaker≤ 500 kcmil One toFour per Phase≤ 750 kcmil One per Phase toMain BreakerBusway or Cable Feedto Line ReactorTop — Directlyon Main BusTopTopTopBottomBottomTop or BottomTopTopTop or BottomCable EntryTop or BottomEitherEitherTopTopBottomBottomEitherBottomTopEitherTechnical / DimensionsSpace Requirementsin Inches (mm) NotesNone See Figure 3Top Wireway plus12.0 (305) orSee Figure 118.0 (457)Top Wireway plus18.0 (457)Top Wireway plus24.0 (607)Bottom Wireway plus18.0 (457)Bottom Wireway plus24.0 (610)Full StructureSeeBreaker / DisconnectSeeBreaker / DisconnectConsult SiemensSee Figure 1—600 A MaximumSee Figure 2600 A MaximumSee Figure 2Consult SiemensSee Figure 4See Figure 5Consult Siemens15MOTOR CONTROLCENTERSSiemens MCC’s are equipped with a 12 in. (305 mm) high, full-width horizontal wireway in the top and 6 in. (152 mm) in the bottomof each structure. A separate vertical wireway connects the top and bottom wiring areas in each vertical section. This wireway is 4in. (102 mm) wide by 10 in. (254 mm) deep, or 38.25 (972) square inches (mm).Note: All standard Siemens termination schemes shown herein do comply with applicable cable bending requirements of UL and the NEC.Figure 1MainLugsIncoming CableFigure 2Figure 3IncomingCableMainLugsMain Lugs at Top with Top Cable EntryCan accommodate up to two 600 kcmil cablesper phase when using Siemens standardmechanical lugs. A total height of 24 in. (610mm). This includes 12 in. (305 mm) for the topwireway plus 12 in. (305mm) of unit space.Compression lugs require extra vertical spaceor the addition of a top hat.Main Lugs at Bottom with Bottom CableEntryLugs are bolted directly to the bottom of thevertical bus. Can accommodate up to two 350kcmil per phase in 24 in. (610 mm) highcompartment. This includes 6 in. (152 mm) forthe bottom wireway plus 18 in. (457 mm) of unitspace. Can accommodate up to two 600 kcmilper phase in 30 in. (762 mm) high compartment.This includes 6 in. (152 mm) for the bottomwireway plus 24 in. (610 mm) of unit space.Main Lugs at Top with Top or BottomCable EntryIn this arrangement the lugs mount directlyon the horizontal bus, eliminating the need touse unit mounting space. The limitation hereis 350 kcmil cable per phase.Figure 4Figure 5Main Disconnect with Bottom Cable EntryMain Disconnect with Top Cable EntryIf bottom entry is used, cables must be properly laced and supported based upon the available short circuitcurrent. See dimensional requirements for molded case breakers and fused switches, consult local sales office.15-10Siemens Power Distribution & Control, SPEEDFAX 2007-2008 Product Catalog