40Instruction Booklet IB 33-790-1JEffective November 2010Instructions for Low Voltage PowerCircuit Breakers Types DS and DSLEaToN CorPoraTIoN www.eaton.com6.2 STATIONARY CONTACT SUB-ASSEMBLIESThe stationary contact sub-assemblies may be seen inFigures 47, 48, 49, 51, and 53. All main contacts, i.e.:those which carry the main continuous load current, areof the butt type composed of a multiplicity of fingers.Each finger is hinged at the upper end under controlledpressure. Compression springs at the lower end applypredetermined pressure against the moving main contactin closing, and standing in the closed position. Thesesprings are visible in the photograph of the DS206 only.With this construction, the pressure on the main contactsurfaces is increased during the carrying and opening ofhigh short circuit currents because the magnetic field ofthe current pushes the lower end of the finger toward themoving contact. Hinging the finger at the top thus resultsin what is sometimes called “blow-on” action. This greatlyincreases the capability of the entire contact assembly towithstand the high fault currents associated with thesebreaker ratings.The stationary arcing contacts are similar for all ratingsand consist of two parallel fingers, one on each side ofthe stationary terminal member. They are pushed towardeach other by compression springs and have arc resist-ing tips.Fig. 35 Three-pole Assembly of DS-632 Pole Units on Frame.
