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Type W-2 Instrument and Control Switches
Design Features General Construction The W-2 Switch consists essentially of an operating handle, faceplate, control housing, contact frame assembly and rotor assembly. It can be built up in any number of stages from 1 to 8, where stages are clamped together, and to the control housing by two tie bolts. A steel operating shaft ties the contact rotors together. A metal cover on the rear holds the position stop pins and retains the shaft. For push or pull switches, the metal cover is replaced by a polycarbon- ate cover which houses the pull-out mechanism. Switch Positions The Type W-2 Switch has a minimum of two and a maximum of twelve rotary positions with a 30° throw between positions. Each rotary position coincides precisely with the nameplate markings. The degree of throw between positions is fixed and cannot be changed. In addition to rotary motion, the W-2 switch can be provided with a lateral movement (push-pull) of the handle and shaft. Contact Frames Two contact frame sizes are available. The half frame has six sets of contacts; three sets on the top at 11, 12 and 1 o’clock positions and three sets on the bottom at 5, 6 and 7 o’clock positions. The full frame has12 sets of contacts, each set located at 30° intervals around it. The contact frames are made of glass polyester insulating material. Contacts Switches are usually referred to as “so many stages long”. For a W-2 Switch, a stage of contacts consists of a contact frame (either 6 or 12 contact sets) and a rotor. At every position location on the frame, there are two contact terminal studs in line (1 set) per stage. Each of these studs is one piece, made of bronze alloy and silver plated. Rotors The rotors hold the roller contacts. Each rotor, made of glass polyester insulating material, rotates independently between the stage spacer plates. The rotor assembly is equipped with one to six rollers (as determined by the required circuitry) each of which makes contact with two adjacent stationary terminal studs to complete a circuit and so affording a double series break contact. The silver-plated, bronze alloy roller contacts provide a rolling, wiping action; are self-aligning on assembly; and require no adjustment of contact pressure for the life of the switch. Contact springs do not carry current. Switch Dial The Type W-2 Switch Dial consists of two parts: a dial plate and a nameplate. The standard control switch Dial plate is die cast aluminum, with red and green target parts where required, and serves as the base for mounting the nameplate. The nameplate is made of a white Cycolac ABS material on which is engraved in black the desired position marking.