Engineering Bulletin No RW34 Rotary Wafer Switches - Model MSD General Information The MSD is essentially a Heavy Duty rotary switch which is rated at 6amps. at 250Vac. Designed to handle higher currents than is possible with normal types of leaf clip wafer switches. It is eminently suitable for use in a wide variety of electrical equipment. Developed by NSF technical service to incorporate modern materials and techniques which give the switch a greatly extended life at its full current rating. Electrical Characteristics. Maximum working voltage 250Vac. Contact rating. with resistive/non-inductive load 6 amps at 250Vac. (rms) 10 amps at 30 Vdc. Proof Voltage 2000 Vdc for 1 minute. 5 Insulation resistance greater than 10 megohms. between adjacent contact or contact and frame) Contact resistance (initial) less than 5 milliohms at 2.5 Vdc No. of Poles. 1 amp. 1 Pole. 2 to 12 ways 2 Pole. 2 to 6 ways 3 Pole. 2 to 4 ways 4 Pole. 2 or 3 ways Contacts. Contacts are copper, silver plated. Rotor Contacts. Break-before-make only. Index Mechanism. The U type mechanism is used where one or two wafers are required, the type HD for switches with two or three. For more than three wafers please refer to our technical service. The low friction moulded cam and followers in the U type assembly ensure a smooth and positive indexing action. Balanced pressure springs provide consistent and readily reproducible torque values which can be approximated as... - Light - Not greater than 0.18Nm. - Medium - Greater than 0.14Nm. but less than 0.32Nm. - Heavy - Greater than 0.28Nm. Terminals. Solder Lug. Insulation. Stator - Glass fibre loaded diallylpthalate. Rotor - Glass filled nylon. Finish. Standard Ferrous parts zinc plated, non-ferrous parts clean. Mounting Details. Imperial (standard). Metric (alternative) Bush 3/8 x 32TPI (Whit.) M10 x 0.75. Shaft 0.25 dia. 6mm, dia. Nut 0.525 A/F. 14mm A/F. The alternative is optional in each case. Unless otherwise specified, each switch is supplied with an internal tooth steel lock washer. Panel and spindle seals can be fitted allowing sealing to 1cm/hr. Standard contacts. Each wafer comprises two stators interconnected by a rotor. One to six multiple position contacts are fitted to one stator whilst the other has up to 12 individual contacts. The rotor is fitted with up to 4 contacts to give the number of poles and ways required. NSF Controls Limited Keighley West Yorkshire BD21 5EF (+44(0) 1535 661144 Fax: +44(0) 1535 661474 Email: mail nsfcontrols.co.ukRW34 MSD Dimensions Are In Millimetres Key To Details A. Shaft length: optional 0.40 H. Bushing shoulder standard 3,2 B. Bushing thread length: preferred standard 9.5 I. Combined bearing strap and spacer, 6.35 (0.250) available as an alternative. minimum 5,55 Special lengths if necessary C. Flat length: length to specification. Tolerance 0.40. L. Spacing. 5,0 minimum spacing between Special shaft terminations may be provided to special contacts. requirements. D. Angle of flat: to specification 2 specify position of M. Any length spacer desired may be inserted at this flat, with switch shaft in fully anti-clockwise position point. Last spacer dimension will include 5.55 for the when viewed from front or knob end. combined bearing strap and spacer. E. Flat thickness: standard 5.55 0.15 for grub screws N. Thread extension: 3,0mm min x 1/8 whit. any 4.95 0.05 for push-on knobs. length desired. F. Distance of locating lug from shaft, centre line to P. Specify maximum overall length if important. centre line. Type U 9.5 Type HD 15.1 G. Angle of locating lug: Q. Shaft extension at rear: nominal 3 to 6 mm. Type U 45, 135, 225 or 315. any length required may be specified. Type HD 90 or 270. T. Length of locating pin 0.05 to 0.30 below mounting face of bush (Sealed type). unsealed type 4.8. NSF Controls Limited Keighley West Yorkshire BD21 5EF (+44(0) 1535 661144 Fax: +44(0) 1535 661474 Email: