GB590018A - Improvements in grid-type electric resistance equipments - Google Patents

Abstract

590,018. Cooling and casing grid resistances. GRAY, W. T. and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. April 9, 1945, No. 8724. [Class 37] Grid-type resistors are housed within ducting carried by or embodied in the resistor supporting framework so that cooling may be effected by forced ventilation. As shown, resistance grids are arranged on tie bars 3, 4, 5 in rows 1, la, 1b and enclosed in ducts 8, 8a, and 8b, which run perpendicular to the length of the rows. The ducts shown are rectangular in section and formed of metal side-plates 9, 10 secured along flanged edges 9<1>, 10<1> respectively to top and bottom plates 11 and 12 by bolts. Side-plates 9 and 10 are apertured to pass the tie bars 3, 4 and 5 and the associated insulating spacing bushes 13 on which the ducting rides loosely. Primary insulation between the grids and ducting is provided by washers 16, secondary insulating between the tie-bars and support frames 6 and 7 by bushes 17 and tertiary insulation between the frames and the anchoring beams by 18. Connection to the resistance grids is made through terminals la, 1b, carried through the plate 12 by insulated bushings. Duct sections 8 and 8a are connected by a detachable section 19 and similarly 8 and 8b are connected by section 20. The connecting duct sections 19 and 20 are formed of insulating sheet 19<1>, fitting closely into the open ends of the metal duct sections 8, 8a and 8b, and are provided with metal flanges 19<11> which are secured to flanges 11<11>, 12<11> of the ducting at recesses 11<111>, 12<111> by releasable clamps 21. Stiffening of the ducting is provided by side flanges 9<11>, 10<11> which engage with 19<11>. In Figs. 3 and 4 (not shown), resistance grids are arranged in parallel rows in respective sections of ducting superposed in a vertical column.