GB1291043A - Vacuum switch operating mechanism - Google Patents

Abstract

1291043 Vacuum switches, actuating; transformer tap changers WESTINGHOUSE ELECTRIC CORP 14 Jan 1970 [21 Jan 1969] 1815/70 Headings H1N and HIT Forming part of a transformer tap changing system a vacuum switch 102 is operated by a mechanism including dashpots 150, 152 for regulating the rate of axial movement of contact 118 and an actuator 170 arranged to apply a predetermined force to open the contacts and to disengage rapidly on closing so as to apply no restraint on the contact 118 during its closing movement. In Fig. 1A a tap selector 20, diverter switch 52 and the vacuum switch 50 are arranged to connect a selected portion of winding 14 in series with windings 12, 16 of the transformer, either adding or subtracting the voltage depending on the position of a switch 30. The selector 20 has two moving contacts 22, 24 normally interconnected by the diverter switch 52 and vacuum switch 50 through inductances 42, 44 on a common core which limit the circulating current but not the load current. To change taps the contact 58 of the diverter is moved to disengage one fixed contact, say 56 (Fig. 1B, not shown) and the vacuum switch is opened; the disconnected movable contact 22 of the selector then moves arclessly to the next tapping T4 (Fig. 1D, not shown). Vacuum switch 50 then recloses and contact 58 returns to its centre position (Fig. 1F, not shown) thus interconnecting the two taps T4, T5. Subsequently the diverter moves to disconnect the other contact 54 and the second movable contact 24 of the selector moves to the new tapping T4. Thus the vacuum switch, at which all arcing is concentrated, is required to open each time the diverter contact 58 moves, independently of which direction it moves. In Fig. 2 a motor driven shaft 172, which drives the diverter (Figs. 3, 4, not shown) and tap selector, carries to cams 204, 206 and loosely supports the actuator 170 which is held by a latch 250. A heavy spring 192 is carried by the actuator 170 and biases an arm 230 anticlockwise about a pivot 190 also on the actuator. The arm 230 is fixed to a first toggle link 222 a second link 220 being pivoted to a fixed shaft 212. The spring 192 and another 218 tend to bias the toggle to a straightened position. When shaft 172 is rotated in either direction a rise 272 or 282 on cam 204 trips the latch 250; spring 192 expands straightening the toggle linkage 220, 222 and driving actuator 170 clockwise until its forked end 184 engages a block 154 on the vacuum switch shaft 142 opening the contacts 116, 118. The contacts remain open until shaft 172 returns to its initial position when the cam 206 strikes a roller 224 on the knee joint of the toggle, breaking the toggle, restressing spring 192 and allowing latch 250 to re-engage. The cam 206 moves the actuator 170 rapidly to the position shown free of shaft 142 whereupon the contacts 116, 118 are reclosed under control of the dashpots 150, 152 by the air pressure on bellows 120 and/or an auxiliary spring (not shown).