GB835019A - Apparatus for protection of electrical equipment - Google Patents

Abstract

835,019. Protective cut-out systems; electrically released switches; electromagnetic switches. DOMECQ, J. L. May 22, 1956 [May 23, 1955], No. 15822/56. Class 38 (5). The metallic framework enclosing electrical equipment is earthed (or connected to neutral) through a coil, which when energized operates contacts to short-circuit itself by a lower resistance circuit and to interrupt the main supply. In Fig. 4, a terminal 30 is connected to the framework of the equipment and a terminal 31 to earth. They are permanently connected together through a coil 29 which on leakage attracts an armature 36 on a pivoted lever 33 having pivoted at 39, a shorting contact 37 for contacts 30, 31. In the unoperated position a contact 38, also pivoted at 39, connects contacts 45, 46 for the contactor coil circuit of the main supply. When the lever 33 is moved by the armature 36 a roller 40, on pivoted latch 42, passes from the end to the side of the lever and under the action of a spring 44 maintains contact pressure at 37 and holds the lever in the operated position. The lever 33 is reset by a spring 35 when a push-button 47 is pressed to return the latch 42 to the position shown. The arrangement can be tested by a push-button 51. Further contacts energize audible and visible alarms. In Fig. 6, when an armature 74 is attracted to a coil 79, a latch 73 releases a roller 70 so as to allow a spindle 59 to rotate under the action of a spring 72 and close contacts 63, 68 connected to framework and earth, and open the main control contacts 60, 61, 611. Resetting is by push-button action in the direction of arrow 83 and testing by push-button action in the direction of arrow 82. In Fig. 8, the frame to earth short-circuiting contacts 123 are carried on a lever 106 co-pivoted with an armature 104 at 105. Armature 104 has a hook 113 to pull the lever 106 with it when it is attracted by coil 102. When a roller 117 on lever 106 passes the corner between surfaces 119, 120 of latch 115, the action of spring 116 on latch 115 drives cam surface 120 against roller 117 to complete the contact closing action of lever 106 which also operates the spring-loaded auxiliary contacts in casing 122. A spring-loaded pushbutton rod 128 resets the latch 115 and lever 106 and the armature 104 is reset by a spring 107. The armature may also be retained by a coil in the leakage circuit (Fig. 2, not shown) and in a further arrangement, as applied to a single phase and neutral circuit, terminal 4 is taken to the neutral instead of the earth connection so as to blow the main fuses (Fig. 3, not shown). Fig. 10 (not shown) shows a modification wherein the coil is in a local circuit completed by a relay connected between earth and frame terminals.