GB429003A - Improvements in apparatus for the protection of electric machines - Google Patents

Abstract

429,003. Protective cut-out arrangements; control of D.C. motors. SIEMENSSCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Nov. 6, 1934, No. 31913. Convention date, Nov. 6, 1933. [Classes 38 (iii) and 38 (v)] A protective arrangement for a machine 1 which is supplied with energy from A.C. mains 4 through a rectifier when acting as a motor and is arranged to return energy to the mains through a converter when acting regeneratively, comprises switches 5, 6 in the D.C. circuit and a switch 7 or switches in the A.C. circuit, the switches 5, 6, 7 being so interlocked that the interruption of the connection between the rectifier and converter discharge vessels, as 2, 3 and the mains is prevented while switches 5, 6 are closed. Thus, contacts of an overload relay 18 or lower contacts of a no-volt relay 19, on closure, energize from a battery 23 the release coil 9 of switches 5, 6, which, on opening, make at 12 the circuit of the release coil 14 of the switch 7. A similar cycle occurs on closure of the manual switch 20. The switches 5, 6 are held open by a latch which is controlled by a coil 11, responsive to either the voltage or speed of the machine 1, and by a coil 10. When voltage is restored on the mains 4, and assuming 22 is closed, relay 19 picks up and energizes over the closed contacts 13 the release coil 15 of a latch holding 7 open. 7 may therefore be closed by hand or remote control, and when closed, makes at 16 and over contacts 21 of a motor-control device 8 (provided the latter is in the "off" position) the circuit of coil 10, so unlatching and permitting closure of 5, 6. The coil 11 acts to prevent resetting too soon after disconnection and before the motor comes to rest, but if only a momentary fault occurs, coil 14 is not energized when 5, 6 open. The Specification as open to inspection under Sect. 91 states also that switching off may be made responsive to mechanical defects in the vessels 2, 3. This subject-matter does not appear in the Specification as accepted.