GB715300A - Improvements in turning gear for steam turbines - Google Patents

Abstract

715,300. Control of D.C. motors. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Aug. 11, 1953 [Aug. 1, 1952], No. 19563/52. Class 38(3) [Also in Groups XXVII and XXXV] Control circuit. A switch 9 is closed when a starting lever is moved into the " engaged " position [see also Group XXVII] and establishes a circuit which includes a first limit switch 16 connected to the operating lever of an engine starting clutch, a first delay relay 17 and the contact 18 of a second delay relay 19; the contact 20 of relay 17 is in series with relay 19. Relays 17 and 19, which have an adjustable delay, are each provided with an additional contact 21 and 22, respectively, connected in series with the coil 23 of the clutch servomotorvalve. The armature of a starting motor 29 has series and shunt fields 32, 33, the latter being shunted by a surge-suppressing non-liner resistance 38. A two position selector switch 24 may be placed in series with either one of two contactors 25 or 26, which operate interlocking contacts 27, 28 and ahead and astern contacts 27a, 28a in the armature circuit; the contactors may be mechanically interlocked. A contactor 34 in series with contactors 25. 26 controls contacts 35 and 37 and hence both energization of coil 36 operating a starting rheostat 31 in the armature circuit and the shunt field 33. Operation. Movement of the starting lever to the " engaged " position closes switch 9 and energizes relay 17 over switch 16 and contact 18 thereby closing contact 20 and energizing motor 29 over switch 24 and relay 19 so opening contact 18, closing contact 22 and de-energizing relay 17 which drops after 0.5-1 second and closes contact 21 thereby energizing coil 23 and through the servomotor valve causing operation of the servomotor to move the clutch toward the engaged position. Simultaneously contact 20 opens and de-energizes the motor 29 and relay 19 which drops after approximately two second delay; the starting motor has been supplied with current for 0.5-1 second and the clutch moved in the engaging direction for 1-1.5 seconds, the clutch displacement opening switch 16. Switch 30 closes when the clutch engages and enables power to be supplied to the relay 19 and the motor so that contact 22 is kept closed and coil 23 energized until switch 9 is opened upon the starting lever being moved to the " disengaged " position. If the clutch does not engage. switch 30 is not closed and relay 19 drops after its delay period of two seconds and opens contact 22 thereby de-energizing coil 23 and causing the clutch to return to its disengaged position whereupon switch 16 recloses and. another cycle of operations commence. No torque is transmitted by the' motor until the clutch is engaged; in the event of tooth abutment the clutch is withdrawn after a short time delay, the motor is energized for a brief period and a further attempt is made at clutch engagement. Specification 711,250, [Group XXVII], is referred to.