Patent GB-947613-A (GB)
Title: Improvements in or relating to drive means for tilting vessels containing molten metal
Inventor: HOLMES FRANK RICHMOND
IPC: C21C5/50
Filed: 1961-08-24
Abstract: 947,613. Control of D.C. motors. ASHMORE, BENSON, PEASE & CO. Ltd. Aug. 13, 1962 [Aug. 24, 1961], No. 30487/61. Heading H2J. [Also in Division F4] Means for tilting a vessel for molten metal include at least two D.C. motors adapted for series-parallel control. A plurality of pairs of motors may be provided together with means for selectively connecting motors in each pair in series and in parallel. In one arrangement, a pair of motors and a reduction gear unit common to both motors are located at one side of the vessel, the motors being connected through respective disengageable couplings to the opposite ends of an input shaft of the reduction gear unit. In another arrangement, two motors and one reduction gear unit are located at each side of the vessel, the motors in each pair being on opposite sides of the vessel. Two multinotch controllers, one for each pair of motors, may be manually operated either in step with one another, or individually. In the " off " position diverter resistances are connected across armatures AA-AD, the controller being movable for forward or reverse control. On the first notch, full shunt field excitation is provided, armature AA being in series with armature AC, and armature AB in series with armature AD. Brake relays ASBR-DSBR are energized to release the brakes. Signals representing the armature current of motor AA are derived from resistor RM11 and applied to control winding 152 of magnetic amplifier 150, similar signals in respect of motor AC being applied to winding 154. The output of the magnetic amplifier is delivered to shunt field winding CPF of motor AC so as to maintain load sharing between the motors AA, AC. The shunt field of motor AB is likewise modified by magnetic amplifier 160 to promote loadsharing between motors AC, AB, whilst magnetic amplifier 170 operates to provide loadsharing between motors AD, AB. In subsequent notches of the controller, the diverter resistances are removed, and series resistors R11, R21 and R12, R22 are cut out in turn. The series contactors are then opened and the parallel contactors closed, a bridge transistion circuit being formed. This is followed by four stages of field reduction. Operation may continue with only three motors if one motor is out of service. Thus, motor AA may operate on its own whilst motors AB, AD can operate in series and parallel as a pair. Under such circumstances, the single motor operates at similar speeds to that of the pair and the load is shared between the three motors. When the controller is on the " off " notch diverter resistances DR12, DR13, are in series across resistor DR11, the combination being connected in parallel with armature AA. Diverter resistances DR21, DR22 are connected across armatures AB, AD, respectively. Subsequent operation is similar to that described, the values of the various resistors being so chosen as to match the conditions for a single motor to those of a pair. The shunt field of motor AB is adjusted by magnetic amplifier 160 to promote load-sharing between motors AA, AB. The magnetic amplifier 170 provides load-sharing between motors AB, AD. Specification 881,913 is referred to.