GB1454070A - Dynamo-electric apparatus - Google Patents

Abstract

1454070 Dynamo-electric machines ELECTRIC MOTION CONTROL CORP INTERNATIONAL 31 Jan 1975 4299/75 Heading H2A A d.c.-d.c. rotary converter includes a field winding energised by a substantially constant supply voltage; a rotor carrying an armature winding and a commutator, which is engaged by a primary set of brushes connected to the supply voltage to rotate the rotor; two sets of secondary brushes engaging the commutator and mounted for rotation about the rotor axis through equal but opposite angles relative to the axis of the primary brush set and a circuit connecting the secondary brush sets to output terminals to supply output currents therefrom. In Fig. 1, the secondary brush sets 42, 44 are mounted on rings 32, 34 rotated in opposite directions by a pinion wheel 50 engaging bevel teeth 33, 35. The brush output currents are passed via rectifier circuits and over-excitation windings (Fig. 2 not shown) to be parallel connected to the output terminals. The rectifier circuits are arranged to pass the output currents through the overexcitation windings in a consistent direction whatever the sense of the output current. The output voltage varies from positive equality to the energising voltage to negative equality as #=# 1 =# 2 varies from 0-180 electrical degrees. The converter output may thus be used to energise a vehicle drive and as illustrated in Fig. 3 (not shown), power loss in the converter is zero at #=0, 90‹ and 180‹ i.e. at maximum speed and at zero speed when maximum torque is required. In Fig. 4, the converter energises a motor 94 and power output from the system is derived from a differential unit 92 receiving the converter shaft 23 and the motor shaft 96 as its inputs. At # = 0, the shafts 23, 96 rotate at equal speeds in opposite directions and the output collar 90 remains stationary. As # is increased, shaft 96 slows down before rotating in the opposite direction causing the output collar 90 to increase in speed in proportion. Thus converter 10 is also used to transduce power between source 60 and the shaft 23. Since the torques supplied by the shafts 23, 96 are in a fixed ratio, the secondary current of the converter, i.e. the motor 94 armature current represents the torque component in the transducer 10 primary current. Thus, the converter output current is used to compensate for the armature reaction due to this component. Compensation windings 106, 107 are thus provided on the field winding quadrature axis. Compensation windings 112, 113 are also provided for motor 94. Where the converter is used to provide two different output voltages (i.e. the secondary brush sets supply independent loads), e.g. for energising left and right side drive motors on a vehicle, a gearing arrangement is used (Fig. 8 not shown) to enable like variation of the voltages for speed variation by equal and opposite rotation of the brushes as well as differential variation for steering by equal rotation in the same direction.