GB1525563A - Control circuit for an electrically driven vehicle - Google Patents

Abstract

1525563 Control of DC motors JOSEPH LUCAS Ltd 29 Aug 1975 [4 Sept 1974] 38577/74 Heading H2J An electrically driven vehicle control circuit comprises positive and negative supply lines connected to a traction battery, a motor having an armature and a separately excited field winding connected between the supply lines, at least one recirculating diode connected in circuit with the field winding, a field current regulator, means operable to reverse the connections between the ends of the field winding and the supply lines, and switch means which, on operation of the reversal means, opens and causes current flowing in the field winding current to be diverted through the battery so as to increase the rate of decay of flux above that with the recirculating diode alone and thereby allow rapid reversal of the field current. As shown on Fig. 1, a single recirculating diode 45 is provided and the reversal means comprise a pair of switches 34, 35 connected to the ends of the field winding 31 and operable by a relay coil 36, the switch means 38 being operable by a relay coil 74 and a controller for the relay coil. In operation, and with the circuit connected as shown, field current in the direction If flows. When it is desired to reverse the current flow, a signal is removed from an input terminal 0À75 and a signal is applied to an input terminal 76 of the controller. A transistor 46 is immediately caused to conduct thereby turning off transistors 43 and 41 to disconnect the battery from the winding 31, and a transistor 73 is caused to conduct after a delay to energize relay coil 74 to open contact 38. Current then flows from winding 31, through diode 45, battery 42, diode 82 and winding 31, the battery opposing this flow and causing rapid decay of flux in winding 31. When this flux reaches zero, as detected by Hall devices 81, a gate 78 causes a bi-stable circuit 79 to change state to energize a relay coil 59 to change contacts 58, 66 over. Thus relay coil 36 is immediately energized to change over contacts 34, 35, transistor 73 is immediately turned off to de-energize relay coil 74 to close contact 38, and transistor 46 is turned off after a delay to switch on transistors 43, 41 to allow current to flow through winding 31. A field current controller 40 is provided and the armature is not shown. As shown in Fig. 2, two recirculating diodes 103, 104 are provided and the reversal means consist of four thyristors 93, 94, 99, 101. When it is desired to reverse current flow, switch 97 is opened to cause current flow through battery 102 and when the flux is zero, a field controller causes the appropriate pair of thyristors to conduct.