TRACTION MOTOR SPEED REGULATION FOR PROPULSION SYSTEMS PROVIDING SMOOTH STEPLESS CHANGES IN SPEED AND AUTOMATIC WHEEL SLIP CONTROL

摘要

A traction motor tractive effort regulator for propulsion systems employing multiple series type direct current traction motors and providing smooth stepless changes in tractive effort together with automatic wheel slip control. Current controlling resistors are are connected in series circuit relationship with the respective serially connected field and armature windings of a string of serially connected traction motors across a main power source of direct current excitation. Main control switches are provided for variably controlling the value of the current controlling resistors connected in series, series-parallel and/or parallel circuit relationship with the traction motors for variably controlling the torque of the motors and hence the tractive effort of the vehicle. Means are provided for supplying a separate excitation source of direct current connected across the respective field windings of the direct current traction motors in parallel with and in addition to the excitation provided by the main power source. Ancillary control means are included for varying the magnitude of the separate direct current excitation supplied through the respective field windings independently of and in conjunction with the main current controlling resistors. The separate excitation source of direct current is connected across the respective field windings of the traction motor with a polarity such that the separate direct current excitation adds to the normal excitation direct current supplied from the main power source through the variable current control resistor, and the ancillary control means controls the magnitude of the separate direct current excitation supplied to the respective field windings in a manner to steplessly control the magnitude of the armature current and hence the tractive effort of the respective traction motors during each step change in value of the series current controlling resistors whereby smooth, stepless changes in torque of the traction motors can be achieved with the regulator. For this purpose current sensing devices are coupled to the respective traction motors for deriving an output indication of the tractive effort. The output indication of actual tractive effort is compared to an input reference signal in a suitable comparator which derives an output error command signal that controls operation of the ancillary control means. The ancillary control means in turn controls the magnitude of the separate direct current excitation supplied to the respective field windings independently of and complementary with the main current controlling resistors whereby smooth, stepless changes in motor torque are achieved. Additionally, wheel slippage detecting devices are provided for detecting slippage of the respective traction motors and deriving an output indication of such slippage. A wheel slip control circuit is responsive to the wheel slippage detector and is coupled to control the ancillary control means for the slipping traction motor so as to reduce the field current of the slipping motor, and thereby quickly reduce its tractive effort. Simultaneously, the wheel slip control circuit provides an increase in field current to the nonslipping traction motors so as to maintain the tractive effort of each nonslipping motor substantially constant by appropriately decreasing the armature current or at least preventing an increase in the armature current.