Patent GB-436377-A (GB)
Title: Improvements in and relating to power systems
IPC: H02P9/00
Filed: 1934-04-07
Abstract: 436,377. Systems for transmitting mechanical power. BRITISH THOMSONHOUSTON CO., Ltd., Crown House, Aldwych, London. April 7, 1934, No. 10564. Convention date, April 8, 1933. (Class 38 (iv)] [See also Group XXVI] A power system suitable for an electrically propelled vehicle comprises a prime mover, such as an internal-combustion engine 10, which has its throttle 31 controlled by a governor 17 and drives off generator 11 supplying current to traction motors 25 .. 28. The generator field winding 16 is supplied from an exciter 12 the field current being controlled by a rheostat 14 and the arrangement being such that the engine 10 can be set to run at a number of predetermined speeds. An increase in engine speed over any set speed causes the governor controlled contact 75 to earth contact 80 the part of the rheostat 14 between brushes 126, 127 being then shortcircuited and the rheostat arm 125 moved under the control of core 20 to cut resistance out of circuit with the generator field 16. Movement of the rheostat arm continues so long as the increase in speed, which may be too small to effect the governor controlled throttle setting, persists or until all the rheostat resistance is cut out of the generator field circuit. Closure of the contacts 75, 80 is resisted by the action of a coil 91 which causes opening of these contacts when the increase of speed is almost compensated for, the opening of contacts 75, 80 breaking the short circuit across the brushes 126, 127 with consequent reclosure of these contacts so that the final adjustment of the rheostat arm 125 takes place by a series of small steps and hunting is avoided. If the speed of the prime mover decreases below the set speed contacts 75 and 81 close and the rheostat arm 125 is returned by coil 21 to insert resistance in the generator field circuit the arm 125 being prevented from moving past the position shown in the drawing except when the main controller 30 with which is associated the reversing drum 172 is in its fifth and sixth positions. In the first four positions of the controller the current in the generator field 16 is controlled by inserting in circuit with this field part of the rheostat resistance and or one or both of the resistances 174, 175. In the remaining positions of the controller the generator field current is controlled by the rheostat 14 which is operated by a fluid actuated device operated by the coils 20, 21 under the control of contacts 75 80, 81, as above described. Continuous forward movement of the arm 125 to decrease the field resistance also causes the motor connections to be changed from series to series parallel by energization of the series parallel switch 112, one pair of motors being connected in series with an overcurrent relay 240 which, if operated, energizes coil 21 to cause a decrease of generator excitation. Further forward movement of 125 causes the motor fields to be shunted by resistances 117, 118. Section 122-121 of the field rheostat is associated with the generator field 16 when the motors are in series parallel and the section 123-121 when the motor fields are shunted by 117, 118. The motor connections are changed back first to series parallel and then to series when the rheostat arm is moved back the changes being delayed beyond the points at which the corresponding changes took place on forward movement of the arm 125. The generator field is momentarily de-energized when the motor connections are being changed. The throttle 31 of the engine 10 is controlled through a bell-crank lever 43, attached by a pin and slot connection to the governor spindle 46, by the governor 17. The governor is loaded by a spring 57 and also by a spring 60 which acts on the spindle 46 through a floating lever 61 pivoted on a roller 62. Four throttle coils 65, 66, 67, 68 are provided and are energized respectively in the second, sixth, seventh and eighth positions of the main controller drum 30 the roller 62 being moved forwards and the governor setting and the position of the plate carrying contacts 80, 81 being changed, as each coil is energized so that the engine 10 can run at any one of five speeds, the spring 60 producing maximum governorloading when all the coils 65-68 are energized and no loading when all these coils are de-energized. When the engine 10 is running the operating coil of fuel valve 37 is energized from the battery 105, which is charged by the exciter 11 through manual switch 145, contacts of oil pressure switch 158 and overspeed switch 163 to earth. The engine 10 is started by generator 11 running as a motor when switches 143, 142 are closed, switch 158 being shunted and is stopped by opening switch 145 while stoppage also takes place if the oil pressure fails.