GB320032A - Motor control system - Google Patents

Abstract

320,032. Latour, M. May 30, 1928. Exciting.-A motor control system, particularly for traction motors, comprises a main driving motor 1, a separately driven exciter 9 supplying the field winding 2, and an auxiliary series motor 6 coupled to the main motor and connected across it in series with the field winding 8 of the exciter, means such as a resistance 12 having a positive or a negative temperature coefficient being connected across the exciter field winding for varying the excitation of the main motor. The system is particularly applicable to regenerative braking. The exciter 9 is driven at constant speed by a shunt motor 10 which may have a separate low-voltage commutator to supply the field winding 11 if the voltage of the line 3 is too high, and when operating regeneratively, the motor 1 will generate at all speeds an E.M.F. proportional to the line voltage. The resistance 12 may have a positive temperature coefficient so as to cause a more than proportional increase in the excitation of the main machine upon a fall of speed. When the system is used for speed control in normal operation a variable resistance 13 may be connected across the exciter field winding. The field winding of the main motor may be connected in series with the armature, and the exciter may be provided with additional shunt or series windings connected to its own armature or to the armature of the main motor. An auxiliary motor such as 6 having two independent commutators and exciting windings may be provided for each pair of main motors, and any change such as from parallel to series connection of the main motors must be accompanied by a similar change in the connection of the auxiliary motor. The changes of connection or variation of resistance in the motor circuits may be effected automatically by a centrifugal governor on the shaft 5, but for low speeds, manual operation is preferable.