GB578636A - Improvements in and relating to direct current electric motors - Google Patents

Abstract

578,636. Exciting motors. MANDL, A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Jan. 25, 1944, No. 1410. [Class 35] A motor is operated at constant speed by providing it in addition to a shunt winding, with two componentsofexcitation varying with armature current and counterbalancing one another under steady condition, but one component acting with a time lag, so that on armature current increase, a series component becomes effective to oppose the increase in current. In the form shown in Fig. 3, an exciter 6 with a field winding 7 connected across the interpole winding 8 of motor 1 is connected across the series winding 3 of the motor and renders that winding almost ineffective under steady conditions but effective when the motor armature current fluctuates. The exciter preferably also has damping windings. The series winding 3 assists the motor shunt winding 2 and the exciter winding 7 may be assisted by a series coil 10. Instead of being in parallel with the motor series coil, the exciter may supply a third motor field winding opposing windings 2 and 3, and if desired the shunt excitation may be on the exciter instead of on the motor. In such cases the motor series and opposing separately excited windings should be on different poles or separated by leakage paths. In a further modification, an inductor alternator is used as the exciter, feeding the motor field winding opposing the series coil 3 through a rectifier. The exciter may have a series choke 11 and as a further alternative may be of the metadyne type. A non linear resistance 5 may be in series with shunt winding 2 so that its current changes in greater proportion than the line voltage.