July 5, 1949. A. TUSTIN 2,474,872 ELECTRICAL SYSTEM Filed Dec. 7, 1945 12 1. SAPAAD In N/entor: Arnold Tustin, is attorney. Patented July 5, 1949 2,474,872 UNITED STATES PATENT OFFICE 2,474,872 ELECTRICAL SYSTEM Arnold Tustin, Sheffield, England, assignor, by mesne assignments, to General Electric Com pany, a corporation of New York Application December 7, 1945, Serial No. 633,447 In Great Britain May 31, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires May 31, 1961. 4. Claims. (C. 318-331) 2 My invention relates to variable speed elec equal for Speed variations on either side of the trical motor systems in which it is desired to midpoint, of the motor speed range. This inven maintain a Substantially constant torque on the tion is particularly suitable for driving equip motor throughout a range of speed. ment,...Such as oil pumps of oil servo systems, such An object of my invention is to provide an 5 that the pressure developed by the pump will re improved electrical system utilizing a variable main Substantially constant irrespective of the Speed motor adapted to Supply a substantially rate of flow of oil therethrough. Constant output torque. In the drawing, Figs. 1 and 2 are schematic Another object of my invention is to provide diagrams showing the electrical connection of an improved electrical system utilizing a variable 0. two embodiments. of my invention; and Fig. 3 Speed motor and dynamoelectric machine for illustrates the relationship of the Voltage across controlling the current through the motor arma the driving motor to the speed of the motor in ture for maintaining a substantially constant Order to provide the desired constant output motor Output torque throughout a range of torque of the system. Operating speed. -Referring to the drawing, I have shown in Fig. Further objects and advantages of my inven l, an electrical System provided. With an electric tion will become apparent and my invention will motor having an armature adapted to drive an be better understood from the following descrip oil pump, not shown, of the positive displace tion referring to the accompanying drawing, ment type in oil servo systems or for driving any and the features of novelty which characterize 20 other load device to which a constant or substan my invention will be pointed out with particu tially constant torque should be supplied inde larity in the claims annexed to and forming part pendently of the speed of the pump or other of this specification. load device. In the illustration, the armature Electrical Systems have been provided in the is provided with a set of brushes 2 and 3 which past in which a metadyne - or similar machine are adapted to connect the armature to a source has been used as a power converter, or rotary of power Supply, such as a battery 4. In order transformer for Supplying energization to a to maintain the desired armature current, one of variable Speed motor for obtaining a desired the armature brushes is connected in series With speed torque characteristic. Such a system is a metadyne dynamoelectric machine to the described in Patent 1987,417, Pestarini, January 30 Sourec of power supply. As shown, this metady the 8, 1945. According to my improved electrical dynamoelectric machine is provided with an System, a variable Speed electric motor equip arnature 5 having a primary set of brushes 6. ment is utilized to produce a substantially con and which are substantially short circuited by stant output torque from energy which is derived an electrical conductor 8 and is also provided from a substantially constant Voltage source of 35 with a set of secondary brushes 9 and to pro power in which a metadyne dynamoelectric Wide a primary circuit and a secondary circuit, machine is connected in series. With the armature respectively, through the winding of the meta of the motor, Such that the motor armature cur dyne armature 5. The operation of this type rent remains. Substantially constant and the field machine is well known and is described in various of the motor, is also adapted to be regulated to 40 patents, of which Patent 2,203,544, Pestarini, a substantially constant value. In this manner, June 4, 1940, is illustrative. In this figure, the the motor output torque will remain substan armature 5 of the metadyne machine is adapted tially constant, as the armature current and the to be driven at Substantially constant speed by motor, excitation Will both be maintained at. Sub a constant speed electrical driving motor having stantially constant values throughout the range 45 an armature mechanically connected by any of Operating. Speed of the motor. In orde ..to Suitable coupling 2 to the armature of the utilize the metadyne machine at its maximum metadyne machine and provided with a shunt efficiency and to utilize. Such a machine of the field exciting winding 3 connected across the minimum size, it is desirable that the back motor armature of and across the source of electromotive force of the motor should be: Sub 50 electrical power Supply 4. In this system, the stantially equal to the voltage of the sources of metadyne machine is provided with a field ex power supply at the midpoint in the speed range citing. winding 4 which is adapted to provide a of the motor, such that the voltage buck, or boost component of excitation along the load axis of supplied by the metadyne in maintaining the the machine for controlling the secondary cur motor armature current - will be substantially, 5 5 rent of the armature through the secondary 2,474,872 3 4. brushes 9 and 0 and, therefore, control the cur adapted to compensate for the inherent fall of rent through the armature of the main driving motor torque with motor speed due to the in motor. The current through the main driving herent variation of the metadyne current with motor armature can be maintained substan Variations of the Voltage at the secondary brushes tially constant by regulating the energization of 5 9 and 0 of the metadyne machine. Thus, when the metadyne field exciting winding 14 to a sub the neta dyne secondary voltage acts in the same Stantially constant value, and in the arrange direction as the current flowing through the sec nent Shown in this figure, this is obtained by Ondary brushes of the metadyne to the main connecting the field exciting Winding 4 of the driving motor armature f; that is, when the metadyne across the Substantially constant volt O notor Speed is such that the voltage across the age SOurce of electrical power supply through Imain driving motor armature is greater than a carbon pile regulator S having an operating that of the battery 4, the current through the coil 6 connected in series with the carbon pile metadyne and motor circuit falls with increase 5 and the field exciting winding li. This carbon of motor Speed and voltage, and similarly, when pile regulator may be of any conventional type in 5 the motor Speed is such that the Voltage across which the pressure on the carbon pile 5 is varied the main driving motor armature is less than by the coil 6 to provide a comparatively large that of the battery 4, the current in this circuit Variation of resistance for relatively small varia rises With a fall in the motor speed and voltage. tions of current in the coil 6, whereby the regul Therefore, there is a slight increase and decrease lator Will maintain substantially constant cur 20 in the main motor torque with speed variations rent in the field exciting winding 4 irrespective thereof due to the inherent characteristics of of fluctuations in the voltage of the source of the metadyne. In this figure, the same parts of power Supply 4. the System are indicated by the same reference In Order to obtain a substantially constant numerals as those in Fig. 1, and, in addition, a torque from the main driving motor, it is also fixed resistor 2 is connected in Series With the desirable that its eXcitation should remain sub metadyne field exciting winding 4 and the car Stantially constant. In the arrangement, shown bOn pile regulator 5, and another fixed resistor in this figure, a field exciting winding T is 22 is connected with a brush 2 of the main drive adapted to provide the excitation to the arma notor armature and to the connection point ture of this notor, and this field exciting Wind 30 between the metadyne field exciting winding 4 ing is connected across the substantially constant and the first fixed resistor 2. In the operation Voltage source of electrical power supply 4 of this System, the carbon pile regulator 5 will through the carbor pile regulator 5 Which auto autoignatically operate as in the arrangement Imatically maintains the current through the field shown in Fig. 1 to Supply the metadyne machine eXciting winding T Substantially constant. In field exciting winding 14 with a substantially this airangement, the motor is adapted to oper Const2nt current, while a second component of ate at a Speed such that its back electromotive energization for this metadyne field exciting force equals the voltage of the battery 4 at its Winding 4 is provided through the fixed resistor nornal Operating Speed, which is about midpoint 22, and this component of energization depends in its operating Speed range. In Fig. 3, this point 40 upon the Voltage across the main drive motor is indicated at 8 on the curve 9-2 which armature and, therefore, is dependent upon the represents the relationship of the voltage across Speed of this motor.