CA1054216A - Plural electric motors driving common load and having interconnections for load control - Google Patents
Plural electric motors driving common load and having interconnections for load controlInfo
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- CA1054216A CA1054216A CA260,175A CA260175A CA1054216A CA 1054216 A CA1054216 A CA 1054216A CA 260175 A CA260175 A CA 260175A CA 1054216 A CA1054216 A CA 1054216A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P5/00—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors
- H02P5/74—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors controlling two or more ac dynamo-electric motors
- H02P5/747—Arrangements specially adapted for regulating or controlling the speed or torque of two or more electric motors controlling two or more ac dynamo-electric motors mechanically coupled by gearing
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Multiple Motors (AREA)
- Valve Device For Special Equipments (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
PLURAL ELECTRIC MOTORS DRIVING COMMON LOAD AND
HAVING INTERCONNECTIONS FOR LOAD EQUALIZATION
ABSTRACT OF THE DISCLOSURE
A twin electric motor drive for a grinding mill has substantially identical synchronous motors mechanically con-nected to the drive of the mill, and the stator winding which generates a revolving magnetic field in each motor comprises a plurality of phase windings each of which is energized from a separate phase of a polyphase power source and has first and second winding sections which are interconnected with the second and first winding sections respectively of the corresponding phase winding of the other motor to equalize the load between the motors.
HAVING INTERCONNECTIONS FOR LOAD EQUALIZATION
ABSTRACT OF THE DISCLOSURE
A twin electric motor drive for a grinding mill has substantially identical synchronous motors mechanically con-nected to the drive of the mill, and the stator winding which generates a revolving magnetic field in each motor comprises a plurality of phase windings each of which is energized from a separate phase of a polyphase power source and has first and second winding sections which are interconnected with the second and first winding sections respectively of the corresponding phase winding of the other motor to equalize the load between the motors.
Description
~,o54~6 This invention relates to electric motive power systems and in particular to plural electric motors driving a common load and having interconnections to effect a fixed ratio of load division between the motors.
BACKGROUND OF THE I~VENTION
Large ore grinding mills used in the mining industry operate at low speeds and require drives of several thousand horsepower. Electric motive power systems for the larger sizes of such grinding mills often divide the load between two nominally identical electric motors which drive through pinions at different positions on the periphery of a bull gear coupled to the grinding mill so that the two motors are mechanically connected to the common load by the reduction gearing which reduces the speed to the low value required for the grinding ; mill. A sustained unbalance in load between the two motors may exist if the angular positions of the rotors on their respective shafts do not result in the same displacement angle for the two motors. Also, an unbalanced load may oscillate back and forth between the two motors at a frequency corresponding to grinding mill speed and/or multiples thereof as a result of small errors of concentricity or of tooth pitch in the gears or slight mis-alignment of the shafts. Such inherent inaccuracies cause incremental changes of the displacement angle of each motor with respect to its revolving stator field, and the incremental displacement angle change on one motor is usually out of phase with that of the other motor. Such changes in displacement angle result in pulsating swings of load between the two motors. Such pulsating load swings and the sustained load unbalance cause higher peak loading on the gears and can result in motor over-heating, vibration, and damage to the gears.
Twin motor drives for such ore grinding mills areknown which utilize synchronous motors because they permit con-trol of power factor and are more economical than inductionmotors, and certain of such twin synchronous motor mill drives attempt to compensate for undesirable load pulsations between motors by measuring the power inputs to the two motors and continually increasing the field excitation of the motor developing the lower torque and reducing the excitation of the motor developing the higher torque. Such known twin syn-chronous motor drives require special excitation systems and have high initial cost and high maintenance cost and also increase the peak values of stator current and field current on the motors. Another known motor drive for such a grinding mill utilizes twin synchronous motors with an auxiliary field winding which produces a magnetic field having polar axes spaced angularly from the polar axis of the main field and attempts to compensate for load pulsations between motors by adjusting the angle of the magnetic axis of the motor field excitation with respect to the rotor poles so as to shift the load torque angle. This requires a very complicated and expensive rotor structure for at least one of the motors and also necessitates an elaborate and expensive control system.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a plural electric motor drive system having improved means for maintaining the desired division of load between the motors and for eliminating pulsating load swings between the motors.
~ It is a further object of the invention to provide a plural electric motor system mechanically coupled to a common shaft and having improved means to eliminate input power variations, both sustained and oscillating, between the motors.
lOS4Z16 It is a further object of the invention to provide a plural synchronous motor drive system for a large grinding mill having improved means for improving the stability and the load sharing of the motors and which is lower in both initial cost and in maintenance cost than the above discussed prior art systems.
A still further object of the invention is to pro-vide such a plural synchronous motor drive system for a large grinding mill having improved means for effecting load equali-zation between the motors and which, in comparison to known loadequalization systems, does not require special excitatior. or control systems for the motor; is simpler and less expensive;
and has reduced maximum field current and stator current for the motors.
SUMMARY OF THE INVENTION
A load equalization motive drive system in accordance with the invention has plural electric motors mechanically coupled to drive a common load for sharing thereof, and the revolving flux generating stator winding of each motor com-prises phase windings each energized from one phase of a poly-phase source and having plural winding sections interconnected with the winding sections of the corresponding phase winding of another motor to equalize the load between the machines. The preferred embodiment has a pair of substantially identical synchronous motors driving the shaft of a grinding mill so that the flux generated by the field winding interacts with the stator rotating magnetic field to produce motor torque, and each stator phase winding has first and second winding sections with the first winding section connected in series with the second winding section of the corresponding phase winding of the other motor to reduce pulsations in load between the motors.
1054Z~6 DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the invention will be more readily apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:
Fig. 1 is a schematic circuit diagram of a load equalization motive drive system for a grinding mill embodying the invention;
Figs. 2a, 2b and 2c respectively show: (a) typical power input to motor A; (b) typical power input to motor B; and (c) the difference in the kilowatt inputs to motors A and B
during approximately four revolutions of the mill over a twenty second period when the stator windings of motors A and B are of conventional construction with no interconnection therebetween (the kilowatt scale in Fig. 2c being one-half of that in Figs.
2a or 2b); and Figs. 3a, 3b and 3c respectively show: (a) typical power input to motor A; (b) typical power input to motor B; and (c) the difference in the power inputs to motors A and B over approximately four revolutions of the mill during a twenty second period when the stator windings thereof are constructed and interconnected in accordance with the present invention (the kilowatt scale in Fig. 3c being one-half that in Figs. 3a or 3b).
DETAI LED _ESCRI PTION
Fig. 1 illustrates diagrammatically two nominally identical synchronous motors A and B coupled to a common load so that both motors drive the load and share it equally between them. One example of such a drive is a large ore grinding mill 10 (shown in block form) whose drive shaft 11 is affixed to a bull gear 12. Grinding mill 10 preferably operates at low ~.o54Z~6 speed and may require a drive of several thousand horsepower.
Motors A and B drive bull gear 12 through double reduction gearing 14 and lS (shown in block form) respectively coupled to the rotors RA and RB of motors A and B and which drive pinions 16 and 17 that mesh with opposite sides of bull gear 12.
Motors A and B preferably have the same rating, speed and characteristics so as to divide the load equally and in the disclosed embodiment each may be a salient twelve pole synchronous motor of 1000 horsepower rating with DC field windings FW on the rotors RA and RB energized from a common unidirectional power supply.
Motor A has a three phase AC armature winding on its stator comprising three phase windings x, y, z energized from individual phases 0x~ 0y and ~z respectively of a three phase electrical power source and connected in wye to a neutral N, and si~ilarly motor B has a three phase AC armature winding on its stator comprising three phase windings x', y', z' energized from individual phases ~x~ 0y and 0z of the three phase power line and connected in wye to a neutral N'. The neutrals N and N' may be internal, as shown, or the individual neutral leads may be brought out for external connection. The phase windings may have a single path (as shown) or comprise a multiplicity of parallel paths.
If the motor stator windings are of conventional con-struction, a sustained difference in load on motors A and B
may exist if their motors are not angularly positioned relative to their respective shafts to result in the same displacement angle. Also, pulsations or swings in load on each motor A and B occur, in addition to normal mill load variations, because of inaccuracies such as in concentricty or in tooth pitch in the gears or misalignment in the shafts. For nominally identical motors A and B, the kilowatt inputs to the two motors should ~054%~6 be identical if the loads on the motors are equal (assuming identical losses in the two motors). Thus the division of load between motors A and B is shown by their kilowatt inputs. When stator windings of motors A and B are of conventional construc-tion, Figs. 2a, 2b and 2c respectively illustrate over approximately twenty seconds and four revolutions of the grinding mill: (a) typical variation of kilowatt input to motor A; (b) typical variation of kilowatt input to motor B;
and (c) the difference in power inputs to motors A and B, which difference is indicative of the division in load between the motors. The major portions of the amplitude variations of the power inputs shown in Figs. 2a and 2b are imposed by the mill load itself, and similar variations would be observed even if a single motor were driving the grinding mill. It will be noted from Fig. 2c that the unbalance in load between the two motors consists not only of a variation at mill rotational frequency but also of an average sustained variation directly related to a difference in the angular positions of the rotors on their shafts. It will thus be recognized that loads of vary-ing magnitude and phase angle persist on the two motors withconventional stator windings and may cause excessive wear of the gears and overheating of the motors.
In accordance with the invention each stator phase winding x, Yr z of motor A and each stator phase winding x, y, z of motor B is divided into a plurality of sections and the sections of the corresponding phase windings in the two machines are interconnected to promote load sharing between the machines.
Stator phase winding x of motor A may be divided into a first section xl and a second section x2. Stator phase winding x' of motor B may similarly be divided into a first section xl' and a second section x2'. One side of first section xl of motor A
1054Z~6 may be connected to power supply phase 0x and the other side of first section xl may be connected to one end of second sec-tion x2' of the corresponding phase winding o~ motor B and whose other side may be connected to neutral N'. Similarly one side of first winding section xl' of motor B may be connected to power supply conductor 0x and the other side thereof may be connected to one end second section x2 of the corresponding phase winding of motor A and whose opposite end may be con-nected to neutral N.
One side of stator phase winding first section yl of motor A may be connected to power supply phase 0y and its opposite end may be connected to one end of the corresponding stator phase winding second section y2' of motor B and whose opposite end is connected to neutral N'. Similarly one end of phase winding first section yl' of motor B may be connected to power supply phase line ~y and its opposite end connected to one end of the corresponding phase winding section y2 of motor A and whose opposite end is connected to neutral N of motor A.
One side of stator phase winding first section zl of motor A may be connected to power supply phase conductor ~ and its opposite end may be interconnected to one end of the corres-ponding phase winding section z2' of motor B whose opposite end is connected to neutral N' of motor B. Similarly one end of stator phase winding first section zl' of motor B may be con-nected to power supply phase conductor 0z and its opposite end interconnected to one side of the corresponding phase ~inding second section z2 of motor A whose opposite end is connected to neutral N of machine A.
The ratio KA of the number of turns in each phase winding first section, such as Xl, to the number of turns in 10542~6 the second winding section, such as X2, in the illustrated embodiment is one-third. Figs. 3a and 3b illustrate typical power inputs to motor A and to motor B respectively over approxi-mately a twenty second period and during four revolutions of the grinding mill when the stator windings are constructed and interconnected to embody the invention as shown in Fig. 1.
Fig. 3c illustrates the input power differential to motors A
and B and shows that the average or sustained difference in load as well as the pulsations in unbalanced load between the two machines at the speed of the grinding mill are compensated for and substantially eliminated by the disclosed interconnection of motor stator windings even though the normal variations in power input imposed by the mill load itself persist.
In alternative embodiments (not shown) the field windings FW of the two motors A and B may be connected in series across a common power source to minimize the effects of induced field currents arising from oscillations in load between the machines.
It will be appreciated that a different ratio KA of first winding section turns to second winding section turns may be utilized in embodiments of my invention employing motors different than those disclosed in the Fig. 1 embodiment. Fur-ther, in alternative embodiments of the invention a winding section of each stator phase winding of one-motor consisting in coils or coil groups which are not physically located in con-secutive poles may be interconnected with the remaining coils or coil groups of the corresponding stator phase winding of the other motor. ~y in~ention also comprehends interconnection of - stator windings of induction motors such as those of the wound 3Q rotor or squirrel-case types instead of synchronous motors as well as interconnection of winding sections of corresponding lOS421G
stator phase windin~s in two motors through resistances, induc-tances or capcitances to equalize the load between the two motors.
While only a single embodiment of my invention has been illustrated and described, many modifications and varia-tions thereof will be readily apparent to those skilled in the art, and consequently it should be understood that I do not intend to be limited to the particular embodiment shown and described.
BACKGROUND OF THE I~VENTION
Large ore grinding mills used in the mining industry operate at low speeds and require drives of several thousand horsepower. Electric motive power systems for the larger sizes of such grinding mills often divide the load between two nominally identical electric motors which drive through pinions at different positions on the periphery of a bull gear coupled to the grinding mill so that the two motors are mechanically connected to the common load by the reduction gearing which reduces the speed to the low value required for the grinding ; mill. A sustained unbalance in load between the two motors may exist if the angular positions of the rotors on their respective shafts do not result in the same displacement angle for the two motors. Also, an unbalanced load may oscillate back and forth between the two motors at a frequency corresponding to grinding mill speed and/or multiples thereof as a result of small errors of concentricity or of tooth pitch in the gears or slight mis-alignment of the shafts. Such inherent inaccuracies cause incremental changes of the displacement angle of each motor with respect to its revolving stator field, and the incremental displacement angle change on one motor is usually out of phase with that of the other motor. Such changes in displacement angle result in pulsating swings of load between the two motors. Such pulsating load swings and the sustained load unbalance cause higher peak loading on the gears and can result in motor over-heating, vibration, and damage to the gears.
Twin motor drives for such ore grinding mills areknown which utilize synchronous motors because they permit con-trol of power factor and are more economical than inductionmotors, and certain of such twin synchronous motor mill drives attempt to compensate for undesirable load pulsations between motors by measuring the power inputs to the two motors and continually increasing the field excitation of the motor developing the lower torque and reducing the excitation of the motor developing the higher torque. Such known twin syn-chronous motor drives require special excitation systems and have high initial cost and high maintenance cost and also increase the peak values of stator current and field current on the motors. Another known motor drive for such a grinding mill utilizes twin synchronous motors with an auxiliary field winding which produces a magnetic field having polar axes spaced angularly from the polar axis of the main field and attempts to compensate for load pulsations between motors by adjusting the angle of the magnetic axis of the motor field excitation with respect to the rotor poles so as to shift the load torque angle. This requires a very complicated and expensive rotor structure for at least one of the motors and also necessitates an elaborate and expensive control system.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a plural electric motor drive system having improved means for maintaining the desired division of load between the motors and for eliminating pulsating load swings between the motors.
~ It is a further object of the invention to provide a plural electric motor system mechanically coupled to a common shaft and having improved means to eliminate input power variations, both sustained and oscillating, between the motors.
lOS4Z16 It is a further object of the invention to provide a plural synchronous motor drive system for a large grinding mill having improved means for improving the stability and the load sharing of the motors and which is lower in both initial cost and in maintenance cost than the above discussed prior art systems.
A still further object of the invention is to pro-vide such a plural synchronous motor drive system for a large grinding mill having improved means for effecting load equali-zation between the motors and which, in comparison to known loadequalization systems, does not require special excitatior. or control systems for the motor; is simpler and less expensive;
and has reduced maximum field current and stator current for the motors.
SUMMARY OF THE INVENTION
A load equalization motive drive system in accordance with the invention has plural electric motors mechanically coupled to drive a common load for sharing thereof, and the revolving flux generating stator winding of each motor com-prises phase windings each energized from one phase of a poly-phase source and having plural winding sections interconnected with the winding sections of the corresponding phase winding of another motor to equalize the load between the machines. The preferred embodiment has a pair of substantially identical synchronous motors driving the shaft of a grinding mill so that the flux generated by the field winding interacts with the stator rotating magnetic field to produce motor torque, and each stator phase winding has first and second winding sections with the first winding section connected in series with the second winding section of the corresponding phase winding of the other motor to reduce pulsations in load between the motors.
1054Z~6 DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the invention will be more readily apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:
Fig. 1 is a schematic circuit diagram of a load equalization motive drive system for a grinding mill embodying the invention;
Figs. 2a, 2b and 2c respectively show: (a) typical power input to motor A; (b) typical power input to motor B; and (c) the difference in the kilowatt inputs to motors A and B
during approximately four revolutions of the mill over a twenty second period when the stator windings of motors A and B are of conventional construction with no interconnection therebetween (the kilowatt scale in Fig. 2c being one-half of that in Figs.
2a or 2b); and Figs. 3a, 3b and 3c respectively show: (a) typical power input to motor A; (b) typical power input to motor B; and (c) the difference in the power inputs to motors A and B over approximately four revolutions of the mill during a twenty second period when the stator windings thereof are constructed and interconnected in accordance with the present invention (the kilowatt scale in Fig. 3c being one-half that in Figs. 3a or 3b).
DETAI LED _ESCRI PTION
Fig. 1 illustrates diagrammatically two nominally identical synchronous motors A and B coupled to a common load so that both motors drive the load and share it equally between them. One example of such a drive is a large ore grinding mill 10 (shown in block form) whose drive shaft 11 is affixed to a bull gear 12. Grinding mill 10 preferably operates at low ~.o54Z~6 speed and may require a drive of several thousand horsepower.
Motors A and B drive bull gear 12 through double reduction gearing 14 and lS (shown in block form) respectively coupled to the rotors RA and RB of motors A and B and which drive pinions 16 and 17 that mesh with opposite sides of bull gear 12.
Motors A and B preferably have the same rating, speed and characteristics so as to divide the load equally and in the disclosed embodiment each may be a salient twelve pole synchronous motor of 1000 horsepower rating with DC field windings FW on the rotors RA and RB energized from a common unidirectional power supply.
Motor A has a three phase AC armature winding on its stator comprising three phase windings x, y, z energized from individual phases 0x~ 0y and ~z respectively of a three phase electrical power source and connected in wye to a neutral N, and si~ilarly motor B has a three phase AC armature winding on its stator comprising three phase windings x', y', z' energized from individual phases ~x~ 0y and 0z of the three phase power line and connected in wye to a neutral N'. The neutrals N and N' may be internal, as shown, or the individual neutral leads may be brought out for external connection. The phase windings may have a single path (as shown) or comprise a multiplicity of parallel paths.
If the motor stator windings are of conventional con-struction, a sustained difference in load on motors A and B
may exist if their motors are not angularly positioned relative to their respective shafts to result in the same displacement angle. Also, pulsations or swings in load on each motor A and B occur, in addition to normal mill load variations, because of inaccuracies such as in concentricty or in tooth pitch in the gears or misalignment in the shafts. For nominally identical motors A and B, the kilowatt inputs to the two motors should ~054%~6 be identical if the loads on the motors are equal (assuming identical losses in the two motors). Thus the division of load between motors A and B is shown by their kilowatt inputs. When stator windings of motors A and B are of conventional construc-tion, Figs. 2a, 2b and 2c respectively illustrate over approximately twenty seconds and four revolutions of the grinding mill: (a) typical variation of kilowatt input to motor A; (b) typical variation of kilowatt input to motor B;
and (c) the difference in power inputs to motors A and B, which difference is indicative of the division in load between the motors. The major portions of the amplitude variations of the power inputs shown in Figs. 2a and 2b are imposed by the mill load itself, and similar variations would be observed even if a single motor were driving the grinding mill. It will be noted from Fig. 2c that the unbalance in load between the two motors consists not only of a variation at mill rotational frequency but also of an average sustained variation directly related to a difference in the angular positions of the rotors on their shafts. It will thus be recognized that loads of vary-ing magnitude and phase angle persist on the two motors withconventional stator windings and may cause excessive wear of the gears and overheating of the motors.
In accordance with the invention each stator phase winding x, Yr z of motor A and each stator phase winding x, y, z of motor B is divided into a plurality of sections and the sections of the corresponding phase windings in the two machines are interconnected to promote load sharing between the machines.
Stator phase winding x of motor A may be divided into a first section xl and a second section x2. Stator phase winding x' of motor B may similarly be divided into a first section xl' and a second section x2'. One side of first section xl of motor A
1054Z~6 may be connected to power supply phase 0x and the other side of first section xl may be connected to one end of second sec-tion x2' of the corresponding phase winding o~ motor B and whose other side may be connected to neutral N'. Similarly one side of first winding section xl' of motor B may be connected to power supply conductor 0x and the other side thereof may be connected to one end second section x2 of the corresponding phase winding of motor A and whose opposite end may be con-nected to neutral N.
One side of stator phase winding first section yl of motor A may be connected to power supply phase 0y and its opposite end may be connected to one end of the corresponding stator phase winding second section y2' of motor B and whose opposite end is connected to neutral N'. Similarly one end of phase winding first section yl' of motor B may be connected to power supply phase line ~y and its opposite end connected to one end of the corresponding phase winding section y2 of motor A and whose opposite end is connected to neutral N of motor A.
One side of stator phase winding first section zl of motor A may be connected to power supply phase conductor ~ and its opposite end may be interconnected to one end of the corres-ponding phase winding section z2' of motor B whose opposite end is connected to neutral N' of motor B. Similarly one end of stator phase winding first section zl' of motor B may be con-nected to power supply phase conductor 0z and its opposite end interconnected to one side of the corresponding phase ~inding second section z2 of motor A whose opposite end is connected to neutral N of machine A.
The ratio KA of the number of turns in each phase winding first section, such as Xl, to the number of turns in 10542~6 the second winding section, such as X2, in the illustrated embodiment is one-third. Figs. 3a and 3b illustrate typical power inputs to motor A and to motor B respectively over approxi-mately a twenty second period and during four revolutions of the grinding mill when the stator windings are constructed and interconnected to embody the invention as shown in Fig. 1.
Fig. 3c illustrates the input power differential to motors A
and B and shows that the average or sustained difference in load as well as the pulsations in unbalanced load between the two machines at the speed of the grinding mill are compensated for and substantially eliminated by the disclosed interconnection of motor stator windings even though the normal variations in power input imposed by the mill load itself persist.
In alternative embodiments (not shown) the field windings FW of the two motors A and B may be connected in series across a common power source to minimize the effects of induced field currents arising from oscillations in load between the machines.
It will be appreciated that a different ratio KA of first winding section turns to second winding section turns may be utilized in embodiments of my invention employing motors different than those disclosed in the Fig. 1 embodiment. Fur-ther, in alternative embodiments of the invention a winding section of each stator phase winding of one-motor consisting in coils or coil groups which are not physically located in con-secutive poles may be interconnected with the remaining coils or coil groups of the corresponding stator phase winding of the other motor. ~y in~ention also comprehends interconnection of - stator windings of induction motors such as those of the wound 3Q rotor or squirrel-case types instead of synchronous motors as well as interconnection of winding sections of corresponding lOS421G
stator phase windin~s in two motors through resistances, induc-tances or capcitances to equalize the load between the two motors.
While only a single embodiment of my invention has been illustrated and described, many modifications and varia-tions thereof will be readily apparent to those skilled in the art, and consequently it should be understood that I do not intend to be limited to the particular embodiment shown and described.
Claims (13)
1. A drive system comprising a pair of electric motors coupled to drive a common load for sharing thereof, each of said motors having a rotor and a stator with a rotating magnetic field generating polyphase winding thereon comprising plural phase windings energized from individual phases of a polyphase electrical power source to generate a rotating magnetic field within the stator, each of said phase windings including plural winding sections with at least one winding section connected in series with a different winding section of the corresponding phase winding of the other motor to thereby permit the respective winding sections in each said phase winding to have different motor torque effects.
2. A drive system in accordance with claim 1 wherein each said phase winding of each motor includes first and second winding sections connected in series with said second and said first winding sections respectively of the corresponding phase winding of the other motor.
3. A drive system in accordance with claims 1 or 2 wherein said motors are synchronous motors and have a field winding whose magnetic field interacts with the magnetic fields produced by said respective winding sections in each phase winding to produce different motor torque effects.
4. A drive system comprising a pair of synchronous motors each of which has a stator with a rotating magnetic field generating polyphase winding thereon comprising plural phase windings adapted to be energized from individual phases of a polyphase source and a rotor with a field winding thereon, said rotors of said pair of motors being mechanically coupled to a common shaft, each said phase winding of each motor comprising plural winding sections with at least one winding section connected in series with a different winding section of the corresponding phase winding of the other motor.
5. A drive system in accordance with claim 4 wherein each said phase winding of each motor comprises first and second winding sections which are connected in series respectively with the second and the first winding sections of the corresponding phase winding of the other motor.
6. A drive system comprising a pair of wound rotor induction motors whose rotors are mechanically coupled to a common shaft, each of said motors having a stator with a polyphase winding thereon comprising plural phase primary windings adapted to be energized from individual phases of a polyphase source to generate a rotating magnetic field within the stator and a rotor with a secondary winding thereon in which voltage is induced by said rotating magnetic field, each said phase primary winding comprising first and second winding sections and wherein said first winding section and said second winding section of each phase primary winding of each motor is connected in series with the second and the first winding section respectively of the corresponding phase winding of the other motor.
7. A drive system comprising a pair of synchronous electric motors coupled to drive a common load for sharing thereof, each of said motors having a stator with a rotating magnetic field generating polyphase winding thereon comprising a plurality of phase windings adapted to be energized from individual phases of a polyphase electrical power source to generate a rotating magnetic field within said stator, a field winding, and a rotor, means for exciting said field winding, each said phase winding of each motor comprising first and second winding sections connected in series with the second and first winding sections respectively of the corresponding phase winding of the other motor.
8. A drive system in accordance with any one of claims 1, 4 or 7 wherein the respective winding sections in each said phase winding have different numbers of turns and produce different motor torque effects.
9. A drive system in accordance with any one of claims 1, 4 or 7 wherein said winding sections in each said phase winding are discontinous from each other.
10. A drive system comprising two synchronous electric motors whose rotors are mechanically coupled to a common shaft, each of said motors having a stator with a rotating magnetic field generating polyphase winding thereon comprising a plurality of phase windings adapted to be energized from individual phases of a polyphase source, each said phase winding including plural winding sections, and means for interconnecting the winding sections in the phase windings of each motor in series with the winding sections of the corresponding phase winding of the other motor so that the respective winding sections in each phase winding have different motor torque effects and aid in equalizing the output torques of the two motors.
11. A drive system in accordance with claim 10 wherein each said phase winding comprises first and second winding sections and said means for interconnecting connects the first winding section in each phase winding of one motor in series with the second winding section of the corrsponding phase winding of the other motor.
12. A drive system in accordance with claims 2, 5, or 11 wherein the number of turns in said first winding section of each phase winding is different from the number of turns in said second winding section thereof.
13. A drive system in accordance with claim 12 wherein the ratio of the number of turns in said first winding section to the number of turns in said second winding section in each said phase winding is selected to compensate for differences in displacement angles in said pair of motors and to effect equalization of output torques therefrom.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US63394475A | 1975-11-20 | 1975-11-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1054216A true CA1054216A (en) | 1979-05-08 |
Family
ID=24541802
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA260,175A Expired CA1054216A (en) | 1975-11-20 | 1976-08-30 | Plural electric motors driving common load and having interconnections for load control |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5264613A (en) |
| AU (1) | AU508850B2 (en) |
| BR (1) | BR7607762A (en) |
| CA (1) | CA1054216A (en) |
| NO (1) | NO147051C (en) |
| OA (1) | OA05488A (en) |
| SE (1) | SE434103B (en) |
| ZA (1) | ZA766777B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS586336Y2 (en) * | 1979-03-31 | 1983-02-03 | クロスタ−産業株式会社 | Zatsk |
| DE102008036784C5 (en) * | 2008-08-07 | 2013-06-20 | Thyssenkrupp Polysius Ag | Roller mill and method for comminution of regrind |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5443683B2 (en) * | 1972-11-24 | 1979-12-21 | ||
| JPS534890B2 (en) * | 1973-05-24 | 1978-02-22 |
-
1976
- 1976-08-30 CA CA260,175A patent/CA1054216A/en not_active Expired
- 1976-11-10 NO NO763839A patent/NO147051C/en unknown
- 1976-11-11 ZA ZA00766777A patent/ZA766777B/en unknown
- 1976-11-12 AU AU19577/76A patent/AU508850B2/en not_active Expired
- 1976-11-17 SE SE7612836A patent/SE434103B/en unknown
- 1976-11-19 JP JP51139398A patent/JPS5264613A/en active Pending
- 1976-11-19 BR BR7607762A patent/BR7607762A/en unknown
- 1976-11-20 OA OA55990A patent/OA05488A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| BR7607762A (en) | 1977-10-11 |
| SE434103B (en) | 1984-07-02 |
| SE7612836L (en) | 1977-05-21 |
| AU508850B2 (en) | 1980-04-03 |
| ZA766777B (en) | 1978-06-28 |
| NO763839L (en) | 1977-05-23 |
| AU1957776A (en) | 1978-05-18 |
| NO147051B (en) | 1982-10-11 |
| OA05488A (en) | 1981-03-31 |
| JPS5264613A (en) | 1977-05-28 |
| NO147051C (en) | 1983-01-19 |
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