Methods and apparatus for controlling multiple A.C. induction machines from a single inverter
Methods and apparatus are provided that include or provide a first three-phase induction machine including stator windings, a second three-phase induction machine including stator windings, wherein the stator windings of the first machine are coupled in series with the stator windings of the second machine, and an inverter circuit that provides a three-phase output signal coupled to the stator windings of the first machine. Other aspects are also provided.
1. A system comprising:
a first three-phase induction machine comprising stator windings;
a second three-phase induction machine comprising stator windings, wherein the stator windings of the first machine are coupled in series with the stator windings of the second machine;
an inverter circuit that provides a three-phase output signal coupled to the stator windings of the first machine; and
a single feedback circuit coupled to the inverter circuit, wherein the single feedback circuit is coupled to the first machine and/or the second machine.
2. The system of claim 1 , wherein the first machine and the second machine comprise asynchronous induction machines.
3. The system of claim 1 , wherein the system does not provide independent vector control of the first machine and the second machine.
4. The system of claim 1 , wherein the single feedback circuit comprises any of a voltage-per-Hertz control circuit, a current feedback circuit, a voltage feedback circuit and a speed feedback circuit.
5. The system of claim 1 , wherein the first machine produces a torque and the second machine produces a torque that substantially equals the first motor torque.
6. The system of claim 1 , wherein the first machine further comprises a rotor, the second machine further comprises a rotor, and wherein the first machine rotor is coupled to the second machine rotor.
7. The system of claim 6 , wherein the first machine rotor is directly connected to the second machine rotor.
8. The system of claim 6 , wherein the first machine rotor is indirectly connected to the second machine rotor.
9. The system of claim 1 , wherein the first machine rotor is coupled to a first drive shaft and the second machine rotor is coupled to a second drive shaft.
10. The system of claim 9 , wherein the first and second drive shafts are the same drive shaft.
11. The system of claim 1 , wherein the first machine rotor and the second machine rotor are coupled together via any of: a gearbox, a conveyor belt, a pulley, and a wheel.
12. The system of claim 1 , wherein the stator windings of the first machine and the second machine are coupled in a Wye configuration.
13. The system of claim 1 , wherein the stator windings of the first machine and the second machine are coupled in a Delta configuration.
14. A method comprising:
providing a first three-phase induction machine comprising stator windings;
providing a second three-phase induction machine comprising stator windings;
coupling the stator windings of the first machine in series with the stator windings of the second machine;
providing an inverter circuit that provides a three-phase output signal coupled to the stator windings of the first machine; and
providing a single feedback circuit coupled to the inverter circuit, wherein the single feedback circuit is coupled to the first machine and/or the second machine.
15. The method of claim 14 , wherein the first machine and the second machine comprise asynchronous induction machines.
16. The method of claim 14 , wherein the method does not provide independent vector control of the first machine and the second machine.
17. The method of claim 14 , wherein the single feedback circuit comprises any of a voltage-per-Hertz control circuit, a current feedback control circuit, a voltage feedback circuit and a speed feedback circuit.
18. The method of claim 14 , wherein the first machine produces a torque and the second machine produces a torque that substantially equals the first motor torque.
19. The method of claim 14 , wherein the first machine further comprises a rotor, the second machine further comprises a rotor, and wherein the method further comprises coupling the first machine rotor to the second machine rotor.
20. The method of claim 19 , further comprising directly connecting the first machine rotor to the second machine rotor.
21. The method of claim 19 , further comprising indirectly connecting the first machine rotor to the second machine rotor.
22. The method of claim 14 , further comprising:
coupling the first machine rotor to a first drive shaft; and
coupling the second machine rotor to a second drive shaft.
23. The method of claim 22 , wherein the first and second drive shafts are the same drive shaft.
24. The method of claim 14 , further comprising coupling the first machine rotor and the second machine rotor together via any of: a gearbox, a conveyor belt, a pulley, and a wheel.
25. The method of claim 14 , further comprising coupling the stator windings of the first machine and the second machine in a Wye configuration.
26. The method of claim 14 , further comprising coupling the stator windings of the first machine and the second machine in a Delta configuration.