Solar hybrid solution for single phase starting capacitor motor applications
A motor control system for induction-type AC electric motors having starting and run windings has a multiphase VFD drive with first and second phase outputs. A switching device with a first position, where a first output of the VFD drive is coupled to the run winding and a second output of the VFD drive couples to the start winding; and with the switching apparatus in second position, the run winding of the AC electric motor couples to an AC line input and the start winding of the AC electric motor couples through a capacitor and start switch to the AC line input. With the switching device in the first position, the second output of the VFD is configured to discontinue driving the start winding of the motor after the motor begins rotating.
1. A system comprising:
an induction-type AC electric motor having a starting winding, and a run winding;
an AC input connection;
a multiphase variable frequency motor (VFD) drive having at least a first and a second phase output;
a switching apparatus having at least a first and a second position;
wherein with the switching apparatus in the first position, a first output of a variable frequency motor drive is coupled to the run winding of the AC electric motor, and a second output of the variable frequency motor drive is coupled to the start winding of the AC electric motor; and
with the switching apparatus in the second position, the run winding of the AC electric motor is coupled to the AC input connection and the start winding of the AC electric motor is coupled through a capacitor and start switch to the AC input connection;
wherein, with the switching apparatus in the first position, the second output of the VFD is configured to discontinue driving the start winding of the motor after the motor begins rotating.
2. The system of claim 1 wherein the switching apparatus is controlled by a microcontroller.
3. The system of claim 2 wherein the VFD drive is configured with maximum power point tracking (MPPT).
4. The system of claim 3 wherein the VFD drive is a three-phase VFD drive, and wherein a third output of the VFD drive is coupled to a common connection of the run winding and start winding of the induction-type AC electric motor when the switching apparatus is in the first position.
5. The system of claim 3 wherein the VFD drive is a two-output VFD drive with an approximately 90-degree phase shift between the first and second output of the VFD drive.
6. The system of claim 3 further comprising a power price receiving device and configured to minimize cost of power used.
7. A method of operating a single-phase AC electric motor having a run winding and
a start winding on AC line or solar power comprising:
providing a switching apparatus having at least a first and a second position, wherein with the switching apparatus in the first position, a first output of a variable frequency motor drive is coupled to the run winding of the AC electric motor, and a second output of the variable frequency motor drive is coupled to the start winding of the AC electric motor; and
with the switching apparatus in the second position, the run winding of the AC electric motor is coupled to an AC line input connection and the start winding of the AC electric motor is coupled through a capacitor and start switch to the AC input connection;
determining whether solar power is present, and if solar power is present setting the switching apparatus to the first position, attempting to start the motor with a phase shift between the first and second output of the variable frequency drive, and if the motor starts disconnecting the second output of the variable frequency drive;
if solar power was not present or the motor failed to start, setting the switching apparatus to the second position.
8. The method of claim 7 wherein the VFD drive is a three-phase VFD drive, and wherein a third output of the VFD drive is coupled to a common connection of the run winding and start winding of the induction-type AC electric motor when the switching apparatus is in the first position.
9. The method of claim 8 wherein the VFD drive is configured with maximum power point tracking (MPPT).
10. The method of claim 7 wherein the VFD drive is a two-output VFD drive with an approximately 90-degree phase shift between the first and second output of the VFD drive.
11. The method of claim 10 wherein the VFD drive is configured with maximum power point tracking (MPPT).