Packet-based networking of variable frequency drives

1. A method of controlling one or more Variable Frequency Drives (VFD), each VFD configured to generate a Pulse Wdth Modulated (PWM) signal to drive a motor, characterized by:

for each controlled VFD, calculating a plurality of drive signals to switch a plurality of power transistors in the VFD for a first time interval, to generate a desired PWM signal; and

wirelessly transmitting, in advance of the first time interval, the plurality of drive signals to respective VFDs in at least a main downlink (DL) frame of a transmission packet.

2. The method of claim 1 wherein wirelessly transmitting a plurality of drive signals comprises transmitting a plurality of drive signals in a plurality of successive time intervals including the first time interval, wherein the drive signals transmitted in one of the successive time intervals is effective for the next time interval.

3. The method of claim 1 wherein the drive signals comprise separate indications to switch each power transistor on or off, and also indicate the timing of the switching.

4. The method of claim 3 wherein the drive signals further comprise an indication to switch a braking transistor on or off, and also indicate the timing of the switching.

5. The method of claim 3 wherein the timing of each transistor switching signal is an offset from the beginning of the next time interval.

6. The method of claim 3 further comprising:

in one or more of the time intervals, additionally transmitting commands or parameter values to one or more VFDs in an auxiliary DL frame of the transmission packet.

7. The method of claim 6 further comprising:

transmitting a command in an auxiliary DL frame for the VFD to run autonomously; and

ceasing the transmission of drive signals in a main DL frame to the autonomous VFD.

8. The method of claim 7 further comprising:

transmitting a command in an auxiliary DL frame for the VFD to be controlled; and

resuming the transmission of drive signals in a main DL frame to the autonomous VFD.

9. The method of claim 3 further comprising:

in one or more of the time intervals, receiving from one or more VFDs feedback about the VFD or motor state in a main uplink (UL) frame of a received packet.

10. The method of claim 1 wherein the same drive signals, commands, or parameter values are broadcast to two or more controlled VFDs.

11. The method of claim 1 wherein the drive signals, commands, or parameter values are transmitted individually to each controlled VFD.

12. A controller configured to control one or more Variable Frequency Drives (VFD), each VFD configured to generate a Pulse Wdth Modulated (PWM) signal to drive a motor, the controller comprising:

a processor operatively connected to the wireless transceiver, and configured to:

for each controlled VFD, calculate a plurality of drive signals to switch a plurality of power transistors in the VFD for a time interval, to generate a desired PWM signal; and

wirelessly transmit the plurality of drive signals, to each controlled VFD, in advance of the time interval in which they are to be applied, in at least a main downlink (DL) frame of a transmission packet.

13. A method of generating a Pulse Width Modulated (PWM) signal to drive a motor, by a Variable Frequency Drive (VFD) controlled by a remote controller, comprising:

wirelessly receiving from the controller, in a main downlink (DL) frame of a received packet, a plurality of drive signals for a time interval; and

in a subsequent time interval, switching a plurality of power transistors, according to the received drive signals, to generate the PWM signal.

14. The method of claim 13 wherein wirelessly receiving a plurality of drive signals comprises receiving the plurality of drive signals in each successive time interval, and wherein a subsequent time interval comprises the next time interval.

15. The method of claim 13 wherein the drive signals comprise separate indications to switch each power transistor on or off, and also indicate the timing of the switching.

16. The method of claim 15 wherein the drive signals further comprise an indication to switch a braking transistor on or off, and also indicate the timing of the switching.

17. The method of claim 15 wherein the timing of each transistor switching signal is an offset from the beginning of the next time interval.

18. The method of claim 13 further comprising:

in one or more of the time intervals, additionally receiving commands or parameter values in an auxiliary DL frame of the received packet.

19. The method of claim 18 further comprising:

receiving a command in an auxiliary DL frame to run autonomously; and

generating drive signals to switch the transistors.

20. The method of claim 19 further comprising:

receiving a command in an auxiliary DL frame to again be controlled; and

resuming switching the transistors according to drive signals received in each time interval from the controller.

21. The method of claim 13 further comprising:

in one or more of the time intervals, wirelessly transmitting to the controller feedback about the VFD or motor state in a main uplink (UL) frame of a transmitted packet.

22. The method of claim 21 wherein the feedback includes one or more of instantaneous motor speed, instantaneous motor current, power transistor temperature, motor rotor temperature, DC bus voltage, and an indication for the controller to calculate motor speed from current and voltage.

23. The method of claim 21 further comprising:

in one or more of the time intervals, wirelessly transmitting to the controller the value of one or more parameters in an auxiliary uplink (UL) frame of a transmitted packet.

24. A Variable Frequency Drive (VFD) configured to generate a Pulse Width Modulated (PWM) signal to drive a motor, controlled by a remote controller, said VFD comprising:

a transceiver; and

a processor operatively connected to the wireless transceiver, and configured to:

wirelessly receive from the controller, in a main downlink (DL) frame of a received packet, a plurality of drive signals for a time interval; and

in a subsequent time interval, switch a plurality of power transistors, according to the received drive signals, to generate the PWM signal.