Control system for an electric motor

1. A control system for an electric motor, the control system comprising a first control device arranged to control an operation of a first component of the electric motor; a second control device arranged to control an operation of a second component of the electric motor, wherein the first control device is arranged to transmit to the second control device, over a first communication link, a first signal for indicating the transmission of data over the first communication link to the second control device, wherein the second control device is arranged to use the timing of the first signal to synchronise the operation of the second component with the operation of the first component.

2. A control system according to claim 1 , wherein the first component is a first inverter for controlling current flow in a first coil set of the electric motor.

3. A control system according to claim 2 , wherein the second component is a second inverter for controlling current flow in a second coil set of the electric motor.

4. A control system according to claim 3 , wherein the first communication link is a serial peripheral interface bus.

5. A control system according to claim 4 , wherein the first signal is a chip select signal.

6. A control system according to claim 3 , wherein the operation of the first inverter and second inverter is controlled using pulse width modulation signals, wherein the timing of the pulse width modulation signals for controlling the second inverter is synchronised to the timing of the pulse width modulation signals for controlling the first inverter using the first signal.

7. A control system according to claim 5 , wherein the operation of the first inverter and the second inverter is controlled using pulse width modulation signals, wherein the timing of the pulse width modulation signals for controlling the second inverter is synchronised to the timing of the pulse width modulation signals for controlling the first inverter using the timing of the chip select.

8. A control system according to claim 7 , wherein the timing of the pulse width modulation signals for controlling the second inverter is offset with respect to the timing of the pulse width modulation signals for controlling the first inverter.

9. A control system according to claim 1 further comprising a third control device arranged to control an operation of a third component of the electric motor, wherein the third control device is arranged to transmit to the second control device a second signal for indicating the transmission of data over a second communication link to the second control device from the third control device, wherein the second control device is arranged to use the timing of the first signal and second signal to determine a timing correction for allowing the third control device to synchronise the operation of the third component with the operation of the first component.

10. A control system according to claim 9 , wherein the second control device is arranged to transmit the timing correction to the third control device over the second communication link.

11. A control system according to claim 9 , wherein the third component is a third inverter for controlling current flow in a third coil set of the electric motor.

12. A control system according to claim 9 , wherein the second communication link is a serial peripheral interface bus.

13. A control system according to claim 12 , wherein the second signal is a chip select signal.