Control of electrical machines

• US 7,701,164 B2
• Filed: 01/27/2005
• Issued: 04/20/2010
• Est. Priority Date: 02/05/2004
• Status: Active Grant

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Greetham, Stephen, Clothier, Andrew Charlton, Dai, Hanping
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US10/588,281
• Publication Number:
  US 20070278983A1
• Time in Patent Office: 1,909 Days
• Field of Search: 318/701, 318/727, 318/400.03, 318/807, 318/696, 318/717, 318/723, 388/805, 388/815, 363/48
• US Class Current: 318/701
• CPC Class Codes: H02P 25/092 Converters specially adapted for controlling reluctance motors

Abstract

An electrical machine, such as a switched reluctance motor, has a rotor and a controller arranged to energize at least one electrically energizable phase winding in dependence on the angular position of the rotor. The controller may employ a control law table derived by applying a predetermined DC link voltage to the windings. Differences between an applied DC link voltage and the predetermined DC link voltage may be compensated by applying a predetermined correction to the angular position of energization of the phase winding in dependence on the value applied DC link voltage. Such a compensation factor may be derived from a relationship held in memory.

Claims

1. A method of compensating for differences between an applied DC link voltage and a predetermined DC link voltage in an electrical machine comprising a rotor, at least one phase winding, and a controller configured to energize the phase winding in dependence on an angular position of the rotor, wherein the controller comprises a memory storing a voltage compensation map comprising a plurality of correction factors, the method comprising:

measuring the applied DC link voltage;

obtaining a correction factor by addressing the voltage compensation map using the applied DC link voltage; and

applying the obtained correction factor to the angular position of energization of the phase winding.

2. A method as claimed in claim 1, in which the applied DC link voltage is measured periodically.

3. A method as claimed in claim 1, in which the applied DC link voltage is measured when the machine is started.

4. A method as claimed in claim 1, further comprising measuring the applied DC link voltage when the machine is connected to a power supply but before the machine is switched on and applying the obtained correction factor to the angular position of energization of the phase winding on starting the machine.

5. A method as claimed in claim 4, further comprising deriving an average value for the applied DC link voltage at the measurement.

6. A method of controlling an electrical machine, including the method of compensating for differences between the applied DC link voltage and a predetermined DC link voltage as claimed in claim 4.

7. A method as claimed in claim 1, further comprising deriving an average value for the applied DC link voltage at the measurement.

8. A method as claimed in claim 7, in which the step of deriving the average value includes applying a filter to the applied DC link voltage.

9. A method of controlling an electrical machine, including the method of compensating for differences between an applied DC link voltage and a predetermined DC link voltage as claimed in claim 1.

10. A controller for an electrical machine, wherein the electrical machine comprises a rotor and at least one phase winding and the controller comprises a memory storing a voltage compensation map comprising a plurality of correction factors, the controller being configured to:

energize the phase winding in dependence on an angular position of the rotor;

obtain a correction factor by addressing the voltage compensation map using a value of an applied DC link voltage; and

apply the obtained correction factor to the angular position of energization of the phase winding.

11. A controller as claimed in claim 10, in which the memory comprises a predetermined advance angle map representing the energization of the phase winding with respect to the angular position of the rotor over a range of rotor speeds.

12. A controller as claimed in claim 11, in which the memory further comprises an angle correction factor to be applied to a predetermined portion of the predetermined advance angle map, which correction factor relates to the difference between the measured input power and a predetermined power.

13. An electrical machine incorporating a controller as claimed in any one of claims 10, 11, and 12.

14. An electrical machine as claimed in claim 13, in the form of a switched reluctance motor.

15. A cleaning appliance comprising the switched reluctance motor of claim 14.

16. A cleaning appliance incorporating an electrical machine as claimed in claim 13.