METHOD OF PREHEATING A BRUSHLESS MOTOR

• US 20140009099A1
• Filed: 07/02/2013
• Published: 01/09/2014
• Est. Priority Date: 07/03/2012
• Status: Active Grant

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: GREETHAM, Stephen
• Granted Patent: US 9,160,255 B2
• Time in Patent Office: Days
• US Class Current: 318/558
• CPC Class Codes: H02P 1/00 Arrangements for starting electric motors or dynamo-electric converters starting of synchronous motors with electronic commutators H02P6/20, H02P6/22; starting dynamo-electric motors rotating step by step H02P8/04; vector control H02P21/00
• CPC Class Codes: H02P 1/465 for starting an individual single-phase synchronous motor
• CPC Class Codes: H02P 29/62 for raising the temperature of the motor
• CPC Class Codes: H02P 6/26 Arrangements for controlling single phase motors

Abstract

A method of preheating a brushless motor that includes sequentially energising and de-energising a phase winding over one or more drive periods. The phase winding is energised in the same direction throughout each drive period so as to lock a rotor of the motor at an aligned position.

Claims

1. A method of preheating a brushless motor, the method comprising sequentially energising and de-energising a phase winding of the motor over one or more drive periods, the phase winding being energised in the same direction throughout each drive period so as to lock a rotor of the motor at an aligned position.

2. The method of claim 1, wherein the rotor is locked at the aligned position for at least one second during each drive period.

3. The method of claim 1, wherein the rotor is prevented from rotating through a full revolution during the one or more drive periods.

4. The method of claim 1, wherein the method comprises sensing a temperature, and using the sensed temperature to define the length of each drive period or the number of drive periods.

5. The method of claim 4, wherein the method comprises defining a longer drive period or a larger number of drive periods for a lower sensed temperature.

6. The method of claim 1, wherein current is made to flow through at least one switch when energising the phase winding and current is made to flow through at least one further switch when de-energising the phase winding.

7. The method of claim 6, wherein current is made to flow through a first pair of switches when energising the phase winding and current is made to flow through a second, different pair of switches when de-energising the phase winding.

8. The method of claim 1, wherein the method comprises de-energising the phase winding in response to current in the phase winding exceeding a current limit, and increasing the current limit at least once during the one or more drive periods.

9. The method of claim 8, wherein the method comprises increasing periodically the current limit.

10. The method of claim 1, wherein the method comprises de-energising the phase winding in response to current in the phase winding exceeding a current limit, and employing a different current limit for each drive period.

11. The method of claim 10, wherein the method comprises employing a higher current limit for each successive drive period.

12. The method of claim 1, wherein the method comprises sensing a temperature, using the sensed temperature to define a current limit, and de-energising the phase winding in response to current in the phase winding exceeding the current limit.

13. The method of claim 1, wherein the motor is unidirectional and the phase winding is energised in a direction that drives the motor backwards.

14. A control system for a brushless motor, the control system performing a method as claimed in claim 1.