Method for power control of an electric motor

• US 7,342,372 B2
• Filed: 10/05/2005
• Issued: 03/11/2008
• Est. Priority Date: 10/05/2005
• Status: Active Grant

• Current Assignee: Aktiebolaget Electrolux
• Original Assignee: Aktiebolaget Electrolux
• Inventors: Beskow, Jonas, Jonsson, Stefan
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US11/243,918
• Publication Number:
  US 20070075668A1
• Time in Patent Office: 888 Days
• Field of Search: 318/437, 318/799, 318/629, 363/39, 363/45, 323/212, 323/219
• US Class Current: 318/437
• CPC Class Codes: H02P 23/26 Power factor control [PFC]

Abstract

The invention relates to a method for power control of an electric motor, in particular a motor for driving the suction fan of a vacuum cleaner connected to an AC mains power supply. The power control is effected by varying the phase angle of the electric alternating quantity supplied to the motor by the use of semiconductor switches. AC power supplied to the motor is switched by using different delay times for the switching in each half-period of a full AC period to suppress odd harmonics, particularly the third harmonic of the mains power line frequency. Half-periods of a full period are mirrored in the next consecutive full period in order to suppress even harmonics, particularly the second harmonic of the mains power line frequency. A set of delay times t1 and t2 are defined and selected to be used in further avoiding critical delay time areas for harmonics and minimize the generation of vibrations.

Claims

1. A method for power control of an electric motor for driving the suction fan of a vacuum cleaner connected to an AC mains power supply, said power control being effected by varying the phase angle of the electric alternating quantity supplied to the motor by the use of semiconductor switches, the method comprising the steps of

switching AC power supply to the motor by using different delay times for the switching in each half-period of a full AC period to suppress odd harmonics, including the third harmonic of the mains power line frequency;

mirroring half-periods of a full period in the next consecutive full period in order to suppress even harmonics, including the second harmonic of the mains power line frequency.

2. Method according to claim 1, further comprising the step of

defining and selecting a set of delay times t1 and t2.

3. Method according to claim 2, further comprising the step of

selecting t2=f(t1)=a*t1+b*(t1)² for t1<

(t1=t2=f(t1)), and for selecting t2=t1 for t1>

(t1=t2=f(t1)),

wherein a and b are constants.

4. Method according to claim 2, further comprising the step of

selecting t2=2*t1−

9/52*(t1)² for t1<

5.69 ms, and for selecting t2=t1 for t1>

5.69 ms.