Patent ID: 7598687
Filing Date: 2009-10-06
Classification: H02P

Abstract:
1. A method for controlling a first fan motor and a second fan motor, comprising: controlling the first fan motor with a first pulse width modulation signal having a first pulse control factor; controlling the second fan motor with a second pulse width modulation signal having a second pulse control factor; adjusting an overall air output produced by an operation of at least one of the first fan motor and the second fan motor according to a prespecified setpoint air output; smoothing out a voltage fluctuation in a voltage supply line via a low-pass filter connected to the first fan motor and the second fan motor; and adjusting to each other at least two of a position in time of the first pulse width modulation signal, a position in time of the second pulse width modulation signal, the first pulse control factor, and the second pulse control factor, so that, at a given overall setpoint air output, an effective value of a current is minimized by the low-pass filter; wherein: further comprising selecting the first pulse control factor, at which the current through the low-pass filter has a local minimum, such that the value of the first pulse control factor has as small a difference as possible from the value of the second pulse control factor.