Patent ID: 7598687

Claim:
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: a current through the low-pass filter in each case has local minima at certain values of the first pulse control factor and the second pulse control factor, a value of the first pulse control factor is established for one of the local minima, for setting the setpoint air output, and the second pulse control factor is selected such that the overall air output is achieved; and 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.