Patent ID: 6997684

Claim:
A fan arrangement, comprising a radial or diagonal fan ( 370 ); a direct current motor ( 32 ) associated with said fan as a drive motor, a digital control element ( 23 , 24 ; 658 ) associated with said direct current motor ( 32 ), a first signal generator ( 25 ), coupled to an output of said digital control element and having a first internal resistance ( 158 , 152 ), which generates a control signal (u_ 156 ); a PWM generator ( 182 ), responsive to said control signal (u_ 156 ), controlling a pulse duty factor (PWM 2 ) of a pulsed direct current applied to windings of said motor, a comparison arrangement ( 137 , 167 ), having first and second inputs ( 138 , 140 ), said first input ( 138 ) receiving an output signal of said digital control element, and said second input ( 140 ) receiving a signal derived from said pulsed direct current, said comparison arrangement producing a comparison output signal ( 146 ) as a function of the magnitudes of its two input signals; a modification arrangement, responsive to said comparison output signal ( 146 ), for modification of the control signal (u_ 156 ) for the PWM generator, which comparison arrangement has an internal resistance ( 144 , 150 , 174 ) that is smaller than the first internal resistance ( 158 , 152 ) of said first signal generator ( 25 ), in order to enable preferential influencing of the control signal (u_ 156 ) and thus of the pulse duty factor of the pulsed direct current (i_ 2 ; i_ 2 ″), and a program, associated with said digital control element, for controlling the current flowing through the direct current motor ( 32 ), which program is configured to apply a pulsed direct current (i_ 2 ) from a current source to the motor ( 32 ), in a working rotation speed range of the fan, so as to result in a substantially constant current in the direct current motor ( 32 ) in that working rotation speed range.