Patent ID: 7244106

Claim:
A method for flow regulation at a fan ( 3 ) having a suction side, the fan powered by an electric motor ( 2 ), specifically for maintaining the flow from a fan at a constant level, said fan having a filter ( 5 ) positioned at the suction side of the fan, characterized in that values representing actual power consumption and speed of the motor ( 2 ) are determined, in that a pulse signal (p) is created in the motor ( 2 ), which pulse signal indicates the position of the motor's rotor, said pulse signal being converted into a speed indicating signal, a control unit ( 12 ) compares the values representing actual power consumption and speed of the motor with a curve or table stored in a memory ( 14 ), which indicates the correlation between power consumption and speed for a given flow from the fan, the control unit ( 12 ), if one of the values representing actual power consumption and speed of the motor lies at a point on the curve or in the table but another of the values representing actual power consumption and speed of the motor deviates from this point, determines whether the deviating value is too high or too low, the control unit ( 12 ) controls a change of the electrical power supplied to the motor to reduce the deviation, and that new ones of the values representing actual power consumption and speed of the motor are determined repetitively until there is no deviation of the values representing actual power consumption and speed of the motor.