MEASURING METHOD FOR SYSTEM IMPEDANCE

PURPOSE:To facilitate preparation of accurate impedance curves by mounting a fan coupled directly to a motor to a measuring object and determining shaft power by using the various measured values obtained by operating said fan and a motor speed-torque characteristic chart. CONSTITUTION:A fan coupled directly to a motor is mounted to a measuring object such as an electronic apparatus, and is operated under conditions where voltages V1-V3 are constant. Then the rotating speeds n1-n3 of the motor are measured. From these measured values, the torques L1-L3 corresponding to n1- n3 are determined by using the speed-torque characteristic chart of the DC motor used. On the other hand, the static pressure, shaft power-gas volume characteristic of the fan used are determined beforehand, and the gas volumes corresponding to the torques L1-L3 are determined. According to these volumes, the operating points of P1-P3 are determined as shown by the dotted arrow lines. The curve A connecting these points is a system impedance curve.