PURPOSE: To protect an electrical blower and a cooled apparatus by constituting a pressure increasing chamber and an atmospheric pressure chamber in utilization of an electrical motor base and installing a differential-pressure detecting apparatus into the pressure increasing chamber and certainly detecting the anomaly of the equipment according to the pressure difference between the atmospheric pressure and the pressure which a vane wheel generates.

CONSTITUTION: If the anomaly such as the trouble of a vane wheel 10, drawing of foreign material by a suction pipe 11, etc. is generated in the normal operation of an electrical motor 7, the vane wheel 10 generates only the pressure under the max. capacity of the vane wheel 10, even if in the regular revolution of the vane wheel 10, and therefore, the pressure in a pressure increasing chamber 8A constituted in utilization of an electrical motor base 6 reduces, and the pressure difference between an atmospheric pressure chamber 8B reduces. Therefore, the pressure curve forms the descending pressure curve Ag3 shown in the figure, and the pressure difference reduces furthermore, and at the time T2 when Ag3 becomes 10mm Ag, a differential-pressure detecting apparatus 13 installed into the pressure increasing chamber 8A operates, and the power source for a cooled apparatus (not shown in the figure) is cut-off speedily and certainly. Therefore, an electrical blower and the cooled equipment can be protected.