Abstract: A control device of a fan motor includes: a voltage sensor that detects a voltage applied to a fan motor; a switching portion that selectively connects to each of coils of the fan motor and a rectifier circuit; and a switching control portion that reduces a duty ratio of a driving pulse applied to the switching portion if the voltage detected by the voltage sensor exceeds a threshold.

Abstract: A control device of a fan motor includes: a voltage sensor that detects a voltage applied to a fan motor; a switching portion that selectively connects to each of coils of the fan motor and a rectifier circuit; and a switching control portion that reduces a duty ratio of a driving pulse applied to the switching portion if the voltage detected by the voltage sensor exceeds a threshold.

Abstract: An axial-flow fan with double impellers is provided that can produce a larger amount of air and a higher static pressure than can be achieved with conventional fans. The axial-flow fan with double impellers has a first axial-flow fan unit and a second axial-flow fan unit. The first axial-flow fan unit includes a first case, a first impeller and a plurality of webs that fix a first motor to the first case. The second axial-flow fan unit includes a second case, a second impeller and a plurality of webs that fix a second motor to the second case. The first case and the second case are coupled together to form a housing. The webs of the first axial-flow fan unit and the webs of the second axial-flow fan unit are combined together to form a plurality of stationary webs arranged in the housing. The number of front blades provided at the first impeller is set to five, the number of stationary blades is set to three, and the number of rear blades provided at the second impeller is set to four.

Abstract: An axial-flow fan with double impellers is provided that can produce a larger amount of air and a higher static pressure than can be achieved with conventional fans. The axial-flow fan with double impellers has a first axial-flow fan unit Sand a second axial-flow fan unit. The first axial-flow fan unit includes a first case, a first impeller and a plurality of webs that fix a first motor to the first case. The second axial-flow fan unit includes a second case, a second impeller and a plurality of webs that fix a second motor to the second case. The first case and the second case are coupled together to form a housing. The webs of the first axial-flow fan unit and the webs of the second axial-flow fan unit are combined together to form a plurality of stationary webs arranged in the housing. The number of front blades provided at the first impeller is set to five, the number of stationary blades is set to three, and the number of rear blades provided at the second impeller is set to four.