To provide a fan control unit that can prevent the demagnetization of a permanent magnet of a motor and the breakage of a switching element at the negative side of an inverter, even if starting control is conducted in a state that a fan rotates by a natural wind, and to provide a refrigeration cycle device and a revolution speed estimation method.
The fan control unit comprises: the sensorless motor 8M that drives the fan 8F; the inverter 10 that is connected with the switching elements U, V, W, X, Y and Z in a manner of three-phase bridging, and feeds three-phase AC power to the motor; a current detection means 11 that detects a current flowing to the motor; and a control means 13 that turns the switching elements for three phases that form a negative-side arm of the inverter to on-states at the time of starting, and returns the switching elements for the three phases to off-states and stops the starting, when a current detection value of the current detection means in this on-state exceeds a protection level that is set lower than a value that is determined as an arm short circuit.
KAMIYA NAOHITO
KANBE TAKAYUKI
Hidetoshi Tachibana
Yasukazu Sato
Hiroshi Yoshimoto
Yasushi Kawasaki
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