| 摘要 |
PURPOSE:To enable the amount of the blowing open air to be suppressed to a specified value or less, by providing a brake device which generates a resistance force at the specified number of revolutions or more of an exhaust fan. CONSTITUTION:A title ventilator includes an exhaust fan 4, being capable of reversing, and a brake device 6. The brake device 6 consists of a generator 11 and a resistor 12 for radiation. The generator 11 comprises a permanent magnet 13, coupled to a rotary shaft 9 of a motor 5, and a coil 14 supported to a support frame 10. When, during non-running of the exhaust fan 4, the exhaust fan 4 is started to reverse by dint of the blowing open air, the permanent magnet 13 is actuated to generate an electromotive force at the coil 14. The force is converted into heat by means of the resistor 12 for radiation. When the number of reverse revolutions is increased, the electromotive force of the coil 14 is also increased and power consumption by the resistor 12 for radiation is also increased to suppress an increase in the number of reverse revolutions. This constitution forces the amount of the blowing open air to be suppressed to a specified value or less.
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