| 摘要 |
PURPOSE:To provide a safe automatic ventilation fan which does not produce any explosion of gas caused by a spark and an arc by a method wherein an ignition sensing circuit and a ventilation fan driving power supply circuit are electrically insulated by a three-leg core type transformer and a mechanical movable contact is not arranged in the ventilation fan driving power supply circuit to which a high voltage is applied. CONSTITUTION:A three-leg core type transformer 1 is applied to cause its primary winding 6 to be connected to a power supply 12 and a secondary winding 7 to be connected to a manual-automatic change-over switch SW1. A change-over operation of the change-over switch causes a short circuited (manual) and a releasing (stop) to be performed, and various sensor switches SW2 are connected (cooperated) through a sensor terminal, then a third winding 8 is connected between a terminal T1 of a triac 18 of a series-connected circuit comprising an air ventilation fan 16 connected to the power supply, a current sensor 17 and a triac 18 and the gate G through inverse parallel connected diodes 19 and 20, and a series-connected circuit composed of a thyristor 22 of a signal reversing circuit 21 for turning on or off in reference to a signal from a current sensor 17 and an electronic alarm 23 is connected in parallel with a series- connected circuit of the ventilation fan 16 and the current sensor 17 through the diode 24.
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