| 摘要 |
PURPOSE:To regulate rectified voltage to each DC motor and with this, control a blast quantity, by regulating the extent of impressing voltage onto an input terminal of an alternator by means of select making of an operating switch in a variable resistance circuit. CONSTITUTION:When a traveling contact 21a of an operating switch 21 in a variable resistance circuit 20 is made to a fixed contact 21b, an alternator 10 receives feeding voltage from a DC power source B through a resistor 22 at an input terminal F and is driven so that rectified voltage is generated out of an output terminal B. In consequence, each of DC motors M1-Mn rotates at low speed, driving each cooling fan. And, when the traveling contact 21a is selectively made to each of fixed contacts 21c and 21d in order, the feeding voltage out of the DC power source B is fed to the input terminal F of the alternator 10 vi each of resistors 23 and 24 in order. At this time, since each resistance value is set in relation of these resistors 22>23>24, each revolving speed of these DC motors M1-Mn goes up in order. |
