| 摘要 |
<p>Electrical heating apparatus having temperature controllable regulating means. The apparatus includes, in series, heating and PTC resistors and a temperature responsive switch. An electric motor driven variable speed blower is arranged to blow cooling air over the heating and PTC resistors. A temperature sensor and bridge apparatus cooperates to produce a voltage signal which is proportional to the deviation of the temperature from a predetermined temperature. Upon a drop in temperature the proportional voltage signal is produced and, upon being amplified, the series switch is closed to admit current to the resistors and the blower motor is driven at a speed proportional to the voltage signal. The degree or extent to which the PTC resistor is cooled by the blower determines the resistance it presents in the circuit such that increased cooling of the PTC resistors results in a greater heat output by the heating resistor, and vice versa.</p> |
