| 摘要 |
<p>The cine projector is fitted with an electrically driven blower, with the blower motor (2) is connected in parallel with a relay (1). This operates a switch (3) to switch off the projector lamp (4) if the motor fails. The lamp is switched off immediately thus avoiding the delay inherent in a slower acting thermal switch. The system can be improved by electronic switching using a triac, with the switching signal derived from the voltage drop across a resistance connected in series with the motor. In the latter case, the motor is also connected in series with a diode and a fuse which operates if a short circuit occurs in the motor.</p> |
