| 摘要 |
1,239,034. Emergency lighting systems. SOC. DES ACCUMULATEURS FIXES ET DE TRACTION. 7 Oct., 1968 [6 Oct., 1967], No. 47502/68. Heading H2H. Emergency supply system includes a battery which is normally charged by a mains supply, and a number of devices, such as lamps, which are operated by the battery when the mains supply voltage falls. This voltage is detected by a transistor, and another transistor makes or breaks the emergency circuit through a relay or a power transistor. In the circuit shown in Fig. 1, the battery B is normally charged through a transformer Tr, rectifiers D 1 , D 2 , and a pilot lamp Lc. The transistor T 2 is biased to conduction so that the transistor T 1 is blocked and no current flows through the relay Ra. A drop in the mains supply voltage of, say, 50%, results in the blocking of transistor T 2 , so that current can now flow through transistor T 1 , energizing relay Ra and closing a switch K so that emergency lamps Ls1, Ls2 are energized from the battery. The actions are reversed when the supply voltage rises towards its normal value, and the emergency lamps are extinguished. During a period of supply failure, the emergency devices may be turned off either locally by means of a push-button switch P which shorts out the transistor T 1 , or by a remote control method which consists in applying a D.C. voltage to the base of transistor T 2 by way of a terminal 2. The devices may be reactivated by applying a suitable voltage to the base of transistor T 1 through another terminal 3. Resumption of the mains supply over-rides and cancels any preceding actions of local or remote control. In modifications of the circuit shown, the relay Ra and switch K may be replaced by a power transistor, and a further transistor may be used to ensure positive switching of the emergency circuit, Fig. 5 (not shown). Also, the emergency lamps may normally be in series with permanent lamps, Fig. 7 (not shown), and be switched to the battery supply on mains supply failure. The current supplied is insufficient to illuminate the emergency lamps when these are in series with the permanent lamps. |
