| 摘要 |
1,263,891. Control of two motors. AIRFLOW DEVELOPMENTS Ltd., and R. G. SPEAR. 21 Oct., 1970 [5 Jan., 1970], No. 419/70. Heading H2J. Main and stand-by fan units are driven by motors F1, F2, respectively, the fans having individual outlets leading to a common casing containing an L-shaped flap which is centrally pivoted and movable under air pressure into a number of positions. Microswitches S2, S3, are mounted in the angle between the two blades of the flap. When the main switch S1 is closed, motor F1 receives full mains voltage and operates at full speed immediately, while motor F2 has a lower voltage applied to it initially due to the current-limiting action of thermistor TH1 and resistor R1. The air ejected from the main fan pushes over the flap to open switch S3 and disconnect the motor F2 so leaving the motor F1 only in operation. If now the motor F1 fails the flap returns to close switch S3 whereby the motor F2 is energized progressively until it operates at full power at the end of the delay period imposed by the network TH1, R1. The operation of the motor F2 causes the flap to open the switch S2 and to disconnect the motor F1. If the fault on the motor F1 is cleared before the motor F2 approaches full power, the switch S3 is re-opened to disconnect the motor F2. A neon indicator N1 strikes to show that the motor F1 has failed and that the motor F2 is running. When both motors are momentarily connected to the supply after closure of switch S1, the indicator N1 does not strike. |
