| 摘要 |
645,839. Automatic speed - control systems; running alternators in parallel. BRITISH THOMSON - HOUSTON CO., Ltd. May 29, 1947, No. 14324. Convention date, May 29, 1946. [Class 38 (iv)] A regulating system for a dynamo - electric machine comprises a variable speed ratio transmission device between a prime mover and the machine, the device being controlled by a multiple coil solenoid hydraulic valve mechanism, one coil being connected to speedresponsive apparatus, and a second coil being connected to means responsive to the electric load. The arrangement is applicable to a system in which a number of alternators are connected in parallel, each being driven by a variable-speed prime mover such as an aircraft engine. In the Figure, an aircraft engine 1 drives an electric generator 3 through a variable-speed ratio device 2. The output from a tachometer 5 which is also driven from device 2, is used to provide a current in coil 9 proportional to the speed of the generator 3. A further control circuit responsive to the power output of the generator is provided by means of transformer 11, having an output proportional to the 'output voltage of the generator, and resistance 17 which carries a current proportional to the current supplied by the generator. The current vector is added to or subtracted from the voltage vector appearing across the primaries of transformers 12 and 13, so that a current proportional to in-phase power component is produced in coil 18. This arrangement enables a slight droop to be given to the generator load characteristic to facilitate the connection of such generators in parallel. The currents through coils 9 and 18 control the operation of a hydraulic pilot valve 27 which controls oil pressure to operate a servomechanism 34. Mechanism 34 controls the speed-ratio device 2, the arrangement being such that the first speed responsive means acts to maintain constant generator speed, and the second means, responsive to the load, modifies this speed characteristic. Under steady, noload conditions, the force due to current through coil 9 is just balanced by that due to spring 31. A centrifugally-operated switch 35 which operates on severe overspeed of the prime mover, is provided, which when operated forces the pilot valve 27 down to the limit of its movement by means of coil 38, so that latch member 39 operates to lock the mechanism in the reduced speed position until re-set manually by the operator. An over-running clutch 2<SP>1</SP> is also provided to assist in maintaining synchronism during rapid deceleration of the aircraft engine. |
