| 摘要 |
<p>456,795. Automatic control systems. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Jan. 15, 1936, No. 1323. Convention date, Jan. 16, 1935. [Class 38 (iv)] Temperature &c.-In apparatus for the control of a variable wherein triodes, or like discharge devices, are rendered conducting or non-conducting by change in the grid or like control voltage, an opposed voltage in the grid or like control circuit is varied according to the correction effected so that the discharge devices are restored to their initial state and hunting is avoided. In a rotary kiln 10 the temperature of the contents is controlled by a photo-electric cell 18 controlling the grid potential of an amplifier 19 the output circuit of which includes resistance 33. The rate at which the contents travel through the kiln is varied to control the temperature by changing the speed of a commutator motor 12 rotating the kiln. A reversible pilot motor 16 adjusts the commutator brushes as required, relays 22, 23 supplied through triodes 20, 21 being provided. A generator 39 circulates a current in a resistance 36 to give a potential drop therein proportional to the speed of the kiln. The grid circuit of the triodes 20, 21 includes a portion of resistances 28, 29, resistance 22 and resistance 36. The first are adjusted so that the valve 20 is non-conducting and the valve 21 is conducting when the temperature in the kiln is normal, i.e., when a normal current is passing in the resistance 33 in the anode circuit of the amplifier 19. Any variation in the potential drop in resistance 33 due to temperature variation will then cause relay 22 or 23 to close its contact and adjust the speed of the kiln, but the change in speed will vary the current in the resistance 36 so that the potential drop therein equalizes the potential drop in resistance 33 and the valves 20, 21 are restored to their original condition, notwithstanding the speed adjustment. Hunting or over regulation is thus prevented.</p> |
