| 摘要 |
<p>1,106,147. Automatic temperature control systems. PLESSEY CO. Ltd. July 16, 1965 [July 27, 1964], No. 17317/64. Addition to 892, 825. Heading G3R. The control circuit of the parent Specification is modified by replacing the on/off switch by a thyristor type continuously-variable regulator 4 whose firing angle is controlled by a phase shift network 6 and a phase discriminating rectifier 5, the latter being fed from the toroidal core error detector 3 responsive to the temperature of the heater element 1. To ensure that the error signal is dependent only upon the resistance of the heater 1, a sampling network 7 is arranged to control the member 5 so that the latter only produces an output when the heater resistance is at a voltage not variable in response to the firing angle of the regulator 4. This is done by limiting the output of member 5 to the last 45‹ of each half cycle of the supply 2 and by limiting the maximum firing angle of the regulator 4 to 120‹, this corresponding to minimum heater power. Member 7 comprises a thyristor phase shift regulator controlled by a firing circuit that can be preset to give a constant phase shift. Regulator 4 may be of thyratron or saturable reactor type.</p> |
