| 摘要 |
<p>963,703. Automatic temperature control. STANDARD TELEPHONES & CABLES Ltd. Oct. 28, 1960, No. 37140/60. Heading G3R. A furnace 6 having a heating element R4 embedded in an electrical insulating material is supplied through a variable ratio transformer T1 from a mains A.C. supply. The temperature of the furnace is sensed by a device Y connected to a temperature controller 6<SP>1</SP> which actuates contacts TC1, TC2 in dependence on the temperature deviation to drive the motor M and position a slider 8 of the transformer T1 so as to correct the temperature deviation. A current transformer T2 through a rectifier W1 energizes a contact-making meter C/1 having a moving contact arm C1 which normally engages a fixed contact a to actuate a relay D/2 closing contacts D1, D2 in series with contact TC1. When the heating element current is at a preset value the contact arm is free and above the preset value the contact arm engages a contact b to actuate a relay F/1 to close a contact F1 and energize the motor M to move the slider 8 in a direction which will reduce the heating element current below the preset value. Simultaneously, the relay D/2 is deenergized to open the contacts D1, D2 and isolate the temperature controller contact TC1. The preset current is adjusted by resistors R1, R2. The system is started up by closing contacts S2 to operate a contact or A/3 having a hold-on contact A3 in parallel with contacts S2 and contacts Al, A2 in the supply to the transformer T1. A lower limit switch BLS of the transformer T1 is also in series with the contactor and prevents start-up except with minimum heating element-current. Contacts E1 of a relay E/1 across the supply short-circuit contacts BLS when contactor A/3 is closed. The system is manually shut down by opening contacts S1 and a overload relay B/1 automatically shuts down the system by opening contacts B1. The resistance element of the furnace may be tungsten, molybdenum or silicon carbon and hydrogen is passed through the furnace.</p> |
