Patent GB-671595-A (GB)
Title: Maximum demand indicator and regulator
IPC: G01R11/60
Filed: 1950-04-12
Abstract: 671,595. Maximum demand indicators; variable-contact resistances; combinations and sets of two or more resistances. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. April 12, 1950 [April 12, 1949], No. 8986/60. Class 37. Relates' to a maximum demand indicator combined with a potentiometer regulator or control which functions to ensure that the maximum demand does not exceed or fall below a tariff contract or stipulated demand. According to the invention the potentiometer contact disc and the energy pointer contact disc which moves the M.D. pointer are both zeroized at the end of each M.D. registration period, for example at quarter-hour intervals, with momentary energization of an electromagnet effecting release of a friction drive for each disc. In Fig. 1 the rotary members 1, 1<SP>1</SP> driven by impulses representing the consumed or instantaneous power and the stipulated power respectively produce motion of a differential 5 via pinions 2, 2<SP>1</SP>, sun wheels 3, 31, and planet pinion 4. If, during an M.D. registration period the magnitude of the power taken exceeds or falls below the stipulated power, i.e. the speed of rotary member 1 exceeds or is less than the speed of rotary member 1<SP>1</SP>, the motion of the differential 5 transmitted through a pinion 8 and friction roller 9 moves a disc 11 and a contact 12 upon the disc 11 in one direction or the other around the inside of a cylindrical potentiometer 13 (see below) as to effect by means of relays or other appropriate control devices the cutting in or out of load taken from the supply undertakings mains or transfer of load to the consumer's own generators. The motion of the sun wheel 3 driven by the rotary member 1 is transmitted to drive the energy pointer disc 10 via pinion 8<SP>1</SP> and a further friction roller 9<SP>1</SP>. At quarter-hourly intervals the electromagnet 23 is energized momentarily so that its armature is attracted whereby a device 6 is pivoted about a fixed shaft 7<SP>11</SP> against the action of springs 22 by such an amount that the pinions 8, 8<SP>1</SP> do not disengage from the toothed wheels 5, 3 but that the friction rollers 9, 9<SP>1</SP> are removed from engagement with the discs 11, 10 so that the latter are returned to zero by spring means (not shown). As an alternative arrangement the device 6 may be so constructed that the rollers 9, 9<SP>1</SP> are displaced longitudinally out of engagement with the discs 11, 10. Preferably with this arrangement the rollers are conical or bevelled. In Fig. 2 the potentiometer 13 is shown with co-operating base-ring 14 and external segments 15 with contact plugs 16, 16<SP>1</SP> which plug into sockets 17, 17<SP>1</SP> on the base-ring 14. The twopart contact member 12, Fig. 1, runs on a circular track 18 and over a resistance winding 19 and is resiliently mounted to facilitate removal or replacement of potentiometer 13. The voltage input is fed to the two ends of the resistance winding 19 via the two left-hand plugs and sockets 16<SP>1</SP>, 17<SP>1</SP> and the positive or negative output voltage for application to the relays &c. is taken from the moving contact member 12 and a tapping at the mid-point of the potentiometer via the circular track 18 and the two right-hand plugs and sockets 16, 171. In the vicinity of the mid-point of the potentiometer the contact member 12 engages taps (not shown) which replace the turns of the winding 19 and are connected via plugs 16 to the sockets 17. External resistors (not shown) of any desired value are connected between adjacent sockets 17 so that larger voltage steps are obtained at the beginning of a control process than would otherwise be given by a'continuous potentiometer winding.