Patent GB-424654-A (GB)
Title: Improvements in or relating to electricity measuring instruments
IPC: G01R11/60
Filed: 1933-09-13
Abstract: 424,654. Supply meters. PAGE, A., 84, Pendle Road, Streatham Park, London. Sept. 13, 1933, No. 25317. [Class 37] In apparatus for determining the power factor for a maximum mean demand in a system employing two maximum demand meters which are periodically and simultaneously controlled, one measuring the true demand and the other the reactive component, the maximum demand indicator A of the meter measuring the reactive component is controlled by a maximum demand device on the other meter, and is provided with two maximum pointers, one of which takes up and retains the position indicating the reactive component corresponding to the highest mean true demand. In the arrangement shown, the maximum demand indicator A is coupled to the meter measuring true demand through gear wheels 1, 2, 4, 5, the wheels 2, 4 being carried by a shaft 3 capable of oscillation about a bearing 15. The gear wheels 1, 2 are normally held in engagement by a spring 17, but are disconnected at the end of each measuring period by energizing a relay 19, whereupon a return spring 16 restores the parts to their starting position. The maximum demand indicator B is similarly connected to the reactive component meter through gear wheels 21, 22, 24, 25, and shaft 23 with return spring 43, the gears 21, 22 being disconnected at the end of each period by a relay 46. On the shaft of the gear wheel 5 is a slip ring 7, cooperating with a contact brush 6, and an arm 9 adapted, when the previous maximum demand in any period is exceeded, to engage an arm 8 on a shaft carrying the maximum demand pointer 13 and a slip ring 11 co-operating with a brush 10. The gear wheel 25 is connected to a planet wheel 26 which engages a pair of sun wheels 28, 29 connected respectively to the pointers 31, 30. In the position shown, the sun wheel 28 and pointer 31 are locked by the pivoted armature 34 of a relay 35 having oppositely acting windings 52, 53. If, during any measuring period, the previous maximum demand is exceeded, the engagement of the arms 8, 9 prepares a circuit for the relay 35, which circuit is completed at the end of the measuring period by a contact 48 under the control of a time switch, whereupon the armature 34 is rocked to unlock the sun wheel 28 and lock the sun wheel 29, and with it the pointer 30, in the position corresponding to the new position of the pointer 13. Shortly afterwards, the time switch closes the circuits of the relays 19, 46 at contacts 49, whereupon both maximum demand devices are disconnected from their respective meters, and the arm 9 and pointer 31 are returned to their initial positions. Shortly afterwards, the time switch opens the contacts 48, 49, and the maximum demand devices are again connected to the meters. If in any measuring period the previous maximum demand is not reached or exceeded, the relay 35 is not energized, since the contact arms 9, 8 do not engage, and the pointer 30 or 31 indicating the maximum reactive component corresponding to the last setting of the pointer 13 remains locked. A spring 36 is provided to hold the armature 34 in its extreme positions. In a modification, Fig. 2, (not shown), the locking relay acts on a change-over pinion of a gear coupled to the driving gear of the reactive component meter, the change-over pinion being alternately coupled to one of the two maximum demand pointers.