US1782525A - Electrical instrument - Google Patents

Description

Nov. 25, 1930. A. .1. ALLEN l ELECTRICAL INSTRUMENT Filed May 24, 1928 2 Sheets-@Sheet l Nov. 25, 1930. A. J. ALLEN 1,782,525 I.

ELECTRICAL INSTRUMENT Filed May 24, 1928 2 Sheets-Sheet 2 //4 1 I /N VENTO/e A TTORNEY Patented Nov. 25; 19.30

UNITED sTATEs PATENT OFFICE ALBERT J. ALLEN. OF BROOKLYN, NEW YORK, ASSIGNOR TO THE ENGINEERING PROD- UCTS CORPORATION. INC., OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRICAL INSTRUMENT Application tiled May 24, 1928. Serial No. 280,145.

This invention ielates to electrical measuring instruments and while not limited thereto aims particularlyto provide means whereby-a single instrument may be utilized to `graphically indicate successive records of voltage for ditferent circuits.

The invention will be apparent from the following specification when read in connec- 4 tion with the accompanying drawings and voltage of different circuits during successive time intervals.

In the distribution of electrical energy one of the systems in generaluse is known as the three-phase. four wire secondary system. Such a system is diagranimatically indicated in Fig. l wherein feeders. are usually placed in the street from which most light and power consumers are supplied. are indicated at A, B and C. These feeders are connected through `suitable intermediate distribution equipment at the power house, not shown, with the secondary windingsa. b and c of a three-phase alternating current transformer. This connection is the well known, so-called Star or Y arrangement in which there is a phase dii'erence between conductors A, B and C of 120 degrees., The neutral pointO of the circuit is connected to ground as indicated at g and a ground conductor G also parallels the conductors A, B and C through the secondary street mains. It is customary to supply ditierent customers by at some points tapping the wires A and B and at other points by tapping the wires B and C and at still others, by tapping the wires C andvA. In each case the consumers service is also connected with the ground conductor G. Such service connections are indicated diagrammatically at l, Q and 3. One of the necessary and essential requirements of a power distribution s vstein of this kind is to maintain a substantially constant voltage between the phases A, B and C regardless of the load variations occasioned by varying power demands of the diti'erent customersand other disturbing conditions. It is, therefore, very desirable th-ata permanent record be made at the ditl'erent points on the feeders A, B and C so that the power companies can detect the time and extent of any abnormal variations in voltage so as to aidin identifying their cause.

To secure these records itis the present ypractice to insert a recording voltmeter between tlie neutral line G and one of the conductors A, B or C. This is not wholly satis- 'factory because it is a record of but .one of the three phases. The other two phases being in a measure independent of each other and the phase being recorded. niayeach have variations of their own which will not show up to the corresponding extent on the record of the phase in which the instrument ris connected.

Of course. two additional recording instruments could be installed for the other two phases. However. this would require three instruments for each recording station. This .would necessitate a costly .installation of recording instruments. But evenv with three instruments-exact comparison cannot readily be made because ofthe difficulty in exactly calibrating three instruments.

To meet this problem, I provide means whereby a single instrument may be utilized to measure the voltage between each of the wires A, B and C and the neutral wire G. The record for the thre'e phases being made by the same instrument is exactly comparable because any error in calibration is the same for each phase measured. The device is also designed to permit of ready identification of the particular phase for which the record is made. I secure a distinctive identifying record for each phase or circuit by varying the time interval .for whicheach circuit'is operative so that a differenti length of graph `meshes with a gear 18 secured on a shaft 20 carrying a roller 22. The roller 22 is part of a standard recording voltmeter which is driven through a suitable gearing by a timing device diagrammatically indicated at 30 forming part of the recording voltmeter. This timing device may be either clock-driven or electrically driven. The recording voltmetervas shown includes a supply roll 32 on which the record or chart sheet 34 is carried. This sheet passes over roll 36 and a fixed platen 38 and is wound up on a take-up roll 40 which is driven in the usual manner by means not shown or described as they form no part of the present invention.

, The recording voltmeter includes the usual stylus 42 carried on the end of a needle 44 which is pivoted at- 46 a-nd adapted to loe cleflected from one side to the other by variations in voltage by means. of the usual voltmeter coil 4,8.

One end of this coil is connected through a resistance R and Wire 50 with the ground or neutral wire G. The other end of the coil 48 is connected by wire 52 with a brush 54 which rides on a contact ring 56 secured to and carried by an insulated bushing 58 which turns with the shaft 12.

The insulator sleeve 58 is surrounded by a torsion spring 60. one end of ywhich is electrically-and mechanically connected'to the ring56 and the other end of which isv similarly connected to a conductor tooth 62 secured to a fibre insulating collar -64 which loosely engages the shaft 12. v

Located at unequally spaced angular intervals around the axis of the shaft 12. I provide contact members 66, 66b and 66 which are adapted to successively coact with the conductor tooth 62. The brushes 66, 66?

and 66 are connected by wires 68a, 68b and 68. respectively, with the feed wires A, B and C.

The contact members 66?, 66b and 66 are each carried by a respective stud similar to that shown at 70, in Fi 2, and each Contact member is provided wit a volute spring portion 7 2 secured to the stud, the extremity of each contact member being bent at right angles as indicated at 74 so as toprovide a detentadapted to engage the tooth 62 and thus normally prevent counter-clockwise rotation of the collar 64.

Secured to the shaft 12 alongside the collar 64 I provide a cam 76 made of fibre or similar insulating material and having a projection 78 which is adapted to successively engage the detent portions 74 of the respective contact members 66, 66b and 66 so as to free them from the tooth 62. As thus arranged, it is clear that as the cam 7 6 rotates the collar 64 and tooth 62 carried thereby will successively snap to engagement with the three contact members 66a, 66b and 66.

Thus,'it is clear that when the tooth 62 is in engagement with the contact member 66 a circuit will be established from feed Wire A through wire 68, contact member 66, tooth 62, spring`60, ring 56, brush 54, Wire 52, voltmeter coil 48, resistance R, conductor 50 and ground o r neutral wire G. For the interval of time that this connection is made, the stylus B will make the graph indicated at A in Fig. 4. When the cam projection 78 trips contact 66a, the torsion spring will snap the tooth 62 into engagement with the end of the contact member 66. Therefore, for the next time interval, lthe stylus 42 will make the graph indicated at B1 in Fig. 4. Similarly, when the cam projection 78 trips the contact 66, the tooth 62 will snap to engagement with the contact 66, whereupon, for the third interval, the stylus will make the graph indicated at C in Fig. 4. The peripheral spacing between the ends 74 of the contact members 66, 66b and 66 is preferably unequal so that the graphs A', B and C will each be of a different length. The

' contact members 66, 66b and 66, the stylus 42 .will make a quick lateral deflection which will be eifective to mark the lateral dividing o lines d between the different graphs A', B and C. Because of the rapidity with which the torsion spring. 60 acts, the "voltmeter needle 44 will not jump to zero upon breaking of the circuit, thus, the instrument will not be subjected to such an excessive Wear or shock as would be occasioned if thecircuit remained open for a longer period.

The angular spacing between the ends 74 of the respective contact members'66, 66b and 66 being unequal and the shaft.12 vbeing driven at a constant rateby the timing device, itl follows the separate circuits will be sustained through the coil of the meter which actuates the stylus for separate predetermined time intervals. 'Thus, the longest same for all three phases.

graph A of F ig. 4 can be identified with the voltage characteristic of the circuit including wire B and ground conductor G. Similarly, the next shorter graph B- Will indicate the voltage across Wire B and conductor G. And the shortest graph C Will indicate the voltage between the wire C and G. Thus, it is clear that by providing means for successively sustaining separate circuits through the different phases for different time intervals, I provide a novel means of identification.

In recording voltage on electric service distribution networks, it is of no importance that the graph for each phase be of exactly the same length. It is only necessary that the frequency at which the graphs A', B and C are made is such as to give a substantially true record of voltage variations during a given day of twenty-four hours. If the graphs for the circuits Were all the same length, the record would be of little practical use because of lack of identification. But, by making them of varying lengths, one can tell at a glance to which phase or circuit the graph refers.

'Ihe making of separate identifiable voltage graphs of the different phases or circuits on a single chart, instead ofusing a separate instrument for each phase, has the added advantage that the record graphs obtained are exactly comparable, as any error in the instrument or in the calibration is the n the other hand, in using three separate instruments, the calibration is apt to vary and there are three chances for error due to faulty response of each instrument.

From the foregoing it is clear that I provide means whereby a single meter and single chart is operative to produce a distinctive and readily identifiable record graph for each phase of a polyphase circuit or a plurality of separate circuits.

While I have described with great particularity certain specific details of the construction and arrangement of parts, it is not to be construed that I am limited thereto since various modifications and substitution of equivalents may be made by those skilled in the art Without departing from` the invention as defined in the appended claims.

What I claim is:

1. In combination with a recording voltmeter having a timing device and a chart Amoved at a constant rate thereby, a circuit changing mechanism driven at a rate commensurate With that of the chart, said circuit changing mechanism comprising a plurality of unequallyspaced yielding contact to normally oppose the movement of saidv rotary circuit closing member, spring means tending to turn sald circuit closing member and means for periodically tripping said yielding contact members so as to successively release the rotary circuit closing member after a lapse of a predetermined time interval.

2. In combination With a recording voltmeter having an actuatingl core, a chart moved at a substantially constant rate, a circuit changing device including a shaft driven at a rate commensurate with that of the chart, a plurality of contacts electrically connected With separate conductors, a member loosely carried on said shaft for coaction with said contacts, means tending to turn said member relatively to said shaft, said contacts being arranged to prevent said turning movement, means for successively tripping said contact members, a contact ring on said shaft electrically connected with said member and a brush engaging said ring which is connected through the voltmeter coil with a conductor.

In witnesswhereof., I have hereunto signed my name.

ALBERT J. ALLEN.

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