US2043904A

US2043904A - Electrical control board

Info

Publication number: US2043904A
Application number: US617176A
Authority: US
Inventors: Raymond T Pierce
Original assignee: Weston Electric Instrument Corp
Current assignee: Weston Electric Instrument Corp
Priority date: 1932-06-14
Filing date: 1932-06-14
Publication date: 1936-06-09
Anticipated expiration: 1953-06-09

Description

June 9, 1936. R, PgERCE 2,043,904

ELECTRICAL CONTROL {BOARD Filed June 14, 1952 2 Sheets-Sheet 1 June 9, 1936.

R. T. PIERCE ELECTRICAL CONTROL BOARD Filed June lfl, 1952 2 Sheets-Sheet 2 Patented June 9, 1936 ELECTRICAL CONTROL BOARD Raymond '1. Pierce, Millburn. N. J., assignor to Weston Electrical Instrument Corporation,

Newark, N. J., a corporation of New Jersey Application June 14, 1932, Serial No. 617,176

8 Claim.

This invention relates to control boards for electrical apparatus, and particularly to assemblies of miniature indicating instruments and control devices.

In the development of the electrical industries, the panel board assemblies of indicating instruments and control devices have so increased in size that it is difficult to maintain a close supervision over the several generators, motors and other units. It has been proposed to substitute miniature instruments and relay control devices for thelarger size units customarily mounted on the large slate panels, but the design of such miniature control units has followed the established practice for the construction of full size panel assemblies, 1. e., the miniature control units have been individually constructed on panels of a size and shape determined by the number of instruments. required for each particular power plant or generator system.

According to the present invention, the indieating and control devices for each individual machine of an electrical plant are mounted, in vertical alinement, on a steel rack or skeleton strip to constitute a narrow panel. The edges of the panel strips for a plurality of machines may be connected to form a control board that may be readily increased or decreased in size as machines are added to or taken from the plant.

An object of the invention is to provide a simple, economical and compact panel board in which the panel board is formed as a plurality of unit panel strips. An object is to provide a control panel strip in which a plurality of indicating and control units are assembled on a rack to constitute the panel.

A further object is to provide a panel strip of the type stated in which all of the separate units may be inserted or removed from the front of a skeleton frame, and in which all calibration tests may be made from the front of the panel.

These and other objects of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Fig. 1 is a front elevation of a typical control board assembly of two panel units,

Figs. 2 and 3 are fragmentary front and rear elevations, respectively, showing one indicating instrument on the panel strip,

Fig. 4 is a fragmentary side elevation, with parts in section, .of one instrument on the supporting rack, a 4

Fig. 5 is a top plan view of one panel strip,

Fig. 6 is a typical'circuit diagram of the wiring of a panel strip, and of the connections bereceiving indicating and control units that are of such size, viewed in elevation, as to constitute substantiallythe entire exposed face of the panel strip. The openings are all of the same size, and all'indicating and control units are interchangeable as to size and mounting, thus permitting.

any desired arrangement on the front of the rack. In the preferred arrangement, the indicating instruments 2 are mounted in the upper openings, then the panels 3 that carry relay control switches and signal lights 5, and connecting panels are located in the bottom openings, being protected by cover plates 6. In general, a maximum of six instruments will be required for indicating the operation of any electrical unit and the frames are therefore provided with eight openings. For uniformity, all frames are preferably made of the same size and, when less than six instruments are required, the openings in which no instruments are mounted will be covered by dummy plates 1.

As shown in Figs. 2 to 5, inclusive, the instrument covers 8 and cases 9 are of rectangular form. The forward flanged edges of the metallic cases 9 rest against the edges of the openings in the frame I when the cases are inserted from the the base of the instrument movement and project meter having ten terminals I4, the additional terminals ll being provided for lamps (not shown) which illuminate the scale plate IQ of the instrument. The construction of this instrument and its case is typical of that employed for voltmeters, ammeters, frequency indicators and other electrical measuring instruments which may be mounted on the racks i Flanges I'I, preferably of channel form, are welded to the edges of each rack at its rear face and are provided with openings i8 for receiving bolts to secure adjacent panel strips together to form the control panel for a plurality of electrical devices.

The racks I, their attached flanges I1 and the instrument cases 9 are preferably metallic, while the cover plates 8 may be conveniently formed of molded plastics. This permits the racks to be grounded and thus provides a "dead front control board that eliminates all possibility of danger to the operator.

The construction of the connecting panel and a typical arrangement of the circuits established thereto are shown in Figs. 6 and 7. The particular circuit arrangements are appropriate for a control unit such as the panel strip shown at the right of Fig. 1, in which the upper instrument may be a kilowattmeter W, the next lower a voltmeter V, and the lower three instruments are ammeters A A, and A. These instruments will be recognized as the group commonly employed for observing the operating conditions of a three phase generator or transmission line.

The connecting panel 20 comprises a molded insulating plate having bolts i0 secured at the corners thereof for attaching the plate to the rack I, the heads of the bolts being countersunk and threaded to receive the bolts by which the cover plate 6 is secured to the connecting panel. Two sets of four voltage terminals 2| are mounted, in vertical alinement, on and project through the panel 20. At the lower portion of the panel, two sets of six current terminals 22 extend through the panel in vertical alinement and, as will be explained hereinafter, a third set of six current studs project from the front face of the panel. The instrument connections are made to the upper terminals of each set, and the connections to the transmission line are made to the'lower terminals of each set. At the front of the panel 20, the vertically alined terminals are connected by clips.

With this particular arrangement of instrument and transmission line terminals, the circuit connections are established in the usual manner and it is believed that the following general description of the circuits established will be suflicient, without a detailed description of each connecting wire, to make clear the advantages of this panel construction. In Fig. 6, the transmission line or leads from the generator are identifled by the characters L1, L2, L3, and N. Voltage transformers T are arranged in the usual manner with their primary windings connected between the lines L1, L2,.La, respectively, and the neutral wire or ground N, the respective secondary windings being connected between the lower set of voltage terminals 2| and ground N. The several terminals 21 are preferably identified, on the panel, by

legends

1, 2, 3, and N, the fourth terminal N being connected to the grounded line N.

Current transformer windings S are arranged on three lines L1, L2, L3, and connected between the ground or line N and the alternate terminals, labeled S1, S2, and S3, respectively of the lower set of current terminals 22. The remaining terminals of this lower set, labeled L1, 14. La, respectively, are connected to each other and to the ground or line N.

When these connections are made to the panel '20 and the connecting strip properly applied at the face of the panel 20 to join vertically alined terminals of the voltage and current group, as indicated by dotted lines in Fig. 6, the several ammeters are properly connected to indicate the current flow on each line, the voltage between the load lines and ground, and the kilowatt load on the line or generator. In the particular installation shown in Fig. 6, it will be noted that no connection is made to the instrument terminal 2| that is connected to the transformer on line L2. When areactive kilovoltammeter is employed in place of, or in addition to the kilowattmeter, a connection is made, in the usual manner to this terminal.

It is to be noted that all of these connections are made at the back of the connecting panel 20 and that, in practice, all instruments are mounted on the frames l and all connections are made between the instruments and the panel 20 in the shop. This permits a complete testing and calibration of the panel assembly before it is shipped to its place of use. When the panel strip, or a group of panel strips, arrives at the generating plant or factory, the only electrical connections to be made are those to the instrument transformers.

The advantages to be obtained by use of the described type of connecting panel will be apparent from Fig. 7 which illustrates the circuit connections, established at the face of the control board, for calibration of the several instruments. The described arrangement of terminals 2| and 22 makes it possible to test the entire panel assembly without breaking any of the circuit connections at the rear of the panel. In Fig. 7, the permanent wiring of the panel strip is shown in light lines and the wiring between the connecting panel and the testing equipment is shown by heavier lines.

The first step in testing the accuracy of the several instruments is to short circuit the several current transformer windings S by clips 23 which, as shown in Fig. 8, are normally stored within the cover plate 6. These clips 23 are connected between the groups of terminals S1 and L1, S2 and L2, S: and L3, of the third set of current terminals 24 (previously mentioned) which are connected to the lower set of current terminals 22 by the several connecting clips 25. After the application of the short-circuiting clips 23, the clips 26 which normally connect the vertically alined pairs of terminals 22 are removed and two of these clips are connected across the upper set of terminals 22 which are in vertical alinement with terminals 24 labeled L1, S2 and In, S3, respectively. The clips 21 which normally connect the vertically alined pairs of voltage terminals 2| are then removed, and two of the clips are then connected between the three upper voltage terminals 2! which were previously connected to the high voltage terminals of the several voltage transformers T.

It is to be noted that none of the connections between the several instrument transformers T and. S are broken,'but the removal of clips 26 and 21 from their normal positions breaks the circuits between the transformers and the instruments. The replacement of certain of these clips in the positions indicated connects all of the voltage terminals of the voltmeter V and watt- 75 meter W in parallel, and connects all of the current windings of the wattmeter in series with'the three ammeters A A, and A.

With these connections established a testing set including an ammeter A, a voltmeter V wattmeter W and load box L may be appropriately connected to the instrument terminals at the face of the connecting panel Iii. As shown in Fig. 'l, the instruments may be checked from any convenient source 30 of alternating current which may be a generator feeding a line I, 32. A connection is made from one side SI of the source ill to the joined high voltage instrument terminals 2i and to the instrument current terminal 22 that was previously joined to the high voltage side of the current transformer winding 8 on line Li. The terminal N of the voltage group II is connected to an adjustable tap a on a voltage divider it that is shunted across the source 30 and the standard voltmeter V and the voltage winding of the standard wattmeter W, are also connected between the tap a and the lead ll from the source. a

From the upper instrument terminal 22 of the vertically alined group labeled Le, a connection is made through the standard ammeter A to the current winding of the standard wattmeter W and then to one terminal of the adjustable load box L. The other terminal of the load box is connected to the line 32 from the source 30.

With the establishment of these connections between the testing equipment and the connecting panel 20, the current flow through the windings of the several instruments is indicated by the ammeter A, the voltage across the voltmeter V and the voltage winding of the panel kilowattmeter W is the same as that across the standard voltmeter V and the total load on the kilowattmeter is measured by the standard wattmeter W. All of the instruments on the panel strip may therefore be readily and quickly checked without breaking any of the circuit connections at the back of the panel. In the event that a defective instrument is located, the instrument movement it may be removed by disconnecting the wiring to the instrument terminals it and the screws II which retain the movement within the casing I.

As distinguished from the known types of miniature control boards, the invention presents the mechanical advantage of localizing all instruments and control devices associated with a particular electrical unit upon a single panel strip which may be readily assembled with similar panel strips to form a complete control board. From an electrical view point, the invention provides a convenient-means for checking the measuring instruments without necessitating any changes in the wiring of the control board.

I claim:

- 1. In a control board for electrical apparatus, a vertically disposed skeleton strip having a plurality of alined openings, instrument cases inserted into a plurality of said openings from the face [of the strip and having flanges secured to said strip to constitute the sole support for said cases,

instrument movements secured in the several cases, and cover plates secured to each of said cases to complete the housings for the several instrument movements.

2. In a control board for electrical apparatus. a metal plate comprising narrow side strips between which narrow cross bars extend to provide a plurality of vertically alined openings, instrumeat cases extending through said openings from the face of said frame and having peripheral flanges overlying and secured to said plate to constitute the sole support for said cases, instrument movements in and supported by said cases, and 5 cover plates for said instrument movements, said cover plates overlying and concealing the peripheral flanges of said cases.

3. The invention as set forth in claim 2, wherein flanges are secured to the rear of the side 10 strips of said frame, said flanges providing means for securing the said frame to similar metallic frames.

4.'In a control board for electrical apparatus,

a plurality of substantially identical skeleton 15 plates having their lateral edges secured to each other, each of said plates having a plurality of vertically alined openings of uniform size, a plurality of indicating and control devices interchangeably receivable in said openings, means 20 mounting said devices in certain of said openings and supporting the said devices solely from said plates, and cover plates secured over said openings and the devices mounted therein.

5. In a control board for mounting the indi-- eating and control devices employed with a plurality of electrical machines, a skeleton plate for each machine, means securing the plates together with the lateral edges thereof in alinement, said plates being of identical construction and each having vertically alined openings of uniform size,

a plurality of instrument and control devices to be associated with each machine, and adapted to be received in said plateopeninz the number of a5 openings of each plate being not less than the maximum number of instrument and control devices required for any one of said machines, whereby all instrument and control devices for each machine may be mounted on one plate, and means for supporting solely by each plate the instrument and control devices mounted thereon.

8. The invention as set forth in claim 5,

wherein each of said devices is inserted in its plate opening from the front face of the plate and includes a flange overlying the said plate, in a combination with cover plates supported from said skeleton plates and overlying the respective devices.

'l. The invention as set forth in claim 6, wherein each of said devices is inserted in its plate opening from the front face of the plate and includes a flange. overlying the said plate, in combination with cover plates supported from said skeleton plates and overlying the respective devices, and dummy cover plates for covering those plate openings1in which devices are not mounted. v

8. In a control board for electrical apparatus. a vertically disposed skeleton plate having a plurality of vertically alined openings, instrument cases inserted intoa plurality of said openings from the face of the frame and having flanges secured to said plates to constitute the sole supports for said cases, the rear walls of said cases having openings therein, instrument movements 65 secured in and supported by the several cases, said instrument movements having terminals extending through the said openings thereof, and

a cover plate secured to each of said cases to complete the housing of the several instrument movements;

RAYMOND '1. PIERCE.