US3523240A - Tap preselector for load switching system - Google Patents

Description

Aug. 4, 1970 G. BOUVIER 3,523,240

TAP PRESELECTOR FOR LOAD swn'cumu SYSTEM Filed ll rch 18. 1968 4 Sheets-Sheet l FIG/1' er r Aug.- 4, 1970 G. BOUVIER TAP PRESELECTOR FOR LOAD SWITCHING SYSTEM Filed March 18. 1968 4 Sheets-Sheet 2 FIG. 2

JTTORI EYS Aug. 4, 1970 G. BOUVIER 3,523,240

TAP PRESELECTOR FOR LOAD SWITCHING S'YSTEM Filed March 18, 1968 4 Sheets-Sheet 3 64/ X Bear/ER g- 4, 1970 G. BOUVIER 3,523,240

I TAP PRESELECTOR FOR LOAD SWITCHING SYSTEM Filed March 18. 1968 4 Sheets-Sheet 4.

M VE/VTo/z 60 430/4 V/EA I 5y x JTTDRIVEYI United States Patent Ofice 3,523,240 Patented Aug. 4, 1970 Int. Cl. osr 7/00 US. Cl. 323-435 Claims ABSTRACT OF THE DISCLOSURE It is the object of the present invention to allow for a rapid regulation of the voltage at the terminals of a load supplied by a transformer winding having multiple taps. The communication is effected by means of thyristor circuit breakers whose action is controlled in dependence upon the operation of a tap preselector.

The present invention relates to the devices or systems designed for switching under load between two of the taps of a winding having multiple taps, by means of a commutator which is connected to these two taps prior to the commutation with the aid of a preselector. More particularly, the present invention is concerned with devices or systems of this type in which the control of the commutator under load is started by the operation of the preselector.

It is the object of the present invention to propose a device or system of this type which is adapted to rapidly carry out a succession of commutations. I

The commutation device or system under load according to the present invention is characterized in that FIGS. 1, 2 and 3 are schematic diagrammatic views through a tap preselector according to the present invention at different positions of the control shaft thereof, and

FIG. 4 shows the wiring diagram of a position control system associated with the preselector forming a servomechanism control for the operation thereof.

The device in accordance with the present invention is designed to regulate the voltage at the terminals of a load 9 energized by a winding 10 of a regulating transformer, as illustrated in FIG. 1. One of the terminals of the load 9 is connected directly to one of the ends of the winding 10 and the other terminal thereof is connected to either one or another of the multiple taps 1 to 8 of the winding by means of a tap preselector and by either one or the other of two electronic commutation circuit breaker arrangement I and II, each consisting of a pair of thyristors, the thyristors being connected in parallel with opposite polarities.

the tap preselector consists of two circular crowns of fixed contact studs which are connected respectively to the even and to the odd taps of the multiple-tap winding and which are positioned concentrically around a control shaft carrying two movable contacts, either one or the other of which is connected to a load by means of a commutator under load, the provision of the movable contacts and of the contact studs. as well as the respective dimensions thereof being determined so that each of the movable contacts is adapted to occupy stable positions where one of them is in contact with the central portion of a contact stud of one crown at equal distance from the ends of this stud, while the other movable contact is positioned within the interval between two contact studs of the other crown without being in contact with these contact studs.

It is a principal object of the present invention to provide a tap preslector arrangement for control of on load switching between taps of a winding which eliminates or avoids the difficulties and disadvantages inherent in known arrangements of a similar type.

It is another object of the present invention to provide a tap preselector of the type described which is accurate and dependable and yet simple in construction.

It is a further object of the present invention to provide a tap preselector of the type described which permits rapid switching between taps under load and is not susceptible to excessive wear in use.

It is a further object of the present invention to provide a tap preselector of the type described which avoids excessive heating of the commutation device during use thereby also reducing powerloss in the switching system.

These and other objects, features and characteristics of the present invention will become apparent from the following detailed description thereof, taken in connection with the accompanying drawings, wherein,

The preselector comprises a circular crown S of fixed contact studs 11, 13, 15 and 17, respectively connected to the odd taps 1, 3, 5 and 7 of the winding 10, and a circular crown S of fixed contact studs 12, 14, 1-6 and 18 respectively connected to the even taps 2, 4, 6 and 8 of the winding 10. The number of multiple taps of the winding 10 has been limited to 8 for purposes of rendering the drawing and the description thereof clearer, but this number could obviously be greater or less than the number selected for purposes of illustration.

The crowns S and S are positioned perpendicularly around a control shaft 21 and are supported in any satisfactory manner. Two movable contacts 19 and 20 are mounted on respective contact bearers which are secured to the shaft 21, so that one rotation of the contacts 19 and 20 makes it possible to bring the contact 19 successively into contact with studs of the crown S and to bring the contact 20 successively into contact with studs of the crown S The circuit breaker arrangement I is connected between the movable contact 19 and the load, whereas the circuit breaker arrangement II is connected between the movable contact 20 and the load, in such a manner that, since the two movable contacts each are in contact with one contact stud, the opening of the respective one of the circuit breakers under load and the closing of the other one will switch or commutate the load from an even tap to an odd tap of the winding, or vice versa.

The position of the movable contacts and of the fixed contact studs as well as the length of the studs, along the crowns S and S are determined so that the movable contacts 19 and 20 may occupy stable positions where one of them is positioned in contact with the central portion of one stud at an equal distance from the ends of this stud, whereas the other movable contact is positioned within the interval between two contact studs without being in contact with them, as has been shown in FIGS. 1 and 2.

In the stable position of FIG. 1, the movable contact 19 is positioned in contact with the central portion of the stud 13, at equal distance from the ends thereof, and the movable contact 20 is positioned within the interval between the studs 12 and 14, at equal distances from these studs. The circuit breaker arrangement I is then closed and the circuit breaker arrangement II is open. The latter is not only devoid of current, but is moreover devoid of voltage since the contact 20 is not connected to either the stud 12 or the stud 14.

In the stable position of FIG. 2, the movable contact 19 is positioned this time within the interval between the studs 13 and 15 and the movable contact 20 is positioned in contact with the central portion of the stud 14.

Thus, the circuit breaker arrangement I is open and the circuit breaker arrangement II is closed.

The position of FIG. 3 is intermediate between that of FIG. 1 and that of FIG. 2. The movable contact 19 is still in contact with the stud 13 and the movable contact is now in contact with the stud 14. The commutation from the tap 3 to the tap 4 may at this time be effected.

In addition, a crown C/ CI of four equidistant interconnected studs 22 ad a crown C/CII of four equidistant interconnected studs 23 are also disposed around the shaft 21. The studs 22 and 23 are connected together and to that one of the terminals of the load 9 which is connected to the commutation circuit breaker arrangements I and II. A movable contact 24 provided on the shaft 21 is electrically connected to the movable contact 19 and positioned so as to be in contact with one of the studs 22 when the movable contact 19 occupies one of said stable positions where it is positioned in contact with the central portion of a stud of the crown S Similarly, a movable contact provided on the shaft 21 is electrically connected to the movable contact 20 and positioned so as to be in contact with a stud 23 when the movable contact 20 occupies one of said stable positions where it is in contact with the central portion of a stud of the crown S There follows then a short-circuiting of the particular one of the circuit breaker arrangements I and II which is closed on these stable positions. This short-circuiting diverts current from the circuit breaker arrangement and thereby avoids an unnecessary heating of the thyristors thereof after switching is completed. In other words, these switches C/CI and C/II render circuit breaker arrangements I and II effective only when they are needed to switch between taps, i.e. only in the FIG. 3 situation. Otherwise, the switches C/ CI and C/CII short circuit that circuit breaker arrangement I or II which is currently connected between a tap and the load to avoid the unnecessary application of voltage across these switching elements.

The length of the studs 22 and 23 along the crowns thereof is sufficiently short that the circuit breaker arrangement which is in the closed condition ceases to be short-circuited as soon as the shaft 21 leaves one of the stable positions, as has been shown in FIG. 3. The circuit breaker arrangements I and II are then both connected to a tap of the winding 10, one toan even tap and the other to an odd tap. The length of the studs of the crowns S and S along the crowns thereof, and thus the diameter of these crowns are great enough so that the commutation by circuit breaker arrangements I and II may be effected in the course of the passage of the movable contacts 19 and 20 along the two studs between two stable positions.

The commutation is effected by opening the particular one of the circuit breaker arrangements I and II which was under load and closing the other. This result may be obtained by any known means adapted to act in synchronism on the control electrode circuits of the thyristors of the commutation circuit breaker arrangements for transferring the load from the circuit breaker to the other.

It is possible to advantageously utilize a control system in which the commutation is effected by means of a control commutator which is susceptible to being brought to one or other of two conditions where it furnishes on either one or the other of two outputs either a control signal for opening the circuit breaker arrangement I and closing of the circuit breaker arrangement II and closing the circuit breaker arrangement I. In that case, it is of interest that this control commutator be adapted to operate without employing any members which are subject to wear and tear, so as to allow for a rapid operation.

The control commutator may consist, for example, of two contacts in sealed tubes which are magnetically controlled by external magnets provided on the shaft 21.

The control commutator may also advantageously consist of two circuit breakers formed by two photo diodes indicated at 26 and 27 in FIG. 1 where they are positioned adjacent one of the surfaces of a disk 30 secured to the shaft 21. Two optical devices 28 and 29 are positioned on the other side of the disk 30 and generate two pencil beams of light directed respectively towards the photo diodes 26 and 27. The disk 30 is provided with openings 31 located so that the photo diode 26 is illuminated when the shaft 21 is in a stable position in which the com mutation circuit breaker arrangement I must be closed, as in the case of FIG. 1. The ends of the opening 31, which is then positioned in line with the photo diode 26, must be at an equal distance from the photo diode since it must be possible to effect the operation similarly in one or the other direction of rotation of the shaft 21. Conversely, the photo diode 27 must then be in darkness in line with a solid portion of the disk 30 at an equal dis tance from the two openings 31.

The photo diodes 26 and 27 are connected in control circuits (not shown) where they are subjected to an inverse voltage. As is known, a photo diode is only traversed by a weak inverse current when it is in darkness, and this inverse current increases abruptly when the photo diode is illuminated. The photo diodes 26 and 27 thus have the function of a control circuit breaker. Such control circuits being controlled by the position of the shaft of a preselector have been disclosed and illustrated in US. patent application Ser. No. 697,457, filed by Gerald Ebersohl, on J an. 12, 1968. As has been explained therein, the illumination of a photo diode controls the opening of one of the commutation circuit breakers and the closing of the other.

At the stable position of FIG. 1, the circuit breaker arrangement I being conductive and the circuit breaker arrangement II being open-as has been set forth hereinabove-the photo diode 26 must as a result be illuminated and positioned in line with an opening 31 of the disk 30 at an equal distance from the ends of this opening. The photo diode 27 is positioned so as to be in comparative darkness in line with a solid portion of the disk 30 at equal distances from two openings 31.

At the stable position of FIG. 2, the circuit breaker I is open and the circuit breaker II is conductive. The disk 30 must this time have an opening 31 in line with the photo diode 27 and the diode 26 is now in line with a solid portion of the disk 30 as a result of its rotation with the shaft 21. Similarly, the photo diode 27 is at an equal distance from the ends of the opening 31 and the diode 26 is between and at equal distance from two adjacent openings.

The openings 31 have a length which is slightly smaller than the distance between two consecutive openings so as to avoid the risk of a simultaneous illumination of the two photo diodes during the passage from one stable position to the next-following one, which would result in the simultaneous closing of two power circuit breaker arrangements I and II.

The two photo diodes 26 and 27 are thus both in darkness during a short duration in the course of the passage from one to the other of two stable neighboring positions according to FIGS. 1 and 2. This transitory position is represented in FIG. 3 where the shaft 21 is in the course of rotation in the direction of the arrow 1 for passing from a position according to FIG. 1 to a position according to FIG. 2. Each of the movable contacts 19 and 20 is then in contact with one of the studs connected to the taps of the winding 10. On the other hand, neither the movable contact 24 nor the movable contact 25 are in contact with a short-circuit stud. The photo diode 27 becomes very rapidly illuminated by the rotation of the shaft 21 and the commutation is effected by closing the circuit breaker arrangement II after opening the circuit breaker arrangement I.

The passage from one of these stable positions to another adjacent one is accomplished by a control of the angular position of the shaft 21, connected to and controlled by the position of a reference member forming part of a servo control system. This may be obtained by the position servo mechanism illustrated in FIG. 4 by way of example.

A reference potentiometer 32 is provided with a plurality of contact studs 34 equally spaced and in number equal to the number of positions of the shaft 21 to be controlled. The ends of the potentiometer 32 are connected to the terminals of a voltage source 35 providing a constant voltage also to the ends of a potentiometer 33 whose movable contacts 43 are connected to and driven by the shaft 21 of the tap preselector. The movable contacts 42 and 43 of the potentiometers 32 and 33 are connected to the input terminals of an amplifier 36 whose output is connected to a servomotor 37 which is coupled to the shaft 21 of the preselector by means of a speed reducing means 38.

When the angular positions of the movable contact of the two potentiometers 42 and 43 are identical, the resultant of the voltages applied to the input terminals of the amplifier 37 is zero. The servomotor 37 therefore remains immovable and now the shaft 21 of the preselector is at one of the stable positions defined hereinabove. When the movable contact 42 of the reference potentiometer is moved to a neighboring stud, the angle to be transmitted and the reproduced angle become different and an error voltage is generated in the amplifier 36. The servomotor 37 then drives the shaft 27 until the error signal is reduced to zero indicating that the angular position of this shaft once again coincides with that of the movable reference contact.

Other systems of position control may be utilized; for example, potentiometers 42 and 43- may be replaced by selsyns, in which case the servomotor is then supplied by an alternating current.

It is also possible to make use advantageously of a position servo control on the basis of a digital control with a conversion into binary code of the angular positions of the preselector by means of a coding disk. The binary information thus provided is compared with the binary information corresponding to the reference position and this comparision is translated by an error voltage which similarly excites a servomotor until the error is cancelled. These two latter devices have the advantage of setting into operation precision elements which are less subject to wear and tear than the reference and control potentiometers 42 and 43'. The angular positionings are thus obtained with a greater degree of accuracy and reliability.

I have shown and described several embodiments in accordance with the present invention. It is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art and I, therefore, do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

What is claimed is: 1. In a switching system for switching a load between taps of a multiple tap winding a tap preselector comprising a first and a second plurality of fixed contacts connected respectively to the odd and even taps of said multiple tap winding, and

control means carrying first and second movable contacts for selectively positioning said movable contacts in electrical contact with a fixed contact of said first and second plurality of fixed contacts alternatively in successive stable positions,

commutation means connecting said first and second movable contacts to one side of said load for switching said load between taps at the zero crossing of the load current, the other side of said load being connected to one end of said multiple tap winding,

said control means providing simultaneous actuation of said movable contacts to a selective one of a plurality of stable positions with only one of said first and second movable contacts electrically contacting a fixed contact in each stable position.

2. The combination defined in claim 1 wherein said first and second fixed contacts are positioned and dimensioned with respect to said first and second movable contacts, respectively, so that in between said stable positions both of said first and second movable contacts are in electrical contact with a fixed contact.

3. In a switching system for switching a load between taps of a multiple tap winding, a tap preselector comprisa first and a second plurality of fixed contacts connected respectively to the odd and even taps of said multiple tap winding, and

control means carrying first and second movable contacts for selectively positioning said movable contacts in electrical contact with a fixed contact of said first and second plurality of fixed contacts, respectively,

commutation means for switching said load between taps connecting said movable contacts to one side of said load, the other side of said load being connected to one end of said multiple tap winding,

said control means providing simultaneous actuation of said movable contacts to a selective one of a plurality of stable positions with only one of said first and second movable contacts electrically contacting a fixed contact in each stable position,

said first and second fixed contacts are positioned and dimensioned with respect to said first and second movable contacts, respectively, so that in between said stable positions both of said first and second movable contacts are in electrical contact with a fixed contact, and

a third and a fourth plurality of fixed contacts and a third and fourth movable contact actuated by said control means into electrical contact with respective ones of said third and fourth plurality of fixed contacts in each stable position, respectively, each of said third and fourth plurality of fixed contacts being connected to said one side of said load, said third movable contact being connected to said first movable contact and said fourth movable contact being connected to said second movable contact.

4. The combination defined in claim 3 wherein said contacts of said third and fourth plurality of contacts are so short as to contact said third and fourth movable contacts, respectively, only in said stable positions of said control means.

5. The combination defined in claim 4 wherein said first, second, third and fourth pluralities of fixed contacts are positioned in respectively concentric circles, said control means including a shaft carrying said movable contacts respectively in the planes of said circles.

6. The combination defined in claim 4 wherein said commutation means includes first and second circuit breaker arrangements having thyristors and being rendered alternately operable by said control means actuating said movable contacts to successive stable positions.

7. The combination defined in claim 3 wherein said control means includes a control shaft to which said movable contacts are connected and servo control means for selectively driving said control shaft in rotation to one of said plurality of stable positions wherein one of said movable contacts is in electrical contact with a fixed contact associated therewith and the other movable contact is positioned between and out of electrical contact with fixed contacts associated therewith.

;8. In a switching system for switching a load between taps of a multiple tap winding, a tap preselector comprising a first and a second plurality of fixed contacts connected respectively to the odd and even taps of said multiple tap winding, and

control means carrying first and second movable contacts for selectively positioning said movable contacts in electrical contact with a fixed contact of said first and second plurality of fixed contacts, respectively,

commutation means for switching said load between taps connecting said movable contacts to one side of said load, the other side of said load being connected to one end of said multiple tap winding,

said control means providing simultaneous actuation of said movable contacts to a selective one of a plurality of stable positions with only one of said first and second movable contacts electrically contacting a fixed contact in each stable position,

said first and second fixed contacts are positioned and dimensioned with respect to said first and second movable contacts, respectively, so that in between said stable positions both of said first and second movable contacts are in electrical contact with a fixed contact, and

switch means actuated by said control means for short circuiting-said commutation means only in the stable positions of said control means.

9.The combination defined in claim 8 wherein said commutation means includes first and second circuit breaker arrangements having thyristors and being rendered alternately operable by said control means actuating said movable contacts to successive stable positions.

10. The combination defined in claim 9 wherein said switch means includes first and second switches actuated by said control means to short circuit only the circuit breaker arrangement connected to a tap of said multiple tap winding. 1

References Cited UNITED STATES PATENTS 2,719,234 9/1955 Wright 323-435 X 3,233,049 2/1966 Bleibtreu 32343.5 X 3,358,219 12/1967 Biihler 323-435 3,388,320 6/1968 Schoendube et al. 32343.5

ROBERT K. SCHAEFER, Primary Examiner T. B. JOIKE, Assistant Examiner US. Cl. X.R. 307-1 33

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