US2560630A - Overvoltage protector - Google Patents

Description

y 7, 1951 R. L. BROWN OVERVOLTAGE PROTECTOR 4 Sheets-Sheet 1 Original Filed Oct. 15, 1947 INVENTOR BEBE/Q T LUU/ELL BRUll/N July 17, 1951 R. L. BROWN 2,560,630

OVERVOLTAGE PROTECTOR Original Filed Oct. 15, 1947 4 Sheets-Sheet 2 INVENTOR HUBER? LUZ/l L ERMA/N ATTORNEY July 17, 1951 R. 1.. BROWN 2,560,630

OVERVOLTAGE PROTECTOR Original Filed Oct. 15, 1947 4 Sheets-Sheet 5 mm; x z E INVENTOR HUBERT LUH/E BRUll/N BY w M g ATTORN EY R. L. BROWN OVERVOLTAGE PROTECTOR July 17, 1951 4 Sheets-Sheet 4 Original Filed Oct. 15, 1947 s--ss--s HUBERT Lua/Eu BRULl/N ATTORNEY Patented July 17, 1951 UNITED STATES PATENT OFFICE Original application October 15, 1947, Serial No.

Divided and this application October 5, 1949, Serial No. 119,725

3 Claims. I

This application is a division of application Serial No. 779,992, filed October 15, 1947, and relates to overvoltage protection for an electrical generator and more particularly to improvements in the system and protector of the type shown in the copending application for U. S. Patent Serial No. 701,322, filed October 4, 1946, by Robert Lowell Brown, now U. S. Patent No. 2,522,601.

An object of the invention is to provide overvoltage protection which does not respond to sudden surges of short duration of overvoltage.

It is desirable in the event of an overvoltage on one generator of a parallel arrangement that the other protectors do not trip due to surges caused by the finite time of operation of the faulted protector, reverse current relays, regulators and line switches. While the regulators of the normally functioning generators will automatically tend to keep the non-faulted protectors from tripping after a short, an object of the invention is to provide means for effecting an immediately acting time delay (of short duration) to keep the protectors from tripping before the regulators can take over.

Another object of the invention is to provide an immediately acting time delay (of short duration) for the protecto. which is introduced by the use of short circuiting slugs (rings) of copper arranged concentric with the coil on the electromagnet. Thus with the time delay in the protector plus the correcting action of the regulator the non-faulted protector will not trip when a parallel system is disturbed by an overvoltage generator.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example.

In the drawings:

Figure 1 is a perspective view of the overvoltage protector showing the vacuumtight casing and manually operable reset bellows;

Figure 2 is a perspective view of the overvoltage protector showing the vacuumtight casing and manually operable reset bellows;

Figure 3 is an enlarged sectional view of the overvoltage protector with the latch shown in the released position.

Figure 4 is a fragmentary end view of the switch mechanism showing the armature and latch mechanism.

Pigure5isanend-viewofrigure3takenalons the lines 55 and looking in the direction of the arrows.

Figure 6 is a diagrammatic view showing the overvoltage protector connected into a generator system.

Referring to the drawings of Figures 2-3 there is shown the overvoltage protector which includes an electromagnetic coil Ill supported by a bracket II which with a second bracket l2 are fastened to a supporting plate 13 and base member or panel I3A by bolts l4.

The electromagnetic coil HI has an armature i 5 pivoted on an edge It formed at the outer end of the bracket II. A third bracket arm 11 is fastened to the bracket H by a bolt i8 which also fastens thereto a member IS. A spring 20 is connected at the free end of the member l3, while the opposite end of the spring 20 is connected to the upper end of the armature l5 so as to bias the armature l5 about the edge It in a clockwise direction.

Positioned adjacent the armature I5 is a latch member 21 pivotally supported at one end by a spring arm 22. The latch member 2| is arranged to engage a shoulder portion 23 of a reset plunger or push rod 24. The push rod 24 is slidably mounted in portions 25 and 26 of the bracket I2.

At the upper end of the push rod 24 there is provided a head portion 21. Positioned between the head portion 21 and the bracket portion 25 is a coil spring 23 which biases the push rod 24 upwardly. A stop 23 is provided at the lower end of the push rod 24 to engage the bracket portion 26 so as to thereby limit the upward movement of the push rod under the biasing force of the spring 23. A cup-shaped depression 33 is formed in the supporting plate i3 for receiving the lower end of the push rod 24 when in the depressed position.

The supporting plate i3 has an upstanding flanged portion 3| extending about the outer edge thereof to which there is sealingly connected the lower edge of casing 32 which encloses the protector mechanism.

The casing 32 has an opening 33 formed therein through which projects the head portion 21 of the push rod 24. A bellows 34 surrounds the head portion 21 and the opening 33 and is sealingly connected to the casing 32. The upper end of the head portion 21 is operably connected interiorly to the bellows 34 so that depression of the bellows 34 effects downward adjustment of the push rod 24 so as to effect engagement oi the shoulder 23 by the latch member 2|.

The armature it carries a head stud 35, the

shank of which extends loosely through an aperture in the latch member 2|, thus forming a loose or lost motion connection between the armature I5 and latch member 2|. With this arrangement it will be seen that upon energization of the electromagnet ID the voltage at which the armature |5 starts to move is determined by the spring 20. After the armature |5 has approached quite close to the pole face of the electromagnet ID (at which position the pull of the electromagnet I is much greater) the head of the stud 35 engages the latch member 2| and pulls it off the step 23 of the push rod 24, thus permitting the rod 24 to move upward under the biasing force of the spring 28, to operate a plurality of switch contacts, as will be explained.

Mounted on the bracket arm H by bolts 36 is a switch assembly comprising insulating spacers 31, 38, 39, 40, 4|, 42 and 43 and contact carrying spring arms 44, 45, 46 and 41 suitably insulated by the spacers.

As shown in Figure there is further mounted on the bracket arm l1 by bolts 36A a second switch assembly comprising insulating spacers 31A, 38A, 39A, 48A, 4|A, 42A and 43A and con- Also secured to the bracket arm H by the bolts 36 and 36A are insulation strips 50 and 5|. Contact carrying spring arms 52 and 53 are fastened respectively to the insulation strips 50 and 5| at a point intermediate the two switch assemblies 36 and 36A.

Also secured to the insulation strip 50 and at the opposite side thereof from the spring arm 52 is a spring strip 54 which is connected to the contact strip 52 at the contact button 55. The contact button 55 is arranged to cooperate with a contact 56 carried by contact spring strip 53.

As shown in Figure 4, there are positioned. at opposite sides of the contacts 55 and 56 permanent magnets 51 and 58 held in a bracket 59 afiixed at the upper end of the bracket arm The bracket arm H thus closes a magnetic circuit between the permanent magnets 51 and 58 at the lower end thereof while at the upper end a magnetic flux flows across the contacts 55 and 56 tending to blow the arc resulting upon opening the contacts outward toward the left as viewed in Figure 3.

The spring arms 44-45, 44A-45A, 46-41, and 46A-41A likewise cooperate respectively in opening and closin several circuits as will be explained. Arc shields 60 are provided to protect the mechanism from arcing at these contacts.

The spring contact arm 52 is operably connected by an extension 6| to the plunger rod 24, so. that downward movement of the rod 24 will tend to close contacts 55-56 and the upward movement of rod 24 as upon the unlatching thereof will open the contacts 55-55.

Afiixed to the spring arm 54 is a U-shaped member 65 operably connected to spring contact arm 44 and A by insulated connectors 66, while the arms 44 and 44A are similarly connected to spring contact arm 46 and 46A respectively by insulated connectors 61. 1

It will be seen then that upon downward movement of the push rod 24 to a latched position the main switch contacts 55 and 56 will be closed as will the spring switch arms 4445, 44A--45A, 46-41, and 46A-41A. However upon the electromagnet l8 becoming energized and drawing the armature |5 toward it in a counter-clockwise ance, preferably wound of nichrome wire.

direction the stud 35 will draw the latch member 2| from the step 23, so as to release push rod 24. The upward movement of the rod 24 under the biasing force of the spring 28 will then cause switch arm 52 to open contacts 5556 and switch arms 44, 44A, 46 and 46A to open their respective contacts.

In order to compensate for changes in the resistance of the electromagnet |0 due to variations in temperature there is provided a resistance 10 having a small temperature coefficient of resist- The resistor 10 is mounted on the supporting member I3 and is connected in series with the electromagnetic winding ID, the resistance of which is relatively small compared to that of the resistance 10 so that any change in the relative resistance of winding ||l due to temperature effects the total resistance by a negligible amount.

Moreover in order to introduce an immediately acting time delay (of short duration) in the re-' sponse of the electromagnetic winding |0 to change in an energizing current, there are provided short circuited copper rings 1| which are arranged concentric with the winding of the electromagnet ID. The copper rings 1| tend during change in the energizing current of the electromagnet Ill to generate a magnetic flux retarding the build-up of a sufficient magnetic flux by the electromagnet In to actuate the armature I5, thus providing suflicient time lag to prevent tripping of the latch 2| by surge voltages.

The electromagnet l6 and the several switch contacts controlled thereby are connected by conductors 12 leading through a suitable insulation cement 13 provided in the base of the supporting member l3 as shown in Figure 5. The conductors 12 are in turn connected by conductors to suitable external terminals 14 mounted in the base member |3A, as shown in Figures 1 and 5.

The purpose of the overvoltage protector device, heretofore described and claimed in the parent application Serial No. 779,992, filed October 15, 1947, is to prevent damage to an airplane's electrical equipment when malfunctioning of a generating system causes excessively high voltage. The protector device is arranged to open the field circuit of the malfunctioning generator and in addition to effect the disconnection of its control equipment from the generator and to disconnect the generator from the main line without affecting other generating systems connected in parallel to the line. erating systems is provided with a like protector device.

A typical system according to the invention in which the protector device 32 may be used is illustrated in Figure 6 and may include a generator having a field winding 8| and an interpole compensating winding 82. Output line 83 of the generator 80 is grounded, while output line 84 may be connected to a main bu line 85 through a line switch 86 operated by a solenoid 61.

The control equipment for the generator is indicated generally by the numeral 86 and may be of a type described and claimed in the copending application Serial No. 621,515, filed October 10, 1945, by William R. Holmes.

The control equipment 90 inc ude a variable resistance carbon pile 9| connected. in series with the generator field 8| through a conductor 92. The field 8| is connected through conductor 93 to output line 83 and the opposite end of the carbon pile 9| may be corrected ta. the output Each of said gen-- line 04 through a conductor 04 and the main- The variable resistance carbon pile 6| may be controlled by an adjustable armature 36 shown schematically in Figure 8 and which may be of a type described and claimed in U. 8. Patent No. 2,427,805, granted September 23, 1947, in the name of William G. Neild and assigned to Bendix Aviation Corporation.

The armature 06 may be controlled by an electromagnetic winding 36 which may be con nected across the generator output lines I! and 04 by grounded conductor 01 and conductor 50. The conductor may be connected to line 04 through switch members 44-45 of the protector device 32.

Connected across the interpole compensating winding 02 by a conductor 33 and grounded conductor 69A is a potentiometer I00 having a center tap IO0A connected to a compensating winding IOI ior aflecting the carbon pile SI so as to maintain a predetermined division of load between the several parallel connected generators as is explained in the atorenoted copending application Serial No. 621,515.

The opposite end of the compensating winding IOI may be connected to an equalizer line I02 through a conductor I03, relay switch I04, and switch members A and 45A of the protector device 32. The relay switch I04 is controlled by an electromagnetic winding I connected across the output lines 33-64 by grounded conductor I06 including resistance I06A, conductor 98 and switch contacts 44 and 45 of pro-' tector 32.

The relay winding I05 is controlled by a pilot switch I01 biased by spring tension to the position shown so as to close switch contact I06. Switch I01 is connected to conductor 90 while contact I08 is connected to conductor I06 so that upon switch I01 closing contact I00, relay winding I05 is shunted out of operation.

The pilot switch I01 is controlled by an electromagnetic winding I06 connected through conductor 90 and switch contacts 44-45 of the protector device to output line 04 and through grounded conductor IIO to output line 03.

Upon the output generator voltage rising above a predetermined value the relay switch arm I01 is biasedby relay I09 so as to open contact I06 and close a contact I I I. The latter action opens the shunt circuit of relay winding I05 causing the winding I05 to close switch I04 whereupon the compensating winding IOI is connected into operation and to the equalizer line I02.

Moreover upon relay switch I01 closing contact III a current winding II 2 is connected across the open line switch 36 by a conductive passage leading from line 64 through switch con tacts 44-45 01 the protective device 32, conductor 90, switch I01, contact III, current winding I I2, and a conductor II3 to the main bus line 05. The winding I I2 is wound about a permanent magnet H4 and is arranged to cooperate therewith so that upon a current flow from the gener-' ator 00 to the main bus line 05 the magnetic eflect of coil H2 and permanent magnet II4 will exert an additive eflect biasing a relay switch II5 to close contact H6.

The relay switch H5 is connected by a conductor II1 to conductor 04 and through switch contacts 55 and 56 to the output line 04. The contact H6 is connected by conductor II8 through the switch contacts 46-41 of the pro- 6 tector device 32 to the line relay 01. The closing of switch II6 will then cause energization of the line relay 01 and the closing of the line-switch 36 which will shunt difierential current winding 2 out of operation.

Cooperating with the winding H2 is a second current winding I connected across the interpole compensating winding 02 through conductor I2I and grounded conductor I22. So long as the current flow is from the generator 00 to the main line 65 the winding I 20 will exert an additive effect with the permanent magnet II4 tending to hold the control switch II5 closed. However in the event the output of the generator decreases to such a point that the current output 01 the generator is below that of the main bus line 65, then the winding I20 will exert a dif ferential eifect with the permanent magnet II4 tending to decrease the magnetic effect acting on the relay switch I I5 so that the switch II5 under spring force is biased to a position opening contact I I6. The latter action deenergizes the winding 01 causing line switch 86 to open.

As shown schematically in Figure 6 and speciflcally in Figures 2-5 switch contacts 46-41, 44-45, 55-56, 44A-45A, and 46A-41A may be closed by manually actuating the push rod 24. The same may be latched in the latter position through action of the latch mechanism 2I as heretofore explained.

The closing of switch contacts 46A-41A connects a sensing coil, the electromagntic winding I0, across the field BI 01 the generator 00 through conductors I30 and I3I.

line switch 86 to open and efiect deenergization of;

current winding I20. Thecontacts 44-45 open the potential circuits for the carbon pile voltage coil 96, relay voltage coil I05, and relay voltage coil I09. Deenergization of coil I09 causes in turn relay switch I01 to open contact III and thereby the circuit to diiierential current coil I I2. The main contacts 55-56 open the generator field circuit. The auxiliary contacts 44A and 45A open the circuit of the compensating winding IOI. The auxiliary contacts 46A and 41A open the circuit of the sensing coil I0.

As an alternative arrangement the switch 44A-45A may be normally open so that upon the latch 2I releasing the reset rod 24 the switch 44A-45A may close a circuit to energize a warning device such as an electric light or bell to indicate that the overvoltage protector has disconnected one generating system from the main bus.

As shown diagrammatically in Figure 6 and claimed in copending application Serial No. 119,724, filed October 5, 1949, a plurality of generators 80, 00A, 80B and 600 may be parallel connected to the main bus line 05. Each of the enerators 80A, 00B and 600 has similar control equipment to that indicated generally by numeral 90 and indicated herein as 90A, 90B and 30C, respectively. Likewise the generators 00A, 00B and 600 have protector devices similar to the protector device 32 of the generator 00 and indicated herein as 32A, 32B and 32C, respectively.

. Surge voltages due for example to a iaulted tector of the other non-faulted generators. This conditivin is achieved by the incorporation of the copper washers H, which act as shorted turns on the sensing coil ll. Such shorted turns in an inductive system generate flux that opposes the flux generated by the coil ll. Thus during change in the energizingcurrent of the coil II this opposition retards the build-up of suflicient coil flux to actuate the armature ii, so as to provide a suflicient time lag to prevent tripping of the latch 2| by surge voltages. This time lag is fur-- the! insured by the construction or the armature ii and latch II. The armature II has studs 35 arranged to trip the latch 2i after the armature has traveled about two-thirds of its distance to the electromagnet i0. This construction also permits the tripping voltage to be unaiiecied by friction.

Once the overvoltage protector has operated the reset rod 24 may be pushed down to reset the mechanism by manually compressing the bellows 34.

The overvoltage protector is sealed within the casing 32 so as to protect the same from moisture, dirt and atmosphere.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements 01' the parts may be made to suit requirements.

What is claimed is:

1. An overvoltage protector for a generator having a field circuit for controlling the output thereof, comprising a main control switch for connecting said generator to said output, a main electromagnetic winding circuit for controlling said main switch, a regulator connected in said field circuit, a control winding for said regulator and adapted to be connected across the output of the generator, an overvoltage protective relay means including a third electromagnetic winding adapted to be connected across the field circuit, a plurality of switch elements operated as a unit by said'third electromagnetic winding, said switch elements being arranged to open said main winding circuit, said field circuit, said control winding circuit, said main electromagnetic winding circuit, and said third electromagnetic winding circuit, and a short circuited turn about said third electromagnetic winding and so arranged as to retard operation of said switch elements upon a transitory voltage surge aii'ecting said third wind-' 2. An overvoltage protector tor a generator having a field circuit for controlling the output thereof comprising -a main control switch for connecting saidgenerator to said output, a main electromagnetic winding circuit for controlling said main switch, a regulator connected in said field circuit, a control winding for said regulator and connectable across the output of the generator, an overvoltage protective relay means including a third electromagnetic winding connectable across the field circuit, a plurality of switch elements, lost motion latch means operably connecting said switch elements and said third electromagnetic winding; saidswitch elements being arranged to own said main winding circuit, said field circ'it, said control winding circuit, said main electromagnetic winding circuit, and said third electromagnetic winding circuit, and a short circuited turn about said third electromagnetic winding and so arranged as to retard operation of said switch elements upon a transitory voltage surge affecting said third winding.

3. An overvoltage protector for a generator having a field circuit for controlling the output thereof comprising a main control switch for connecting said generator to said output, a main electromagnetic winding circuit for controlling said main switch, a regulator connected in said field circuit, a control winding for said regulator and adapted to be connected across the output of the generator, an overvoitage protective relay means including a third electromagnetic winding adapted to be connected across the field circuit, a plurality of switch elements, lost motion latch means operably connecting said switch elements and said third electromagnetic winding; switch elements being arranged to open said main winding circuit, said field circuit, said control winding circuit, said main electromagnetic winding circuit, and said third electromagnetic winding circuit, and a short circuited turn about said third electromagnetic winding and so arranged as to retard operation of said switch elements upon a transitory voltage surge afiecting said third winding, and manually operable means for actuating said switch elements to a closed position.

ROBERT L. BROWN.

No references cited.

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