US2177109A - Voltage regulator - Google Patents

Description

Oct. 24, 1939. HILL 2,177,109

VOLTAGE REGULATOR Filed April 29, 1935 3 Sheets-Sheet 1 lllll Illl Oct. 24, 1939. H 2,177,109

VOLTAGE REGULATOR Filed April 29, 1955 3 Sheets-Sheet 2 Oct. 24, 1939. H. HILL VOLTAGE REGULATOR Filed April 29, 1935 3 Sheets-Sheet 3 Patented Oct. 24, 1939 UNITED STATES PATENT OFFICE lis-Chalmers' Manufacturing Company,

Mil-

waukee, Wis., a corporation of Delaware Application April 29,

13 Claims.

This invention relates in general to improvements in voltage regulators and particularly to tap changing systems and apparatus for transformers which are utilized to maintain a constant voltage on a circuit.

It is an object of this invention to provide an improved system and apparatus of the above type which is more simple in construction; more rugged and reliable in operation and which may be more economically manufactured than such systems and apparatus heretofore proposed.

It is another object of this invention to provide in a tap changing system of the above type a mechanism for moving the tap changing contacts from one position to the next position with an exceedingly fast snap action yet stopping the contact after such snap action at its exact tap position without shock to the apparatus.

It is another object of this invention to provide an improved system of and apparatus for ontrolling the motor which operates the quick break mechanism in regulators of the abovetype so as to maintain a constant circuit voltage.

It is another object of this invention to provide a means for manually operating the quick break mechanism of tap changers of the above type whereby safety from interference of the automatic control is maintained during manual operationand whereby the oil-tight relation of the tank a d tlie manually operated shaft which extendst erethrough is easily maintained.

It is also an object of this invention to provide a new method of assembling electrical apparatus of the type having cores and windings submerged in a tank containing insulating liquid.

These and other objects and advantages are obtained by this invention various novel features of which will be apparent from the description and drawings herein and will be more particularly pointed out in the claims.

An illustrated embodiment of this invention is shown in the accompanying drawings in which:

Fig. 1 is a front elevation, with the casing partly cut away so that the tap changing switch compartment can be viewed, of a tap changing mechanism embodying the present invention.

Figs. 2, 3 and 4 are views of the quick break mechanism taken on the line II--II of Fig. 5 and showing the quick break mechanism in the various steps of moving the tap switch from one position to the next.

Fig. 5 is a partial section view taken on the line VV of Fig. 1.

Fig. 6 is a view taken on the line IIII of Fig.

1935, Serial No. 18,829

5 showing the quick break mechanism in another position and showing the reversing switch.

Fig. 7 is a detailed view showing the safety stop feature of the reversing switch mechanism.

Fig. 8 is a view taken on the line VIIIVIII of Fig. 5.

Fig. 9 is a detailed view of the latch mecha- IllSm.

Fig. 10 is a view taken on the line X--X of Fig. 11.

Fig. 11 is a detailed view of the means for manually operating the tap changing mechanism of Figs. 1 and 5.

Fig. 12 is a schematic diagram illustrating the essential elements of the control system and apparatus of the present invention.

As shown in Fig. 12 the voltage regulating system of the present invention consists generally in means for maintaining the voltage supplied to a load circuit I9 by a source of current supply l8 at a constant value regardless of load changes. regulation is accomplished by adding to the load voltage or subtracting therefrom the voltage of the transformer 23 which voltage is varied by energizing the transformer 23 from various taps of an exciting auto-transformer connected across the supply system l8. The primary winding 22 of the transformer 23 is connected, in boosting or bucking relation to the line voltage IE, to the various taps on the winding by means of a dial tap switch generally designated as 26. The bucking or boosting relationship of the voltage supplied to winding 22 is controlled by a reversing switch generally designated as 30.

The movable contacts of the dial switch are moved from one position to the next with a snap action, the motive power being supplied by a capacitor type reversible motor 21. The motor 21 is operated in one direction or the other in response to changes in load circuit voltage to raise or lower the voltage on the load circuit. The motor 21 is reversibly controlled through a time delay mechanism generally designated as 28, by a primary relay or contact making voltmeter generally designated as 29. The primary relay 29 is responsive to voltage changes on the load circuit l9.

The tap changer mechanism as shown in Figs. 1 and 5 comprises in general a casing l5 forming the lower or tap changing compartment, a casing l6 forming an upper or transformer winding compartment and a casing ll forming a control compartment. The tap changing compartment and the transformer winding compartment generally contain oil or similar insulating liquid.

This

An oil-tight relation is maintained between these two compartments in order that oil carbonized by any arcing of the tap changing switches will not reduce the insulating strength of the oil in the transformer winding compartment.

The tap changing switch generally comprises an insulating panel 3| upon which are mounted the stationary contacts I50 to I58 as shown in Figs. 5 and 8. These contacts are connected to the various taps on the winding by means of conductors which are carried through the top member of the casing 5 in a gang bushing 34. The bushing 34 is suitably held in the member 68 in a manner to maintain the oil-tight relation between the two compartments. The series transformer 23 is mounted on a bridge member 36 bridging over the bushing 34. The core of the winding 28 is suitably fastened to the member 60 and mounted thereon is the coiland winding of the preventative auto-transformer 25.

The moving contacts of the tap changing switch are carried on an insulating member 39 which is in the shape of a key hole as shown in Fig. 8. There are two movable contacts 4|] and 4| and each comprises two spring held contact pieces one bearing on one side and the other bearing on the other side of the face of the stationary contact member. The movable contacts 40 and 4| are connected respectively to current collecting brushes 42 and 43 which bear respectively on collector rings 31 and 38 of conducting material. As shown in Fig. 12, the collector rings 31 and 38 are connected to the ends of the preventative auto-transformer for a purpose which will be explained hereafter. The collector ring 38 is formed as an upstanding portion of a bearing member for shaft 44 which bearing member has a shoulder 49 clamped rigidly against the panel 3| by such means as a nut 58. The shaft 44 carries the movable contact carrying member 39 and is coupled to a shaft 46 by means of an insulating coupling 45.

Two upright members 5| are rigidly fastened to cross pieces 2| and 32 and support a notched disk 41 rigidly fastened thereto in a suitable manner as by screws as shown. This notched disk 41 forms a bearing for the member 33 and the coupling 45. The shaft 46 is suitably connected at one end to the member 33 so as to rotate therewith. Mounted on the shaft 46 is a member 12 which carries a latch '14 which cooperates with the notches 88 in the disk 41. The member 12 is fastened to rotate with the shaft 46 by suitable means shown as a pin 13 and mounted on the left hand end of the shaft 46 as viewed in Fig. 5- is a pinion 53, the function of which will appear later. The pin-ion 53, the shaft 46,

' the member 12, the latch 14, the member 33, the

coupling 45, the contact carrying member 39, the shaft 44 and the movable contacts and 4| all move together with a rapid snap action.

The novel quick break mechanism of the present invention provides the double function of translating the relatively slow uniform rotation of the motor 21 into the intermittent exceedingly rapid snap action rotation of the parts above mentioned and further provides for the stopping of the snap acting moving parts in the next tap position without shock to the apparatus. The motor shaft 59 is connected to a gear 64 by means of a reduction gearing, the gear 64 being mounted on the shaft 46 but rotating freely relative thereto. Suitably fastened to the gear 64 is a substantially triangular shaped member 65 which is fastened to the gear 64 so as to rotate therewith by a suitable means shown as a key 66. The members 65 and 64 rotate together freely on the shaft 46. The triangular member 65 has a long extension 61 which has the double function of operating the reversing switch 38 and providing a positive stop for the tap changing switch and in its limit position as will be more fully explained hereinafter. Mounted on the member 65 are two stops 68 and 69 which move with member 65 as it moves. Two arms 18 and 19 are mounted on the shaft 46 so as to rotate freely relative thereto, the arm 18 cooperating with the stop 68 and the arm 19 cooperating with the stop 69. Connected to one end of the arm 19 is a spring 8| the other end of which is connected to one side of the latch carrying member 12. Similarly, a spring 82 is connected between the outer end of the arm 68 and the other end of the latch carrying member 12. These spring members 8| and 82 supply the forces necesssary for the snap action of the tap switch contact.

The latch member 14 is pivoted at '15 between upstanding portions of the member 12 as shown more clearly in Fig. 9. The latch 14 has springs 11 which bias it to a position engaging the notch 8|] of the disk 41. The latch 74 carries a bolt 16 the head of which is engaged by the' arm 18 or 19 to disengage the latch from a notch 80 of the disk 41.

The operation of the quick break mechanism is shown more clearly in Figs. 2, 3 and 4. Fig. 2 shows the mechanism as it has stopped when the motor 21 has come to rest after movement of the tap switch to the position there shown. If the motor is now energized to move the tap changing switch to the next position in a clockwise direction the gear 64 and the triangular member 65 will be slowly rotated in a clockwise direction by the motor shaft 59 through the gear reduction. As the triangular member 65 takes the position as shown in Fig. 3 the stop member 69 is brought to bear against the arm 19 forcing it to rotate in a clockwise direction about the shaft 46 thereby stretching the spring 8| as shown in Fig. 3. The left hand end of the spring 8| as viewed in Fig. 3 cannot move as it is rigidly connected to the member 72 which is rigidly held by the latchto the stationary disk 41. As the spring 8| is stretched movement of the stop 68 in the clockwise direction allows spring 82 to contract and move in a clockwise direction until it is stopped against a lug or abutment 10 as shown in Fig. 3. In this position a very slight amount of tension is kept in the spring 82 to hold the coils thereof in place. As the member 65 is further rotated in a clockwise direction, the end of the arm 19 is brought into contact with the bolt 16 and forces the latch 14 out of the notch 8|) as more clearly shown in Fig. 9. As soon as the latch 14 is released, the member l2 and therefore the shaft 46 and the contacts 48 and 4| are very rapidly moved to the position as shown in Fig. 4 by the tension of the spring 8|.

Due to the exceedingly rapid movement of the member 12 and the inertia of the shaft and moving contact, the member 12 tends to move past the position as shown in Fig. 4, however, upon any movement of the member 12 past this new position brings the contact arm 18 into engagement with the stop 68 and any further movement of the member 12 in a clockwise direction will stretch the spring 82. This stretching of the spring 82 effectively stops the member 12 in its new position without any shock to the mech- 7 anism and also returns the member 12 in a' counterclockwise direction sufliciently to allow the latch member to drop into the new notch 80. If the new tap position does not provide the voltage change necessary to meet the load requirement the motor 21 remains energized and the same cycle of operation is again repeated. The operation of the mechanism in the reverse direction is similar but with the spring 82 providing the force necessary to move the contact to the next position and the spring 8| providing the shockless stop and the positioning for the latch to drop into the new notch.

The pinion 53 on the shaft 46 cooperates with a member 54 which has teeth on its lower end forming a rack. The relative position of the member 54 is shown in dotted lines in Fig. as this member would not show in this section view, being to the right of the pinion 53 as viewed in Fig. 1. The member 54 is carried by the upright 52 and has a position indicator 55 which in conjunction with a numbered scale shows exactly the position of the tap changing switch. Also mounted on the upper end of the member 54 is a switch operating member 56 which operates limit switches 51 and 58 to break the motor circuit when the tap changing switch is in limiting boost or buck position. It is to be noted that the position indicator 55 does not move with a uniform motion but moves with a quick motion corresponding to the movement of the tap switch contact, thereby always showing exactly the position of the tap switch.

The moving contact of the dial switch makes two complete revolutions in moving from the position of maximum boost to the position of maximum buck. As the tap switch goes through the neutral position, that is, the position where the load voltage corresponds to the line voltage, the reversing switch 30 is operated from one position to the other by the member 61. The reversing switch comprises a moving contact 94 and a contact carrying member 93 which is mounted on a pivot secured to the dial switch panel 3|. Also mounted on the panel 3i are the two fixed contacts 95 and 96 one connected to each end of the exciting auto-transformer winding 20. Mounted on the under side of the member 93 are two round headed bolts or pins 98 which cooperate with a roller 99 mounted at the outer end of the reversing switch member 61 to move the reversing switch from one contact making position to the other.

The cooperation of the roller 99 and bolts 96 is shown in Fig. 6 in the dotted line position of the roller and member 61. In the position shown in Fig. 6 in dotted lines, the member 61 has been rotated in a counter-clockwise position from the full line position shown and further movement thereof will rotate the bolts 98 in a clockwise direction so that contact 94 will leave contact 96 and engage contact 95. The full line position of Fig. 6 shows the maximum buck position and in this position the limit switch 58 should operate to deenergize the motor 21. However, failure of this limit switch to properly operate would cause serious trouble and probable burning out of the winding so a safety stop is therefore provided by the end of the operating member 61 and the end of the reversing switch member 93. The end of the member 93 is cut at the same angle as the angle of the upper part of the member 61 and a notch I02 is provided for the roller 99 so that a solid stop is provided as shown more clearly in Fig.

This prevents undue operation of the regulating apparatus, that is, a voltage change whichfor example may be due to a surge -condition, is merely a transient effect and if such change immediately ceases no movement of the regulating apparatus should occur. A time delay is therefore desirable between the action of' the primary relay and the operation of the tap changing mechanism. The control system of the voltage regulator of the present invention as shown in Fig. 12 provides the desired time delay and also provides a control system sensitive to small changes in voltage yet is rugged and simple and is provided with safety features.

In the prior art Where primary relays such as 29 have been utilized to initiate the control of tap changing mechanism it has been the usual process to energize these primary relays from a potential transformer connected across the load circuit, in order to transform from the line voltage down to approximately 120 volts which is the required voltage for the usual primary relay. While this arrangement is generally satisfactory from the operating point of view it requires the use of a potential transformer which necessarily has to be wound with very fine wire and would ordinarily require protection by means of high tension fuses. A potential transformer wound with such fine wire is not as reliable as the other units in the transformer compartment and hence it would be preferable to use'some other means if possible. Likewise it is not desirable to mount high tension fuses in the transformer compartment. If the primary relay 29 were energized merely from a winding such as shown as 86 the voltage of this winding would not increase and decrease in proportion to the voltage on the load side of the regulator. Such a winding is satisfactory for obtaining voltage for operating the driving motor but obviously is not satisfactory for operating the primary relay.

In order to make possible the use of a winding such as 86 and thereby eliminate the hazard of a potential transformer connected 'across the line the novel arrangement shown in Fig. 12 is utilized in the present invention. An auxiliary winding 86 is used which is connected in series with the secondary of a compensating potential transformer 81 connected across the primary 22 of the series transformer 23. When the regulator is on the zero buck or boost position, that is, the neutral position, the voltage across the primary of potential transformer 8'! is zero, hence no voltage is added to the voltage developed by the auxiliary winding 86 which gives the correct voltage for the primary relay 29. As the tap changer moves off the neutral position to raise or lower the voltage, the voltage across the primary of the compensating potential transformer 81 is increased which adds to or subtracts from the voltage of the auxiliary winding 86 so that the voltage applied through the primary relay is at all times proportional to the load circuit voltage. The use of a potential transformer such as 81 has several advantages over the use of a potential transhas only one-tenth of the load circuit voltage across it and can therefore have a smaller core section than a potential transformer connected across the load circuit. This means that the compensating transformer 81 can be made with very much heavier wire than would otherwise be feasible thereby making a much more reliable unit. Also, the space required for the unit is much smaller and with a higher degree of reliability obtained the compensating transformer can be solidly connected into the circuit so that no fuses are required.

The energizing coil of the primary relay 28 is therefore energized from the transformer 81 and the winding 86. The core member of the primary relay is biased against the weight of the core by means of a spring so that both contacts 84 and 85 are open when the voltage of the winding 86 only is applied to the winding 83. Upon a decrease in the load circuit voltage, the voltage across the winding 20 and therefore across the winding 83 decreases and the spring pulls the moving contact member of the relay 28 into engagement with the contact 85. Closure of these contacts completes a short circuit around the winding 80 of a shading pole motor I60 causing the armature I04 to rotate the shaft I05 through reducing gears in the arrow direction. Mounted on the end of the shaft I05 is a disk I06 having lugs I01 which may be positioned in any one of the holes IOI. When the shaft I05 and hence the disk I06 is rotated one of the lugs I0'I engages an upstanding portion I08 of an arm I08 mounted to rotate freely on the shaft I I4. Movement of the upstanding portion I08 to the right as viewed in Fig. 12 raises the left hand end of the arm I08 thereby tipping the mercury relay 82.

Closure of the contact of the mercury switch 82 so energizes the fields I24 and I25 through the capacitor I21 that the motor 21 rotates in such direction as to move the dial switch 26 through the next tap'position to increase the voltage supplied to the load circuit by the transformer 23.

Also mounted on the shaft I05 are two cams H5 and H6 which operate switches Ill and I I8 respectively. As the shaft turns in the arrow direction the contacts II8 will be closed whichshort circuit the winding 88 through the resistance II8. This tends to rotate the armature I04 in the reverse of the arrow direction, however, due to the resistance I I8, this energization is less than that of winding 80 so the armature rotates in the arrow direction. However, upon movement of the tap switch to its new position and upon change in the load voltage accompanying such movement the contact making voltmeter 28 comes to balanced position thereby opening the short circuit about the winding 80 if the change in voltage has been suificient to regulate the load voltage properly. The energization of the winding 88 will then run the motor I60 in the reverse of the arrow direction until the disk I06 returns to the neutral position whereupon the cam II5 allows the contact II8 to open. The cam H5 operates in a similar manner upon reverse operation of the motor I60. An additional bar II3 mounted on the shaft H4 so as to freely rotate thereon provides protection against both mercury switches 8| and 82 being operated at the same time. This bar I I3 has pins at either end so that upon operation of one mercury switch the other one is held in non-operative position.

Provision is made for manual operation of the mercury switches 8I and 82 by means of the arm IIO which is keyed to the shaft Ill so as to rotate therewith. An interlock is provided to prevent automatic control by the primary relay while the manual control is used. Due to the interlocking segment I20 on the shaft Ill, the shaft Ill can be manually operated to close one mercury switch or the other only after the switch I2I has been manually operated to open its contacts, which prevent operation of the motor I60. Thus the tap changing mechanism can be operated to'lower or raise the voltage without any interference from the automatic control. This provides for manual operation utilizing the same switches that are utilized for automatic operation, and avoids additional contacts or change of circuit connection to provide this manual control.

Provision is also made for manual operation of the tap changer mechanism without utilizing the motor 21. In the tap changers of the prior art provision for operation of this type has brought up the problem of extending a shaft which normally runs at high speed through the casing I5 and still maintaining an oil-tight relation between shaft and casing. In the present invention this problem is avoided by having a short shaft I36 extending through the casing I5, which shaft is stationary in normal operation of the tap changer thus eliminating the necessity of a high speed stuffing box. For manual operation the shaft I36 is coupled to the motor shaft 58 in the novel manner as shown more clearly in Figs. 10 and 11. The shaft I36 has a square head I31 which when the shaft I36 is moved to the left as viewed in Fig. 11 engages the square edges of the member 63 whereby rotation of the shaft by the crank I28 rotates the motor shaft and thereby the tap changing mechanism. During normal operation of the tap changing mechanism, the shaft I36 is held to the right as viewed in Fig. 11 so that the head thereof is in the dotted line position and is held in such position by the cover member I 38 as shown in Fig. 5. The crank I29 has a set screw which is utilized to engage the shaft I36 to pull the head thereof into the full line position as shown in Fig. 11. As it is necessary that during normal operation the electrical control be disabled, provision is made for carrying the crank I29 during normal operation as shown in Fig. 5. During normal operation the crank is held on a D-shaped stub I35 secured to the member 52 and the handle of the crank I28 holds a switch I33 closed by means of the set screw tightened down on the stub I35. Upon removal of the shaft from the stub, the switch I33 opens due to spring bias and opens the motor circuit.

This embodiment of the present invention utilizes a newmethod of assembling transformers or electrical apparatus of a similar type in a casing for containing oil or insulating liquids. The transformer structure is assembled on the member 60 which forms the top of the'tap changer compartment and the bottom of the transformer compartment. This can be easily done and the electrical connections of the windings easily made before the casing I6 is lowered into place. The casing I6 is then lowered around the transformer structure and is held in oil-tight relation with the floor member 60 by means of bolts (not shown) through the flanges 35 and a gasket between the flanges. This method has great advantages over that of the prior art where a tank was made in one piece and the transformer built right into the tank, not only in simplicity of manufacture and ease of assembling, but also providing for accessibility for purposes of inspection and repair.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a voltage regulating system, an alternating current circuit, a tapped transformer winding connected to said circuit, a dial switch having its fixed contacts connected to the taps of said winding, a contact rotatable from connection with one of said fixed contacts to connection with the next adjacent fixed contact to define a new regulating position, means for latching said rotatable contact in a tap connecting position, a motor, means operable in response to a change in load conditions on said circuit for continually operating said motor at a substantially uniform speed, means for coupling said motor to said rotatable contact, said means comprising means for unlatching said latching means and for translating the relatively slow angular motion of said motor to a relatively rapid step-by-step motion of said rotatable contact, and means for utilizing said motion translating means to stop said rotatable contact in said new position.

2. A tap changing mechanism comprising a dial switch provided with a plurality of fixed contacts and a rotatable contact cooperating with said fixed contacts, a shaft carrying said rotatable contact, a disk providing a bearing for said shaft and arranged to be rigidly held against rotation therewith and provided with apertures therein corresponding to the positions of said fixed contacts, a second shaft electrically insulated from said first shaft, a member rigidly carried by said second shaft, a latch carried by said member and arranged to latch in one of said apertures of said disk, a first latch trip arm freely rotatable on said second shaft, a second latch trip arm freely rotatable on said second shaft, a first spring connecting said first arm to said member and providing a biasing force in one direction, a second spring connecting said second arm to said member and providing a biasing force in the opposite direction, a second member freely rotatable on said second shaft and provided with a first stop arranged to bear against said first arm in a direction opposing the biasing force of said first spring and said second member provided with a second stop arranged to bear against said second arm in a direction opposing the biasing force of said second spring and means for rotating said second member at a substantially uniform slow*velocity whereby said rotatable contact is continually moved from one of said fixed contacts to the adjacent fixed con tact with a rapid snap action and stopped at said adjacent fixed contact.

3. In a voltage regulating system, an alternating current circuit, a transformer provided with a tapped winding connected to said circuit, a dial switch provided with fixed contacts connected to the taps of said winding and provided with a movable contact cooperating with said fixed contacts, a casing containing said dial switch, insulating liquid in said casing, means for rotating said movable contact to change the voltage supplied by said winding to said circuit, means for controlling said contact rotating means in response to changes of voltage on said circuit.

a shaft extending through an aperture in said casing, means for manually fotating said shaft, said means comprising means for operatively disabling said controlling means, means for coupling said shaft to said contact rotating means, and means sealing said aperture and operatively disabling said coupling means.

4. In an electrical apparatus, a casing, insulating liquid in said casing, a tap changing switch in said liquid, motor means for rotating one contact of said switch, a shaft extending through said casing, manually operated means for rotating said shaft, means in said liquid for coupling said shaft to said motor means, and means for operatively disabling said coupling means comprising a cover for the end of said shaft extending through said casing.

5. A voltage regulating system comprising a current supply circuit, a load circuit; a regulating transformer connecting said circuits and provided with an exciting winding connected across said supply circuit, said transformer having an additional winding connected in said load circuit, means for varying the effective number of turns of one of said windings whereby the voltage of said load circuit is raised or lowered relative to the voltage of said supply circuit, said means comprising a reversible motor and switch contact means for connecting said motor to said supply circuit, means'interlocking said switch contact means so that said motor cannot be energized for rotation in both directions at one time, means for manually operating said switch contact means, and means including said last said means providing an interlock between said switch contact means and said manually operating means whereby either of said means is disabled when the other of said means is operatively effective.

6. A tap changing apparatus comprising a winding provided with taps thereon, a tap changing switch provided with fixed contacts and a movable contact cooperating therewith, a motor, means coupling said motor to said movable contact providing snap action thereof from one tap position thereof to the next tap position thereof, a casing adapted to contain insulating and lubricating liquid surrounding said tap changing switch, said motor and said coupling means, a cover member for said casing, means for supporting said winding on said cover member, casing wall members, means utilizing said cover member and said wall members to provide a liquid tight easily detachable casing for said winding separate from said first said casing, a cover for said winding casing, and high voltage connections for said winding extending through said winding casing cover.

7. A tap changing mechanism comprising a tapped winding, an additional winding, a tap changing switch provided with a movable contact providing connection of said additional winding to said tapped winding at various taps thereon, a motor, means coupling said motor to said movable contact providing snap action thereof from one tap position to the next tap position, a liquid tight casing surrounding said tap changing switch, said motor and said coupling means to form a tap changing compartment, a cover for said casing, means for supporting said windings on said cover member, casing wall members, means utilizing said cover and said wall members to provide a liquid tight easily detachable casing for said windings to form a transformer compartment separate from said tap changing compartment, means comprising said cover and one of ment, and means in said control compartment for indicating the position and movement of said movable contact.

8. A tap changing mechanism comprising a tapped winding, an additional winding, a tap changing switch provided with a movable contact providing connection of said additional winding to said tapped winding at various taps thereon, a motor, means coupling said motor to said movable contact providing snap action thereof from one tap position to the next tap position, a liquid tight casing surrounding said tap changing switch, said motor and said coupling means to form a tap changing compartment, a cover for said casing, means for supporting said windings on said cover member, casing wall members, means utilizing said cover and said wall 'members to provide a liquid tight easily detachable casing for said windings to form a transformer compartment separate from said tap changing compartment, means comprising said cover and one of said wall members providing a control compartment, means in said control compartment for deenergizing said motor when said movable contact is in a limit position, and means in said control compartment for operating said deenergizing means and for indicating the position and movement of said movable contact.

9. In a voltage regulating system, an alternating current circuit, a tapped transformer winding connected to said circuit, a dial switch having its fixed contacts connected to the taps of said winding, a contact rotatable from connection with one of said fixed contacts to connection with the next adjacent fixed contact to define a new regulating position, means for latching said rotatable contact in a tap connecting position, a motor, means operable in response to a change in load conditions on said circuit for continually operating said motor at a substantially uniform speed, means for coupling said motor to said rotatable contact, said means comprising means for unlatching said latching means and for translating the relatively slow angular motion of said motor to a relatively rapid step-by-step motion of said rotatable'contact, means for utilizing said motion translating means to stop said rotatable contact in said new position, and means for indicating the position and movement of said rotatable contact, said means comprising a mechanical connection between said indicating means and said rotatable contact coupling means.

10. Electrical apparatus of the character described comprising tap changing mechanism immersed in a casing containing insulating liquid, transformer structure mounted on the top of said casing and electrically connected to said mechanism, removably connected walls surrounding said transformer structure in liquid tight relation to said casing top.

11. A tap changing apparatus comprising a winding provided with taps thereon, a tap changing switch connected to said taps, a first casing adapted to contain insulating and lubricating liquid surrounding said switch, a cover member for said casing, means for supporting said winding on said cover member, casing wall members detachably connected to said cover member so as to provide a second liquid tight casing surrounding said winding and separate from said first casing.

12. In manually non-portable electrical apparatus, a base member, a plurality of relatively heavy cores and windings supported on said base member, insulating liquid surrounding said cores and windings, means for electrically interconnecting said windings after positioning thereof on said base member, and means comprising relatively light weight metal casing walls easily detachably connected to said base member for enclosing said cores and windings and said liquid after interconnection of said windings and for providing accessibility for inspection and repair of said cores, windings and connections.

13. A heavy, manually non-portable tap changing apparatus comprising a core, a tapped winding thereon, a tap changing switch, a first casing adapted to contain insulating liquid surrounding said switch, a cover for said casing, means for supporting said core and winding on said cover member, electrical conductors detachably connecting said switch and said winding, and means comprising relatively light weight metal casing wall members easily detachably connected to said cover member to provide a second liquid tight casing surrounding said core and winding and for providing accessibility for inspection and repair of said core and winding and connection and disconnection of said conductors to and from said winding.

LELAND H. HILL.

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