US2020941A - Electrical apparatus - Google Patents

Description

NOV. 1'2, 1935. H C. GUHL ELECTRICAL APPARATUS Filed May 3, 1933 2 'Sheets-Sheet 2 [zo T27/ /3/ -132 -/7// auf' /3/ -laa Sfar Combcs Bring-cd WITNESSES: @7

ATTORNE Patented Nov. l2, 1935 inghouse Electric Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania i Application May 3, 1933, Serial No. 669,192

5 Claims.

My invention relates to electrical apparatus such as polyphase transformers In which provision is made to vary the ratio of transformation between the primary and secondary windings and 5 to vary the connections between the primary windings of the transformers for varying the current output from the secondary windings thereof.

My invention is particularly applicablev to transformers employed for supplying power to l electric arc furnaces, although' it is not limited in its application to such service.

In .polyphase transformers employed for supplying power to electric arc furnaces, it is possible to control the'voltage of the secondary windings l and, therefore, the current output therefrom by controlling the ratio of voltage transformation between the primary and secondary inductively related windings, by changing the tap connections to the primary windings to eliminate portions thereof from the winding circuit, by changing the connections between the several primary windings, and by inserting additional outside reactance in circuit with the several primary windings.

It is an object of my invention to provide a transformer of the above indicated character and tap changing switching mechanism therefor so constructed and so operated as to provide a relatively large number of voltage steps with a relatively small number of taps to the transformer windings.

Other objects of my invention and advantages thereof will appear from the following description of apparatus and circuits embodying certain preferred embodiments thereof.

Referring to the drawings, Figure 1 is a diagrammatic view illustrating circuits and apparatus organized in accordance with one preferred embodiment of my invention.

Fig. 2 is a chart showing the sequence of operation of the switches forming part of the tap changing equipment illustrated in Fig. l.

Fig. 3 is a diagrammatic view illustrating circuits and apparatus employed in the second preferred embodiment of my invention, and

Fig, 4 is a chart showing the sequence of operation of the tap changing equipment illustrated in Fig. 3.

Referring to Fig. l of the drawings, transformer primary'windings I, 2 and 3 are illustrated, one end of which is connected, respectively, to the three phase conductors A, B and C by meansof the three pole circuit breaker I I, and inductively related, respectively, *to three secondary windings 4, 5 and 6 that are illustrated as connected in delta relation to each other and to the electrodes l, 8 and 9 of an electric furnace. Three reactor windings I2, I3 and I4 are illustrated as associated respectively with the three primary windings I, 2 and 3. A tap changing mechanism illustrated generally at I5, is provided comprising a set of tap changing switches, indicated as TCI, on the drawings and a set of tap changing switches, indicated as TC2 on the drawings. The tap changer TCI l0 comprises three tap changing switches for the three phases A, B and C, respectively, of the three-phase circuit, and a shaft I6 for actuating the three moving contact members I1, I8 and I9, respectively, of the three tap changing switches. 15 The tap changer TC2 also comprises three tap changing switches and a shaft 2I that operates the three moving elements 22, 23 and 24 thereof, respectively, for the three phases A, B and C of the three-phase circuit. A'

Associated with the -movable contact members I1, I8 and I9 of the three switching mechanisms comprising tap changer TCI (on drawings) are sets of fixed contact members, similarly numbered 25 to 32, inclusive, for the three tap changing 25 switches associated with the windings I, 2 and 3 representing phases A, B and C, respectively, of the three-phase circuit. The moving elements 'of the three switching mechanisms will. therefore, bridge similarly positioned and similarly 30 numbered contact members for a given position of the tap changer mechanism to complete similar circuits respecting the three windings I, 2 and 3 of the three phase circuit. For the same reason, the three sets of fixed contact' members 35 associated with each of the three switching mechanisms of tap changer TC2 and similarly cooperating, respectively, with themovable contact members 22, 23 and 24 thereof, are similarly numbered 33, 34 and 35 for the three switching 40 mechanisms. The position of the complete tap changer mechanism is determined by the position of the operating shaft 36 which may be driven either manually or by an electric motor, and

l which is connected to a gear 31 which cooperates 45 with a gear 38 of a Maltese cross gear mechanism for intermittently operating the shaft I6 through a given arc during a portion of each revolution of the shaft 36. The shaft I6 is operatively connected to the shaft 2Iof the tap changer TC! by 50 means of the bevel gears 39, a shaft 4I, the gears 42 and the gears 43 and 44 of a Maltese cross gear mechanism.

The illustrated position of the several switches comprising the tap changing mechanism corre- 55 spends to position i in the chart of Fig. 2, in which the movable elements I'I, I8 and I9, respectively, ne tap changer TCI each bridge rs 25 and 26 of their respective 'tches and the movable contact and 24 of the tap changer TC2,

circuit switches thus connectbe three primary windings I, 2 Lich with the reactor windpectiveiy, and in delta rem each other. Tracing the c changers TCI and 1`C2v for on 'the winding I .is connected fifi the fixed contact member e movable contact member I1 uctor 41 to the terminal i2, through the reactor I2 contact members 34 and 33 TG2 for phase A that are e contact member 22, and e terminal 52 of the winding e tap changing switches TCI and for phase i3 connect the point 53 on the winding by conductor 54, fixed contact members 25 and of the tap changing switch TCI for phase B that are bridgedA by the movable contact member 53, conductor 55 to the terminal point 5t of reactor i3, through the reactor I3 and by conductor 1, the contact member 34 of the tap changing switch TG2 for phase B, through the movable contact member 23 thereof, Contact member 33', and conductor 58 to the termina-1 552 of the winding 3 that is connected to the phase conductor C. Similarly, the tap changswitches for phase C complete a circuit from the point Si ci Winding 3, by conductor 62, 'through fixed contact members 25 and 26 of the tap changing switch TCI for phase C that are bridged by the movable contact member I9, tlnough conductor S3 to the terminal 84 of the reactor i4, through the reactor I4 and by conductor and the fixed contact members 33 and 34 of the tap changer switch 'IC2 for phase C that are bridged by the movable contact member 24, and by conductor 66 to the terminal 61 of the winding I that is connected to the phase conductor A. In the position I of the tap changer mechanism it is seen, therefore, that a delta circuit is completed comprising that portion of the winding I between the terminal 61 and the point 45 in series with the reactor I2, that portion of the winding 2 between the terminal 52 and the point 53 in series with the reactor I3 and that portion of the winding 3 between the terminal 59 and the point 6I in series with the reactor I4, thus providing a relatively low excitation for the primary windings I, 2 and 3 and a corresponding low voltage and current supplied from the secondary windings 4, 5 and 6 to the terminals 1, 8 and 9 of the furnace.

If now it is desired to operate the tap changing equipment from position I to position 2 indicated on the chart in Fig. 2, the shaft 36 and the gear wheel 31 are revolved through one revolution in a counter clockwise direction, thus causing the pin 88 of the gear 31 to engage the slot 38 in the gear 38 and actuate this gear onequarter turn in a clockwise direction, thus moving the shaft IS and the contact members I1, I8 and i9 carried thereby to a position to bridge the contact members 21 and 23 of the switch mechanisms for their respective phases A, B and C. The gear 43 of the tap changing mechanism TC2 is operated through a one-quarter turn simultaneously with the gear 38 by means of the interconnecting pinion gears 39 and 42 and the shaft 4I. The pin 1I of the gear 43 is accordingly moved from its illustrated position to a position adjacent to the slot I2 of the gear 44, but the movement of the gear 43 is not sufficient to move the gear 44 from its illustrated position and the contact members 22, 23 and 24 carried 10 by the shaft 2I are, accordingly, maintained in their illustrated positions bridging the contact members 33 and 34 of the tap changer TG2 for the phases A, B and C, respectively.

It will be seen that the circuit now closed 15 through the tap changing switches TCI and TCZ for phase A extends from the terminal 13 of the winding I through conductor 14, contact members 21 and 28 bridged by the contact member I1, the conductor 'I5 to the point 16 on the 20 reactor I2 through the lower portion of the reactor and by conductor 49, contact members 33, 34 and 22 and conductor 5I to the terminal 52 of the winding 2. Continuing the delta circuit through the winding 2 to the terminal 1l thereof, 25 through conductor 18, through contact members 21, 28 and I8 of the tap changer TCI for phase B and conductor 19 to the point 8| on the reactor winding I3, through the lower portion of the reactor winding, conductor 51, contact 30 members 34, 23 and 33 of the tap changer 'ICZ for phase B, and conductor 58 to the terminal 59 of the Winding 3, thence through the winding 3 to the terminal 82 thereof and by conductor 83, contact members 21, 28 and I9 of the tap changer TCI for phase C, conductor 84 to the point 85 on the reactor winding I4 through the lower portion ofthe Winding I4 and tl .rough conductor 65, contact members 33, 34 and 24 of the tap changer TG2 for phase C, and conductor 66 to the terminal 61 of the winding I. The circuit just traced, thus completes a delta circuit including all of the Winding turns of the windings I, 2 and 3 and a portion of the reactor windings I2, I3 and I4. The excitation of the primary windings I, 2 and 3 is, therefore, increased, thus 4J increasing the voltage and the current supplied from the secondary windings 4, 5 and 6 to the arc furnace.

If now It is desired to operate the tap changing equipment to position 3, indicated on the chart in Fig. 2, the shaft 36 is rotated through another revolution in a counter-clockwise direction, thus actuating the gear 38 and the shaft I6 through another quarter turn in a clockwise direction and causing the contact members I1, I8 and I9 to bridge the contact ' members 29 and 30, respectively, of the tap changer TCI for the phases A, B and C. The gear 43 is similarly actuated through a second quarter turn in a clockwise direction, thus rotating the pin 1I from a position in advance of its illustrated position to a position of in advance thereof. During this quarter turn the pin 1I engages the slot 12 of the gear 44 thus actuating the gear 44 and the shaft 2| in a counter-clockwise direction causing the contact members 22, 23 and 24 of the tap changer TC2 for the phases A, B and C, respectively to be actuated In a. position to bridge the contact members 34 and 35 of their respec- 70 tive switch mechanisms.

In this position of the tap changing switches, the terminal 13 of the winding I that is remote from the phase conductor A is connected by conductor 'I4 to the contact member 3| of the tap 75 changing switch TCI for phase A. and through the contact member I1 thereof, contact member 30, conductor 30 .to the point 01 on the reactor I2, through the lower portion of the reactor i2, conductor 40 and contact members 34, 33 and 22 of the tap changing switch TC2 for phase A to a conductor that is a common conductor connecting the three contact members 3l of the tap changer 'PC2 for the phases A, B and C, together, thus forming a neutral point for the star connected windings. Similarly, Vthe terminal 11 of the winding 2 that is remote from the phase conductor Bis connected by the conductor 10, contact members 3|, I0 and 30 of the tap changing switch TCI for phase B through conductor 03 to the point 33 on the reactor winding |3, through the lower portion of the reactor I3 and through contact members 34, 35 and 23 of the tap changer TC! for the phase B to the common neutral point conductor 30. In the same manner, the terminal 32 of the winding 3-that is remote from the phase conductor C is connected by conductor 03, contact members 3|, I3 and 30 oi' the tap changer TCI for phase C through conductor 0| to the point 92 on thev reactor I4, through the lower portion of the reactor I4, conductor 03 and contact members 34, 35 and 24 of the tap changer TC2 for phase C to the common neutral conductor 90. The third position of the tap changing equipment, therefore, connects the three primary windings I, 2 and 3 in star relation with a portion of the reactors I2, I3 and |4, respectively, in series therewith.

The fourth position of the vtap changing equipment shown on the chart in Fig. 2, connects the primary windings of the transformer in star relation with the reactors I2, I3 and |4 entirely out of the circuit. This position of the equipment is effected by rotating the shaft 33 and the gear 31 through a third revolution in a counter clockwise direction, thus rotating the gear 30 and the shaft I6 through a third quarter turn in a clockwise direction, thus causing the contact members I1, I3 and I0 for the phases A, B and C, respectively, of the tap changer TCI to bridge the contact members 3| and 32. This position of the tap changer TCI connects the terminal 13 of the winding I through conductor 14, contact members 3 I, 32 and I1 of the tap changing switch TCI of phase A to a conductor 03 that is a common or neutral conductor connecting the three contact members 32 of the tap changing switches for the phases A, B and C, respectively. In a similar manner, the terminal 11 of the winding 2 is connected by conductor 10 and contact members 3|, 32 and I3 of the tap changing switch TCI for phase B Yto the neutral conductor 33, and the terminal 02 of the winding 3 is connected by conductor 33 and contact members 3|, 32 and I9 of the tap changing switch TCI for phase C to the neutral conductor 03, thus connecting the windings I, 2 and 3 in star relation with no outside reactors in circuit therewith.

Obviously, a different number of voltage ratios may be obtained with the system described above employing a different number of taps on the windings I, 2 and 3 and on-the reactor windings I2, I3 and I4, with a corresponding number of positions of the tap changer switches being provided. It will be apparent that a relatively large number of tap positions and secondary voltage values are obtainable withthe above described system without employing a large number of tap .connections to the primary windings of the transformer.

formers.

Referring to Fig. 3 which shows another embodiment oi' my invention having tap changer positions and sequence of operating steps shown in Fig. 4, the primary conductors |0I, |02 and |03, each comprising upper and lower winding sections, are connected, respectively, to the phase conductors A, B and C. For the sake of simplicity in Fig. 3, the secondary windings of the transformers that are connected to the furnace electrodes andthe usual three pole circuit breaker switch connecting the primary windings to a three-phase supply circuit are omitted from this figure although it will be understood that these parts would ordinarily be used in practice in the same manner as shown in Fig. l. Reactor windings |04, |03 and |00 are provided, associated respectively with the primary windings I 0 I, |02 and |03, the high voltage terminal ends of the associated reactor and transformer windings being connected together.

A tap changing mechanism that is, in general, similar to that provided in Fig. 1 is indicated at |01, the gearing mechanism thereof being driven from a shaft |08 and driving, through suitable Maltese cross gears for effecting an intimate motion of the shafts |03 and which actuate, respectively, tap changers TCI and TC2 each having a tap changing switch for each of the phases of the three-phase system. The tap changer TCI comprises the movable contact members I2, I|3 and ||4 associated respectively with phases A,

' `B and C and similarly operated by the shaft |03.

Each of the tap changer switches TCI for the three phases are provided with stationary contact members numbered ||5 to 2|, inclusive, that are engaged by the movable contact members ||2, |I3 and |I4, respectively, of the three switches. The ltap changing switches TC2 for the phases A, B and C of the system are respectively provided with moving contact members |22, |23 and |24, all similarly actuated by the shaft ||I, and each of the switches are provided with stationary contact members |25 to |32, inclusive. It will be noted by reference to Fig. 4 that the embodiment of the invention illustrated in Fig. 3 provides twelve positions of the tap changing equipment giving twelve different voltages in the secondary windings of the trans- The gearing mechanism controlling the shafts |09 and are so designed that there are six operative positions for the shaft |09 and the tap changer TCI, which six positions are repeated from the seventh to twelfth positions of the tap changing equipment as a whole, and the relation of the gears are such that the shaft III and the tap changer TC2 driven thereby are operated from one switch closing position to the next succeeding switch closing position of the tap changer during every third operation of the tap changing mechanism, there being a, total of four positions for the tap changer TC2.

'Ihe primary winding |0| is provided with a series of tap connections numbered |33 to |39, inclusive, and connected, respectively, to the contact members ||5 to |2I, inclusive, of the tap changing switch TCI for phase A. In a similar manner, the primary winding |02 is' provided with a similar number of taps numbered |40 to |46, inclusive, and connected, respectively, to the contact members ||5 to |2I, inclusive of the tap changing switch TCI for phase B, and the primary winding |03 is also provided with a Asimilar arrangement of taps connecting the CII members IIE to I 2I of the tap changing switch TCI for phase C.

In the illustrated position of the tap changing equipment which corresponds to position I on the chart in Fig. 4, the contact members II2, I|3 and II4 of the switches of tap changer TCI. for the three phases, bridge the contact members II5 and IIS of their respective switches, thus cutting out of circuit, the winding turns between the points |33 and I34 of the winding |0I, between points |40 and I4| of the winding |02, and between the points |41 and |48 of winding |03. The lower terminal of the winding |0| is connected through the contact members |26, |22 and |25 of tap changing switch TC2 for phase A and conductor |54 to the lower terminal of the reactor |05, the upper terminal of which is connected to the phase conductor B. The lower terminal of the winding |02 is connected through contact members |25, |26 and |23 of vthe tap changing switch TG2 for phase B, and by conductor |55 to the lower terminal of the reactor |06, the upper terminal of which is connected to the phase conductor C, and the lower terminal of the winding |03 is connected through the contact members I 26, |24 and |25 of the tap changing switch TG2 for phase C and conductor |56 to the lower terminal of the reactor |04, the upper terminal of which is connected to the phase conductor A. In this position of the tap changing mechanism all of the reactance of the reactors |04, I 05 and |06 is connected in series with the windings IOI, |02 and |03 in delta relation.

In the second and third positions of the tap changing mechanism, as indicated in the chart in Fig. 4, the tap changer TCI remains in its rst position while the movable contact members of the tap changer TCI bridges consecutively the contact members ||6 and II`I, and then contact members IIT and I I8, thus introducing two additional sections of the primary windings into the circuit. In the second position of the tap changer TCI the points I 34 and |35 on winding |0|, |4I and |42 on winding |02, and |48 and |49 on winding |03 are, respectively, connected together through the contact members I|6 and II`I, and in the third position of the tap changer TCI the points |35 and |36 on winding IOI, |42 and |43 on winding |02, and |49 and |50 on winding |03 are, respectively, connected together through the contact members III and I|8 of their associated phase switches.

During the next three positions of the tap changing equipment numbered 4, 5 and 6 in the left-hand column of Fig. 4, the tap changer TCI bridges consecutively the contact members III- II9, IIS-|20, and I20--I2I, thus introducing step by step the entire winding turns of the windings I0|, |02 and |03 into the primary or energizing circuit of the transformers. When the tap changing mechanism moves from its third to its fourth position, the movable elements |22, |23 and |24 of the tap changer TC2 move in a counter clockwise direction to bridge the contact members I3I and |32, thus eliminating the reactors |04, |05 and |06 from the transformer winding circuits and connecting the lower terminal of the winding IOI through the conductor 57 to the phase conductor B, the lower terminal of the winding |02 through conductor |58 to the phase conductor C, and the lower terminal of winding |03 through conductor |59 to the phase conductor A. The tap changer TC2 remains in this position for positions 4, 5 and 5 of the tap changing mechanism.

When the tap changing mechanism is operated from its sixth to the seventh position, as indicated in the column at the left in the chart in Fig. 4, the tapchanger TCI is moved from its sixth to its first or illustrated position bridging the contact members II5-I I6 and the tap changer TCZ is moved from a position bridging the contact members I3 I--I32 to a position bridging the contact members IZB-|30, thus connecting the lower ends of the three windings IOI, |02 and |03 to a common or neutral conductor IBI. In this position of the tap changing mechanism, all of the tapped sections of the primary windings are excluded'from the primary winding circuit. During the remaining steps of the tap changing mechanism, the several tapped sections are introduced by the tap changer TCI in the same manner as in the first six positions of the tap changing mechanism. During the last six positions of the tap changing mechanism, the lower terminals of the windings IOI, |02 and |03 are maintained connected to the neutral conductor IGI changer TCZ and one of the contact members |20 or |30, depending upon the position of the tap changing switch TG2.

It will be apparent to those skilled in the art that a number of modifications of the circuits and l apparatus described may be made without departing from the spirit of my invention, and I do not wish to be limited other than by the scope of the appended claims.

I claim as my invention:

1. The combination with a transformer comprising a plurality ofv primary and secondary windings, of reactors for connection with said primary windings, and means for varying the voltage supplied from said secondary windings comprising circuits and tap-changing switching mechanism operative in a predetermined sequence of circuit establishing positions for connecting consecutively, portions of said primary windings in series circuit relation, respectively, with their associated reactors and in delta circuit relation to each other, then said primary windings in series, respectively, with portions of their associated reactors and in delta circuit relation to each other, then said primary windings in series, respectively, with portions of their associated reactors and in star relation to each other, and then in star relation to each other with said reactors excluded from said circuitl 2. 'I'he combination with a polyphase power circuit comprising three conductors, of three transformers, each having a primary winding and a secondary winding, one terminal of said primary windings being connected respectively to each of said conductors, a reactor associated with each primary winding, said primary windings being provided with terminal and intermediate taps and said reactors being provided with terminals and intermediate taps, a tap-changing switchingmechanism for selectively connecting oneterminal tap or an intermediate tap. to a selected tap on its associated primary winding, and a second tap-changing switching mechanism for selectively connecting the other terminal taps of said reactors together, or to selected conductors of. said power circuit.

3. 'I'he combination with three transformers for connection to a polyphase system, each having a primary winding and a secondary winding, of a reactor associated with each primary winding, means for varying the voltage supplied from said through the contact members |29 of the tap lll secondary windings comprising a plurality of tap connections on said primary windinsl. a tapchanging switching mechanism for each winding for correspondingly changing the circuit connections between said taps to remove selected portions of said winding from the primary winding circuits, and a second switching mechanism for each winding for connecting said windings in star and delta relations at predetermined circuit connecting positions of said first named tap-changing mechanism, and for connecting said reactors in circuit with their associated windings in certain of the above-mentioned positions in which said windings are connected in delta relation.

4. In a transformer system having primary and secondary windings, in combination, reactors associated with the primary transformer windings, a plurality of. tap-changing switching m disposed to connect the primary transformer windings in delta circuit relation with the reactors in series circuit relation with their corresponding primary windings, means for driving the tapchanging switching mechanisms step-by-step at different speeds to perform switching operations in a predetermined manner, a plurality of circuit connections associated with the tap-changing switching mechanisms, the circuit connections and tap-changing switching mechanisms being so disposed that the latter are operated to shunt the reactors and change the circuit connections of the primary transformer windings to star circuit connections. y

5. In a transformer system having primary and secondary windings, in combination, reactors as- 5 sociated with the primary transformer windings, a plurality of interconnected tap-changing switching mechanisms, means for driving the tap-changing switching mechanisms step-by-step at diierl ent speeds to actuate them to different positions 10 l to perform predetermined switching operations, a

plurality of circuit connections associated with the tap-changing switching mechanisms, one of the tap-changing switching mechanisms disposed to control the circuitgconn'ections of the primary 16 windings, another tap-changing switching mechanism disposed to cooperate with said one of the tap-changing switching mechanisms to connect the primary windings in delta circuit relation with the reactors in series circuit relation with 20 their corresponding primary windings when said tap-changing switching mechanisms are moved to predetermined circuit connecting positions, `the tap-changing mechanisms further cooperating with each other in a predetermined manner to 25 shunt the reactors from the circuit and connect the primary windings in a predetermined star circuit relation.

HENRY C. GUHL.

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