US2156997A - Transformer voltage regulating system - Google Patents

Transformer voltage regulating system Download PDF

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Publication number
US2156997A
US2156997A US69789A US6978936A US2156997A US 2156997 A US2156997 A US 2156997A US 69789 A US69789 A US 69789A US 6978936 A US6978936 A US 6978936A US 2156997 A US2156997 A US 2156997A
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Prior art keywords
voltage
winding
switch
circuit
taps
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US69789A
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English (en)
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Orin P Mccarty
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General Electric Co
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General Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F29/00—Variable transformers or inductances not covered by group H01F21/00
    • H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
    • H01F29/04—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings having provision for tap-changing without interrupting the load current

Definitions

  • My invention relates to transformer voltage regulating systems and more particularly to means for changing the connections'between the taps of a transformer winding for adjusting the voltage ratio, of the transformer.
  • the voltage of an electrical circuit be maintained substantially constant under varying load conditions and this is particularly true if the load includes essentially constant potential electrical devices such as incandescent lamps. It is also usually desirable that any voltage regulation of an electrical circuit be accomplished without interrupting the supply of current to the load.
  • the general object of the invention is to provide an improved transformer tap-changing system which shall be simple in construction and reliable in operation and which can be used to change transformer tap connections without interrupting the transformer load.
  • FIG. 1 is a diagrammatic view of a transformer winding provided with tap-changing mechanism constructed and arranged in accordance with the invention
  • Fig. 2 shows explanatory curves of voltages and currents in various parts of the tap-changing mechanism while a change of tap connections is being made
  • Figs. 3, 4 and 5 show modifications of the arrangement shown in Fig. 1.
  • the transformer winding shown in Fig. 1 includes a common winding l0, a series winding II and a voltage winding l2. This transformer winding is connected between a primary or supply circuit I3 and a load or secondary circuit I4. The circuit I4 is connected across the common winding l0 and one side is also connected to some point of the series winding H such as its center.
  • the series winding II is provided with taps l5,
  • of the switch I5 is operated by a Geneva gear 22 driven by a motor 23 through a lost motion connection 24, the motor being controlled by a contact-making voltmeter 25 connected to the voltage coil
  • This driving member 28 carries a pivoted arm 29 with a pin 30 arranged to engage slots 3
  • the angular travel of the arm 29 relatively to the driving member 28 is limited by pins 33.
  • Rotation of thedriving member 28 tensions a spring 34 until just as the pin 30 reaches one of the slots 3
  • a by-pass 36 is connected between the movable contact and the series winding, the connection to the series winding being shown at the center or electrical mid-point of the winding.
  • This by-pass 36 may be any suitable impedance, one satisfactory form of' which is a resistor which has a normally high resistance but a high negative voltage-resistance characteristic so that its resistance will decrease considerably as the voltage across it is increased and will increase considerably as the voltage across it is decreased.
  • a suitable material for this resistor is disclosed in the United States Patent No. 1,822,742, granted September 8, 1931, upon an application of K. B. McEachron and assigned to the assignee of the present application.
  • the curves shown in Fig, 2 indicate the relative-voltage and current conditions in different parts of the tap-changing mechanism which has been described.
  • the broken line 31 of Fig. 2 indicates the instant at which the movable contact 2
  • the curve C39 indicates the current in 'the tap connection 39 from ,the tap B8.
  • curve C40 indicates the current in the tap connection 46 from the tap H.
  • the curve C21 lnd1- cates the current in the movable contact 2i of the switch IS.
  • the curve C13 indicates the cur-' rent in the supply circuit l3.
  • the curve E36 indicates the voltage across the resistor 36.
  • the curve C36 indicates the current in the resistor 36.
  • the curve 013 shows that the current in the supply circuit l3 flows continuously and is not interrupted while a change in tap connections is being made.
  • the curves C39, C4o,"C21 and C36 show that the current flows inthe movable contact 2
  • the current is then transferred to the resistor 36 until the movable contact 2! reaches the tap connection 39 at which instant the current is transferred from the resistor to this tap connection 39.
  • the curve E36 shows that the voltage across the resistor 36 is at least small enough to be negligible except while the currrent is broken through the switch I5.
  • the invention provides a very simple and reliable tap-changing mechanism, the provision of the by-pass resistor 36 permitting a very simple form of switch to be used for changing the tap connections without interrupting the current in the load circuit. It is desirable that the switchoperating mechanism and the distance between the fixed contacts 20 be so arranged and proportioned that the load current normally flowing through the movable contact 2
  • the modification shown in Fig. 3 is particularly well adapted for use as a branch feeder circuit step voltage regulator. In general principle it is similar to Fig. 1 but it differs therefrom in the following particulars.
  • the primary relay or contact-making voltmeter 25 is provided with holding coils M and 42 which are connected so as to be deenergized when the floating contact 26 is not in engagement with the stationary contacts 21 and 35 but which are energized, respectively, when the floating contact 26 engages the fixed contact 27 or the fixed contact 35.
  • These.holding coils may be energized in any suitable manner and as shown they. are connected in parallel with the motor energizing circuits. The purpose of these holding coils is to insure a firm non-chattering or arcing contact between the fixed contacts and the floating contact 26.
  • is energized, thereby magnetically holding the contact 26 in engagement with the contact 21 and preventing a trembling or vibratory engagement between these contacts, which type of engagement produces injurious pitting and burning of the contact-making voltmeter contacts.
  • the holding coil 42 is energized so as to insure a firm and positive engagement between the contacts.
  • Another result of the holding coils is to cause the contacts of meter 25 to open and close at difierent voltage values. For example, the voltage resulting in the engagement of contacts 26 and 21 is lower than the voltage required for this separation because of the pull of coil 4
  • Fig. 3 the circuit is provided with a manually operable selector switch or terminal board 43.
  • a manually operable selector switch or terminal board 43 By means of this additional switch it is possible to have what may be described as a "five in one regulator.
  • the regulator of Fig. 1 only produces two steps of voltage increase or boost and two steps of voltage decrease or buck and the amounts of buck and boost are equal.
  • the connection changing switch 43 it is possible to provide selectively five difierent ranges of regulation.
  • Switch 43 is provided with a movable contact 44 which,
  • the illustrated position of the switch 43 may be termed the 10% boost position because operation of the tap changing movable contact 2
  • a 5% boost is being produced and if the contact 2
  • the 5% boost which is produced with the parts in the position shown in the drawings is due to the fact that the load current flows from the lower conductor of the supply circuit I3 through the movable contact 2
  • the return current path of course,'is through the upper conductors of the load and supply circuits l4 and I 3.
  • will be from a maximum of '7 boost through zero to a maximum of a 2 voltage buck.
  • in the position shown there will be a 2 voltage boost produced, while if the contact M is moved clockwise the boost will first be reduced to zero as the first fixed contact 10 is engaged and as the next contact 20 is engaged there will-be a 2 /2% voltage buck produced.
  • the tap changing circuit will be the equivalent of that shown in 'Fig. 1 and 5% boost and 5% buck will be produced in equal 2 /2% steps. This is because the load circuit will then be connected directly to the midpoint of the winding II as in Fig. 1. If the movable contact 44 is moved to the next contact 48 it will be possible to secure a 2 voltage boost and a l voltage buck in 2 steps. Finally if the movable contact 44 is moved into engagement with the stationary contact 49 the connection will be the reverse of that shown in the drawings and it will be possible to secure a 10% voltage buck in four 2 steps.
  • the range selecting switch 43 will be set at the position giving the range of regulation which is desired for any particular location and circuit in which the regulator is used and in order to change the range of regulation it will be necessary to disconnect the regulator from the circuit so that no current is flowing through the switch 43.
  • this is not necessarily essential and if a load current by-pass impedance similar to resistor 36 is connected in shunt with the switch 43 this switch may be operated to change the range of regulation while the regulator is carrying load current.
  • the resistor 50 may be taken as such a resistor.
  • resistor 50 serves another purpose whichis described immediately below and preferably is not designed to carry the load current of the circuit as this would unnecessarily increase the cost of the regulator.
  • resistor 50 which is preferably made of the same material as the resistor 36, is to complete a protective by-pass circuit or shunt around the series winding I l.
  • resistors 36 and 50 in series completely shunt or by-pass the series winding II and due to their characteristic of instantaneously reducing their resistance with increases in applied voltage they form a protective non-linear by-pass for preventing excessive voltages across the series winding II.
  • a capacitor 53 is connected in parallel with the load by-pass resistor 36.
  • the action is similar to the action of a saturable reactor in that after the arcing current has passed through zero and starts rising the capacitor forms a low impedance to the rising current thereby consuming the current and allowing the arc to become extinguished.
  • the capacitor becomes charged, the voltage across it rises to a value which will cause the resistance of the non-linear resistor 36 to decrease.
  • This non-linear resistor then, forms a low impedance path for the flow of current until the moving contact 2
  • FIGs. 1 and 3 it consists p'rimarily'of an auto-transformer having a common winding l0 and a series winding H.
  • An electro-magnetically operated contactor 54 of the two-position type is provided with two sets of contacts 55 and 56, only one of which sets can be closed at one time.
  • contacts 55 are closed and contacts 56 are open the series winding H is completely out of circuit and the load current flows through the contacts 55.
  • the contacts 56 are closed and the contacts 55 are open the entire series winding II is connected in the load circuit through conductors 51, 58 and contacts 56.
  • the load current by-pass impedance 36 carries the current and as shown this impedance is connected from an'intermediate point in the series winding H to the load circuit H.
  • the operation of tap changing is therefore similar to the corresponding operation of Figs. 1 and 3.
  • the booster of Fig. 5 is also provided with an over-voltage protective by-pass 50 which in this case is connected in shunt to the winding H, or,
  • This resonant relay control circuit consists of a capacitor 60, an adjustable saturable core reactor 10 and a resistor H connected in series through a switch 12 across a part of the series winding I II As the voltage of the series winding is directly proportional to the load circuit voltage the voltage applied to the resonant relay circuit is a direct measure of the load voltage.
  • This circuit including the capacitor 50 and the reactorlfl, is capable of being tuned or becoming resonant, it being so arranged that it becomes resonant at a value of voltage determined by the'adjustment of the reactor 10 and becomes dissonant at a lower voltage determined by the setting of the adjustable resistance 1
  • the reason that the resonant phenomenon is responsive to voltage is because changes in voltage change the current flowing through the resonant circuit thereby changing the magnetic saturation of the owed the reactor which in turn changes the inductive value of the reactor and at a particular inductive value corresponding to the'capacitive value of the capacwhich is lower than the voltage causing res-.
  • the contacts of the relay 59 are connected across a portion of the series winding H in series with the alternating current input terminals of a rectifier l3 whichmay be of any well known type and is shown by way of example as a bridge connected copper oxide rectifier.
  • the direct current output terminals of the rectifier 13 are connected to the operating coil of the contactor 54.
  • a transformer including a winding having taps, a ratio changing switch having a transformer side connected to said taps and having a circuit side connected directly to said circuit independently of any part of said winding, and aload current bypass connected between the electrical midpoint of said winding and the circuit side of said switch, said bypass being" connected and proportioned to carry the full load current of said winding during a positional change of said switch.
  • a transformer including a winding having taps, a switch having fixed contacts connected to said taps and having but one movable member for successively engaging said fixed contacts so as to change the voltage ratio of said transformer, and an impedance connected to bypass said movable member, said impedance having one end thereof connected to an intermediate point on said winding and being proportioned to carry the full load current of said winding during operation of said switch, said point on said winding being difierent from the points where current normally enters and leaves said winding whereby the current. through said impedance passes through a portion of said winding.
  • an alternating current circuit a transformer winding one end of which is permanently connected to said circuit, a two position ratio changing switch having a winding side and a circuit side, said switch being arranged so that in one position it completes a circuit connection through said winding and in another position it interrupts said connection and bypasses said winding, and an-impedance connected between substantially the electrical midpoint of said winding and the circuit side of said switch, said impedance being proportioned to carry the full load current of said winding during the positional change of said switch;
  • a transformer including a winding having taps, a switch having a movable contact member for successively making connection to said taps so as to change the voltage ratio of said transformer, and a nonlinear resistor connected to bypass said switch and being proportioned to,
  • a transformer including a winding having taps, a switch having a movable contact member for successively making connection to said taps so as to change the voltage ratio of said transformer, and a negative resistance current characteristic impedance connected to bypass said switch and being proportioned to carry the full load current of said winding during operation of the switch.
  • a transformer including a winding having taps, a switch connected to said taps for changing the voltage ratio of the transformer, and normally high resistance means connected to bypass said switch, said means having a high nega-. tive voltage-resistance characteristic and being proportioned to carry the full loadcurrent of said winding during operation of the switch.
  • a transformer includingaJ-winding having taps, a switch connected to said taps for changing the voltage rattio of the trransformer, and a normally high resistance resistor connected to by-pass said switch, said resistor having a high negative voltage-resistance characteristic and being proportioned to carry thefull load current of said winding during operation of the switch.
  • a transformer including a winding having taps, a switch connected to said taps, means for operating said switch rapidly to change tap connections, and normally high resistance means connected to by-pass said switch, said by-pass means having a high negative voltage-resistance characteristic and being proportioned to carry the full load current of said winding during operation ofthe switch, and said switch and switch operating means being proportioned and arranged to assure a zero value of current through the switch during the period of its operation.
  • a transformer including a winding having taps, a switch having fixed contacts connected to said taps, said switch also including a movable contact, means for moving said movable contact rapidly from one fixed contact to another to change the voltage ratio of the transformer, and a normally high resistance by-pass 7 connected between said movable contact and said 'taps so as to change the voltage ratio of said transformer, and an impedance network having a plurality of impedances with different voltampere characteristics connected between said movable contact member and said winding and being proportioned to carry the full load current of said winding during operation of said switch. 11.
  • a transformer including a winding having taps, a switch having a movable contact member for successively making connection to said taps so as to change the voltage ratio of said transformer, and an impedance network connected between said movable contact member and said winding and being proportioned to carry the full load current of said winding during operation of said switch, said impedance network comprising a resistance element and a reactance element connected in parallel.
  • a transformer including a winding having taps, a switch having a movable contact member for successively making connection to said taps so as to change the voltage ratio of said transformer, and an impedance network connected between said movable contact member and said winding and being proportioned to carry the full load current of said winding during operation of said switch, said impedance network comprising a nonlinear resistance-voltage characteristic resistance and an inductive winding connected in parallel.
  • A- transformer including a winding having taps, a switch having a movable contact member for successively making connection to said taps so asto change the voltage ratio of said transformer, and an impedance network connected between said movable contact member and said winding and being proportioned to carry the full load current of said winding during operation of said switch, said impedance network comprising a negative resistance-voltage characteristic resistance and a saturable core reactor connected in parallel.
  • Voltage adjusting means for an electrical circuit comprising a transformer having a secondary winding adapted to carry the circuit load current and a primary winding energized by the circuit voltage, a two position electromagnetically actuated spring returned contactor adapted in its actuated position to connect said secondary winding in series circuit relation with the circuit and in its returned position to interrupt this connection and bypass said secondary winding, a primary relay sensitive to changes in an electrical characteristic of the circuit for controlling actuation of said contactor from one to the other of the two positions above named, and negative impedance-current characteristic impedance adapted to carry the circuit load current during the period of contactor positional change.
  • a transformer including a winding having taps, a switch connected to said taps for changing the voltage ratio of said transformer, a connection changer connected to said taps for changing the range of adjustment of the voltage of said winding, a switch current bypass connected around said switch, and an overvoltage protective device connected around said connection changer.
  • an autotransformer having ,a series winding provided with taps, a ratio changing switch connected to said taps and having a movable contact connected to said circuit on one side of said winding, a switch current by-pass impedance connected around said switch, a connection changing range adjuster connected to said taps and having a movable contact connected to said circuit on the other side of said winding, and a negative resistance-voltage characteristic resistance connected as an overvoltage protective means around said connection changing range adjuster.
  • a transformer including a winding having taps, switching means for successively making in-- dividual connection to said taps so as to change the voltage ratio of said transformer, said switching means having apparatus which interrupts the circuit therethrough without making a bridging connection between any pair of taps during a tap changing operation, and non-linear impedance means connected to by-pass said switch and being proportioned to carry the full load current of said winding when said switch is open, said nonlinear impedance means being continuously conductive at all values of voltage thereacross and having a percentage change in voltage drop which isalways less than any percentage change in load current therethrough.
  • a transformer including a winding having taps, switching means for successively making individual connection to said taps so as to change the voltage ratio of said transformer, said switch- 1 ing means having apparatus which interrupts the circuit therethrough without making a bridging connection between any pair of taps during a tap changing operation, and non-linear impedance means connected to by-pas's said switch and being proportioned to carry the full load current of connection between any pair of taps during a tap,
  • a non-linear resistor connected to by-pass said switch and being proportioned to carry the full load current of said winding during operation of said switch, said resistor being continuously conductive at all values of voltage thereacross and having a resistance which varies instantaneously inversely with variations in the instantaneous value of the current therethrough.
  • a transformer including a winding having taps, switching means for successively making individual connection to said taps so as to change the voltage ratio of said transformer, said switching means having apparatus which interrupts the circuit therethrough without making a bridging connection between any pair of taps during a tap. changing operation, and non-linear impedance means connected to by-pass said switch and being proportioned to carry the full load current of said winding during operation of said switch, said non-linear impedance means being continuously.
  • a transformer including a winding having taps, switching means for successively making individual connection to said taps so as to change the voltage ratio of said transformer, said switching means having apparatus which interrupts the circuit therethrough without making a bridging connection between any pair of taps during a tap changing operation, and non-linear impedance means connected to by-pass said switch and

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)
US69789A 1935-04-16 1936-03-20 Transformer voltage regulating system Expired - Lifetime US2156997A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295053A (en) * 1963-09-13 1966-12-27 Superior Electric Co Automatic voltage regulator
US3474326A (en) * 1967-01-27 1969-10-21 Gen Electric Tap changing apparatus for inductive windings

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295053A (en) * 1963-09-13 1966-12-27 Superior Electric Co Automatic voltage regulator
US3474326A (en) * 1967-01-27 1969-10-21 Gen Electric Tap changing apparatus for inductive windings

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GB467866A (en) 1937-06-24
DE724503C (de) 1942-08-28
GB487354A (en) 1938-06-20

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