US2440983A - Tapped transformer system - Google Patents

Tapped transformer system Download PDF

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Publication number
US2440983A
US2440983A US634573A US63457345A US2440983A US 2440983 A US2440983 A US 2440983A US 634573 A US634573 A US 634573A US 63457345 A US63457345 A US 63457345A US 2440983 A US2440983 A US 2440983A
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United States
Prior art keywords
reactor
contactor
circuit
contactors
current
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Expired - Lifetime
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US634573A
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English (en)
Inventor
Palley Zoltan O St
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General Electric Co
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General Electric Co
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Publication date
Priority to BE482065D priority Critical patent/BE482065A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US634573A priority patent/US2440983A/en
Priority to GB36754/46A priority patent/GB619484A/en
Application granted granted Critical
Publication of US2440983A publication Critical patent/US2440983A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/0005—Tap change devices
    • 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

  • This invention relates .to electric circuits and more particularly to improvements .in doublefinger switching-type load-ratio-control circuits.
  • a load-.ratioecontrol circuit is a circuit for varying the ratio of a transformer while under load, and a double-finger switching circuit of this type is one in which -the transformer circuit is in effect forked .and the .two tines or branches of the fork contain separate switching mechanisms for. making selective connection with different taps on a transformer winding. .In certain positions of the system, known as halfcycle .or bridging positions, .the branches of the forked circuit are connected to different voltage taps. This tends to produce a circulating current and the value of this .current is limited by a reactor which can either be a mid-tapped reactor or -a split reactor whose .two halves are in .the two branches of the forked circuit.
  • the electrical mid-point is connected to the circuit at the junction of the branches of the fork, while if it is a split reactor its two halves are separated so that other circuit elements may be effectively connected inside the reactor, it being understood that the main circuit conductor which is divided to form the branches of the fork is connected inside 'or between the two halves of the reactor.
  • each branch has both an arcing duty contactor and a so-called ratio adjuster switch which does the actual tap changing and which is not adapted to perform any arcingduty .or current interruption, these different types of switches usually being serially connected in each branch.
  • contact life is actually meant the number of operation which the arcing duty contactors can perform without failure, but as in most systems the operations take place .at a fairly uniform rate, the life can also be thought of in terms of time.
  • the interrupting capacity of a switch is measured in volt-amperes, the .amperes being the current which is to be interrupted and the voltage being the recovery voltage.
  • the recovery voltage is the voltage which appears between the separating contacts following the first current zero after the contacts begin to separate.
  • the reactance of the reactor is made low enough so that the recovery voltage does not exceed the maximum voltage interrupting capacity of the contactor under short circuit load conditions, then the circulating current will be so high that the useful life of the contactor is very materially shortened below its maximum possible, In most systems of this kind the reactance of the reactor is a compromise between that which will give maximum contact life and that which will insure that the recovery voltage under the worst short circuit conditions will not exceed the maximum voltage rupturing capacity of the contactor.
  • means for changing the eifective value of the reactor to a lower but finite value when the system is operated from its half-cycle position to its quarter-cycle position.
  • An object of the invention is to provide a new and improved electric circuit.
  • Another object of the invention is to provide a new and improved load-ratio-control system.
  • a further object of the invention is to provide a load-ratio-control system with a circulating current limiting impedance having multiple finite values.
  • An additional object of the invention is to increase the operating life of the arcing duty contactors of a load-ratio-control system.
  • Still another object of the invention is to increase the short circuit interrupting ability of a load-ratio-control circuit.
  • FIG. 1 illustrates diagrammatically an embodiment of the invention
  • Fig. 2 is a modification
  • Fig. 3 is a detailed view of a suitable form of double arcing contactor for use in the circuits shown in Figs. 1 and 2.
  • a main transformer winding I which is connected in'a load circuit 2.
  • the winding l is provided with at least two spaced taps 3 and 4.
  • the load circuit 2 is forkedor branched at point 5, the right-hand branch, which is indicated generally at 6, serving to interconnect point 5 and tap 3,
  • an iron cored reactor 8 is connected directly together and to point 5.
  • This reactor may be either a mid-tapped reactor or a split reactor but its two halves are preferably closely interlaced so as to have a very low leakage reactance.
  • the arcing or current interrupting duty of the two branches is performed respectively by arcing duty contactors II and I2.
  • the arcing duty contactor II is shown in its full open position and an arc is indicated be substantially the same as the reactor 8 in that it has two equal windings.
  • One winding I4 is connected between the branch circuit 1 and an auxiliary or back contact I5 on the arcing duty switch H, while another winding IE on the reactor i3 is connected between the branch circuit 6 and an auxiliary or back contact I! on the arcing duty switch I2. 7
  • Fig. 1 The operation of Fig. 1 is as follows: With the ratio adjuster contact fingers 9 and It) in the position shown and with the arcing duty contactor! l closed in a position corresponding to that in which the contactor I2 is, the system is in its so-called half-cycle position.
  • the reactor l3 will be completely out of the circuit and the reactor 8 will act as an autotransformer to give the point 5 a voltage half-way between the voltages of the taps 3 and 4.
  • Any load current in the circuit 2 will divide equally through the two branches 6 and 1 and there will be substantially no load current produced voltage drop in the reactor 8 because the two halves of the reactor are so wound or connected that their magnetic effects cancel each other when load current flows through them.
  • the reactance of winding i4 is X0
  • the circulating current at short circuit loads which may be designated as In
  • the current I0 can be made of the order of 250 per cent of normal full load current, which of course will be very much below the current which would be produced by a dead short circuit between the taps other words, this connection reduces the regula tion 'of the system in its quarter-cycle position substantially below what it would be if all of the load current flowed through only one-half of the reactor 8.
  • Fig. 1 The system shown in Fig. 1 is symmetrical and therefore the operation of the circuit elements in the branch I will be the same as for the branch 6, the only difference being that the contactor l2 when it is moved to the full open position will place thewinding l6 of the reactor l3 in parallel circuitrelationship with the reactor 8 so far as circulating currents and short circuit loads are concerned.
  • Fig. 2 differs from Fig. l-primarily in that the control of the effect'i've value of the circulating current limiting impedance is by 's'eries'circuit connections instead of by arallel circuit connections. Another'difference is that the main reactor '8 and the auxiliary reactor l3 have their positions effectively interchanged so that main reactort now becomes a split'reactor instead of amid-tapped reactor.
  • the contactors l and 12 are so arranged that when they make contact with their back contacts'in their full open position they "respectively short circuit the difierent halves of the main'rea'ctor 8' which has theeffectof short-circulting the entire reactor because the volts per turnoi any turn on the reactor'will be held substantially to zero by the short circuiting of any otherturn or turnsthereon due to the very close coupling between alltheturns.
  • the reactors Band l3 are connected in series between the taps 3 and 4 so that the circulating current at'normal load conditions will be given by the formula where X0 in this case is the reactance of both of the windings l4 and 16 in series.
  • X0 in this case is the reactance of both of the windings l4 and 16 in series.
  • the value-of circulating current I - can be given any desired value by making the sum of X and X0 of the proper value without regard to circuit conditions under short circuit loads.
  • Connections are madethrough thepanel board by the three leadsshown extending therethrough.
  • a load-ratio-control system comprising, in combination, an arcing duty contactor having a predetermined maximum voltage rupturing capacity, connections for causing said contactor to establish a half-cycle operating condition of said system when said contactor is closed and for establishing a quarter-cycle operating condition of said system when said contactor is open, impedance means whose value controls the amount of circulating current through said contactor when said contactor is closed and the amount of recovery voltage on said contactor when said contactor is open, said impedance having a normal value such that the operating life of said contactor under normal load conditions is a maximum, and means operative when said contactor attains its full open position for reducing the value of said impedance to such a value that the recovery voltage of said contactor under short circuit load conditions is just under said maximum voltage rupturing capacity of said contactor, said reduced value of said impedance being sufficiently great to prevent a tap-to-tap short circuit.
  • an electrical winding having I at least two taps
  • impedance means having two end terminals and an intermediate terminal
  • separate' circuit making and breaking means for respectively connecting the end terminals of said impedance means to said taps
  • an electric circuit for said winding including a conductor connected to said intermediate terminal, and means responsive to a circuit breaking operation of either of said circuit making and breaking means for decreasing the effective value of said impedance means to a lower but finite value.
  • a transformer winding having a plurality of taps, an electrically mid-tapped reactor, means including a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps and disconnecting them therefrom, a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an impedance element, and means associated with an opening operation of one of said contactors for connecting said impedance element in shunt circuit relation with said reactor and associated with a closing operation of said last-mentioned contactor for open circuiting said impedance element.
  • a transformer winding having a plurality of taps, an electrically mid-tapped reactor, means including a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps and disconnecting them therefrom, a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an impedance element, and means operative upon one of said contactors reaching its full open position for connecting said impedance element in shunt circuit relation with said reactor through said other contactor and associated with a closing operation of said one contactor for open circuiting said impedance element.
  • a transformer winding having a plurality of taps, an electrically mid-tapped reactor, means including a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps and disconnecting them therefrom, a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an impedance element, means associated with an opening operation of one of said contactors for connecting said impedance element in shunt circuit relation with said reactor and associated with a closin operation of said last-mentioned contactor for open circuiting said impedance element, a second impedance element, and means associated with an opening operation of the other of said contactors for connecting said second impedance element in shunt circuit relation with said reactor and associated with a closing operation of said other of said contactors for open circuiting said second impedance element.
  • a transformer winding having a plurality of taps, an electrically mid-tapped reactor, means including a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps and disconnecting them therefrom, a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an impedance element, means operative upon one of said contactors being actuated to its full open position for connecting said impedance element in shunt circuit relation with said reactor through the other of said contactors and associated with a closing operation of said one contactor for open circuiting said impedance element, a second impedance element, and means operative upon the other contactor being actuated to its full open position for connecting said second impedance element in shunt circuit relation with said reactor through the first-mentioned contactor and operative upon a closing operation of said other contactor for open circuiting said second impedance element.
  • a transformer winding having a plurality of taps
  • a main reactor having end terminals and an electrically mid-tapped reactor
  • a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an auxiliary two-winding reactor, means associated with an opening operation of one of said contactors for connecting one of the windings of said auxiliary reactor in shunt circuit relation with said main reactor, and means associated with an opening operation of the other of said contactors for connecting the other winding of said auxiliary reactor in shunt circuit relation with said main reactor.
  • a transformer winding having a plurality of taps, an electrically mid-tapped reactor, means including a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps and disconnecting them therefrom, a circuit for said transformer including a conductor connected to the mid-tap of said reactor, an auxiliary two-winding reactor, means operative upon one of said contactors reaching its full open position for connecting one of the windings of said auxiliary reactor in shunt circuit relation with said mid-tapped reactor through the other of said contactors, and means operative upon said other contactor reaching its full open position for connecting the other Winding of said auxiliary reactor in shunt circuit relation with said one of said contactors.
  • a transformer winding having a plurality of taps, an electrically midtapped reactor, a pair of impedance elements, a pair of arcing duty contactors for respectively connecting the terminals of said reactor to different ones of said taps by way of a series connection through difierent ones of said impedance elements, and means associated with an opening motion of either contactor for efiectively short circuiting the impedance element in series therewith.
  • a transformer winding having a plurality of taps, a split main reactor, a pair of arcing duty contactors for respectively connecting the terminals of opposite halves of said reactor to different ones of said taps, an electrically mid-tapped auxiliary reactor having 15 Number 10 end terminals connected respectively to the remaining free terminals of said split reactor and having its mid-tap connected to a load circuit for said transformer winding, and means associated with an opening operation of either contactor for efiectively short circuiting one ofthe halves of said split main reactor.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)
US634573A 1945-12-12 1945-12-12 Tapped transformer system Expired - Lifetime US2440983A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE482065D BE482065A (no) 1945-12-12
US634573A US2440983A (en) 1945-12-12 1945-12-12 Tapped transformer system
GB36754/46A GB619484A (en) 1945-12-12 1946-12-12 Improvements in and relating to load-ratio-control circuits for transformers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US634573A US2440983A (en) 1945-12-12 1945-12-12 Tapped transformer system

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US2440983A true US2440983A (en) 1948-05-04

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3493847A (en) * 1965-12-01 1970-02-03 English Electric Co Ltd On-load tap changing circuits

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1626970A (en) * 1925-03-18 1927-05-03 Asea Ab Voltage regulator-for transformers

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1626970A (en) * 1925-03-18 1927-05-03 Asea Ab Voltage regulator-for transformers

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3493847A (en) * 1965-12-01 1970-02-03 English Electric Co Ltd On-load tap changing circuits

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GB619484A (en) 1949-03-09
BE482065A (no)

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