3,262,036
`C. D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. 19, 1962
`7. Sheets-Sheet
`
`t 6 +23+23+45+45+6, +6lit 23+ 23:45+4.5-6+ 6. -- 23:2
`FIG5C
`
`
`
`o->
`
`FIG5F
`
`1 C
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 1
`
`

`

`3,262,036
`c. D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. 19, 1962
`7 Sheets-Sheet 2
`
`
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 2
`
`

`

`3,262,036
`C.D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. 19, 1962
`7 Sheets-Sheet 3
`
`
`
`FIG6.
`
`Al A2
`FIG8C
`
`4-7 15+165+164+7 4+75+ 65+16 4+7
`---
`- -
`FG8E.
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 3
`
`

`

`3,262,036
`C. D. CLARKE ETA
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. 19, 1962
`7 Sheets-Sheet 4
`
`
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 4
`
`

`

`3,262,036
`C. D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. 19, 1962
`7 Sheets-Sheet 5
`
`
`
`
`
`is."
`32 Ti, Fl All 44
`E.
`t
`
`
`
`
`
`4O C-7 HH
`
`
`
`FIG 11
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 5
`
`

`

`3,262,036
`C. D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED OF A STAR-CONNECTED
`POLYPHASE ENDUCTION MOTOR
`Filed Sept. 19, 1962
`7 Sheets-Sheet 6
`
`
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 6
`
`

`

`3,262,036
`C. D. CLARKE ETAL
`July 19, 1966
`MEANS FOR SMOOTHLY WARYING THE SPEED of A STAR-CONNECTED
`POLYPHASE INDUCTION MOTOR
`Filed Sept. l9, 1962
`7 Sheets-Sheet 7
`
`
`
`y
`
`HHH is:
`"...I
`Bal
`t
`I
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 7
`
`

`

`United States Patent Office
`
`3,262,036
`Patented July 19, 1966
`2
`an adjacent one to cause a smooth change in the current
`therein and to establish a smooth change in the angular
`position of the magnetic field developed in the electric
`motor.
`It will be seen that as the angular position of the
`magnetic field is made to change gradually a substantially
`smoothly rotating field is produced which enables the
`motor to deliver substantially smooth torque at low,
`and very low speeds.
`According to a further feature, in the case where a
`single inverter means has two separate D.C. supplies,
`one of the D.C. supplies develops a positive voltage,
`and the other a negative voltage with respect to the
`common terminal; while according to an alternative fea
`ture both D.C. supplies develop a positive voltage and
`have their negative poles connected to a common ter
`minal.
`According to another aspect of the invention each
`motor phase has its own D.C. supply and an individual
`inverter means.
`Means for commutating the controlled switching el
`ements of the inverter means can be connected in circuit
`between the inverter means and the D.C. supplies, or
`between the inverter means and the motor phases.
`According to a further feature in the case where a
`single inverter means is associated with two D.C. sup
`plies the outer end of each motor phase is connected
`to each D.C. supply through a silicon controlled rectifier
`acting as controlled switching element, and the silicon
`controlled rectifiers are actuated in pairs by respective
`gating circuits which are selected sequentially by a driven
`selector switch such that each motor phase in turn will be
`connected to one of the D.C. supplies while the voltage
`of the latter is increasing, and the motor phase cyclically
`in advance will be connected to the other D.C. supply
`while the voltage of the latter is falling.
`In such a case, and according to yet another feature,
`use is made of a bistable circuit actuated by an oscillator
`for first commutating the silicon controlled rectifiers
`connected to one of the D.C. supplies, and then those
`connected to the other D.C. supply, alternately, the oscil
`lator also actuating the rotary switch through a delay
`means whereby, immediately after commutation, to ener
`gise a gating circuit to fire its associated pair of silicon
`controlled rectifiers for connecting the phases appropri
`ately to the D.C. supplies.
`The invention will now be described further with ref
`erence to the accompanying drawings, in which:
`FIGURE 1 is a block diagram of the aforesaid known
`form of variable frequency D.C. inverter means for driv
`ing a 3-phase, squirrel-cage induction motor;
`FIGURE 2 is a diagram of the output potentials of
`the inverter means of FIGURE 1;
`FIGURE 3 is a diagram illustrating the torque de
`veloped by the motor when driven in the manner of
`FIGURE 1 at low and very low speeds;
`FIGURE 4 is a block diagram illustrating one em
`bodiment of the present invention;
`FIGURE 4A is the same as FIGURE 4 but shows a
`commutating arrangement in a different position;
`FIGURE 5 is a composite diagram concerning the
`embodiment of FIGURE 4 and showing at FIGURES
`5a and 5b the waveforms associated with the two D.C.
`supplies; at FIGURE 5c the sequencing of the switching
`elements of the inverter; and at FIGURES 5d, 5e and
`5f the voltages developed across the three phases of the
`motor;
`FIGURE 6 is a block diagram illustrating another em
`bodiment of the invention;
`FIGURE 7 is a block diagram illustrating yet another
`embodiment of the invention in which a 2-phase motor
`
`10
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`20
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`25
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`30
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`35
`
`40
`
`3,262,036
`MEANS FOR SMOOTHLY WARYING THE SPEED
`OF A STAR-CONNECTED POLYPHASE INDUC
`TION MOTOR
`Christopher D. Clarke and David A. Jones, Lough
`borough, England, assignors to Brush Electrical Engi
`neering Company Limited, Falcon Works, Lough
`borough, England
`Filed Sept. 19, 1962, Ser. No. 224,768
`Claims priority, application Great Britain, Sept. 21, 1961,
`33,779/61
`7 Claims. (CI. 318-230)
`The invention relates to controlling the speed of a
`star-connected polyphase induction motor of which the
`phases are star-connected or independent, and has ref
`erence to a variable frequency D.C. link inverter means
`for supplying such a motor (e.g., a squirrel-cage-type mo
`tor). With a known form of variable frequency D.C.
`inverter means for supplying such a motor the inverter
`has been fed from a single D.C. supply, but at very low
`motor speeds the motor rotor moves in discrete steps
`thus rendering the arrangement unsuitable for use in
`applications where a smooth motor torque is required at
`such low speeds (e.g., in the case where the motor is
`for locomotive traction). The main object of the in
`vention is to mitigate that disadvantage by providing
`a variable frequency drive to a polyphase star-connected,
`induction motor such that the speed of the electric motor
`may be varied smoothly, at low speeds ranging from
`zero, and that the electric motor develops substantially
`smooth torque at all motor speeds down to Zero, an
`essential characteristic of the drive being that if the
`electric motor is a squirrel-cage induction motor, there
`are no electrical contacts in the power circuit of the
`drive which rub, slide or move during operation of
`the drive, on-off contactors and overload contactors be
`ing permitted in the power circuit as no sliding, rubbing
`or moving of the electrical contacts occur in these units
`during normal operation.
`According to one aspect of the invention, two variable
`voltage D.C. supplies, which operate at identical vari
`able frequencies but are out of phase, are connected
`through one or more inverter means to the motor wind
`ings, such that for a period in each half cycle an increas
`ing current, derived from the one of the variable voltage
`D.C. supplies whose voltage is increasing, is fed through
`an inverter means to one phase or section of the motor
`windings while in the same period a decreasing current,
`derived from the other variable voltage D.C. Supply
`whose voltage is decreasing, is fed through the same
`or different inverter means to another phase or section
`of the motor windings displaced from the first, the alter
`nate increasing and decreasing variation of voltage of
`the D.C. supplies being so synchronised to the Switching
`action of the inverter means that the magnetic field in
`the motor rotates continuously in a substantially smooth
`manner to exert a substantially smooth torque on the
`rotor at low and very low speeds.
`According to a feature of this aspect of the invention,
`the two D.C. supplies have a common terminal con
`nected to the star-point of the motor phases and supply
`a single inverter means, the D.C. supplies being arranged
`such that the voltage of one of them will be at its max
`imum value when that of the other is at a minimum,
`and vice versa, and the inverter means includes controlled
`switching elements which are controlled in phased re
`lationship to the D.C. supplies and cause the motor
`phases to be connected, sequentially, to the inverter volt
`age input first from one of the two D.C. supplies, and
`then the other, alternately, whereby an A.C. voltage is
`developed across each selected motor phase such that
`as the voltage increases in one motor phase it wanes in
`
`45
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`50
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`HALLIBURTON EXHIBIT 1024
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`

`

`3.
`has each phase supplied from a separate D.C. supply and
`inverter combination;
`FIGURE 8 is a composite diagram showing at FIG
`URES 8a and 8b the waveforms associated with the two
`D.C. supplies of FIGURE 7; at FIGURE 8c the arrange
`ment of the two windings of the motor; at FIGURE 8d
`the firing sequence for the controlled switching elements
`of the two inverters of FIGURE 7, and at FIGURE 8e
`the manner in which the direction of the magnetic field
`of the motor varies due to the fluctuation of the D.C.
`supplies and the Switching action of the inverters;
`FIGURE 9 is a circuit diagram corresponding with
`FIGURE 4 illustrating the power circuit;
`FIGURE 10 shows how the commutation and the fre
`quency of the D.C. supplies shown in FIGURE 9 are
`controlled;
`FIGURE 11 shows how the inverter of FIGURE 9 is
`controlled;
`FIGURE 12 is a circuit diagram of one of the paired
`gating circuits of FIGURE 11;
`FIGURE 13 is a circuit diagram of an electronic pulse
`generator shown in FIGURE 11; and
`FIGURE 14 is a circuit diagram combining the circuits
`of FIGURES 10, 11 and 13.
`Referring firstly to FIGURE 1, the said known form
`of D.C. link inverter has, as shown, a single, steady D.C.
`Supply, and the inverter, shown generally at 20, has a
`3-phase output. The inverter has controlled switching
`elements CS1 to CS6 which are extinguished by a com
`mutating arrangement 21, in either of the positions shown,
`So as to become conducting in the sequence 1--6, 1-2,
`3-H2, 3--4, 5-4, 5-6, repeated, the frequency of op
`eration of the commutating arrangements and the in
`verter being controllable by means (not shown) for
`varying the speed of the motor. The outputs of the in
`35
`verter to motor phases A, B and C will follow the po
`tentials shown in FIGURE 2, and the torque from the
`electric motor will be as shown in FIGURE 3 for low in
`verter frequencies, and thus, for the consequent low motor
`speeds.
`Reference to FIGURE 3 shows that at slow, or very
`slow speeds the output torque alternates between a maxi
`mum and zero, thus causing the motor rotor to rotate in
`a series of jerky steps; but it will be realised that as the
`motor speed increases the time interval between the jerks
`becomes progressively reduced until such time as the
`motor will, to all intents and purposes, run smoothly.
`This jerky operation at low speeds is a great disad
`vantage in many motor applications, particularly in the
`cases where the motor is for propelling a locomotive.
`The invention overcomes this disadvantage of discon
`tinuous torque at low speed, as will be appreciated by
`referring to FIGURE 4. The latter shows a positive D.C.
`supply DC1 and a negative D.C. supply DC2 having a
`common terminal T. These supplies are such as to de
`velop rising and falling voltage waveforms at a common,
`controlled variable frequency as hereinafter more fully
`described. The voltage waveform of the positive supply
`DC is shown in FIGURE 5a and that of the negative
`supply DC2 in FIGURE 5b, and these waveforms con
`stitute the input to the inverter 20. The latter, as in the
`known case, includes controlled switching elements CS
`to CS5 with a commutating arrangement 21 in one of the
`positions shown in FIGURE 4 or FIGURE 4A and con
`stituting a 3-phase output bridge for feeding a 3-phase,
`star-connected, squirrel-cage induction motor of which
`the phases are indicated at A, B and C. The star-point
`of these phases is connected to the common terminal T
`of the two D.C. supplies.
`The controlled switching elements of the inverter CS1
`to CS6 are made conducting in the sequence 1--6, 1-2,
`3--2, 3--4, 5-4, 5-6, repeated, being correlated in
`respect of frequency and time to the variation of the
`D.C. supplies such that CS1 and CS6 are made conduct
`ing when the positive D.C. inverter Supply DC1 is Zero
`
`45
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`40
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`50
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`55
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`60
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`65
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`70
`
`75
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`3,262,036
`
`O
`
`5
`
`20
`
`25
`
`30
`
`4.
`and the negative ED.C. inverter supply DC2 is a maximum
`as shown in FIGURE 5c. Thereafter the controlled
`switching elements of the inverter are made conducting
`in the sequence detailed above, the action of Switching
`to the next inverter pair of controlled switching elements
`coinciding with the next maximum occurring in the out
`put of either the positive or negative D.C. supply to the
`inverter. In this way, the potentials at the outputs of
`the inverter and the voltage developed across the phases
`of the electric motor are as shown in FIGURES 5d, e
`and f.
`A comparison between the output voltages of the known
`arrangement as shown in FIGURE 2, with the output
`voltages shown in FIGURES 5d, e and f discloses that
`the latter output voltages change far more smoothly.
`Thus, the application to the motor phases of the wave
`forms shown in FIGURES 5d, e and f will cause the
`magnetic field of the motor to rotate substantially smooth
`ly and provide a substantially smooth output torque from
`the motor. The above description is for illustration only,
`and the application of the invention is described later.
`By using this system, and arranging a suitable number
`of controlled switching inverter elements each arranged
`to be made conducting at a suitable time, any number
`of A.C. outputs may be provided by the inverter in cor
`rect phase relationship to provide a smoothly rotating
`magnetic field in an electric motor with a corresponding
`number of phases and will result in the development of
`a Smooth torque by the motor.
`Further, it is not essential that the rise and fall of
`voltage of the positive and negative D.C. supplies should
`be linear or absolutely smooth. The rise in voltage may
`follow any law which is suitable for use with the system
`to provide at least a substantially smooth torque from
`the electric motor, and the actual rise and fall of the volt
`age of the D.C. supplies may be in the form of a stair
`case or any other form suitable for providing at least
`a substantially smooth torque from the electric motor.
`In addition to the foregiing, it must be understood that
`some methods of commutation may produce short dura
`tion transient voltages on the waveforms developed at the
`output terminals of the inverter, and that any such transi
`ents shall be acceptable, provided that the torque output
`from the electric motor is substantially smooth.
`The modification shown in FIGURE 6 differs from
`that in FIGURE 4 in that the two D.C. supplies are posi
`tive and have their common terminal T1 connected both
`to the star-point of the motor and to a commutating cir
`cuit 21. The waveforms of the two D.C. sources are in
`dicated respectively beneath them in the figure. The
`switching elements 1 to 6 are silicon controlled rectifiers,
`and the odd numbered elements are commutated by a sili
`con controlled rectifier 7, and the even numbered ones by
`a silicon controlled rectifier 8, and the said elements 1
`to 6 are made conducting in the same sequence as in
`FIGURE 4, and the arrangement operates in a manner
`similar to that described with reference to the latter
`figure.
`FIGURE 7 shows an application of the invention in
`which each phase of a motor is supplied from a separate
`D.C. source and inverter combination. The figure shows
`the arrangement for a 2-phase motor, but this embodi
`ment of the invention is of equal application when the
`motor has more than two phases, the provisions made
`for each phase being precisely the same.
`In the figure the two motor phases are shown at A
`and B, and their respective, variable D.C. supplies at
`DC and DC2. The inverter 20a for phase A includes
`controlled switching elements CR10 to CR13, and the
`inverter 20b for phase B includes controlled switching
`elements CR4 to CR17. Between each D.C. supply
`and its associated inverter is a commutating arrangement
`21 for the controlled switching elements.
`It will be seen from FIGURE 8c that the ends marked
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 9
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`

`

`3,262,036
`
`O
`
`5
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`20
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`25
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`30
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`35
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`40
`
`5
`A2 and B4 of phases A and B respectively may be con
`nected together.
`Referring now to FIGURES 8a, 8b, 8d and 8e, it
`will be seen from FIGURES 8a and 8b that while the
`voltage of D.C. supply DC1 rises from zero to maximum
`positive, the voltage of D.C. supply DC2 falls from maxi
`mum positive to zero, and vice versa. By firing the con
`trolled switching elements in the order shown in FIG
`URE 8d the direction of the magnetic field of the motor
`is changed as indicated in FIGURE 8e. Thus, and taking
`the first firing combinations at the left of FIGURE 8d,
`an increasing voltage will be applied at end A1 of phase
`A relative to end A2 at the same time as the voltage ap
`plied at end B3 of phase B is decreasing relative to end
`B4, during the next firing combination the voltage ap
`plied at end A1 of phase A will decrease relative to end
`A2 while the voltage applied to end B4 of phase B in
`creases relative to end B3, and during the third firing
`combination the voltage applied to end B4 of phase B
`decreases relative to end B3 while the voltage applied to
`end A2 of phase A increases relative to end A1.
`The benefits of performance due to the action above
`described, as opposed to the performance of the said
`known D.C. link inverter, reduce as the speed of the
`drive is increased. There is a point, when increasing the
`drive speed from zero, where the torque from the known
`D.C. link inverter is sufficiently smooth, due to the fly
`wheel effect of the motor and load, and to the inductive
`effects of the motor windings, to be as suitable as the
`torque at the same speed from the D.C. link inverter of
`the invention. At drive speeds above this point more
`power can be developed from the electric motor if it is
`fed from the known D.C. link inverter than if it is fed
`from the D.C. link inverter of the invention. It may
`therefore be desirable in some instances to switch from
`the new system to the old at this point.
`FIGURE 9 shows the power circuit involved in FIG
`URE 4 in greater detail. The controlled switching ele
`ments CS1 to CS6 are, however, in this case shown as
`silicon controlled rectifiers 1 to 6. The positive and
`negative D.C. supplies DC and DC2 are respectively
`derived from the outputs of devices 30 and 31 which are
`respectively fed from steady D.C. sources indicated at
`32 and 33. The devices 30 and 31, which can be of any
`known kind, are for providing the fluctuating voltages re
`quired for DC and DC2, and the fluctuation is controlled
`as presently described with reference to FIGURE 10.
`The DC1 and DC2 supplies are connected to the common
`terminal T through capacitors 34 and 35 to provide a
`reference point of Zero potential connected to the star
`point of the motor phases through line 36.
`The silicon controlled rectifiers are fired in the appro
`priate order by gating circuits, as will presently be de
`scribed with reference to FIGURE 11, and before each
`new pair of them are fired a commutating pulse is fed
`either to the even, or odd numbered ones whereby to
`extinguish the silicon controlled rectifier, of the pre
`viously fired pair, which is not required.
`For convenience of the subsequent description rectifiers
`1, 3 and 5 will be referred to collectively as the odd recti
`fiers, and 2, 4 and 6 as the even rectifiers.
`Having regard to the order in which the rectifiers are
`fired (i.e., 1--6, 1-2, 3--2, 3--4, 5-4, 5-6) it will be
`assumed that the pair 1--6 has already been fired and that
`it is now desired to fire 1-2. Before this can be done
`it is necessary to extinguish 6. The latter is among the
`even rectifiers, of which 2 and 4 were previously extin
`guished. For extinguishing rectifier 6 it is necessary to
`make phase-connection point 37 negative with respect to
`point 38, and this is done by firing a silicon controlled
`rectifier C1 which is in series with a D.C. source 39
`whereby to convey the charge of capacitor 40 which is
`at a voltage equal to the positive voltage DC2 plus the
`positive voltage of source 39. The capacitor 40 applies
`this positive voltage plus the positive voltage of Source
`
`45
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`6
`39 to point 38 whereby point 38 is made more positive
`than point 37 by an amount equal to twice the voltage
`of source 39. This commutates rectifier 6.
`Capacitor 40 recharges negative while current flows
`through choke 41, source 39 and silicon controlled recti
`fier C1, until the capacitor 40 reaches a potential equal
`to the negative voltage of DC2 plus the negative voltage
`of source 39. At this point the silicon controlled recti
`fier C1 extinguishes itself and the current that is flow
`ing through choke 41 is now carried by diode 42.
`In a somewhat similar manner, when one of the odd
`rectifiers is to be commutated, silicon controlled recti
`fier C2 in series with a D.C., source 43 acts to convey the
`negative charge on capacitor 40 to line 44, common to
`the odd rectifiers, so as to make it more negative than
`their respective motor phases.
`Capacitor 40 recharges positive while current flows
`through choke 45, source 43 and silicon controlled recti
`fier C2 until the capacitor 40 reaches a potential equal to
`the positive voltage, of DC plus the positive voltage
`of source 43. At this point the silicon controlled recti
`fier C2 extinguishes itself and the current flowing through
`choke 45 is now carried by diode 46.
`When any of silicon controlled rectifiers 1 to 6 are
`commutated it is important to dispose of reactive cur
`rent of the motor phase concerned, and this is done
`through respective diodes 47.
`FIGURE 10 repeats the showing of FIGURE 9 and
`shows, in addition, how the commutation of the silicon
`controlled rectifiers 1 to 6, and the frequency of the varia
`ble-voltage D.C. supplies DC1 and DC2 are controlled.
`In this figure is shown an oscillator 50, of which the
`frequency can be controlled, which is connected to the
`devices 30 and 31 so as to operate them at its own fre
`quency, and, at the said frequency, to a bistable circuit
`51 for firing the commutating silicon controlled rectifiers
`C1 and C2 in turn.
`FIGURE 11 also repeats the showing of FIGURE 9,
`but additionally shows the oscillator 50 of FIGURE 10
`performing another function of synchronising the action
`of the inverter.
`The said oscillator drives a rotary switch 60, through a
`delay device 61 of any suitable known kind, in Synchro
`nism with its own frequency. The rotary switch feeds a
`signal pulse, having a square waveform, from a device 62,
`more fully described with reference to FIGURE 13, Selec
`tively to gating circuits for each associated pair of odd
`and even silicon controlled rectifiers 1 to 6. The gating
`circuits for the rectifiers are shown in block form and are
`identified in the figure by the reference numerals of the
`rectifiers they respectively fire (i.e., 1--6, 1+2, 3--2,
`3-4, 5-4, 5-6).
`The outputs from these gating circuits, which latter are
`more fully described with reference to FIGURE 12, are
`applied across their associated pairs of rectifiers, in the
`order dictated by rotary switch 60, to fire them for feed
`ing the associated motor phases with the outputs from
`DC1 and DC2, as appropriate.
`It will be observed that each adjacent pair of gating cir
`cuits controls one of the silicon controlled rectifiers in
`common. Thus, rectifier 1 is common to gating circuits
`1--6 and 1-2, and rectifier 2 is common to gating circuits
`1-2 and 3-4-2, and so on. For this purpose gating circuit
`1--2 is shown as having a connection to the output circuit
`from gating circuit 1--6 for supplying rectifier 1, but in
`order to avoid a feed back into gating circuit 1--6 when
`gating circuit 1+2 is operating, the path to rectifier 1 from
`gating circuit 1--6 is through a diode 63. Another diode
`64 performs the same function when gating circuit 1-6
`is operating and gating circuit 1-2 is not. The corre
`sponding diodes for gating circuits 1--6 and 5-6 are
`shown at 65 and 66. It will be seen that a similar pro
`vision is made as between gating circuit 1-2 and 3-1-2,
`and between gating circuits 1--6 and 5-6, but for the
`
`HALLIBURTON EXHIBIT 1024
`Halliburton Energy Services, Inc. v. U.S. Well Services, LLC, IPR2023-00558, Page 10
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`3,262,036
`
`10
`
`5
`
`20
`
`25
`
`35
`
`45
`
`50
`
`30
`
`7
`purpose of simplified reading the equivalent provisions
`for the other gating circuits are not shown.
`Each of these gating circuits includes a transformer
`of which the primary winding is fed with the square
`Wave form output from device 62, and which has two
`Secondary windings whose outputs are applied to the
`respective rectifiers for firing them. Such a gating cir
`cuit for firing the pair of rectifiers 1 and 6 is shown in
`FIGURE 12.
`In FIGURE 12 the square waveform output from de
`vice 62 is indicated at 70 and is applied to the primary
`winding 71 of a transformer of which the magnetic core
`is shown at 72. The core has secondary windings 73 and
`74 about it, and these are respectively connected for firing
`rectifiers 1 and 6.
`The secondary winding 73 has a central connection to
`point 75 and its ends are connected to the grid 76 of
`rectifier 1 through diodes 77 and 78 which make the grid
`positive with reference to point 75 whereby to fire the
`rectifier. The secondary winding 74 and its diodes 79
`and 80 fire rectifier 6 in precisely the same manner.
`The device 62 is shown in FIGURE 13 as a typical,
`known circuit employing transistors 81 and 82, and di
`odes 83 and 84 whereby to induce a square waveform
`pulse in a secondary winding 85 to be fed to the rotary
`switch 60, the associated components shown being a
`steady D.C. source 86 connected to a central tapping of
`a primary winding 87, a capacitor 88, a feed-back wind
`ing 89 and a resistor 90. The square waveform pulse is
`fed to the movable contact of the rotary switch 60 for
`selective feeding to the gating circuits.
`For ease of comprehension the various circuits have
`been described separately with reference to FIGURES
`9 to 13, but are shown co-ordinated in FIGURE 14, in
`which latter the power circuit has been drawn in heavy
`lines, and the various control circuits have been drawn
`in lighter lines. Thus, FIGURE 14 shows the oscillator
`50 controlling the frequency of the voltage fluctuations
`of the supplies DC and DC2, the firing of the rectifiers
`and their commutation. Delay 61 ensures that com
`40
`mutation takes place before the rotary switch 60 selects
`a new pair of rectifiers to be fired. It will therefore be
`seen that by increasing the frequency of the oscillator
`from zero the motor can be accelerated smoothly from
`rest.
`What we claim as our invention and desire to secure
`by Letters Patent of the United States is:
`1. A variable frequency D.C. link inverter means for
`supplying a star-connected polyphase induction motor
`such that its speed can be varied smoothly from zero to
`very high speeds and such that it develops substantially
`smooth torque at all speeds within its range, comprising
`an inverter having a number of output phases equal to
`the number of phases of the motor, said inverter includ
`ing controlled switching elements for sequentially con
`necting its said output phases to said motor phases re
`spectively, a commutating circuit for artificially commutat
`ing said switching elements, a firing circuit for firing said
`switching elements for sequentially connecting said out
`put phases of said inverter to said motor phases respec
`tively, a D.C. voltage supply for said inverter, a connec
`tion from said D.C. voltage supply to the star point of
`said motor, a circuit for repeatedly varying the voltage
`of said D.C. supply in synchronism with the operation
`of the switching elements of the inverter, and a circuit
`for varying the frequency at which the voltage variations
`OCCU.
`2. A variable frequency D.C. link inverter means for
`supplying a star-connected polyphase induction motor
`such that its speed can be varied smoothly from zero to
`very high speeds and such that it develops substantially
`smooth torque at all speeds within its range, comprising
`an inverter having a number of output phases equal to
`the number of phases of the motor, said inverter includ
`ing controlled switching elements for sequentially con
`
`necting its output phases to said motor phases respec
`tively, a commutating circuit for artificially commutat
`ing said switching elements, a firing circuit for firing said
`Switching elements for sequentially connecting said out
`put phases of said inverter to said motor phases respec
`tively, two D.C. voltage supplies for said inverter, a com
`mon terminal to which said D.C. voltage supplies are
`connected together, one of said D.C. voltage supplies hav
`ing a positive voltage with respect to said common termi
`nal and the other of said D.C. voltage supplies having a
`negative voltage with respect to said common terminal,
`a connection between said common terminal and the star
`point of said motor, a circuit for smoothly and repeatedly
`varying the voltages of said supplies from zero to maxi
`mum inversely and in synchronism, a circuit for varying
`the frequency at which the voltage variations occur, and
`means for operating said commutating means and said
`firing means in timed relation to the voltage variations
`of said sources, and at the same frequency.
`3. A variable frequency D.C. link inverter means for
`Supplying a star-connected polyphase induction motor
`such that its speed can be varied smoothly from zero to
`very high speeds and such that it develops substantially
`smooth torque at all speeds within its range, comprising
`an inverter having a number of output phases equal to
`the number of phases of the motor, said inverter includ
`ing switching elements for sequentially connecting its said
`output phases to said motor phases respectively, two
`D.C. voltage supplies for said inverter, a common termi
`nal to which said D.C. voltage supplies are connected
`together, one of said D.C. voltage supplies having a posi
`tive voltage with respect to said common terminal and
`the other of said D.C. voltage supplies having a negative
`voltage with respect to said common terminal, a con
`nection between said common terminal and the star point
`of said motor, a circuit for smoothly and repeatedly vary
`ing the voltages of said supplies from zero to maximum
`inversely and in synchronism, a circuit for varying the
`frequency at which the voltage variations occur, said
`Switching elements adapted sequentially to connect one
`motor phase during a period in each half cycle to be sup
`plied from said inverter with an increasing current de
`rived from the one of said variable voltage D.C. supplies
`whose voltage is increasing, and in the same period to
`connect another motor phase to be supplied from said
`inverter with a decreasing current derived from the other
`of said variable voltage D