DE1166925B - Device for generating multiphase alternating voltages from direct voltages - Google Patents

Description

Applicant:

Westinghouse Electric Corporation, East Pittsburgh, Pa. (V. St. A.) Representative:

Dr. jur. G. Hoepffner, lawyer, Erlangen, Werner-von-Siemens-Str. 50

Named as inventor:

Rudy P. Putkovich, Export, Pa.,

Thomas M. Corry, Monroeville, Pa. (V. St. A.)

Claimed priority:

V. St. v. America January 24, 1958 (710934)

TX- cc α u · &<. ■ τ ·· ■ u τ device for generating multiphase

The invention relates to a device for Erzeu- _"r, X ■ ■.

generation of multiphase, in particular square-wave alternating voltages from direct voltages

AC voltages from DC voltages below
Use only dormant, controllable
Circuit elements, preferably transistors, as 5
Switching means in one of the number of phases corresponding
Number of inverters, phase shifting means for shifting the output voltages of the individual inverters by one of the
Phase number corresponding phase angle provided io
are. Each inverter consists of a transformer and two switching means that are controlled by the transformer and that
a DC voltage alternately to one of the two
Apply primary windings of the transformer, see 15
that on the secondary winding an alternating voltage
occurs, which is generally rectangular in shape
Has. The known bodies of this type have
thereby a mutual dependency, ie a mutual control of the individual change 20
rectifier and therefore do not have a distinct master inverter that controls the other inverters as dependent slave inverters. 2 These known devices are in terms of

Number of transformers and their windings 25 Figs. 1, 2 and 4 show arrangements for as well as the necessary chokes are expensive and therefore generate three-phase alternating voltages expensive and also to a certain extent more prone to failure. DC voltage,

The invention is based on the object, FIG. 3 shows a graphic representation of the

Disadvantages of these known devices on different parts of the arrangement according to FIG. 1 multiple ways to eliminate and properly working 3 ° and 2 occurring voltages. In Fig. 1 is the entire circuit arrangement

switching elements required for this. The solution denoted by 1; it contains three each of one task succeeded according to the invention in that a DC voltage source fed inverter 3, for frequency control of the device an alternating 3 α and 3 b. At the output of each inverter, a square-wave alternating voltage can be designed as an inverter that is independent of the other, and an additional one can be added for this purpose. The frequency of the alternating voltages is proportional to the borrowed, in series with a variable impedance in the size of the direct voltages. The control circuit of both switching means of the lead alternation phase number is equal to the number of inverters, contains the transformer winding arranged rectifier The three inverters 3, 3 a and 3 b have the same and that the impedance of the 40 structure and mode of operation, so that only the output voltage of the Master inverter or inverter 3 needs to be described in more detail, the preceding slave inverter dependent. The inverter 3 is used to control the

Phase shifting means of the slave inverters two other inverters 3 a and 3 b and is referred to below as lead inverter for switching the switching means of the slave inverters, is also used and for this purpose in the control circuit of the switching 45 while the dependent inverters controlled by it are arranged. Preferably, α than comparable converters 3 and 3 b, referred to as Folgewechseländerbare impedance for switching and / or phase are referred to judge. The master inverter 3 move saturable iron chokes used, which is fed by a DC voltage source 5. He iron cores have rectangular hysteresis loops. converts the DC voltage into an AC voltage to further details, reference to a plurality in 50 located at the output terminals 7. 9 The exemplary embodiments of the master inverter 3 shown in the drawing contain a transformer, subject matter of the invention, explained in more detail. 11, the core of which is 13 to achieve good operational

properties is operated in the unsaturated range. The core 13 can be made of any material, such as. B. made of silicon steel.

A primary winding consisting of two partial windings 17 and 19 is used to magnetize the core 13 15. A secondary winding 21 has the output terminals 7 and 9.

The partial windings 17 and 19 are through parallel

to prevent any reversal of the polarity of the voltage induced in winding 31.

Thus, the switching transistor 27 opens in accordance with that originating from the direct voltage source 5 Current through the emitter and base of the circuit containing the capacitor 45 and the resistor 47. As soon as the switching transistor 27 is open, a current originating from the direct voltage source 5 flows through the partial winding 17 and generates a magneto

paths 23 and 25 so with the DC voltage source 5

connected that a magnetization of the core 13 io motor force, which a corresponding magnetic

is possible in both directions. Induces two switching transient flux in the core 13. This river

Sistors 27 and 29 are used to control the excitation induced in the windings 31 and 33 voltages

of the partial windings 17 and 19. The switching transistors with the indicated by the plus and minus signs

are for this purpose with their emitter-collector electrodes in NEN polarities. This will make the switching transistor

the parallel paths 23 and 25 are inserted. 15 27 can be kept open, and the switching transistor 29

Transistors of the p-n-p type or of the n-p-n type continue to have a blocking effect.

be used. The switching transistors 27 and, which always have opposite operating states 29 work as control switches, with the operating

The flux also induces a voltage of the specified polarity in winding 35, which is a current through which the windings 31, 33 and 41 as well as the

states of both switching transistors in a known manner 20 resistors 43 and 44 containing circuit

drives. With an unsaturated core 39 of the iron choke 37, the impedance of the winding 41 is very high, so that essentially the entire voltage of winding 35 is applied to winding 41.

This state lasts until the core 39 goes into saturation and the impedance of the winding 41 drops to a very small value. Kick it at the resistors 43 and 44 voltage drops with the indicated polarities. These tensions

are periodically reversible.

Auxiliary windings applied to the core 13 are used to control the switching transistors 27 and 29 31 and 33. The two auxiliary windings provide the readiness for switching the switching transistors necessary base voltages. For the actual switching of the switching transistors, one is arranged on the core 13 Winding 35 connected on the one hand to the base of the switching transistor 29 and on the other hand

Via the winding 41 of an iron choke 37 with 30, the switching transistors 27 and 29 are fed to a saturable iron core 39 - which is preferably made of a material with a rectangular hysteresis transistor 29 so that the switching transistor 27 blocks and the switching opens. The described periodic loop exists - at the base of the switching transistor repeating process is connected with the opening of the switching 27. The windings 31, 33, 35 and 41 transistor 29 terminated. There is a permanent Schwinsind connected in series, between the windings of the inverter 3, with two resistors 43 and 44 in the winding 21 of the transformer 11 in a rectangular series in the secondary windings 31 and 33. The emitters of both switching transistors
and the positive pole of the DC voltage source 5 are
to the connection between the two resistors 43
and 44 connected. A capacitor 42 is located par 40
allele to winding 41 and serves to reduce the
on the switching transistors during the switching activity
occurring voltage peaks.

How the lead inverter works 3
is as follows: If the DC voltage source 5 takes over the 45 state of the switch, it has been determined that switching means, not shown, is switched on, then it has been determined that at saturation a high magnetization will one of the two switching transistors 27 and 29 current occurs during the switching process. After the head, and the facility begins to work. In the invention, however, there are two saturable cores per alternation. The willingness to start depends on the energy loss in the transistor being considerably reduced by the presence of sufficient inequality. This results in a higher efficiency of the circuits and of the amplification of the switching degree of the inverter 3.

transistors off. When using switching transi- The structural correspondence of the subsequent reversing gates with greater amplification will reliably start the inverter3 α and 2> b with the master inverter even when there is a load. On the other hand, this is expressed by the fact that the corresponding lower parts, which are reliably sufficient for starting, are provided with the same reference numerals under the strengthening factor, according to a further development, with the addition of the indices α and b . To the invention means for deliberately inducing a three-phase AC output voltage to be disparate is provided. For this purpose 60 aim, the subsequent inverters 2> a and 3 b , an impedance between the negative terminal can be controlled by the lead inverter 3 so that the direct voltage source 5 and the base of one of the alternating voltages of the individual inverter transistors are arranged. In Fig. 1, this is each offset by 120 ° from one another, a capacitor 45 between the negative terminal. According to the invention, the arrangement 1 contains

the DC voltage source 5 and the base of the trans- 65 the AC voltages controlled phase shift

shaped alternating voltage is induced, the frequency of which is proportional to the voltage of the direct voltage source 5 is.

The above-mentioned switching arrangement results in an improved mode of operation of the inverter 3. In previous arrangements where a single saturable magnetic core had both effects, namely the Switching activity and maintaining the switching

sistors 27 arranged. An appropriately selected resistor 47 is connected upstream of the capacitor 45,
to the flow of an excessive base current

means that a phase shift between the alternating voltages of the subsequent inverters and of the lead inverter. Since the fre-

5 6

The frequency of the alternating voltages is determined by the sweep frequency voltage source 5. On the other hand, the phase relation of the switching transistors is determined, the above between the alternating voltages of the alternating arrangement is a three-phase voltage generator 3 and 3 α of changes in magnitude

gen, in which each phase voltage is independent of that voltage by 120 °. The voltage drops

other is postponed. 5 at the resistors 57 and 59 are something advantageous

For said phase shift between the greater than the amplitudes in the windings 31 a

AC voltages of the inverters 3 and 3 a are held and 33 a induced voltages. Through this

both via a saturable iron choke 49 with each other is a better and safer switching activity of the

coupled. The iron choke 49 has a saturated transistor.

ble core 51, which consists of a material with a substantially rectangular hysteresis loop in the io The alternating voltage at the subsequent inverter 3 b. The core 51 carries a winding 53. Depending on the inverter 3, a phase shift of 240 ° excitation thereof, the core will have more or less. For this purpose the sequence change is saturated. The winding 53 is in series with a hopper 3 b of a second secondary winding 67 feeding the second secondary winding 55 of the transport 15 of the subsequent inverter 3 α with the interposition of a formators 11 of the guide inverter 3 overall another saturable iron ballast 61 energized. To toggles. Furthermore, in series with the winding 53 magnetization of the iron choke 61 is one of two auxiliary windings 31a and 33 a of the transformer phase shift of 120 ° with respect to the changeover gate 13 a and two resistors 57 and 59. The voltage of the subsequent inverter 3 α corresponding connection between two resistors is needed with 20 time. The iron choke 61 completely corresponds to the emitters of the two switching transistors 27 a and the iron choke 51. It contains a magnet 29 a and the positive pole of the DC voltage source 5 a core 63 and a winding 65. Resistors 69 and 71 connected. are in turn in series with a winding 31b when the switching transistor 27 of the lead changeover or 33 & is connected to the winding 65. The converter 3 is current-permeable, a voltage 25 becomes wise and the effect of the iron choke 61 is as in the winding 55 with the indicated polarity at the iron choke 49.

induced. This voltage drives a current through to the follow-up inverters 3 a and 3 ft with the

the winding 53. The initially unsaturated core 51 lead inverter 3 safe after a few work

causes a large impedance of winding 53, so to synchronize clocks, it is desirable that

that essentially the entire voltage of the 30 following inverters are uncontrolled oscillations

Secondary winding 55 lies on winding 53. With perform whose frequencies are slightly lower than that

the saturation of the core 51 becomes the impedance of the oscillation frequency of the lead inverter

Winding 53 greatly reduced, so that they are in the.

Secondary winding 55 induced voltage now instead of the three DC voltage sources 5, 5 a

the resistors 57 and 59 with the indicated 35 and Sb in FIG. 1, the inverters 3, 3 α

Polarities occurs. These voltages have one and 3 b of a common DC voltage

such size and polarity that the switching transistor source can be fed. As a DC voltage source

27 a opens and the switching transistor 29 a blocks. It can be any conventional one, for example a battery,

to note that the positive half-wave of the subsequent- are used.

Inverter 3a only after saturation of the core 51 40 In Fig. 2, a further embodiment of the begins. Furthermore, the winding 53 is shown de-energized until the subject matter of the invention. The total at the beginning of the positive half-wave of the guide arrangement is denoted by la. The three inverters 3. As a result, the size of the inverters 3, 3 a and 3 b are of the same design, phase shift between the alternating voltages as in Fig. 1, but in a different way with the inverters 3 and 3 α being 45 other connected. The subsequent inverters 3 α and 3 b are correct, which is required to bring the core of the are both directly controlled by the alternating voltage of the positive saturation into the negative saturation, or lead inverter 3, vice versa. This time depends on the of which polarities of opposite directions occur in the secondary winding 55. The induced voltage decreases. Through corresponding secondary windings, each of the various components can be saturable iron chokes 77 or 79 with the following changes via one tuning of the various components, the inverters 3 α and 3 b for controlling the original magnetization of the core 51 and 3 b for controlling or the time required equals one third of the period of the 55 prepare the switching operations connected. The alternating current of the master inverter 3 must be ζ. B. be the alternating voltage of the subsequent inverter. In this case, an alternating voltage occurs on the following inverter 3a by 120 °, the alternating voltage of the follower 3 α, which is offset by 120 ° from the inverter 3 b by 240 ° against the alternating voltage compared to that of the lead inverter 3, offset from the lead inverter 3 is. 60 For this purpose, an iron choke 77 is used with a saturation point, as already mentioned, the time necessary for reversing the magnetization of the supply time, which corresponds to 120 ° of a period of the AC core 51 also from the change of the lead inverter 3, and voltage on the secondary winding 55 Depends on, have an iron choke 79 with a saturation time, the 60 ° changes in the voltage of the DC voltage of a period of the lead inverter 3 entquelle 5 speaks a change in this magnetization time 65, as well as opposing voltages result. The frequency is also that of the windings 73 and 75. This means that an additional alternating voltage of the master inverter 3 is obtained from a displacement of 180 °, so that a "loud" of. aet size of the voltage of the equal total displacement of 240 ° is given. The We-

according to the arrangement according to FIG. 2 is completely consistent with the mode of operation already described the arrangement according to FIG. 1.

In the F i g. 3 a to 3 e are time functions of the voltages of the devices according to FIG. 1 and 2 shown when the different inverters work synchronously. The F i g. 3 a to 3 e apply to the Cooperation between inverters 3 and 3 a.

In Fig. 3a, curve 89 represents the rectangular one AC voltage curve at the output of the master inverter 3.

In Fig. 3 b, the curve 91 shown represents the course of the voltage which occurs at the winding 83 of the iron choke 77 in FIG. This voltage is also rectangular and has a time interval in each period in which the voltage is zero. During this time interval, the iron choke 77 is saturated, and the winding 83 has a very low impedance, so that practically no voltage occurs across it. It is to be noted that this time interval is 120 ° of a period of the in FIG. 3 a corresponds to the alternating voltage shown.

In Fig. 3c two curves 93 and 95 are shown, which represent the phase blocking voltages that occur at the transistors 27 a and 29 a of the subsequent inverter 3 a. The dashed curve 93 applies to the voltage between the base and emitter of the transistor 27 a, while the solid curve 95 represents the voltage between the base and emitter of the transistor 29 a. These two tensions are in opposite phase. During the time in which the iron choke 77 goes into saturation, the voltages 93 and 95 are practically zero. When the iron choke is saturated, the phase blocking voltages reach a negative and positive value and maintain these values until the saturation disappears as a result of reversing the polarity of the AC voltage of the lead inverter.

Curves 97 and 99 in FIG. 3 d represent the course of the voltages that occur on the auxiliary windings 31 α and 33 α of the slave inverter 3 α . The dashed line 97 shows the voltage on the winding 31 α again, while the solid line 99 shows the voltage on the winding 33 α. The voltages according to curves 97 and 99 reverse their polarity at a time when the voltages according to curves 93 and 95 increase from the value zero to a positive or negative value corresponding to the saturation state; they retain their opposite polarity, even if the voltages according to curves 93 and 95 have become zero. The maximum values of the voltages according to curves 93 and 95 are somewhat greater than the amplitudes of the voltages according to curves 97 and 99. This ensures that the transistors switch properly.

In Fig. 3e, the AC voltage of the slave inverter 3 α is designated by 101 . This voltage reverses its polarity every time the voltages 97 and 99 on the auxiliary windings 31a and 33a reverse their polarities. Therefore, at this point in time, the direction of magnetization of the transformer cores dependent thereon is also reversed. To compare FIGS. 3a with 3e, it should be noted that the beginning of the positive half-waves of voltage 101 lags behind the beginning of the positive half-waves of voltage 89, as desired, by 120 °. The voltages on the slave inverter 3 b are corresponding, the AC voltage of the slave inverter 2> b lagging behind the AC voltage of the lead inverter 3 by 240 °.

In Fig. 4 shows a further embodiment of the subject matter of the invention. It is used to generate three alternating voltages in a delta connection. The three inverters 3, 3 α and 3 b are designed in exactly the same way as those according to FIGS. 1 and 2.

The interconnection is made so that the algebraic sum of the individual alternating voltages is zero in every moment. With this arrangement, high harmonics like them would otherwise occur with non-sinusoidal alternating voltages according to FIG. 3a, avoided. In the exemplary embodiment AC voltages are generated with a waveform according to FIG. 3b. There the three Voltages with a waveform according to FIG. 3b are each shifted by 120 ° from one another, is their algebraic sum equals zero at any moment.

To generate the single AC voltages according to Fig. 3b serve iron saturable reactors 103, 105 and 107 to the inverters 3, 3 a and 3 b are connected. It is recalled that the in Fig. The voltage 91 shown in FIG. 3 b occurs at the winding 83. If an additional winding is added to each core of the iron chokes, voltages will appear across them which have the same waveform as appear on the input winding of each iron choke.

The iron chokes have saturable magnetic cores 109, 111, 113 with a preferably rectangular hysteresis loop. In addition to the input terminals 115, 117 and 119, which are in series with secondary windings 121, 123, 125 of the transformers 11, 11a and Ub , each iron choke contains an output winding 127, 129 and 131 , respectively. Thus, voltages occur on the windings 127, 129 and 131 as a function of the excitation of the associated input windings 115, 117 and 119 , which have a waveform according to FIG. 3b. The windings 127, 129 and 131 are connected to output terminals 133 and 135, 137 and 139 and 141 and 143 . A phase voltage can be picked up between two of the terminals 135, 139 and 143.

Claims (8)

Patent claims: 1. Device for generating multiphase, in particular square-wave AC voltages from DC voltages using exclusively static, controllable circuit elements, preferably transistors, as switching means in a number of inverters corresponding to the number of phases, phase shifting means being provided for shifting the output voltages of the individual inverters by a phase angle corresponding to the number of phases are characterized in that formed an inverter as of the other independent guide inverter (3) for frequency control of the device and for this purpose an additional, in series with a variable impedance (37) in the control circuit of the two switching means (27, 29) of the guide inverter disposed transformer winding ( 35) and that the impedance of the output output voltage of the lead inverter or the preceding slave inverter Phase shifting means of the slave inverters are also used for switching the switching means of the slave inverters and for this purpose in Control circuit of the switching means are arranged. 2. Device according to claim 1, characterized in that as variable impedances saturable iron chokes are used for switching and / or phase shifting, their iron cores have rectangular hysteresis loops. 3. Device according to claim 1 or 2, characterized in that the iron throttle in Series with auxiliary and supply windings of the transformer and with two ohmic resistors is in the control circuit of the two transistors. 4. Device according to claim 3, characterized by such a dimensioning of the circuit elements, that the voltage across the ohmic resistors is greater than that of the auxiliary windings is. 5. Device according to one of claims 1 to 4, characterized in that in the control circuit of a transistor detuning means in the form of an impedance with optionally connected upstream Resistance are arranged between the DC voltage source and the base. 6. Device according to one of the preceding claims, characterized in that the Follower inverters with each other and the first follower inverter like a chain, each via iron chokes is coupled to the lead inverter via its iron choke. 7. Device according to one of claims 1 to 5, characterized in that all Follow-up inverters directly via their iron chokes with the secondary side of the transformer of the master inverter are coupled. 8. Device according to the preceding claims, characterized in that the iron chokes have a secondary winding which are connected to one another in a delta connection and serve to draw three-phase electricity. Considered publications:
AIEE-Transactions, November 1955, p. 591. 1 sheet of drawings 409 557/218 3.64 © Bundesdruckerei Berlin