DE1638506A1 - Circuit arrangement for controlling the drive and braking torque of a three-phase asynchronous motor - Google Patents

Description

PHII. 2551 . Kts / MNV.

Circuit arrangement for regulating the drive and brake rotation ' moments of a three-phase asynchronous motor.

The invention relates to a circuit arrangement for regulation the drive and braking torque of a three-phase asynchronous motor 3 through phase control with the help of controlled rectifiers! in the case of a first of the three phase connections of the liotor with the corresponding lhase and with at least one other Phase of the network over in the same first forward direction switched to the first controlled rectifier and at least one of the remaining phase connections to a corresponding phase of the. Network connected via at least one further controlled rectifier are. .

Such holding arrangements are from the French Patent I.4O6.3O9 known, and the invention aims to provide a to create a considerably simplified circuit arrangement of this type, thereby also the disruptive doii / arto times between the switchover from "drifting" to "braking" and vice versa and the point in time

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at which the motor is actually braked or driven, can be avoided. The invention is based on the knowledge that during which the motor is braked strongly enough that the current is rectified through one or at most two of its windings, provided that each of these windings is fed from at least two of the mains phases, the motor can start and run practically without disadvantage on two phases plus one phase in the same direction or even on one phase plus two phases in the same direction,

and that the mentioned times can be avoided in this way.

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The circuit arrangement according to the invention is thereby

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indicates that the first phase connection is exclusively via one of the first controlled rectifiers is connected to the corresponding phase of the network, and that when driving only the controlled rectifier, via which the phase connections to the corresponding mains phases are connected - alternately and periodically made conductive, while braking only each further controlled rectifiers are kept locked

The invention preferably applies to a synchronous motor with a star connection of three windings, the star point of which is connected to the neutral conductor of the supply network, application »This Circuit arrangement with a fixed star point of the motor enables a better defined general structure and a better one defined current pattern in the motor and thereby reduces the difficulties that occur when controlling the controlled rectifier, in particular with phase control with large angles of incidence can · In this preferred application, controlled rectifiers are connected in series with each of the three motor windings,.

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while a first of these windings with the corresponding phase and with at least one further phase of the feed network via in the same first forward direction connected first controlled rectifier and each of the two other windings with one. corresponding phase of the network via a further controlled rectifier, preferably via two further, anti-parallel connected controlled rectifier, is connected,

Embodiments of the invention are shown in the drawings and are described in more detail below

Fig. 1 is a desired in most cases Regelcharak- λ toriatik,

2 shows the circuit diagram of a known control circuit,

3 shows the basic circuit diagram of a control device for the Control circuit according to Fig. 2,

FIG. 4 shows the circuit diagram of a first exemplary embodiment of FIG Control circuit according to the invention,

FIG. 5 shows the basic diagram of a control device for the control circuit according to FIG. 4t

6 shows the circuit diagram of a second exemplary embodiment,

7 shows the basic circuit diagram of a control device for the Control circuit according to Fig. 6

In Fig. 1, an electric drive is iüotor .zugeführte g and Bremleistung P in dependence on the difference between the rotational speed Δ η η of the engine and the desired speed plotted η. As shown, it is usually desired to supply the motor with a maximum drive or braking power P in the case of larger deviations & n and to reduce this approximately proportionally to the deviation in the case of smaller deviations.

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The number of motors can quickly approach the set value η brought, ie. in the range between η - Δη and η + Δ π. ι while oscillation around the value η is avoided.

Such a control characteristic can be achieved in a known control circuit, for example a circuit according to Fig. 2, by phase control with the aid of controlled rectifiers connected in series with each winding of the motor. This requires however, a control device which is provided with a suitable logic circuit. The "known control circuit" shown in Fig. 2 corresponds to that of Fig. 3 of the French patent 1.406.3 ^ 9 under the condition that only one direction of rotation is desired. The three-phase asynchronous motor to be controlled is only represented by its three windings UVW, which form a star connection, whose star point with the neutral conductor N of the supply network connected is. In series between each winding U, V or W and the The corresponding phase conductors R, S or I are two controlled rectifiers connected in anti-parallel, e.g. controlled semiconductor rectifiers, 1 and 2, 3 and 4 or. 5 and 6 inserted. It should be without It is also evident that the electrical power P supplied to the motor via the controlled rectifiers 1 to 6 is by means of this controlled rectifiers, which are referred to below as thyristors, can be regulated by phase control. The braking takes place by the fact that a braking current duroh one or equal through two of the motor windings', which comes close to a correct direct current by being rectified by the current is obtained from at least two of the three phases If the braking direct current actually flows alternately through different windings, bo is the braking torque starA from the slip of the motor *, Hangig1 in the height of the synhron speed let it be very small or so-

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even Hull} when the motor is at a standstill, it has a maximum value of 1, but the braked motor often does not stand still, but runs as a result an asymmetry in the three phases with a very low one Speed further. * "

The thyristor 1 and two others are used for braking Thyristors 7 and ü only one winding U the. i / winding U, V and tf A direct current is supplied from the three phase conductors R, 3 or T, while the other thyristors 2 to 8 remain blocked.

The üeborgang from driving to braking .and vice versa berei- _Λ tet some difficulty * .muss it be ensured that the thyristors can be conductively 7 and 8 before the thyristor is extinguished 2, DASD and in the other case the thyristor conductive nioht 2 can be before the thyristors 7 and 6 are extinguished. Jonst there would be a short circuit between phases II and S or R and T via thyristors 2 and 7 or 2 and 0. Depending on the moment of the transition from driving off / braking or vice versa, this condition means a delay or waiting time that can amount to up to 270 * of the overrun period * If, for example, at the moment of a transition from Troibon to braking, the voltage ™ of phase K in the direction of positive to negative passes through the word Hull, you have to wait 160 ° * before the thyristors 7 and 6 may be ignited, because only then you can be sure that the thyristor 2 has gone out and does not re-ignite unintentionally Moment of a transition from braking Attjf driving the voltage of phase S or T in the direction of negative • su positive through which V / ert zero passes »must nooh 27Ο * waited

* before the thyristor, 2 is allowed to ignite, because only then is it safe is "that the thyristors 7 and 0 are extinguished"

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The fulfillment of the explained condition requires a logic circuit in the control device for the thyristors 1 to 8, the will now be described with reference to FIG. 3 ". This device contains an oscillator 10, the control pulses with a proportional high repetition frequency generated · These pulses are multiple AND gates 11 are supplied through which they depend on a control voltage derived from the three-phase supply network HST and from the output voltage of a control amplifier I3 to the pulse amplifier 12 with output transformers I4 passed or not · The secondary windings / of these transformers are connected to the control electrode-cathode circuits of the various thyristors 1 to 8. ' The half-waves of tension each Phase are each more or less sawtooth-shaped by a network I5 Stresses converted, and the part of this SS tooth stresson, which exceeds a control level is passed through a cut-off amplifier 16 to one or more of the gates 11, in the .Gate assigned to each phase to control cyclically one after the other, so that they alternate the pulses of the oscillator 10 let through «

The level amplifier 13 compares the dio by a tachometer generator; 17 generated voltage with a reference voltage supplied by a source 18, by which the desired speed is determined Depending on the sign of the difference An between the Jvoltage of the tachometer generator 17 and the corresponding speed Voltage of the source 18 provides corresponding desired speed η the Jteßolversturker an output voltage on a first output 19 (Trcibon) or to a second output 20 (brakes) · The Voltage oji oinon or other of the outputs 19 and 20 is through a

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OR gate 21 of the cut-off amplifiers "16", in which ßie da3 "Hegel level and thereby the i'lu, 3en gate angle is determined.

The logic circuit of the control device contains AND gates 22, through which the control voltages for the gates have passed or not, depending on the different states of two bistable trigger circuits or flip-flops 23 and 24, which are via AND gates 25 and 26, respectively 27 and 2Ö on the one hand through you; Voltages at the two outputs 19 and 20 of the ilegelver3tärker3 13 and andororaeits through the. The voltage of the irhiise R and the voltage of the phase S or T are controlled v / earth.

The gate 11 for the thyristor 1 is directly through the

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Cut-off amplifier 1 (3 of phase R controlled because thyristor 1 Must become conductive during both driving and braking and no short circuit with phases S and T with conductive thyristor 7 or ö can bring about.

The three gates 11 for the thyristor 2, the thyristors 3 and 4 and the thyristors 5 and 6 are via corresponding gates 22 through the Absolineide amplifier 16. Of phases R, S and T controlled. The latter gates are in turn controlled via an AND gate 29 by the flip) flopa 23 and 24, so that the thyristors 2 and 6 can only be made conductive when both flip "flops 23 and 24 are in state I (driving).

The gutter 11 for the thyristors 7 and 8 Bchlieuolich has been through gates 22 controlled by the Flijrflop 23 and 24, respectively the subscription without eide amplifier 16 of the phase ü or T controlled, in such a way, that each of the thyristors 7 and 0 are only made conductive can if the FlipTlop 23 or 24 is in state 0 (braking)

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Has, ζ, ϋ. As a result of a sudden significant reduction in the load, the speed η increased so that the LIotor has to be braked, the voltage of the tachogeneratora 17 is much greater than that of the source 1G, and the control amplifier supplies a voltage similar to '20. Via the OR gate 21, this voltage determines the starting angle by setting the Kegeini level in the cutting amplifier 16 - / ZLopa open the gates 22 to control the thyristors 7 and Q. Because the gates 26 and 20 also receive a voltage conducted by the phase al>, the FlipTlopD 23 and 24 only tilt 90 ° after the The moment in which this voltage generally goes from negative to positive through the value zero ". Thyristor 2 is therefore definitely extinguished before the control circuits for thyristors 7 and C have been released,

.If the Liotor, for example, after a mostly short Br em G ₁ Je r iod e, T / icder start to drive, which is effected by the control controller 13, this supplies a voltage at the output 19 because the voltage of the tachogenerator 17 is now is less than the reference voltage of the source 1U, Uber the ODKR gate. 21 influences this voltage in turn d'as control level of the cutoff preamplifier 16 and it causes; Via the gates 25 and 27 that the FlipTf-Lops 23 and 24 flip over to the state I (driving), Dioso3 flip-over takes place - again erot 90 ° after the moment in which one derived from phase 3 or T and the gate 25 or 27 applied voltage in the direction of positive to negative by passing the value zero. Only when both flip-flops 23 and 24 have flipped over will the three upper ones

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UlID-Gat gate 22 opened via the AND gate 29 and also the control circuit for the thyristors 2 to 6 released the JlipVlops and 24 3ind for overturning in the Q-Zuat.; N <l from the Γϊ-Phaao and for overturning in the ! -State from the S or T phase with the network. synchronized. ISs therefore gives complete security that the thyristors 7 and 0 have been extinguished at the moment in which the control circuit for the thyristor 2 is to be released.

".Via was detected with reference to FIG 3, hat.die known circuit arrangement of Fig. 2 the disadvantage that aie vorhaltnismÜ33ig a complicated .and thus costly Stouervorriohtunng% requires a Lagik3chaltung and dads ausaerdem in

Switching from driving to Breu3en or vice versa a waiting time occurs that can reach up to 90 ° of the supply voltage and cannot be avoided. Should any speed be adjustable □ a, whereby for each speed and each load a balance has to be found between the supplied drive energy and the pulp organism, oo the engine has to goochalbet over and over again from the browser and vice versa the Uiaschaltzeit and oomit the \ 7artezoit possible ä be small, uia an acceptable control of otabilitilt maintain. Jio discussed ϊ / artezeit fluctuating between 0 ° and 90 * soir.it 3ohr is disadvantageous.

Yes3 Execution report according to Fi _1;. 4 differs from the circuit arrangement according to Pig. 2 d by that the Fhc-.senanschluaa dor './icklung U is exclusively connected via one of the first thyristors 1,7 and 0, namely via the thyristor 1, with the corresponding i'huao ά dos Ifotzeo. When drifting, only thyriotors are 1 »3» 3 »5 and 6 woohaolwoiso and periodically

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Made conductive, via which the phase connection of the windings U _t V and W with the corresponding phases H ₁ S or · T of the network

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connected are the engine running / the S and T phases and a half the R-phase and can therefore not achieve its normal Höohattrehmoment to develop. Its speed, however, can be as good as $ 93 of the synhron speed of ζ · Β 2800 revolutions per minute and up to 60 or even fewer revolutions per minute can be scrolled down

When braking, only the other thyristors 3 »4t 5 and 6 are kept blocked, so that the winding U is fed with a three-phase current derived from all three phases H, 3 and T via the controlled rectifiers 1, 7 and Q · This winding is so -

ti

heated with the braking current, and it is a good thing that they'bein Drift less strongly than the windings V "and V / is loaded ·

As a result of the fact that the controlled rectifier 2 of FIG. 2 is absent in the circuit arrangement according to Pig · 4, there is no waiting time, and the control device can be greatly simplified, as shown in FIG. This device contains two separate Abeohneidevorstfirker 16 for the thyristors 7 and 0, which are controlled via the corresponding network I5 through the phase S and T, and the level in all Abachneidever is controlled directly by the level amplifier I3, eliminating the Plipflops 23 and 24 and the AND gates 22, 25, 26, 27, 28 and 29 of FIG I3 controlled, because this thyristor is made conductive both when braking and also when driving · The control level in the Absohneideverötärkern 16 of the thyristors 3t 4. » 5 and 6 are derived from output 19 (driving) of the

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Control amplifier 15 and the control level in the cutoff amplifiers .16 Cost-controlled for thyristors 7 and 0 from output 20 (braking). In the case of small motors, e.g. up to etv / a l / g PS, it has it turns out that the braking power is ample enough, if a winding, e.g. the winding U, is fed with a direct current which, due to the rectification of the current, only has four phases, z.3. R and S, is obtained. This means that one of the thyristors 7 and 8 of Figure 4 as well as its control circuit with the lilementen 16, 11, 12 and 14 can be omitted. Both the circuitry as well as the associated control device are hereby much more simplified and cheaper.

When the drive torque of the Liotore is for its intended purpose amply sufficient, for example, is more than twice dea arforderlichen torque and aiicH daa required starting torque is very small _s can daa Auaführungsbeispiel of Figure 4 according to a waiteron variant can be simplified and through / eglasson dex Thyristors 4 and S, possibly 7 or 8. In this case, when driving, the iiqtor is fed with direct current pulses which are fed alternately from phases R, S and T to windings TJ, Υ and W, respectively. However, this does not significantly simplify the control device according to FIG. 5. Only one of the two secondary windings of .zwei of the transformers 14 and possibly the control circuit 16, 11, 12, 14 for one of the thyristors 7 and u is unnecessary.

In certain cases, when you are dealing with a smaller one Part of normal drive torque and especially normal Starting torque ο of the motor available can, the invention can also be used with a supply network without garbage

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or, in the case of a motor without a star point terminal, e.g. a motor with three windings connected in delta, are used. Fig. 6 shows an embodiment of this application.

In the Pig. 6 the three windings U, V and W of the motor are connected in delta. A first phase connection X, which consists of the common point of the windings U and V, is connected to the phases S and T of the feed network via first thyristors 3 and 9 connected in the same forward direction. xJin the second phase connection3 Y, which consists of the common point of the windings V and W, is connected to the corresponding phase T of the network via two anti-parallel connected thyristors 5 and 6, and the third phase connection 7 % of the common point of the windings V / and U is directly connected to the corresponding phase R.

When driving the thyristors 3ι 5 and 6 alternate · wisely made conductive, and the motor runs on two phases (R and T) plus a half (rectified) phase (S). When braking ' the thyristors 3 and 9 are made conductive, and a rectified current flows from the phases S and T to the phase R. the parallel connection of the winding U and the series connection of the windings V and W.

The windings U, V and V / of the motor could also be connected in star, whereby they would be connected to the phase connections X ₁ Y or «Z. When braking, the braking current would flow through the series connection of the windings U and V /.

The thyristor 5 does not disturb the current pattern, but its presence increases both the starting torque and the available drive torque considerably.

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Υ / ie shown in Pic · 7 X3t, iöt dio! Control device for-the circuit according to 'Pic 6 even simpler_ala the one according to FIG. 5 by the fact that D for braking, only one additional thyristor 9 is used in place of the thyristors 7 and O, and in particular in that the entire control circuit for "the thyristor 1 phase R is missing. '.

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Claims (2)

PHN. 2351 PATENT CLAIMS ι .Ay circuit arrangement for regulating the drive and braking torque of a three-phase asynchronous motor by phase control with the aid of controlled rectifiers, in which a first of the three phase connections of the motor with the corresponding phase and with at least one further phase of the supply network via the first controlled in the same first forward direction Rectifier and at least one of the other phase connections is connected to a corresponding phase of the network via at least one further controlled rectifier, characterized in that the first phase connection (R) exclusively via one (i) of the first controlled rectifiers (1,7,8) the corresponding phase (R) of the network is connected and that when driving ^ only the controlled rectifiers (1,5,5,8), via which the phase connections (u ", V, W) with the corresponding phases (R, S, T) of the network are connected, which are made non-periodically conductive, while during braking nu r every further controlled rectifier (5 »4» 5 »6) is kept blocked (Fig. 4). 2. Sohaltungsanordnung according to claim 1, & ^ei d-er the motor is provided with a star connection of three windings whose star point is connected to the neutral conductor of the supply network, characterized in that each of the other phase connections (S ₁ T) with a corresponding Phase (V ₁ V) of the network is connected via two further anti-parallel controlled rectifiers (4 »6) . 3 _f holding arrangement according to claim 2, characterized in that the first phase connection is connected to the corresponding phase and to a further phase of the network. 109835/0285 ßAD ORIGINAL