DE2241674C3 - Start-up control device for asynchronous motors with wound rotor - Google Patents

Description

The invention relates to a start-up control device for asynchronous motors with a wound rotor, Slip rings and brushes containing a controllable semiconductor valve connected to the brushes Valve block and one acted upon by the rotor circuit, the opening lines of the semiconductor valves determining control block.

In a known Aniaufregelungsvorrichtung this type (US-PS 35 86 935) is the control block in essentially of three current transformers, one three-phase voltage transformer with two secondary windings each phase and three control loops, each with the control electrodes connected to the brushes Semiconductor valves are connected. The primary windings of the current transformers are each between the Brushes of the rotor and the star-connected semiconductor valves switched on and the Primary windings of the voltage converter, formed in a star connection, are connected to these brushes.

Each control loop contains a potentiometer fed by an auxiliary DC voltage, with the slider of which the target speed is set. This wiper is connected via a series circuit consisting of a first and second resistor and a capacitor to a pulse generator fed by an auxiliary DC voltage and containing a transistor, the output of which is connected to the control electrode of the associated semiconductor valve via a pulse transformer.
The secondary winding of the relevant control

circuit associated current transformer is connected to a rectifier with the mentioned first resistor of the control circuit is connected, so that a DC voltage drops across this, which the Rotor current is proportional The one secondary winding

Development of the voltage converter is also connected to a rectifier, which feeds the second resistor of the control circuit, so that a DC voltage drops across it, which is inversely proportional to the rotor speed. Finally, the second is

Secondary winding of the voltage converter to the

Connected capacitor, on which therefore a rotor voltage proportional, rotated by about 90 ° AC voltage is present.

The disadvantage of this known device is the high construction cost with numerous components, which overall can lead to an impairment of operational safety.

Also known is a control device for asynchronous motors with a wound rotor (US-PS 27 17 349), in which thyratrons are connected to the rotor circuit instead of semiconductor valves. On these The rotor circuit is also connected to the primary winding of a transformer via a capacitor outputs a control voltage to its secondary winding, the amplitude of which is inverse to the speed of the runner changes. This control voltage is rectified and used in a DC voltage amplifier amplified, its output to the series-connected first windings of saturable inductors connected. As the current through the chokes increases, the reactance of the decreases second windings arranged thereon, from which a phase shift of the grid voltage the thyratron and thus derived from their ignition point.

In this known control device, capacitors are attached to the rotor winding of the asynchronous motor turned on. Such capacitors are also used in the context of the present invention, However, without claiming an independent protection for this.

The explained known control device needs a variety of complex and sensitive! Components such as the DC voltage amplifier, which affects operational reliability. Tuesday the voltage and also the frequency of the rotor with increasing approach to the synchronous speed both go to zero, taking into account the decrease in the control voltage via a capacitor Even in the vicinity of the nominal speed, the tax savings assume very small values and thus ei reliable regular operation endangered.

Also known is a special design asynchronous motor with adjustable speed (DL-PS 60 366), in which steuerbai semiconductor valves are switched on in each armature coil. On the Läuferwe Ie an auxiliary rotor is arranged, which for each Pa; of semiconductor batteries contained in the motor rotor circuit

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It is the task of formation. eme energizing device for asynchronous motor mn frewiefcelrem rotor. Create slip-rings and beards which are simply designed, have great reliability and allow three small-scale arrangements to be carried out.

This task is mentioned at the beginning According to the invention, the start-up excitation device is therefore 3s solved that the control block an Induknonsphascmimfor mer with a stand and a corresponding wtnkeMorrmg rotatable runner is that the stander of the Induk tion phase converter one with the first AuferwTckhmgdes As \ nchronmotors associated excitation and has a control winding that the rotor of the induction phase converter a mn the Steuere'iCktroden of the semiconductor valve block has connected further control winding, which has a larger Wmdungs? than the control winding of the stand and is connected in series with this and that to the The rotor winding of the asynchronous motor capacitors are connected.

In a further development of the invention, the Et'cgcr winding and the control winding in the stator of the induction phase converter / u of a stationary winding united and connected via an isolating transformer nut to the rotor bucking of the asynchronous motor being.

According to a further embodiment of the invention, the semiconductor valve block and the capacitors are fixed on the shaft of the asynchronous motor and directly on its rotor winding avoiding it connected by slip rings and brushes and it is the induction phase converter via rotatable Trans t> o formators each with the rotor development of the Asynchronous motor or connected to the control electrodes of the semiconductor valve block. Through this training wear-dependent components 1111 electrical part of the asvnehron engine are completely destroyed the.

Embodiments of the invention are shown in the drawings and are eowlnetieiud ^ below
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⁵ F ig fe «ine Schatortj: the run with en.m thyristors in star connection containing half-ker-ner valve block.

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The control device according to FIG. 2 differs from that illustrated in FIG. connected im In this case, f \ i ·. <1o> i induction phascnumVormet 4, only one stands' development 20 needed, the development glciclueitig the functions of Frreger ^1J and mi Ständet .inpeordnctp "tax wicklung6erfüllt

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the semiconductor valves of thyristors in a delta connection or star connection are formed.

The F i g. 7 illustrates the structural design of an asynchronous motor, which is rotatable with Transformers 10, 15, capacitors 8 and a semiconductor valve block 3 is equipped. On the The motor shaft is on one side of the rotor 24, the semiconductor valve block 3 and the rotatable transformers 15 attached, while on the other side of the rotor the capacitors 8 and the rotatable Transformers 10 are attached.

To explain the mode of operation, reference is made to the vector diagrams in FIGS. 8a-8d. Herein, the electromotive forces of the stator control winding 6 and the rotor control winding 7 are designated with E \ and £ 2 and the control voltage of the induction phase converter 4 supplied to the semiconductor valves is designated by Uy.

First, the case of the switched on, stationary asynchronous motor with it in the zero position Induction phase converters are considered. At the one with the rotor winding 2 of the asynchronous motor 1 connected excitation winding 5 is therefore a voltage which is equal to the rotor open-circuit voltage of the asynchronous motor and its frequency corresponds to the furling frequency.

An EMF E \ is induced in the stator control winding 6, the magnitude of which is proportional to the rotor voltage, its frequency corresponds to the rotor voltage and this is permanently assigned with regard to the phase position. For the sake of simplicity, in the following the EMF £ 1 is assumed to be in phase with the rotor voltage.

An EMF E _{1 is} induced in the rotor control winding 7, which is greater than the EMF Ei and because of the somewhat larger number of turns of this winding, as required. is phase shifted by 180 ° with respect to this and thus the rotor voltage (Fig. la). Due to the series connection of the Stündcr control winding 6 and the rotor control winding 7, the control voltage Uy is obtained by geometrically adding the phasors of E \ and Ej (in the case of FIG. 8a, by simple addition). The control voltage / Λ is 180 out of phase with respect to the rotor voltage and the half-liter valves are completely blocked.

If the rotor of the induction phase converter 4 is rotated slightly, the phase position of the EMF shifts. ti and, albeit not at the same angle. that of the control voltage Uy. As a result, the semiconductor valves become conductive for a small fraction of each period and a runner current begins to flow, causing the rotor of the asynchronous motor to rotate.

As a result of this rotation, the frequency and the voltage of the rotor of the asynchronous motor decrease and

S thus also proportionally the EMFs £ Ί and E ₂ (Fig. 8b). If the rotor of the induction phase converter 4 is rotated by a larger angle, the phase position of the EMF Ei and consequently also the control voltage Uy shifts more compared to the EMF £ 1, whereby the semiconductor valves remain conductive for a larger part of each period, the rotor current of the asynchronous motor increases and whose rotor increases its speed, which in turn decreases the rotor voltage (FIG. 8c).

In the fully ON position of the induction phase converter 4, the EMFs £ 1 and £ 2 and the control voltage Uy are in phase with the rotor voltage of the asynchronous motor. The semiconductor valves therefore remain conductive for most of a period and the rotor reaches its highest speed. The voltage of the rotor of the asynchronous motor and the EMFs £ 1 and £? small. It is advantageous, however, that in this case the control voltage U ν is equal to the sum of the EMKs £ 1 and £ 2 (Fig. 8d) and therefore a control voltage that is sufficiently large to control the semiconductor valves is made available up to close to the synchronous speed can.
The same applies as FIG. 8a-8c, also for the operating states explained above.

The mode of operation described is also given in the embodiment according to FIG. The one with A three-phase isolating transformer 22 formed with a suitable transformation ratio isolates the inductor tion phase converter 4 galvanically from the rotor winding 2. The stator winding 20 of the induction phase converter simultaneously exercises the function of the excitation winding 5 and the steep winding 6 of the embodiment according to FIG. 1 and is therefore with the Laufcr control winding 21 connected in series.

In the embodiment according to FIG. J the rotatable transformers 10 take the place of the aforementioned isolating transformer. The other rotatable transformers 15 transmit the control voltage emitted by the induction voltage converter 4 to the semiconductor valve block 3. The capacitors 8 connected to the air winding 2 improve the effectiveness of the rescue device.

so moderate load on the asynchronous motor required.

In addition 6 sheets of drawings

Claims (3)

Patent claims: 1. Start-up control device for asynchronous motors with wound rotor, slip rings and Brushes, a valve block that is connected to the brushes and contains controllable semiconductor valves and one acted upon by the rotor circuit and determining the opening times of the semiconductor valves Control block, characterized in that the control block is an induction phase converter (4) with a stand and a rotor that can be rotated at an angle thereto is that the stand of the Induction phase converter connected to the rotor winding (2) of the asynchronous motor (1) Excitation winding (5) and a control winding (6) that the rotor of the induction phase converter a further control winding connected to the control electrodes of the semiconductor valve block (3) has, which has a larger number of turns than the control winding (6) of the stator and is connected in series with this and that capacitors are connected to the rotor winding (2) of the asynchronous motor (8) are switched on. 2. Start-up control device according to claim 1, characterized in that the excitation winding and the control winding in the stator of the induction phase converter (4) to form a stationary winding (20) combined and via an isolating transformer (22) with the rotor winding (2) of the asynchronous motor (1) are connected. 3. Start-up control device according to claim 1 or 2, characterized in that the semiconductor valve block (3) and the capacitors (8) are fixedly arranged on the shaft of the asynchronous motor (1) and connected directly to its rotor winding (2) avoiding slip rings and brushes are and that the induction phase converter (4) via rotatable transformers (10, 15) each with the rotor winding (2) of the asynchronous motor or with the control electrodes of the semiconductor valve block (3) is connected.