SU1621137A1 - Ac electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in mechanisms with an asynchronous motor. The chain is to increase reliability and simplification. The electric drive contains a two-speed three-phase electric motor, the stator windings of which are phase-wise made in the form of two semi-windings each and С ч 022 L HH - gt EN ho shgs $

Description

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connected to each other according to the series delta circuit, contactors 7, 8 for connecting the motor to the network and switching the connection of its half windings. In this case, the engine half windings are switched phasewise and counter-phase. Turning on the power contacts 10 of the contactor 8 between the intermediate valves of the semi-windings and the corresponding input terminals to the successive triangle leads to a simultaneous change in the value of the speed and its sign, i.e. The invention relates to electrical engineering and can be used in various mechanisms with asynchronous electric motors, providing reversing and changing the frequency of rotation.

The aim of the invention is to simplify and improve the reliability of the device.

Figure 1 shows the electrical circuit diagram of an AC drive; FIG. 2 shows the mechanical characteristics of an asynchronous electric motor; FIG. 3 a, b, c - a variant of including a circuit in a serial triangle; in fig. 4 a, b, c is a variant of including a circuit in two parallel triangles.

An AC electric drive contains a two-speed three-phase asynchronous electric motor with a squirrel-cage rotor, the stator windings of which are made in the form of two semi-windings 1-2, 3-4, 5-6 each and are interconnected according to a triangle, two contactors with a coil 7, 8 with three power 9,10 and one closing 11, 12, contacts, two control buttons 13, 14, each interlocking respectively with their opening and closing contacts 15, 16, two thermal protection relays with a coil 17, 18 and opening contact 19, 20, two fuses 21, 22, Kno pku 23 Stop, one output of which is connected to one output of the first control button 13, to one output of an open contact interlocked with it, to one output of the closing contact 11 of the first contactor, the other output of which is connected to another output of the first control button 13 interlocked with the second By means of the control button 14, the closing contact 16 is shunted by the closing contact 12 of the second contactor, one terminals of the fuses 21, 22 are connected respectively to the first and third phases of the power supply network. The ends of the semi-windings 1-6 of each phase are combined into intermediate

It reverses the engine without disconnecting it from the mains. For this reason, transients from one speed to another occur with smaller amplitudes of the torque current. The new reversal circuit allows you to switch from a serial triangle circuit to a circuit of two parallel triangles with a simultaneous change in the number of pairs of poles and the order of alternation of the supply phases. All this allows us to simplify the device and increase its reliability. 4 il.

terminals and are connected respectively to the same terminals of the power closing contacts 10 of the second contactor, the beginnings of the stator half-windings 1-6 are connected to

to other terminals of the corresponding closing contacts 10 of the second contactor and to one terminal of the second power closing contact of the first contactor, the other terminals of the power contacts 9 of which are intended to be connected to the corresponding phases of the mains supply. One output of the coil 17 (18) of each thermal protection relay is connected to one output of the first and third closing respectively

contacts 9 of the first contactor, another output of the coils of each of the thermal protection relay is connected to the other terminals of the first and third contact contacts 10 of the second contactor, respectively, the other output of each fuse 21 (22) is connected to one output of the opening contact 19 (20) of the corresponding thermal protection relay, another output of the opening contact 19 of the first thermal relay

connected to another terminal of button 23 Stop, another terminal of disconnecting contact 20 of the second thermal protection relay is connected to one terminal of coil 7, 8 contactors, another terminal of coil 7 of the first contactor is connected to another terminal of button 13, 14 of control, another terminal of coil 8 of a second contactor is connected to one output of the closing contact 12, the other output of which is connected to the other output of the disconnecting contact 15 engaged with the button 13.

-Electrical AC operates as follows.

The proposed device can be used as an electric drive of a general industrial cyclic action mechanism controlled by an operator (for example, a drilling machine feed mechanism) with the following mechanical characteristics of the engine and mechanism, given in Fig. 2, where: 24 is the mechanical characteristic of an asynchronous engine, corresponding to its operation with increased rotational speed and lower moment value; 25 is a mechanical characteristic of an asynchronous motor, corresponding to its operation with a reduced rotational speed and an increased amount of torque; 26 is a mechanical characteristic of a drive mechanism corresponding to its operation in idle mode, for example, returning the working member to its initial position in order to prepare for the next working cycle; 27 is a mechanical characteristic of a driven mechanism corresponding to its operating mode, i.e. the moment of static resistance of the working body; 28, 29 are respectively the intersection points of the characteristics 24 and 25 of the engine with the characteristics 26 and 27 of the driven mechanism, characterizing the modes of long steady-state operation of the engine in the idling mode (point 28) or in the operating mode with nominal load (point 29).

The operation of the device is characterized, for example, by a small sequence of operation of its elements and assemblies. When the operator pushes the first control button 13, its closing contact leads the line voltage AC through the mains to the coil 7 of the first three-phase contactor, which operates, switching to self-feed mode, by shunting the first contact terminal 11 of the contact 13 of the first button; as well as the closure of the power contacts 9, supplies the three-phase supply voltage to the input terminals (tops) of the serial triangle circuit of the connection of the semi-windings 1 6 of the asynchronous motor. Due to the sequential and counter-coupling of the windings 1-2, 3-4, 5-6, the asynchronous motor has a single number of poles () and relatively small torques in each phase, since only half of the linear voltage of the supply network is applied to each half winding. Therefore, the acceleration of an asynchronous engine, which causes the mechanism to its initial state in idle mode, occurs according to the mechanical characteristic 24 in the conventional Backward direction (3rd quadrant of Fig. 2), but rather quickly due to the relatively small moment of resistance of the mechanism and ends quickly increased steady-state rotational speed at the point 28 of the intersection of the mechanical characteristics (24 and 26) of the engine and mechanism.

Further, the engine can be stopped by pressing the operator to stop the stop button 23 or, as shown in FIG. 2, be switched to reverse and operate at a reduced speed of rotation in the conventional Forward direction (1st quadrant 10 of FIG. 2) by pressing the second 14 control buttons.

Due to the simultaneous closure of the contacts 15,16, the former on state of the first contactor 7 and 15 is maintained, the supply voltage is applied to the winding 8 of the second three-phase contactor, which operates, switching to self-feeding mode, bypassing the second block contact contact 12 of the second button 16

0 controlling and closing the power contacts 10 reconnects the initial circuit of the series triangle of the stator half windings 1-6 of the induction motor to the circuit of two parallel parallel co5 common triangles (1-3-5 and 4-6-2 of FIG. 4a). In this case, the stator winding of the motor has twice the number of poles () and a full linear voltage of the network is applied to each half winding.

0 changed order of phase rotation. Therefore, the acceleration of a short-circuited asynchronous motor, which drives the mechanism in the conditional working direction Ahead, occurs according to the mechanical characteristic 25 and ends with the achievement of a lower steady-state rotational speed with an increased (nominal) torque of the engine at the intersection point 29 of the working mechanical characteristic 25 of the engine and operating characteristic 27 the moment of resistance of the mechanism (see the 1st quadrant of figure 2)

At the end of the working interval of the operation cycle, the operator presses the first button 13 of the control, in which its coil 8 of the second contactor is disconnected by its second contact 15, the induction motor is reversed again without disconnecting it from the network by the first coil contact 7 and again switches to the mechanical characteristic 1, those. quickly, in the idling mode of the driven mechanism, returning its working body (for example, a drill) to the initial state,

5 preceding a new repetition of the specified closed working cycle

FIG. 3, a, b, c, and Figures 4, a, b, c respectively illustrate the mechanism for reversing an asynchronous motor: connection diagrams of six stator semi-windings 1-6 of an induction motor into a series triangle (Fig. 3 a) or two parallel triangles (fig.4a); schematic diagrams of switching on half windings 1 and 2 of one (first) phase of a motor stator winding, providing changes in the number of pole pairs from a single (, FIG. 36) to double ((FIG. 46)); vector voltage diagrams on the semi-windings of the motor stator, showing the change in the voltage value and the change in the order of the phase alternation on them when the switching circuits change (Figs. 3c and 4c).

So, for the initial connection circuit of the stator semi-windings into a series delta (Fig. 3a) with its power from the three-phase network A, B, C when the first three-phase contactor 7 is triggered in the circuit of Figure 1, the device is typical (for the selected conditional linear voltage vector A, B, C) equality of the values of the voltages on the series and counter-connected semi-windings in each phase of the stator of an induction motor connected to the corresponding linear voltage of the mains supply.

The construction of voltage vectors in the form of a separate vector diagram in Fig. Zv allows you to set the order of their alternation (counterclockwise), which corresponds to the conventional direction Backward rotation of the magnetic field of the stator and the rotor of the induction motor in the circuit of Fig.1 with its mechanical characteristic 24, located in the 3rd quadrant of figure 2.

The schematic diagram for switching on the half-windings 1-2 of the first phase of the stator of the engine with their series and counter connection is shown in Fig. 36 and corresponds to a variant that has an extended pole division and a single number of pole pairs ().

When the second three-phase contactor 8 is triggered in the device of Figure 1, the six semi-windings 1-6 of the asynchronous motor stator are connected according to the scheme of two parallel-connected triangles, the connection of which by the first three-phase contactor to the mains A, B, C is shown in Figure 4, and for the former The chosen conditional direction of the linear voltage network vectors is characterized by the equality of the magnitudes of the linear voltages on the parallel-disconnected half windings in each phase of the asynchronous motor stator.

The construction of the stress vectors as a separate vector diagram in Fig. 4b makes it possible to establish their order.

alternation (clockwise), which corresponds to the conditional direction of forward rotation of the magnetic field and the rotor of the induction motor in the circuit of figure 1 with

its mechanical characteristic is 25.

The schematic diagram of the adjacent semi-windings 1-2 of the stator of the engine shown in FIG. 46 with their independent connection to various (A – C and B – C) phases of the power supply

0 the network has a narrowed pole division TZ Ti / 2 and a double number of pole pairs (PZ 2), since independently connected to different, with an alternating phase shift of 120 °, the line voltages of the power supply network of half-winding 1-6 asynchronous motor now acquire each function and-properties of six independent stator windings of an asynchronous motor with its doubled number of pole pairs (.Pi).

0Application of the proposed device

for reversing drive mechanisms for various purposes provides a simplified control scheme for a two-speed asynchronous motor containing (in

5 difference from the prototype) twice the number of contactors and double-link control buttons; improving the reliability of the device, due to its simplification, as well as more favorable (in contrast to

0 of the prototype) by the process of reversing an asynchronous motor that occurs without disconnecting its gripping chain from the three-phase supply network.

Claims (1)

Invention Formula 5Electrical AC, containing a two-speed three-phase asynchronous electric motor with a short-circuited rotor, the stator windings of which are made in the form of two half-windings 0 each, and two interlocking with a coil, t three power and one make contact each, two control buttons, each interlocking 5, respectively, with its own opening and closing contacts, two thermal protection relays with a coil and each opening contact, two fuses, a Stop button, one output of which is connected 0 to one terminal of the first control button, to one terminal of a break contact interlocked with it, to one terminal of a closing contact of the first contactor, the other terminal of which is connected to another terminal 5 of the first control button, coupled with the second control button, the closing contact is shuffled with the closing contact of the second contactor, one fuse terminals are connected respectively to the first and third phases of the mains supply, characterized in that, in order to simplify and improve reliability, the half windings of each phase are combined and equipped intermediate terminals connected respectively to one pins of the power closing contacts of the second contactor, the beginnings of the stator windings are connected to other pins according to contactors of the second contactor, to one output of the second power closing contact of the first contactor, the other terminals of the power contacts of which are intended to be connected to the corresponding phases of the power supply network, one coil terminal of each thermal protection relay is connected to one output of the first and third contact contacts, respectively, different output coils of each of the relays -and The second protection is connected to the other terminals of the first and third contact contacts of the second contactor, the other terminal of each fuse is connected to one output of the opening contact of the corresponding thermal protection relay, the other terminal of the opening contact of the first thermal protection relay is connected to another output of the Stop button, the other output of the second contact of the second contact a thermal protection relay is connected to one terminal of the coils of the contactors, another terminal of the coil of the first contactor is connected to the other terminals of the button approx control, the other terminal of the coil of the second contactor is connected to one terminal of its normally open contact, the other terminal of which is connected to the other terminal of the interrupter contact is engaged with the first button control. 25 (Reg. 2 TO / / /