SU93406A1 - The control method of the electric drive with asynchronous motor - Google Patents

Description

When slaves of many mappings and mechanisms driven by an asynchronous motor, it is often necessary either to smoothly and steplessly regulate the speed or maintain a given constant number of revolutions irrespective of the load when the engine is running at low speeds, i.e. with resistance introduced into the rotor circuit).

As examples of the use of such installations, you can specify the following:

1. Work of the lifting machine with an asynchronous rivce and tilting vessels, when the latter are moving in the discharge curves; in this case, the drive asynchronous motor operates at a lower frequency || glS rpm and overcomes a variable external torque;

2. The work of some special machines (machines for production; ELECTROTHE HHF ix racks) lasts a long time on an ion; g of fresh revolutions, the adjustment range of which must be very wide, and the speed of the machine does not have to; depending on the change in external load.

3. The test benches of pumps and Bent41lors require a drive that allows both a wide and infinitely variable rkz of the speed, and the maintenance of the latter's stability irrespective of your load.

It is known that an asynchronous drive gives a very limited number of intermediate low speeds, the number of which is determined by the number of stages of the starting rheostat and usually does not exceed 5-6. Ko and these speeds can not be

an exactly specified value is obtained, since the asynchronous motor, working on artificial characteristics, is very sensitive to load fluctuations: with an increase in load, the engine turns off, and with efficiency, it rises.

This property of the engine asiatic one made it necessary in a number of cases to use the expensive motor-generator group, and in another number of cases (np: i the supersimpression or undesirability of the use of the moter-septum group) reconciled with the non-continuous operation and control of the machine.

An example of the imperfect work of the mine is to serve as a shaft lifting machine with tilting vessels, in which the asynchronous motor at low speeds dol: к ken to overcome the variable moment of resistance during the movement of the vessels in the discharge curves. Due to the specified properties of the asynchronous avkgatel in this case, the work of the iiauninbi did not succumb to the precise control of i: all attempts to automate its work were unsuccessful.

The proposed invention; it is necessary to solve the problem of smooth and infinitely variable rpm control of the asynchronous motor and obtaining stable operation at any speed regardless of the load.

This is achieved by supplementing the supply of the stator of the asynchronous motor with direct current and automatic control of this current depending on the difference between the two voltages of the analog and current proportional load ;: the motor.

FIG. 1 to 2 As an example, iipiJannanrpy are two variants of the implementation of the proposed method of controlling an electric cabinet unit with aooixiiOHHbiM locator.

In the device, showing 5 (in Fig. 1.) the asynchronous motor receives from the two pstochniki - from the ground current network, which ensures its driving:; 1 :;: um, and from the direct current (GDT), the iMTopHM provides the braking ,

To regulate the speed of aspxH1) onnogo D1 Ig; 1tel. 1) work 10P1 of artificial surface;; krististiko with some nystpnsy load-oh. It is necessary to change the value of the direct current supplied to the stator. When this current increases, the braking torque created by it. also increases and, the follower) 1 (:, increases the load of the engine, which is now folded with two parts: the load is loaded with D15; one with a dope; 1 gatelem. and the brake) of the first load created by the constant TiiuOM, which is given in the winding of its stator.

Since the motor operates with a mechanical mechanical characteristic, its engine speed (sensitivity varies as a function of load loading. By changing the value of direct current, iodine Moro in the stator winding, even in nutpo), and their limits change the total load of the engine, and therefore and the number of revolutions.

The change in the magnitude of the residual current, lodged in the stator of an induction motor, is made by varying the magnitude of the current excited by the generator (DGT).

The excitation winding (Seam) of the generator (DGT) is powered by selenium extractor (CBi), the voltage on which can be fixed 1) with a rheostat (IIM). Consequently, the rheostat (RSH.1) is also regulated by pressure. produced by the generator (DGT). Thus, by varying the resistance of the rheostat (PUIi), a smooth and unregulated regulation of the speed of the asynchronous motor is achieved.

To solve the second part of the problem, i.e., supporting the constant speed of a synchronous engine operating on soft characteristics, it is necessary to fulfill the condition iderderzhannom constants of the moment overcome dpggatelem, i.e., to change the load ag / homically proportional and opposite. side change and braking torque. This is achieved by the principle of electrical connection between the generator (DGT) and the AC network. and Ttayuy; to her irivodnaya engine.

The winding (Excitement) (Gene) gene (ATD) generates n “tapie not only from the specified selenium rectifier (CBi) independent thread, but also from the selenium rectifier (CBO) connected to the secondary winding of the current transformer (GT). The primary winding of this transformer is connected to an alternating current circuit that detects the driving induction motor. When increased; the load of the electric drive and the current in the airway 1 increases; it values it and, consequently, the radiation increases at the terminals of the fresh rectifier (CB2).

The selenium rectifiers (CBi) and (CB) are turned on and the excitation winding (Seam) in such a way that they are subtracted. Such switching on of the generator exciter winding makes it possible to automatically receive the current generated by it at increasing and the load of the drive motor.

In order to separate 11 current and alternating currents supplied simultaneously to the stator winding of the motor, there are choke, sel (Other) on the other hand, and alternate current (1C) in alternating current.

If necessary, the speed of the asynchronous motor is adjusted to include the contactor coil (DT). The latter closes its power contacts in the circuit of the stator winding of the d1P1gatel with direct current and the SOBIM blocking contact turns on the starter (IMDT), which starts the generator (MDT) of the generator (GDT). The closure, the breaker (II), is disconnected from the value of the switch.

In this way, the mouth) the implementation of stepless speed control, which is produced by means of a rheostat (RS) and a generator excitation generator (DGT).

In order to maintain the rotation speed of the asynchronous rubilN engine, the NK (K) opens and a rectifier (CB2) is turned on, which acts opposite to the rectifier (CB).

During the operation of an asynchronous motor on a natural character; the whole device for adjusting its rotational speed is short-circuited in the rotor resistance; the device for adjusting its rotational speed is automatic; the copm tpm (char), and the eu coil of the contactor (dt) is broken by a block-cocktail (char) visible on the drawing, as a result of which the geyirator motor (gdt) is turned off.

FIG. 2 shows a variation of the device with the use of a 5 pin amplifier (V) with three field windings: the coil (I) is powered by a rectifier (CBi). winding (II) is from rectifier (CB2), (windings (I) and (II) act towards each other), and winding (III) is stabilizing.

This scheme imposes a greater sensitivity than the diagram in FIG. one.

Other sources can be used to obtain direct current supplied to the stator winding of the induction motor, in particular, selenium output with 1 saturation saturation.

Subject invention

A method of controlling an electric drive with an asyn.hroin motor regulated by applying a direct current to the stator winding, characterized in that, in order to obtain stable operation at any speed regardless of the load, the current supplied to the stator is automatically controlled depending on the voltage difference - reference and proportional engine load.

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