SU797049A1 - Device for obtaining creeping rate - Google Patents

Description

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The invention relates to electrical engineering, namely to the control of three-phase induction motors.

The closest to the invention to the technical essence and the achieved result is a device for obtaining a creeping speed, containing two three-phase induction motors with a common secondary element, the beginning of the phases of the winding of one: of which are connected to a network of three-phase AC, and winding; A second motor is connected to a special low voltage 11J source.

However, to supply one of the induction motors, a low voltage direct current source is required. One of the elements of such a source is a step-down transformer. The presence of a step-down transformer complicates the design of the device and increases its cost.

The purpose of the invention is an uproar. devices and reducing its cost

This goal is achieved by the fact that in the proposed device for obtaining a creeping speed, the DC source is made in the form of a three-phase-1-phase bridge rectifier, the input of which is connected to the ends of the winding phases of the first motor.

- Figure 1 shows the diagram of the device; figure 2 - curves of the efforts and the current from the speed. The device contains two inductors 1 and 2, the common secondary element

0 3 and a three-phase bridge rectifier 4. On the surface of the inductor 1 there is a three-phase winding, the beginning of which A, B ICs are connected to the AC power supply, and its ends X, Un Z are connected to the input of a three-phase bridge rectifier 4. On inductor 2 is also placed three-phase winding, which is connected to the output of the three-phase bridge output, direct 4.

The device works as follows.

When connecting three-phase ob-; coils of the inductor 1 to the AC network .;

5, a traveling magnetic field arises in the gap separating inductor 1 from working medium 3. This field induces in the working body 3 electric; | The currents, the interaction of which with the magnetic field of the inductor 1 creates a dangling force F. At the same time, the windings of the inductor 2 will flow around the rectified 4-current rectifier, the value of which is proportional to the current of the inductor i. The rectified current in the windings of the inductor. 2 creates a magnetic field stationary in space in the gap, which induces a moving current to the moving body. These currents when interacting with the magnetic field of inductor 2 create a braking force - F.

Thus, in the creeping mode, there are two forces acting on the working body 3: traction F and braking - F.

In Fig. 2, curves 5-7 depict the dependences of traction F, braking, F, and total F of forces on speed V of the movement of working medium 3. Curve 8 shows the dependence of current J of inductor 1 on speed V. From the graph (-curve 8) it follows that with decreasing speed V the current of the inductor 1 increases. This leads to an increase in the rectified current in the windings of the inductor 2. As the braking force — F is pro-square to the square of the rectified current, then at the speeds V of the working body's movement, the braking force increases sharply (curve 6). This leads to an increase in the stiffness of the mechanical characteristic in the creep speed mode.

The use of the invention allows to simplify the source of the constant

current, reduce its cost and increase the rigidity of the mechanical characteristics when three-phase induction electric machines operate in a creeping mode. Using the proposed device allows reducing the costs of developing a direct current source, which provides savings in the national economy. In addition, an improvement in the adjustment characteristics of the induction electric machines is achieved.

Claims (1)

1. Andreev V.P., Sabitsin Yu.A. Fundamentals of the electric drive. ML , Gosenergoizdat, 1967, p. 157, Figure 2-137