SU1205247A1 - Method of controlling three-phase a.c.motor in step mode with splitting step - Google Patents

Description

one

The invention relates to electrical engineering, and in particular to methods of regulating AC motors with a step-wise enemy of a rotor. It can be used in positional power electric actuators. machines and mechanisms based on synchronous or asynchronous electric motors, when the mosh; the capacity or moment of serial stepping motors is insufficient.

The purpose of the invention is to increase the synchronizing torque of the engine and simplify the control circuit.

Figure 1 shows a schematic diagram of a device that implements the proposed method of control of the vector diagrams of magnetizing forces in Figure 2. generated by the windings of phases 5, and the resultant force for all fractional steps between, two adjacent basic steps.

In the diagram (FIG. 1), the phases of the motors 1 2 and 3 are connected respectively to the outputs of reversible three-phase thyristor converters and 6 current regulators 1 8 and 9 at the input. Current sensors 10 are connected to the input of the current regulator of each phase, 11 and 12 and the general conclusions of the contact groups 13-16 17-20 and 21-24, respectively. The voltage sources 25 and 26 of equal effect to the opposite polarity are connected to the contacts 13 17 21 and ISj 19, 23, respectively, as well as to potentiometers 27 and: 28, whose conclusions are connected to contacts 14, 18p 22 and 16, 20, 24, respectively,

The voltages of the sources 25 and 26 are used to set the maximum current in the phases and the voltage to the code of the potentiometers 27 and 28 is to set the intermediate values of the currents in the phases. Setting the current equal to zero in each phase is ensured by breaking all the contacts in the corresponding reference circuit, for example in phase 1 by disconnecting the 13-16 contacts. The desired set voltage in each phase is ensured by closing the corresponding contact in the reference circuit.

If there are no permanent magnets g in the motor rotor, then the magnetic flux of the rotor is created by applying the excitation current to the rotor winding.

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The device works as follows.

During each step, the two phases are closed in one of the contacts 5-24, The comparison circuits match the set voltages, brought through the contacts, to the signals of the current sensors 10-12, and then the current regulators 7 -9 control 10 converters 4-6 and set the required currents in phases 1-3. To complete the fractional odd pitch, the contact in the third phase is closed, and for the next even pitch, the contact is opened in the first phase.

The essence of the method is explained using a vector diagram (Fig. 2) constructed for a three-phase AC motor with a number of fractional steps.

Let, for example, in the initial state, maximum currents flow in the first and second phases with the opposite direction, which correspond to the magnetizing vectors

t5

20

25

thirty

forces FI and FjQ and their resulting vector FJJ. Testing by the engine of the first fractional step is performed by rotating the resultant vector of magnetizing forces K. to a fractional

30 ° angle (., - to the DL position

0

such a rotation in the third phase of the exciting current, coinciding in direction with the current in the second phase,

5, a magnetizing force F is created when: the magnetising forces F, g in the first phase are kept constant and F in the second phase.

To test the engine second

0 fractional pitch is the rotation of the vector F by the angle Cf

by reducing the magnetizing force of the second phase from the Fj value to 5 value.

At the third fractional step turn

thirty

the vector by the angle CjJ to the position Fg is increased in the third phase by the magnetizing force from the intermediate value F.

to maximum F

31

Js

At the fourth fractional step of 30 °

the mouth of the vector F at an angle f 4 -

5 to the position F, which corresponds to the next neighboring state, is produced by decreasing in the second phase the magnetizing force to zero.

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VNISH1I Order 8537/56 Circulation 645 Subscription Branch PPP Patent, Uzhgorod, Proektna St., 4

Claims (1)

METHOD FOR CONTROL OF A THREE-PHASE AC MOTOR IN A STEP MODE WITH CRUSHING A STEP, consisting of three sequentially repeating cycles, in each of which in the initial position set in two phases equal in absolute value and opposite in direction currents, and then in the third - current equal to zero change the currents in two phases until the initial position of the next cycle is established, characterized in that, in order to increase the synchronizing moment of the motor and simplify the control circuit, equal in mode are set in the first cycle s and opposite currents in the first and second phases, then in each odd fractional step increase the current in the third phase, and in each even fractional step reduce the current in the second phase, in the second cycle in each odd fractional step increase the current in the second phase in the direction coinciding with the current of the first phase, and in each even fractional step reduce the current in the first phase, in the third cycle in each odd fractional step increase the current in the first phase in the direction coinciding with the current of the third phase, and in each even fractional stepok in the third phase. > 205247