RU2454785C1 - Regulated three-phase motor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in three-phase current motor the control of rotor speed is achieved only by combination of supply current phase windings located on two pairs of stator poles so that three-phase motor is changed into two-phase motor, with shift through 90 electric degrees between magnetic fluxes of pairs of poles, the control of rotation speed of which is performed by changing the voltage value on windings of one of the pole pairs.

EFFECT: smooth mechanical regulation of processes in wide range.

4 dwg

Description

The invention relates to the construction and operation of electric motors and can be used in various fields of industry and technology where smooth mechanical control of technological processes in a wide range is necessary.

An analogue of the invention is patent RU 2150781 C1 "Method for controlling the speed of a three-phase AC motor."

The method allows you to discretely control the rotation speed of the motor by changing the frequency of the supply current using a very complex, multi-element electronic device, potentially reducing the reliability of the engine, increasing its cost.

In the proposed engine, the speed is regulated smoothly in a wide range, does not contain electronic devices, except for one autotransformer, a simple and reliable device.

The invention consists in a special arrangement of phase windings at the poles of the stator and in a special order connecting them to a three-phase network, as a result of which the motor becomes two-phase, with smooth regulation of the speed of rotation by changing the voltage of one of the phases.

The invention, device and engine operation is illustrated by figures 1 ÷ 4.

Figure 1 shows: graphs of sinusoidal oscillations of the currents of phases A, B, C;

graph of sinusoidal oscillations of the phase C current in antiphase: - C;

graph of sinusoidal oscillations of the total current of the phase B + (- C).

Figure 2 shows the location of the phase windings at the poles of the stator and the order of connecting the windings to the network, where:

1 - autotransformer.

Figure 3 shows a diagram of a rotating magnetic field of the poles at moments 1 ÷ 5, equivalent to 90 ° electrical.

Figure 4 shows graphs of the rotor speeds of the engine rotor at different loads depending on the voltage of the phase B + (- C).

From the graphs of figure 1 it follows: phase B + (- C) lags behind phase A by 90 ° electrical and its amplitude is 1.74 times greater than the amplitude of the current of phase A;

phase B lags behind phase -C by 60 ° electrical;

phase B + (- C) lags behind phase -C and is ahead of phase B by 30 ° electrical, respectively.

числа витков обмотки фазы А.From figure 2 it follows that the number of turns of the windings of phase B and phase-C are equal to each other and contain

the number of turns of the winding phase A.

In the diagrams of Fig. 3, the poles of the phase A are arranged vertically, the poles of the phase B + (- C) - horizontally. Changes in the magnetic poles N and S are determined by the rule of the right hand in accordance with fluctuations in the amplitudes of the currents in Fig. 1 with respect to O at times 1 ÷ 5 and the direction of the turns of the windings of phase A and phase B (for phase B + (- C)).

To excite the stator's circular rotating magnetic field, it is necessary to equally reduce the amplitude of the currents of phases B and C to a value at which the magnetic fluxes of the poles of phase A and phase B + (- C) will be equal to each other. The reduction is performed using the autotransformer 1 in figure 2, which includes two autotransformers controlled by one drive.

The degree of decrease in the amplitudes of currents (voltages) is estimated by the following calculation.

1. Magnetic flux of phase A windings at rated voltage

where Ф _А - magnetic flux;

B - magnetic induction;

µ is the magnetic permeability;

H is the magnetic field strength;

i is the current amplitude;

U is the voltage;

L is the inductance of the winding;

S is the area of the pole;

l is the height of the winding;

W is the number of turns of the winding;

f is the current frequency;

K is a coefficient including all constant values.

2. Magnetic flux of phase B windings (or -C) at rated voltage

далее по п.1

further according to claim 1

числа витков обмоток фазы А возрос вдвое вследствие уменьшения индуктивного сопротивления обмоток в 4 раза и уменьшения числа витков в 2 раза.Phase B magnetic flux with number of turns

the number of turns of phase A windings doubled due to a decrease in the inductance of the windings by 4 times and a decrease in the number of turns by 2 times.

The magnetic flux of phase B + (- С) is doubled taking into account the correction coefficient cos 30 ° = 0.87

3. The excess of the magnetic flux of the phase B + (- C) windings over the magnetic flux of the phase A windings at rated voltage

Therefore, to equalize the magnetic fluxes of the poles of phases A and B + (- C), it is necessary to reduce the voltage of phases B and C by 3.48 times with respect to the voltage of phase A.

The control of the rotor speed of the motor rotor is made by changing the voltage on the windings of the poles of the phase B + (- C) using the autotransformer 1 of Fig.2. In this case, the rotating magnetic flux becomes elliptical, the sliding of the rotor increases and the speed decreases, up to 0.

The range of control of the rotor speed at different loads reaches a double value compared to the nominal speed.

The engine design does not differ from the classical one, therefore, the implementation of the invention should not cause difficulties.

Claims (1)

An adjustable three-phase motor, including two pairs of poles, 90 ° shifted between each other along the stator arc, and a squirrel-cage rotor, characterized in that the windings of one of the phases are located on one pair of poles, the windings of two phases are located on the other pair of poles, which are connected via an autotransformer to the mains, and the windings of one of these phases are connected out of phase to the windings of the other phase.

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