RU2375813C1 - Method for two-band amplitude-phase overexcitement of synchronous-hysteresis motors - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention refers to the field of electric engineering. For this purpose in the method simultaneously with increasing and subsequent lowering supply voltage to initial level following is performed: resulting voltage vector is adjusted, free vibration period of motors T₀ with inertial load at initial pressure level is predetermined. Voltage increase from initial level is performed within time period that is considerably less than T₀ (for instance 0.01 T₀), and simultaneously voltage vector phase is turned in direction opposite to engine rotor rotation by angle Δα=15-20 el. dg. relative to phase of synchronous coordinates system. Subsequent voltage lowering to initial voltage level is performed within time period not exceeding T₀ (less than 0.01 T₀) simultaneously turning voltage vector in rotor rotation direction by the same angle Δα.

EFFECT: increase in energy effectiveness of synchronous-hysteresis motor (SHM), lowering fluctuations of moment and speed during regulation, and providing stability.

2 cl, 4 dwg

Description

The invention relates to the field of electrical engineering and can find application in electric spindles, centrifuges, mainly in multi-motor drive of technological lines.

A known method of overexcitation and control of synchronous-hysteresis engines (SRS), in which, after the motors enter synchronism, increase the supply voltage for 1-3 seconds, and then reduce [Delektorsky B.A., Tarasov V.N. Controlled hysteresis drive. M .: Energoatomizdat, 1983,

,p. 78-79]. At the stage of increasing voltage, the rotor is magnetized and the EMF increases from the level E ₀₁ to E ₀₂ > E ₀₁ , and when the voltage decreases, the EMF level is approximately preserved E ₀₃ ≈ E ₀₂ , and the degree of excitation

,

, т.к. уровень начального напряжения сохраняется U₁=U₃, a E₀₃>E₀₁. Этот процесс принято называть режимом перевозбуждения СГД.where U ₃ - voltage, increases compared to

because the initial voltage level is maintained U ₁ = U ₃ , a E ₀₃ > E ₀₁ . This process is commonly called the SRS overexcitation regime.

Such regulation gives a satisfactory result only when idling the SRS and with a smooth increase and decrease in voltage. Otherwise, due to a change in the position of the magnetization vector of the rotor relative to the rotor body, oscillations of the rotor occur, which are accompanied by its demagnetization and a decrease in the efficiency of overexcitation.

The closest technical solution is a method of overexcitation and control of synchronous hysteresis motors with inertial load, in which simultaneously with the increase and subsequent decrease in the supply voltage to the initial level, the phase of the supply voltage is regulated [A. USSR No. 674181, MKI Н02Р 7/44. Publ. 07/15/1979. The method of overexcitation of synchronous hysteresis motors / NN Rudanovsky and others]. This solution can fundamentally eliminate the disadvantages of the above method, if the time intervals of the voltage rise and the phase rotation angles of the resulting voltage vector are agreed. However, the specified technical solution does not determine these intervals, therefore, its use is limited and not effective enough.

The objective of the invention is to increase the energy efficiency of overexcitation of the SRS, reduce fluctuations in torque and speed during regulation and ensure stability.

This goal is achieved by the fact that in the method of two-zone amplitude-phase overexcitation of synchronous hysteresis electric motors with inertial load, in which simultaneously with the increase and subsequent decrease in the supply voltage, the phase of the resulting voltage vector is regulated, and the period of natural oscillations of the motors T ₀ with the inertial load is additionally preliminarily determined at the initial the level of supply voltage, an increase in voltage from the initial level is produced in a time significantly less than T ₀ (for example, less than 0.01 T ₀ ), and the simultaneous rotation of the phase of the voltage vector against the direction of rotation of the rotor is carried out at an angle Δα = 15 ÷ 20 e. column relative to the phase synchronous coordinate system, the subsequent reduction to the initial voltage level is also produced in less time than 0.01 T _0, while phase rotation of the voltage vector in the direction of rotation of the rotor at the same magnitude angle Δα. The time to increase and decrease the voltage during overexcitation is chosen from the condition of eliminating the influence of natural oscillations of the SRS on the magnetization process, as well as the need to reduce energy costs. The angle Δα = 15 ÷ 20 e. column obtained by calculation, taking into account the fact that the maximum angle of rotation of the rotor relative to the synchronously rotating coordinate system according to the angular characteristic does not exceed 55 ÷ 60 el. column

Additionally, in the method of two-zone amplitude-phase overexcitation of synchronous hysteresis motors, after reducing the voltage to the initial level, an excess supply is determined by the moment and a subsequent smooth decrease in voltage to the operating level is performed during a time much greater than T ₀ (for example, more than 10 T ₀ ). This time is chosen from the condition for the completion of the oscillatory processes of the motion of the SRS rotor.

To implement the method when powering the motors from a static frequency converter, which includes a voltage inverter, various voltage control methods can be used:

- pulse-width voltage regulation in the inverter according to one of the known modulation methods;

- the use of volt-additives of alternating current at the inverter output;

- the use of a DC voltaic additive in the DC circuit of the inverter.

To explain the essence of the method, it is most simple to consider regulation using a volt-additive of direct current.

Figure 1 shows a schematic diagram of the implementation of a two-zone amplitude-phase method of overexcitation of synchronous-hysteretic motors.

On figa shows transient changes in the position of the rotor on the angular characteristic.

On figb - magnetization of SRS by an increase in the current pulse for 3 periods of power.

On figv - fluctuations in current, moment as a result of magnetization.

Figure 3 - similar dependence of the optimization of the magnetization process during magnetization of the SRS with a single current pulse.

Figure 4 shows the curves of the spatial distribution of the magnetomotive force of the stator MDS (F ₁ , F _max ) and changes in the level of induction of the rotor (B _P and B _1P ) during magnetization: figa - characteristics with amplitude regulation, fig.4b - with amplitude phase regulation.

A device for implementing the method (Fig. 1) contains one or a group of synchronous-hysteresis motors 1 connected to a voltage inverter 2, the input of which is connected to a rectifier 4 through a controlled volt-additive unit 3. The frequency control circuit contains a pulse distributor 5, which controls the keys inverter 2, a phase 6 regulator, one input of which is connected to a master oscillator 8 through a frequency divider 7, and a second control input is connected to the block through the control unit of the 9 phase Δα regulator of the resulting voltage vector control 10 modes of over-excitation of the SRS, the input of the control unit 10 can be connected to a software device 11 that implements either periodic magnetization or magnetization, depending on the degree of excitation of the SRS, and the other output of the control unit 10 is connected to the unit 3 of the controlled volt-additive.

The work according to the method of two-zone amplitude-phase overexcitation is illustrated by the example of the operation of the implementation device.

An engine or group of motors 1 is started when the inverter 2 is turned on according to one of the following laws:

- frequency method;

- at a constant frequency and forced voltage;

- at a constant frequency and rated supply voltage.

Consider the basic mode, when the engine starts to the rated frequency f _H ends at a rated voltage U _H equal to the starting voltage U _P. In this case, the magnetic system of the engine is unsaturated, i.e. it is possible to magnetize the engine and achieve overexcitation by increasing the voltage to a forced level U _f .

A discrete increase or decrease in voltage is carried out by turning the volt-additive on or off, which is accompanied by a sharp change in the electromagnetic moment of the SRS and the appearance of swings. This reduces the efficiency of overexcitation and leads to a long oscillatory process of rotor movement, respectively, of torque, current and power in the power supply circuits.

определяется моментом инерции j ротора двигателя с присоединенной нагрузкой и синхронизирующим моментом

, где М_эл - электромагнитный момент, θ - угол поворота ротора по отношению к синхронно вращающейся системе координат. М_эл=f(θ) - характеризует наклон угловой характеристики.Oscillation frequency

determined by the moment of inertia j of the rotor of the motor with the connected load and the synchronizing moment

where M _el is the electromagnetic moment, θ is the angle of rotation of the rotor with respect to the synchronously rotating coordinate system. M _el = f (θ) - characterizes the slope of the angular characteristic.

As a rule, for high-speed electric spindles, centrifuges, the period of natural vibrations is 0.3–5 s, and ω ₀ = 3.3–0.2 Hz and lower.

The appearance of oscillations with a discrete increase in voltage is associated with a shift of the magnetization vector of the rotor relative to the rotor body by an angle Δθ and a change in the slope of the angular characteristic. On figa shown respectively:

- initial angular characteristic A - at U _H = U _P ;

- characteristic B - when the magnetization voltage U = U _Ф ;

- characteristic C - when the voltage decreases again to a voltage of U _H = U _P.

Installed [see the above analogue, p. 86-90], that the process of magnetization of the rotor ends with discrete regulation of the voltage for tenths of a period of the supply voltage. Therefore, during the magnetization, the inertial rotor does not change its angular position in the synchronous coordinate system, and its movement begins after magnetization in accordance with the change in moment on the angular characteristic. In the case considered above, this is a change in the equilibrium point, when the electromagnetic moment M _el is equal to the moment of resistance M _s along the path A ₁ B ₁ C ₁ C ₂ . Point A ₁ is the initial equilibrium position, point C ₂ is the final equilibrium point. The shift of the angular characteristic by the angle Δθ ₁ and the change in its inclination causes an oscillatory process of the rotor motion, which is shown in the oscillogram of Fig.2c.

To reduce the oscillatory process, it is necessary to increase the voltage created by the volt-additive unit 3, to accompany the phase change of the resulting voltage vector in the transient magnetization, turning it against the direction of rotation by an angle Δα = 15 ÷ 20 el. column The choice of this angle was determined by calculation and experimentally for the majority of SRS, taking into account the fact that the maximum θ in angular characteristic does not exceed 55 ÷ 60 el. column

As a result, the shift in the angular characteristic (Fig. 3a) will be less than the similar displacement in Fig. 2a (Δθ ₂ <Δθ ₁ ), and ideally, a transient magnetization process can be achieved without any oscillations or with minimal perturbation in time. On figb shows the process of pulsed magnetization, ensuring the coordination of the positions of the angular characteristics, the magnitude of the electromagnetic moment and the moment of resistance in figa, which ensures minimal oscillation of the rotor (figv).

On figb shows the transient process of pulsed magnetization, where figure 1 reflects the current before magnetization, figure 2 - current in the pulse i ₂ , figure 3 - current SRS after magnetization i ₃ . Additionally, the simultaneous change in current pulses over all phases of the SRS leads to the required rotation during magnetization of the resulting voltage vector.

Usually 3-5 periods of nutrition are sufficient to achieve the required magnetization. On figb shows the transient magnetization during 3 periods of supply, where, respectively, the numbers 1, 2, 3 show the currents before magnetization i ₁ during magnetization i ₂ and after magnetization i ₃ when the over-excitation mode is reached. Additional phase control of the resulting voltage vector by the angle Δα in this case also minimizes rotor vibrations.

In addition, the rotation of the voltage vector during magnetization introduces an additional factor in increasing the magnetization level of the rotor due to both an increase in the magnetization of the entire volume of the rotor and the creation of rotational magnetization, when the vector of the stator magnetomotive force changes relative to the rotor not only in amplitude but also in phase, sliding relative to the rotor body.

For example, FIG. 4a shows the process of amplitude magnetization of the rotor volume, shown in the form of an expanded pole division (Ψ _P ) with division into sectors (Ψ _P1 , Ψ _P2 ... Ψ _P6 ). An increase in the stator MDS from level F ₁ to F _max leads to magnetization of the rotor (curve B _P = f (Ψ)) with the first harmonic B _1P = f (Ψ _P ) being released. The rotor volumes Ψ _P1 and Ψ _P6 received a slight bias, because were at the beginning and end of the MDS half-wave.

The same increase in the stator MDS from the level F ₁ to F _max and with an additional rotation of the MDS vector by the angle Δα (Fig. 4b) creates additional magnetization in these volumes (Ψ _P1 and Ψ _P6 ). The resulting magnetization curve B _P = f (Ψ _P ) takes on a flattened form with an increase in the first harmonic B _P1 = f (Ψ _P ) in comparison with the similar dependences in figa.

As a result, two-zone magnetization forms, as it were, by increasing the stator MDS and, additionally, by rotating the MDS vector. This leads to an increase in the counter emf of the engine, an increase in the electromagnetic moment, power factor and engine efficiency. The approximation of the magnetization increment is insignificant and amounts to 5–10%, but if you want to achieve the limiting energy indices, this increment should be taken into account and implemented through the regulation of the phase of the voltage vector using block 6.

Thus, amplitude-phase magnetization when changing the phase and time of magnetization in the established ranges allows us to solve two problems - reducing the swing of the rotor and increasing the total magnetization of the rotor, which increases the efficiency of the motor to a level of 91-93% when optimizing all components: engine parameters and control algorithms .

An increase in the torque margin during magnetization can be additionally used to increase the output power of the SRS, or with a constant load power, it can further reduce the level of operating voltage, thereby reducing losses in steel and in the product structure.

Stabilization of energy indicators is possible in two ways:

- control over the manifestation of destabilizing factors in the system:

frequency failure, power interruption, etc. followed by a repetition of the cycle of regulation of excitation of SRS

- either by periodic magnetization with a pulse frequency of 3-5 times higher than the frequency of the natural rotor rotations, which is created by the program unit 11. In addition, the rotor vibrations are damped.

Claims (2)

1. The method of two-zone amplitude-phase overexcitation of synchronous hysteresis motors with inertial load, in which simultaneously with the increase and subsequent decrease in the supply voltage, the phase of the resulting voltage vector is regulated, characterized in that the period of natural oscillations of the motors T ₀ with the inertial load is preliminarily determined at the initial voltage level voltage increase from the initial level produces a time, T ₀ is significantly less (e.g. 0.01 T ₀₎ and simultaneous SWIVEL t phase voltage vector against the rotor rotation direction is carried through the angle Δα = 15 ÷ 20 e. column relative to the phase of the synchronous coordinate system, a subsequent decrease in voltage to the initial voltage level is also produced for a time less than T ₀ (less than 0.01 T ₀ ) with simultaneous rotation of the phase of the voltage vector in the direction of rotation of the rotor by the same angle Δα. 2. The method of two-zone amplitude-phase overexcitation of synchronous hysteresis electric motors according to claim 1, characterized in that after reducing the voltage to the initial voltage level, an excess supply is determined by the moment and a subsequent smooth decrease in voltage to the operating level when the excess supply by the moment in time is exhausted much greater than T ₀ (greater than 10 T ₀ ).

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