RU121969U1 - AC VOLTAGE STABILIZATION SYSTEM - Google Patents

Abstract

An AC voltage stabilization system containing a magnetoelectric generator directly connected to the shaft of the primary engine with a working and additional windings connected in a star circuit, a filter to the inputs of which the output terminals of the working winding are connected, and its outputs are connected to the load, a comparison unit, one of the inputs which is connected to the load, and the second to the source of setting the load voltage, a controlled short-circuiter, to the input terminal of which the output of the comparison unit is connected, characterized in that capacitors are sequentially connected to the output terminals of each phase of the additional winding, the second leads of which are connected to the outputs of the short-circuit.

Description

The proposed utility model relates to the field of electrical engineering and can be used in the design of power supplies based on mechanoelectric generation systems used in aircraft, ships, other vehicles and autonomous objects.

Known systems for stabilizing AC voltage when changing rotation speed in a wide range [Electrical equipment of aircraft: a textbook for high schools. T. 1, ed. S.A. Gruzkova. - M .: MEI Publishing House, 2005, p.180-184], which contain contactless generators with combined excitation. The increased overall dimensions of the electromechanical converter and the high complexity of manufacturing limit the use of such systems.

There is also known a system for stabilizing AC voltage [RF Patent for Utility Model No. 81609 of December 5, 2008], which contains a magnetoelectric generator with working and additional windings connected in the form of a star, a filter, to the inputs of which are connected the output terminals of the working winding, and its outputs connected to the load, a comparison node, one of the inputs of which is connected to the load, and the second to the voltage reference source. Stabilization of the output voltage is carried out due to the source of formation of the reactive current of the generator. The structural complexity of the source of generation of the reactive current of the generator reduces the reliability of the device, and the need for an intermediate filter of large dimensions between the output terminals of the generator and the load to smooth out the ripples created by the switch of the reactive current source leads to an increase in the dimensions of the entire system.

Also known is a system for stabilizing AC voltage of an unstable frequency [RF Patent for utility model No. 115134 publ. 04/20/2012], which is the prototype of the proposed utility model, which contains a magnetoelectric generator directly connected to the primary motor shaft with the working and additional windings connected in the form of a star, a filter, the outputs of the working winding are connected to its inputs, and its outputs are connected to the load, comparison node, one of the inputs of which is connected to the load, and the second to the voltage source, controlled by a short circuit, to one of whose outputs is connected the output of the comparison node, and to a friend them conclusions output conclusions of the additional winding. The disadvantages of the system for stabilizing the AC voltage of the prototype include the oversized dimensions of the additional winding.

The objective of the utility model is to reduce the size of the system generator by reducing the required number of ampere-turns of its working winding.

The task is achieved by the fact that in the AC voltage stabilization system containing a magnetoelectric generator directly connected to the primary motor shaft with a working and additional windings connected in a star pattern, a filter, to the inputs of which are connected the output terminals of the working winding, and its outputs are connected to the load , a comparison node, one of the inputs of which is connected to the load, and the second to the source of the load voltage setting, a controlled short circuit to the input terminal of which connecting a comparison output node to the output terminals of each phase of the additional winding capacitors are connected in series, the second terminals of which are connected to the outputs for short.

Figure 1 presents a structural diagram of the proposed system for stabilizing AC voltage.

Figure 2 shows a simplified equivalent circuit of one phase of the generator of the proposed system for stabilizing the voltage of an alternating current with a shorted short circuit.

Figure 3 is a vector diagram explaining the operation of the system for stabilizing the voltage of alternating current in idle mode with the inductive nature of the phase resistance of the additional winding.

Figure 4 is a vector diagram explaining the operation of the system for stabilizing the voltage of alternating current in idle mode with the capacitive nature of the phase resistance of the additional winding.

The AC voltage stabilization system (FIG. 1) consists of a synchronous generator 1 with magnetoelectric excitation, which contains a working (main) winding 2 and an additional 3 (to form the required excitation flow). The generator is directly connected to the shaft of the primary engine 4. From the output terminals of the working winding 2 of the generator through the intermediate filter 5, the load (consumer) 6 is supplied with a stable voltage of variable frequency. In parallel with the load, a comparison unit 7 is connected, to the second input of which a source 8 for setting the required (reference) voltage U _{ass of} consumers of electric energy is connected. The output of the comparison unit 7 is connected to the input of the controlled short circuit 9, to the outputs of which are connected capacitors 10, the second terminals of which are connected in series to the output terminals of the additional winding 3.

The controlled short circuit 9 shown in the circuit (FIG. 1) is based on a rectification bridge circuit, to the output of which a controlled key (transistor) is connected. Other modifications of the short circuit are possible.

The operation of the system is as follows.

The phase of the generator of the system of FIG. 1 can be modeled by the equivalent circuit shown in FIG. 2. In accordance with the equivalent circuit, the voltage at the output of the generator is determined by the expression

,

where: E ₁ = K ₁ ωФ - rotation EMF induced by the resulting magnetic flux Ф in the phase of the working winding;

K ₁ - coefficient of proportionality;

ω is the angular frequency of rotation of the rotor;

I ₁ - phase current of the working winding;

I ₂ - phase current of the additional winding;

- EMF of mutual induction induced by the current of the additional winding and proportional to the angular frequency of rotation of the rotor;

M is the coefficient of mutual induction between the working and additional windings;

L ₁ - synchronous inductance of the working winding.

Thus, the main factors determining the stability of the generator output voltage are the change in the rotation frequency ω, the load current I ₁ and the current of the additional winding I ₂ .

Consider the influence of the rotation frequency and current of the additional winding on the output voltage of the generator in idle mode, when the phase current of the main winding I ₁ is zero. When the primary motor 4 (and the related pole system of the rotor made with permanent magnets) rotates in the phases of the additional winding 3 of the generator 1, in accordance with the law of electromagnetic induction, an EMF E ₂ equal to

E ₂ = K ₂ ωФ _В ,

where: K ₂ - coefficient of proportionality;

Ф _В - magnetic flux created by permanent magnets of the pole system of the rotor.

This EMF is 90 ° behind the magnetic flux vector Ф _В , as shown in the vector diagrams of Fig. 3 and Fig. 4. In this case, in the phases of the additional winding, a current I ₂ occurs, which is determined by the expression

and to the corner shifted relative to the EMF E ₂ .

where: R ₂ is the active phase resistance of the additional winding;

L ₂ - inductance of the additional winding;

X ₂ = ωL ₂ - reactance of the additional winding;

C is the capacitance of the capacitor;

X _C = 1 / ωC is the reactance of the capacitor.

This current creates a magnetic flux of the reaction of the armature Ф ₂ , which, depending on the ratio of the reactance of the inductance of the additional winding X ₂ and the capacitor X _C with respect to the magnetic flux of the pole system Ф _В, can be either longitudinally demagnetizing or longitudinally magnetizing.

When X ₂ > X _{C, the} current I ₂ at an angle φ ₂ lags behind the EMF E ₂ . The magnetic flux of the reaction of the armature f _{2 is} longitudinally demagnetizing. As a result, the working magnetic flux in the air gap of the machine Ф decreases. The vector diagram for this case when neglecting the scattering flux is shown in Fig.3. The working magnetic flux induces in the coils of the main winding of the EMF armature E ₁ , which is 90 ° behind this flux. In addition, in the turns of the main winding by the current of the additional winding, the mutual induction EMF E _M2 is also induced. As a result, the voltage at the output of the working winding in idle mode will be equal to

.

As can be seen from the vector diagram, the output voltage U _{10 is} less than the emf of rotation, since the vector and are practically in the counter-phase.

Thus, we can conclude that at X ₂ > X _{C, the} additional winding reduces the output voltage of the main winding due to two factors: a decrease in the resulting magnetic flux due to the longitudinally demagnetizing response of the armature, and counter-EMF of mutual induction.

When X ₂ <X _{C, the} current I ₂ at an angle of φ _{2 is} ahead of the EMF E ₂ . The magnetic flux of the reaction of the armature f _{2 is} longitudinally magnetizing. As a result, the working magnetic flux in the air gap of the machine Ф increases. A vector diagram for this case when neglecting the scattering fluxes is shown in Fig. 4.

As can be seen from the vector diagram, the output voltage U _{10 is} greater than the emf of rotation. From the analysis of the vector diagram, it can be concluded that at X ₂ <X _{C, the} additional winding increases the output voltage of the main winding due to two factors: an increase in the resulting magnetic flux due to the longitudinally magnetizing reaction of the armature and counter-EMF of mutual induction.

At rated speed, the reactance of the auxiliary winding phase must be equal to the reactance of the capacitor

ω _n L ₂ = 1 / ω _n C,

where ω _n is the nominal angular frequency of rotation of the rotor.

Therefore, with a decrease in the rotation speed, the phase resistance of the additional winding will be capacitive in nature. The current of the additional winding will create a magnetizing reaction of the armature, which, in combination with the EMF of mutual induction induced by the current of the additional winding, compensates for the decrease in the EMF of the working winding with a decrease in the number of revolutions of the generator shaft.

With increasing speed relative to the nominal phase resistance of the additional winding will be inductive. The current of the additional winding will create a demagnetizing response of the armature, which compensates for the increase in the EMF of the working winding with an increase in the number of revolutions of the generator shaft.

The parameters of the working winding in the absence of current in the additional winding (I ₂ = 0) must provide the rated voltage of the generator at the maximum permissible value of the load current and the rated rotational speed of the rotor.

When increasing the rotor speed relative to the nominal or decreasing the load current, in order to maintain the generator output voltage level, it is necessary to set the corresponding value of the additional winding current (I ₂ ≠ 0). As a result, the EMF of the working winding will decrease to the value necessary to ensure the nominal output voltage of the generator.

The parameters of the additional winding should be selected from the condition of ensuring the rated output voltage in idle mode (I ₁ = 0) at the maximum permissible revolutions of the generator shaft and a closed short circuit (I ₂ = I _2max ).

When the rotor speed is reduced relative to the nominal value, the generator output voltage level is also maintained by adjusting the additional winding current (I2 ≠ 0).

The magnitude of the current of the additional winding is determined by the comparison unit 7, the output signal of which is proportional to the difference between the levels of the specified voltage and load voltage. Current regulation is carried out by pulse-width method. The required value of the additional winding current is determined by the duty cycle of the width-modulated output signal of the comparison node.

Unlike the prototype, where the parameters of the working winding in the absence of current in the additional winding should provide the rated voltage of the generator at the minimum permissible rotor speed, the number of turns of the working winding in the proposed utility model can be significantly reduced, since here the rated voltage must be provided at more high rated rotation speed.

In the idle mode of the generator I ₁ = 0 and the absence of current in the additional winding I ₂ = 0, the voltage of the generator for the proposed device can be described by the equation

U ₁₀ = E ₁ = C ₁ ω _n WF _B ,

where W is the number of turns of the working stator winding for the generator of the proposed stabilization system;

C ₁ is a constant coefficient.

The same voltage should be provided in the prototype circuit at the lowest possible speed.

U ₁₀ = C ₁ ω _min W _P f _V ,

where W _P - the number of turns of the working stator winding for the generator of the prototype device.

Thus, the number of turns of the working stator winding of the generator of the proposed voltage stabilization system can be reduced in accordance with the ratio of the minimum permissible rotor speed and nominal

.

If the minimum allowable speed is equal to half the nominal ω _min = 0.5ω _n , then W = 0.5W _P , that is, the number of turns of the working winding in the proposed device compared to the prototype can be reduced by half.

The reduction in the number of turns of the working winding allows not only to reduce the dimensions of the generator of the system, but also to further reduce its cost by reducing the volume of copper of the windings, and by reducing the resistance of the working winding to reduce power loss and voltage drop under load.

Claims (1)

An AC voltage stabilization system containing a magnetoelectric generator directly connected to the primary motor shaft with a working and additional windings connected in the form of a star, a filter, to the inputs of which are connected the output terminals of the working winding, and its outputs are connected to the load, a comparison unit, one of the inputs which is connected to the load, and the second to the source of the load voltage setting, a controlled short circuit, to the input terminal of which the output of the comparison unit, which differs by the fact that to the output terminals of each phase winding coupled successively more capacitors, the second terminals of which are connected to the outputs for short.