RU2234793C1 - Method for attaining torque on contactless inductor-type valve motors - Google Patents

Abstract

FIELD: electrical machines; traction drives of vehicles, load-lifting machines, machine tools, oil-extraction and compressor pumps.

SUBSTANCE: proposed method involves following procedures. Inverter is supplied with dc voltage from power supply and phase windings are connected through the latter to respective circuits thereby affording ac current through phase windings, dc current being fed from this power supply. Field winding is connected to supply voltage circuit in series with semiconductor switch and to phase windings so that instant value of field current is proportional to sum of absolute values of phase currents.

EFFECT: provision for attaining valve motor characteristics equivalent to those of series-wound commutator machines.

1 cl, 22 dwg

Description

The invention relates to electric machines and is used in drives used in various fields of human activity to convert electrical energy into mechanical energy. The maximum effect can be achieved by using the proposed method in traction electric drives of vehicles, lifting machines, in a machine drive, in drives of pumps for pumping oil from wells, as well as in drives of compressor pumps.

The inventive method of obtaining torque for contactless induction valve motors will allow to obtain the output characteristics of these electric machines, equivalent to the characteristics of a collector DC machine of sequential excitation.

Electric machines are devices for converting electrical energy into mechanical energy. An electric machine is based on the principle of interaction of one magnetic flux created by natural or artificial magnets with another, also created by natural or artificial magnets. The conversion of electrical energy spent on the creation of magnetic flux into mechanical, removed from the shaft of the electric motor in the form of torque, can be described by the expression, which is a vector product of two magnetic fluxes

where M is the torque on the motor shaft;

F _I - the magnetic flux of the anchor;

Фв - magnetic flux of excitation;

k is the coefficient of proportionality, taking into account design features.

The magnetic flux generated by the phase windings is called the magnetic flux of the armature, and the magnetic flux generated by the permanent magnets or field windings is called the magnetic flux of the excitation.

The magnitude of the torque taken will depend on both the magnitude of the magnetic fluxes and the angle between them. Therefore, to obtain large torques for given dimensions, it is necessary to use special magnetic materials, special rotor designs, or relatively large currents flowing through the windings of an electric machine. The fulfillment of these two conditions is always associated with the complexity of the design of the drive. Torque can also be increased by approaching the angle between the magnetic fluxes of the armature and excitation to 90 ° due to the use of the collector assembly in DC machines or rotor position sensors [2, pp. 72-75] in non-contact AC machines.

Currently, various methods for producing torque are known, implemented in DC machines with independent, sequential and mixed excitation, as well as in asynchronous electric machines with a squirrel-cage rotor, in synchronous non-contact machines with permanent magnets [4, p.205], in superconducting valve induction machine [1, patent RU 2178942 C1].

In DC machines with independent excitation, the formation of magnetic fluxes of the armature and excitation is carried out by independently connecting the armature winding and the excitation winding. With this method of forming magnetic fluxes, it is possible to simultaneously and independently change them, which makes it possible to obtain a torque in a fairly wide range of values. However, in this case, two independent controllers are required, which leads to a complication of the drive design.

A similar method of obtaining torque is used in sequential excitation DC collector machines, where the magnetic flux of the armature is created by the anchor winding, and the magnetic flux of the excitation by the excitation winding connected through the collector assembly by sequentially connecting this winding with the anchor so that one of the terminals of the anchor winding is always connected to the beginning or end of the field winding. The special advantages of machines of this class include the fact that it is possible to obtain high values of torques and angular velocities due to changes in the magnitude of the magnetic flux of excitation. This simplifies the control of the machine by the magnetic flux of the excitation, since there is no need to introduce an additional controller.

However, it is impossible to implement this method of obtaining torque for contactless induction valve machines by connecting the armature winding and the field winding in series, since, first, they are AC machines, and the direction of the current in the field winding should not change, and, secondly , the magnetic flux of the armature in DC machines is created by a winding placed on the rotor, and the presence of a collector assembly is mandatory in contrast to the inductor, in which the magnetic flux of the armature aetsya phase windings are always placed on the stator.

Fundamental structural differences of electric machines of these classes allow us to conclude that the claimed method of producing torque is new and the authors are not aware of the application of the anywhere proposed method of producing torque for electric machines with phase windings. The proposed method of obtaining torque will allow to obtain the output characteristics of contactless induction valve machines, similar to the characteristics of DC collector machines with sequential excitation, but the presence of a regulator and a semiconductor switch can expand the capabilities of machines of this class.

The closest analogs from the point of view of design, where the method of obtaining torque developed by the authors can be implemented, are various types of non-contact valve motors in which the armature magnetic flux is created by passing electric current through phase windings: asynchronous electric machines with a squirrel-cage rotor [4 , p.272-274], synchronous contactless machines with permanent magnets [4, p.205], a superconducting valve inductor machine [1, patent RU 2178942 C1].

In an asynchronous electric machine with a squirrel-cage rotor [4, p.272-274] by connecting the phase windings to an alternating current network, a rotating magnetic flux of the armature is created, which, in interaction with the magnetic flux of excitation created by the currents induced in the “squirrel cage” of the rotor, leads to obtain torque on the motor shaft. In this case, due to the phase shift during the formation of the magnetic flux of excitation, which is called slip [5, p. 390], it is possible to change the angle between the magnetic flux of the armature and the magnetic flux of excitation, which allows to obtain the required mechanical characteristics.

полупроводникового коммутатора 2, с магнитным потоком возбуждения, создаваемым постоянными магнитами (N-S), размещенными на роторе 7 двигателя 1. Вращение магнитного потока, создаваемого фазными обмотками, обеспечивается за счет специальных способов их коммутации устройствами 3, 4, 5 по сигналам от датчиков положения ротора, поступающим на контакты 3к и 4к устройства согласования 6 в виде управляющего напряжения U_упp.In a synchronous contactless machine with permanent magnets [4, p.205] (Fig. 1), the torque on the shaft of the electric motor 1 is obtained due to the interaction of the armature magnetic flux created by the phase windings A, B, C through their coordinated connection to the supply voltage

a semiconductor switch 2, with a magnetic flux generated by permanent magnets (NS) placed on the rotor 7 of the motor 1. The rotation of the magnetic flux generated by the phase windings is provided by special methods of switching them with devices 3, 4, 5 by signals from the rotor position sensors coming to the contacts 3k and 4k matching device 6 in the form of a control voltage U _CPR .

To control the magnetic flux of the armature of FIG. 2, various microcircuits 2 are used, which make it possible to obtain the required values of the torque of the electric motor 1 with permanent magnets N-S on the rotor [3, p. 189] and, accordingly, expand the scope of applications of machines of this class.

In a superconducting valve induction machine [1, p. 8], torque is obtained by creating a multiphase winding of the magnetic flux of the armature and forming a combined magnetic flux of the excitation due to the placement of a permanent magnet on the rotor of the electric motor and an excitation coil on the stator. A consonant or counter inclusion with a built-in magnet (“frozen in” magnetic flux) of an independent field coil allows you to change the magnitude of the magnetic field flux, thereby achieving a change in torque. With this method of obtaining torque, the field winding is connected separately and independently of phase windings [1, p. 8].

.The magnetic flux of the armature in a non-contact induction valve motor 1 (Fig. 3) is created by alternately connecting the phase windings A, B, C through a semiconductor switch 5, which generates currents in the phase windings of the motor according to the selected law. In this case, the power elements 6 of the semiconductor switch 5 operate in a key mode, and the shunt diodes 7 are designed to close currents from the self-induction EMF when a particular power element is disconnected. The torque is obtained due to the interaction of two magnetic fluxes: the magnetic flux of the armature, which is created due to the current flowing through the phase windings A, B, C connected to the corresponding elements of a special inverter 5, and the magnetic flux of excitation created by an independent excitation winding of the OB connected through regulator 4 to the supply voltage

.

With this method of obtaining torque, two options for changing its magnitude are possible. In the first case, by controlling the magnitude of the magnetic flux of the armature by changing the currents flowing through the phase windings, and in the second case, by changing the magnetic flux of the excitation, carried out by changing the magnitude of the current in the field winding connected to an independent power source. This method of obtaining torque provides the required torque values for a certain power range, but an independent power source is needed, to which the field winding must be connected.

With such a connection of the field winding, the currents in the phase windings are formed through a switching device, and the field winding is fed from an external source through a separate controller, such as, for example, in the device described in [1, p. 8].

The disadvantage of this method is that the controller for controlling the currents in the field winding must be powerful enough and there will be a significant release of energy, while the total cost of the drive increases.

The closest in essence is the method of producing torque, implemented in the device [1, patent RU 2178942 C1, Superconducting valve inductor machine], described above and in [2, p.16-18], and taken as a prototype, which includes :

1) supplying direct voltage to the semiconductor switch and through it connecting the phase windings through their circuits, obtaining alternating current in the phase windings and creating an armature magnetic flux;

2) independent connection of the field winding to the supply DC voltage and the creation of a magnetic field flux;

3) the interaction of magnetic fluxes of the armature and excitation;

4) obtaining torque on the motor shaft.

The aim of the invention is to obtain the output characteristics of non-contact induction valve electric motors, similar to the output characteristics of DC collector machines of series or mixed excitation, by connecting the field winding in series with phase windings, which will expand the scope of application of electric machines of this class.

The goal is achieved through the application of a new method of obtaining torque, which consists in the following sequence of operations:

1) the supply of constant voltage to the semiconductor switch and through it the connection of the phase windings through their circuits, ensuring that the phase windings receive alternating current to create an armature magnetic flux;

2) connecting the field winding in series with the phase windings to supply a constant voltage to it so that a direct current flows through it, the instantaneous value of which is proportional to the sum of the absolute values of the phase currents for various methods of connecting the phase windings, and creating a magnetic field flux;

3) the interaction of magnetic fluxes of the armature and excitation;

4) obtaining torque on the motor shaft.

The invention consists in the following. When receiving torque on the motor shaft, various methods are used to create magnetic fluxes of the armature, which can be divided into groups. The first group includes methods with a passive pause, characterized in that during a pause between control pulses the phase winding of the machine is disconnected from the power source by locking the power switches of the switch. In this case, two options are possible [2, p.16-18].

.The essence of the first of them is illustrated in figure 4. When a pulse is generated, taking into account the signals of the rotor position sensor, power transistors corresponding to a given rotor position are unlocked to the control circuits of the switch 2. Suppose that transistors T ₂ , T ₄ , T ₆ are open on the overlapping section. In this case, the current from the positive bus of the power source flows through the collector circuit of the transistor T ₂ , all three sections of the winding and the collector circuit of the transistors T ₄ and T ₆ to the negative bus. In a pause between control pulses, all the switch keys are locked. The current from the self-induction EMF continues to flow through the winding and closes through the shunt diodes D ₁ D ₃ and D ₅ to the power source, and the voltage of the source is applied counter to the self-induction EMF, which contributes to the fastest current decay in the pause. The on-off switching of the source voltage and EMF of self-induction in the pause between the control pulses introduces specificity in electromagnetic processes and has a significant impact on the type of mechanical and adjustment characteristics of the motor. In this case, the excitation flow is created by an independent excitation winding ОВ, which is connected via a regulator 4 to an independent power source with voltage

.

In the second embodiment of FIG. 5, with a passive pause, in the pause between control pulses, only one group of power switches of the switch is locked, for example, the anode one. The transistors of the second group remain in the state in which they were during the previous pulse, i.e. are controlled only by taking into account the signals of the rotor position sensor. Since the transistors of the cathode and anode groups are connected in series with sections of the armature winding of the motor, in a pause this winding is disconnected from the power source. However, the current from the self-induction EMF flows already in a different way than in the first embodiment, which also affects the mechanical and adjustment characteristics of the motor.

Another group of methods for creating magnetic fluxes of an anchor include methods with dynamic braking in a pause. Different implementations of dynamic braking are possible. To decelerate the engine according to the circuit shown in Fig. 3, it is enough to disconnect it from the power source with switch 3 and close the input buses of the switch 5 to the current-limiting resistance 2. In this case, the power transistor switches 6 must be locked. The current passing through the current-limiting resistance 2 creates a moment of dynamic braking, and the bridge semiconductor switch 5 allows dynamic braking in a pause without the use of additional elements in the power unit due to the organization of special control algorithms.

Depending on the method of connecting the phase windings (into a triangle, into a star, independently), which are known and described in [7, p.12. Figure 1-4. The classification table.], As well as [6, p.146, Fig.5.9 (where diagrams with several triads of phase windings are shown)] and their numbers, the connection circuit of a series excitation winding to create an excitation magnetic flux can have the following forms.

полупроводникового коммутатора 2, а общие точки шунтирующих диодов Д1-Д6 подключены до обмотки возбуждения OB₁. При этом магнитный поток возбуждения создается током, который оказывается пропорциональным сумме абсолютных величин фазных токов, что дает возможность для создания магнитного потока возбуждения частично использовать токи от ЭДС самоиндукции и обеспечивает получение необходимой величины вращающего момента.When connecting the phase windings into a triangle (Fig.6), the inventive method of obtaining torque for contactless induction valve motors is implemented by connecting the field winding OB ₁ in such a way that it is connected to the supply voltage circuit

semiconductor switch 2, and the common points of the shunt diodes D1-D6 are connected to the field winding OB ₁ . In this case, the magnetic flux of the excitation is created by a current that is proportional to the sum of the absolute values of the phase currents, which makes it possible to partially use the currents from the self-induction EMF to create a magnetic flux of excitation and provides the necessary torque.

In Fig.6 and all subsequent figures, the structural elements of the electric machine, located inside the zones limited by the dashed line with the number 1, are placed directly in the electric machine and are elements of its construction. Also in FIG. 6 and all subsequent figures, elements located inside zones limited by a dotted line with the number 2 are elements of a semiconductor switch or inverter.

Similarly, you can connect the field winding for a machine in which the phase windings are connected to a star (Fig.7). As described above, in the presence of several groups of phase windings connected in a triangle, a star or in general phase windings connected independently of each other, the connection circuit of the series field winding of Figs. 8, 9, 10 has the same form. In this case, the current flowing through the phase windings will be used to create a magnetic field flux, i.e. the proportionality between the generated magnetic flux of the excitation and phase currents will be maintained for each phase connection circuit of the phase windings. When applying this method of obtaining torque with this scheme of connecting a series field winding, the design of the electric machine is simplified.

так, что токи от ЭДС самоиндукции полностью будут проходить через обмотки OB_1-1 или OB_1-2.In the event that it is possible to carry out the field winding OB ₁ split into two branches or consisting of two parts, it is possible to turn on each section of the field winding OB _1-1 and OB _1-2 (Fig. 11) to a constant voltage supply

so that the currents from the self-induction EMF will completely pass through the windings of OB _1-1 or OB _1-2 .

Similarly, it is possible to connect a serial split excitation winding OB _1-1 and OB _1-2 (Fig.12) and when connecting the phase windings to the star. Moreover, the instantaneous value of the excitation current is proportional to the sum of the absolute values of the phase currents.

будет иметь вид, представленный на фиг.13, 14, 15. Последовательная обмотка возбуждения OB₁, состоящая из двух секций (расщепленная) OB_1-1 и OB_1-2, включена в цепь постоянного питающего напряжения

последовательно с инвертором и фазными обмотками.To implement the inventive method of producing torque for contactless induction valve motors with several groups of phase windings connected in a star or delta, as well as for independently connecting phase windings, connecting a serial split field winding OB _1-1 and OB _1-2 to constant voltage source

will have the form shown in Fig.13, 14, 15. The series excitation winding OB ₁ , consisting of two sections (split) OB _1-1 and OB _1-2 , is included in the constant voltage supply circuit

in series with the inverter and phase windings.

. Вместе с тем пропорциональность мгновенного значения тока возбуждения сумме абсолютных величин фазных токов сохраняется, изменяется лишь коэффициент пропорциональности.To obtain an external characteristic of the motor, similar to the characteristic of a DC motor of mixed excitation, or the need to vary the type of characteristic in different modes of operation of an electric machine, it is also possible to use an independent excitation winding ОВ ₂ . The presence of an independent field winding allows even wider limits to change the magnetic field flux, which leads to the expansion of the range of regulation of torque at the same speed. Depending on the type of sequential field winding (solid or split) for various schemes of connecting phase windings (in a triangle, in a star, in several triads, independently connecting phase windings), a method of obtaining torque for non-contact induction valve motors can be implemented for account of the connection circuits shown in FIGS. 16, 17, 18, 19, 20, 21, 22. In this case, an additional excitation flow is created by an independent excitation winding ОВ ₂ , which is connected through the regulator 3 to voltage source

. At the same time, the proportionality of the instantaneous value of the excitation current to the sum of the absolute values of the phase currents is preserved, only the proportionality coefficient changes.

The inventive method of obtaining torque differs from the existing ones in that the connection of the phase windings and the field winding is carried out sequentially and simultaneously.

The implementation of this method is impossible using designs of electric machines of a certain class that do not have field windings, such as, for example, asynchronous AC machines or non-contact AC machines with permanent magnets.

Thus, the claimed method meets the criteria of the invention of "novelty."

The need to use this method of obtaining torque can arise when using non-contact induction valve electric machines as traction motors in transport, in hoisting machines, in a machine drive and in pump drives for pumping oil from wells, when it is necessary to achieve the same in electric AC machines output characteristics, as in collector DC machines of sequential excitation.

The inventive method of producing torque allows to improve the output characteristics of contactless induction valve electric machines and thus expand the scope of this class of machines.

Sources of information

1. Patent RU 2178942.

2. Avdolotkin N.P., Grashchenko V.T., Lebedev N.I., Ovchinnikov I.N., Stytsyna A.K. Controlled non-contact DC motors. L .: Energoatomizdat. Leningra. Department, 1984, 160 p.

3. Encyclopedia of repair. Issue 12. Microcircuits for controlling electric motors. M .: DODEKA, 1999, 288 p.

4. Yuferov F.M. Electric machines of automatic devices. Textbook for high schools. M .: Higher school, 1976, 416 p.

5. H.E. Zeidel, V.V. Kogen-Dalen, V.V. Krymov, V. G. Gerasimov, D. N. Morozov and others. Electrical engineering for universities. M .: Higher School, 1985, 480 p.

6. Booth D.A. Contactless electric machines. Textbook for electromechanical and electric power specials. technical colleges .. M .: Higher school, 1985, 255 p.

7. Ovchinnikov I.E., Lebedev N.I. Contactless DC motors. L .: Science, Leningrad Branch, 1979, 270 p.

Claims (1)

A method of obtaining torque for contactless induction valve electric motors, comprising supplying direct voltage to the inverter from the power source and connecting phase windings through its circuits, allowing passage of alternating current in the phase windings, supplying direct current to the excitation winding and obtaining magnetic fluxes as a result of the interaction armature and excitation of torque on the motor shaft, characterized in that the direct current in the field winding is supplied from the specified Power supply, the field winding is connected to the power supply circuit in series with the inverter and the phase windings, so that the instantaneous value of the excitation current proportional to the sum of the absolute values of the phase currents.

Images