DE3507425A1 - DC Machine having thyristors for commutation - Google Patents

Abstract

A DC machine having thyristors for commutation has an electrical armature winding having a plurality of active conductors (3 and 4) which participate in the electromechanical energy conversion of the machine. Furthermore, a commutating device having a plurality of thyristors or comparable switching elements (1) is provided, in which switching elements the change from the non-conductive state to the conductive state is carried out by means of external control signals, but the opposite change can take place only when the conductor current is zero. In this case, the switching elements or thyristors are connected to the electrical armature winding in such a manner that they control the conduction or non-conduction of the electrical current in the active conductors for commutation. <IMAGE>

Description

Description :

The invention relates to a direct current machine with thyristors for commutation according to the preamble of the claim

It should be the commutator and the commutator brushes in the rest of the usual heteropolar DC machines be replaced by thyristors.

More particularly, the present invention relates to an improved heteropolar DC machine, the electrical winding is designed so that the current reversal of the electrical conductor in the corresponding winding - known as commutation - can be done through the use of thyristors or similar semiconductors in this way a conventional commutator and commutator brushes and the associated disadvantages to avoid.

Common DC machines, the design and manufacture of which has long been known (e.g. "The Performance and Design of Direct.Current Maschines "by A.E. Clayton and N.N. Hancock) are divided into two types of construction: unipolar and heteropolar machines.

In unipolar machines only one active pole is arranged in such a way that the active conductors through a magnetic field of constant strength can be moved. The series connection of the active conductors of the armature winding, whose The purpose of achieving a suitable operating voltage is, however, only problematic with this type of machine and difficult to realize, although various possible

Arrangements of the magnetic circuit and the electrical armature winding are known.

Because of this problem in particular, unipolar machines are rarely used, although these disadvantages of Avoid using a commutator and commutator brushes. Your bet is essentially on low Tensions and high armature currents are limited.

On the other hand, the arrangement of the magnetic field of heteropolar machines consists of a large number of active north- and southern poles, which are arranged alternately with each other. With this type of distribution, usually for heteropolar DC machines is provided, the active conductors are moved by a magnetic field, the strength of which is periodic changes. Because of this, the voltage induced in each of these conductors also fluctuates, with the frequency being dependent on the product the speed of rotation is determined by the number of pole pairs.

However, the series connection of the active armature conductors causes no problem in heteropolar machines, and these machines can be manufactured for operation with normal operating voltages will.

Preferably the connection is always between the conductors which are at the same time under opposite poles, and their induced voltages are therefore opposite are the same.

This is why such conductors can be connected to the corresponding ends on the same side on the anchor core. This allows an un-

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interrupted electrical winding can be produced. The armature winding is preferably electrically balanced (steady) shape without discontinuities produced in such a way that groups are more active at every point in time of the rotary movement Conductors are connected in series, in which the induced electromotive force (EMF) during a certain period of time the desired voltage at the external connection of the machine remains the same.

Since the voltage induced in each group of series-connected conductors changes, the use of a commutation device is necessary to establish an electrical connection between the corresponding conductors and the external connections of the machine only during suitable time intervals in order to achieve a constant voltage at the connections.

The commutation device, as is usually the case for heteropolar DC machines, regardless of size or use of such machines - DC generators for industrial applications, large DC mill motors, DC drive motors for locomotives or trolley buses, small DC motors for industrial applications Equipment - used is essentially a mechanical commutation device that acts as a commutator and brushing is called.

The commutator, which is arranged in a stationary manner opposite the armature, comprises a multiplicity arranged next to one another Lamellae made of electrically conductive material such as copper, which are electrically insulated from one another. Each of these slats is electrically connected to one of the ends of the group of active armature conductors that are connected in series.

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Usually the slats are on a practically closed position annular surface, such as a cylinder surface, arranged so that each lamella the place of their adjacent lamella occupies when the armature at a predetermined angle with respect to the active pole in the electrical Field is rotated.

The brushes, which are fixed to the active poles of the magnetic field, essentially consist of surfaces made of a conductive material such as carbon, graphite and metal compounds, and are arranged around the commutator, that they slide over this and are in electrical connection with the slats in associated positions.

When the armature is rotated with respect to the active poles, the brushes come into electrical contact with each other the lamella that has come into the correct position and interrupt contact with the lamellae that has the correct one Leaves position, whereby the current reversal takes place.

During the operation of the machine the friction gets between the commutator bars and the brushes wear on both parts.

The commutator and the brushes are preferably constructed in such a way that the wear and tear on the commutator, its production costs are usually large, kept smaller than on the less expensive brushes.

The brush arrangements are made so that a compensation of the wear during a certain Operating time is possible. The brushes then have to be replaced.

During the operation of the machine, physical phenomena that are part of this mechanical commutation to smaller or larger wear of the commutator and the brushes, for example a film formation on the commutator surface, which is usually useful, and sparking, which is usually undesirable. These Appearances can lead to permanent damage to the machine and an increased risk of accidents.

These phenomena are closely related to external influences such as vibrations, mechanical misalignments, foreign matter in the atmosphere or in contact with the commutator and brushes, extreme temperatures and relative humidity, high speeds, increases in armature current, presence of AC components in armature voltage and others Factors together that worsen the reversal of the current.

More advanced machines usually use special techniques, such as the use of additional reversing poles applied, which increase the effectiveness, the service life and the reliability of the commutator and the brushes, but also increase the manufacturing costs.

Notwithstanding the relatively high manufacturing costs and some shortcomings, such as the necessary replacement of brushes, the special care to avoid vibrations and dirt to avoid and the speed limitation are heteropolar DC machines with commutator and brushes manufactured and used for most applications.

Other techniques are known to replace the commutator and brushes on heteropolar DC machines, which relate to a commutation device with transistors or similar semiconductors.

Machines that are called "brushless" or "electronically commutated", for example, are a thing of the past manufactured and used in certain limited application cases.

In this type of machine, the commutation device consists essentially of several transistors or the like Semiconductors, which are expediently arranged at the ends of the groups of active armature conductors that are connected in series and which can be switched on or off at appropriate moments. In the usual way, an electronic flips Control circuit the signals that control the switching off and on here, as a function of the relative position of the Armature to the active poles of the magnetic field.

This technique necessarily uses semiconductors whose conduction state, like the blocking state, is provided by externally emitted Control signals are commanded, such as transistors that conduct when the base current is applied and when the base current is absent are locked.

Despite the advanced semiconductor industry, the Technology of manufacturing semiconductors with such characteristics related to the use of such semiconductors restricted for higher performance. The reliability and durability of these semiconductors decreases significantly, if they are designed to control relatively high electrical currents, and there are physical limits to that do not allow commercial manufacture for currents in the usual range of DC machines.

The power range of the machines, which according to the previous techniques to replace the commutator and the brushes

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a communication device with transistors or the like Semiconductors built is so limited by the semiconductors themselves, relatively small and their usability is only limited to those cases in which machines with low capacities are required. Besides, it does relatively large destructibility of such commutation devices impossible that these are used in the cases where the requirements are more stringent or where reliability is an essential requirement.

Despite the progress made in the past, the usual mechanical commutation devices in To replace DC machines with commutation devices with transistors or similar semiconductors - the only used satisfactorily in limited applications There is still a real need for a heteropolar DC machine with a non-mechanical one Commutation device that is at least as robust and reliable as conventional machines Brushes and commutators are and they are advantageous in a wide range of applications regardless of size, power and other electrical parameters.

Accordingly, it is an object of the present invention to provide a DC machine with a semiconductor element to create using commutation device that meets the technical requirements mentioned above Fulfills.

This object is achieved by the structure of the machine and the commutation device with those mentioned in claim 1 Features solved.

ORIQtNAL INSPECTED

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The present invention is generally based on the recognition that in heteropolar DC machines, advantageous a commutation device can be used which has thyristors or similar components. the The armature winding of these DC machines can be produced in a way that is inexpensive to manufacture according to a special criterion getting produced. This eliminates the need to use conventional brushes and a commutator. in the individual, the anchor winding must be made in such a way that the ladder or the groups more active Conductors that are connected in series with the external connections (of the machine) via thyristors or similar Elements are connected and that the winding itself changes from the conductive state to the blocked state this semiconductor determined at the appropriate time when the corresponding semiconductors from the external connections are to be disconnected and the current in them is to be interrupted.

The use of thyristors as semiconductors for commutation is therefore an essential feature of the invention, although the Thyristors are mentioned in the preambles of the claims.

The switching status of thyristors or similar elements can be determined by externally generated control signals, for example by a trigger current or a current pulse.

On the other hand, the state of locking cannot be determined by externally generated control signals alone, but can adjust only when the conductor current in the semiconductor is zero and at the same time no control signals are present that otherwise cause the conductive state. Therefore, there is the criterion according to which the armature winding according to the invention is to be interpreted in that the armature winding has the zero passage]

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of the electric current of a group of active semiconductors is determined exactly at the appropriate moment when the current must be interrupted to make a change of one conductive to a blocked state of the corresponding semiconductor or a similar element.

An auxiliary device that receives the control signal - such as a Trigger current or a trigger current pulse - emits which the switching of the transistor or similar component from a blocked to a conductive state exactly the right time is determined when the appropriate group of active semiconductors with the external connections must be connected, completes the arrangement, the continuous and sequential operation of the machine evokes.

Thus, according to the invention, thyristors or the like are used Components used commercially for a wide variety of applications. Such thyristors are produced for fractions of amperes to conduct electrical currents up to a thousand amps and in widely used in industry. They are characterized by their exceptional robustness and reliability the end. These properties are also transferred to the commutation device according to the present invention, which determines the commutation of a heteropolar DC machine. So this machine is at least like that robust and reliable like a conventional machine with mechanical commutation and can benefit from this replace virtually any required size, power, or other electrical parameter.

Since no mechanical commutator and brushes are required for commutation, there is also no need for frequent

maintenance of these components, which is the case with conventional DC machines was necessary. The machines commutated with thyristors are therefore also used in other areas of application opened up in which commutator machines could otherwise hardly be used, especially in applications in which the machine is submerged, such as for driving centrifugal pumps in pipes in which the Penetration of water into the machine has hitherto prevented the use of such machines with brushes and commutators.

Thus, according to one embodiment of the present Invention a heteropolar DC motor is provided which has a commutation device with several thyristors.

Further advantageous designs of the DC machine with a commutation device are set out in the subclaims 3 to 9 indicated.

In the following the invention is explained with reference to a drawing, in which are shown:

Fig. 1 shows the arrangement of the electrical winding of the motor armature, including the commutation device Thyristors and the active poles of the magnetic field.

Fig. 2 is a schematic representation of the commutation device, the additional drive current (Trigger current), which is responsible for the change from the blocked to the conductive state of each thyristor in commands at the appropriate moment.

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Fig. 3A is an illustration of the waveform of the electromotive Force (EMF) in the coils of the armature winding, as it can be seen in an oscilloscope, when the motor is driven at a constant rotational speed.

Fig. 3B is an illustration of the waveform of the drive voltage (trigger signal voltage) generated by a additional device for commutation is released, the curve shape in turn in one Oscillograph can be displayed.

In Figures 3A and 3B, the thick lines represent the data pertaining to a particular coil.

4 shows the electrical winding of the motor armature and the commutation device with thyristors as well as the active poles of the magnetic field.

Fig. 5 is a schematic representation of the additional device that generates the control current (trigger current) gives away.

• Fig. 6A is an illustration of the waveform of the electromotive Armature coil force.

Fig. 6B shows the waveform of the signal output from the additional device.

Again in Figures 6A and 6B, the dotted curves correspond to the thyristors connected to one of the terminals connected to the machine - e.g. the positive connection - and the solid curves correspond to the

Thyristors connected to the other terminal, e.g., the negative terminal, with lines showing the data of a specific coil (2) are highlighted.

The following explanation therefore relates to a heteropolar one DC motor as an embodiment of the invention.

As indicated in Fig. 1, the armature winding consists of several similar coils 2, which are connected to external connections via thyristors. The coils 2 are in Armature slots arranged in such a way that a distributed and balanced winding is achieved. Every Coil 2 consists of two coil elements: a main coil element 3 of a main winding screw equal to the polar pitch and an auxiliary coil element 4, the winding pitch of which is more typical wise is like a tooth. Each of the coil elements 3 and consists of numerous turns, but is through in Fig.l only one turn shown. In each coil, the main coil element 3 comprises a group of active conductors connected to the participate in the electromechanical conversion in the machine.

The auxiliary coil element 4 comprises a group of active conductors, which, in addition to their contribution to the electromechanical conversion, are primarily intended to ensure the zero crossing of the Current in the corresponding coil 2 to cause exactly at the desired moment when the coil from the outer Connections of the machine must be disconnected. For this purpose, each auxiliary coil element 4 is so on the armature core arranged just at the end of the winding polar pitch that a sufficient increase in the EMF of the corresponding coil 2 is reached at the end of the conductive period of the coil.

In Fig. 3A, such an increase in EMF is shown by a Stronger line indicated waveform of one of the coils 2

highlighted by a broken circle. Also in Fig. 3A are the conductive periods of each coil indicated. It is apparent that the electromotive force of the coil 2 when an increase occurs is greater than is the average emf during the conductive period.

It can also be seen from Fig. 3A that the waveforms of the EMF of the coils 2 are periodic, equal and also sequential are, and that the corresponding conductive time periods follow one another in such a way that there is always one Coil 2 is connected to the external connections of the machine and the EMF of this coil 2 does the electromechanical conversion subdivided determinatively. When the machine is working as a motor, its emf has a practically continuous one Voltage level during any given rotation depending on the average emf of coil 2 and during each conductive time segment with a small deviation at each point in time of the commutation. At the beginning of the conductive time segment of each coil 2 commands the additional device (for the control current or trigger current) in Fig. 2 the change of the blocked state of the corresponding thyristor 2 in the conductive state and thus the connection of the corresponding coil 2 with the connection of the machine.

At the end of the conductive time segment of each coil 2, its EMF increases and exceeds the EMF of the machine, so that insofar as the corresponding coil 2 acts as a generator and the direction of the electrical current tends in its conductors is reversed. The electric current in the coil 2 reaches a zero crossing and the corresponding one Thyristor changes its state from the conductive to the

powered state, removing the coil from the external machine connections is disconnected and the commutation has ended.

As shown in Fig. 3B, there is the additional commutation device from a control current (trigger current) that each thyristor 1 only during the corresponding complete Controls the duration of the conduction and thus allows the corresponding coil 2 to be connected to the machine on the terminals To be disconnected at the end of this period, but it also allows it to be disconnected at any moment during this period (of conducting) to be connected, and so with every relative position of the armature and the active pole in one Period of time to be connected according to the conductive length of time. That's why the machine runs out of time Standstill in every relative position of the armature to the active poles when it is energized and the additional The circuit for delivering a control current is activated.

As indicated in Fig. 2, there is the additional commutation device the control current (trigger current) of the thyristor as a function of the relative position of the armature and the active Poles of the magnetic field from, which is determined in particular by sensors, the Hall effect components or photoelectronic Components or magnetic encoders can be realized. Using a transducer to do the Shaping the signal to trigger the thyristor may also be necessary.

As indicated in Fig. 1, additional capacitors used in the practice of the present invention to improve physical appearances,

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which cause the commutation and to ensure that this at the desired moment even in the case of extraordinary ones unfavorable circumstances.

During operation, the conductive thyristor 1 changes to the blocking state at the moment of commutation, during the the following thyristor switches to the conductive state. The capacitor 5, which connects the two thyristors mentioned, is charged during the conductive period preceding the present commutation to at this moment to cause a current flow in the electrical circuit, which at that moment consists of the three components mentioned, which in the conductive thyristor 1 is subtractive acts and additive in the next thyristor. In this way the circulating current (of the capacitor) becomes zero Accelerate the passage of the current in the conductive thyristor 1 as well as the rise of the current in the next thyristor 1, as soon as the command signal - control current (or trigger current) is applied to the following thyristor 1 and this switches conductive, and thus overall ensure the effectiveness of the commutation process. The diodes 6 are useful provided in order to discharge the corresponding capacitor 5 at each commutation instant To prevent coils 2 and to ensure that during each conductive period of time that such a commutation goes ahead, the corresponding capacitor 5 is sufficiently charged electrically.

During the conductive period, the connection of the corresponding Capacitor 5, which is connected to the conductive thyristor 1, at the same voltage level as the terminal of the machine that is connected to this thyristor 1.

section, the EMF of the next coil absolutely reaches values that are lower than the machine voltage itself an analysis of the circuit in Fig. 1 concludes that the voltage level of the other terminal of said Capacitor 5, which is itself connected to this coil 2 via the diode 6, has a polarity which is the same as the voltage level of the other terminal of the machine and cannot return to the voltage level of the first terminal of the machine thanks to the effectiveness of diode 6. In this way, the corresponding capacitor 5 is charged with the correct polarity during each conductive time segment and only discharged at the moment of commutation to contribute to this process.

As found in the practice of the present invention, capacitors with capacities of two up to ten μΡ can be used successfully.

In another embodiment of the present invention, illustrated in Figures 4, 5, 6A and 6B, the Armature winding and the commutation device designed so that the thyristors 1 the connection of the conductors of each of the Coils 2 in the opposite direction - in addition to the usual direction - allow with the connections of the machine if the voltage induced in them is also inverted.

This will have a better overall amount of time directing everyone Coil 2 over one revolution of the machine as determined in the previous embodiment, the entire Period of conduction are the sum of the conduction sections in normal and inverted directions. The active conductor during both time periods during an induced voltage cycle to the electromechanical conversion at.

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As a result, the total number of active conductors can be reduced.

Since the sum of the cross sections is all active conductors actually limited by the available surface in the armature slots, reducing the total number of active conductor provides a corresponding enlargement of its cross section, which in turn means a reduction of the ohm ¹ see resistance of the armature, and thus an increase in the Machine efficiency.

The above special features also apply to other embodiments of the present invention.

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Claims (9)

Claims; DC machine with thyristors for commutation, characterized by an electrical armature winding with several active conductors (3 and 4) attached to the electromechanical Share energy conversion of the machine, a commutation device with several switching elements (1), in which the change from a non-conductive state to a conductive state is triggered by external control signals takes place, but the reverse change only takes place when the conductor current becomes zero, whereby the Switching elements (1) are connected to the electrical armature winding in such a way that they conduct or Control the non-conducting of the electrical current in the active conductors for commutation. 2. DC machine with thyristors for commutation according to claim 1, characterized in that the electromechanical conversion is also in the direction from electrical energy to mechanical energy. 3. DC machine with thyristors for commutation according to claim 1 or 2, characterized in that the switching elements of the commutation device Thyristors or similar semiconductors (1) are. 4. DC machine with thyristors for commutation according to claim 3,
characterized, that the disappearance (becoming zero) of the conductor current in every thyristor or similar semiconductor of the commutation device due to the increase in EMF is effected on the corresponding armature coil (2). 5. DC machine with thyristors for commutation according to claim 3, characterized in that the disappearance of the conductor current in each thyristor or similar semiconductors (1) of the commutation device through the use of capacitors (5) and diodes (6) takes place, which at the appropriate time a brief current opposite to the electrical conductor current produce. 6. DC machine with thyristors for commutation according to claim 4, characterized in that the capacitors (5) and diodes (6) in the manner are arranged so that they generate a brief electrical current at a suitable time, that opposes the conductor current of each thyristor or similar semiconductor (1) of the commutation device is, so that the disappearance of the electrical conductor current is supported and guaranteed. 7. DC machine with thyristors for commutation according to one of claims 1 to 6,
characterized in that an auxiliary device is provided which transmits the control signals which control the transition from the non-conductive state to the conductive state in the thyristors or similar semiconductors (1) of the commutation device control at the appropriate moment, depending on the relative position of the active anchor conductor and the active one gives off magnetic poles. 8. DC machine with thyristors for commutation according to claim 7, characterized in that the relative position of the active armature conductor and the active poles of the magnetic field through sensors (7), such as Hall effect sensors, optoelectronic Sensors, magnetic coils, is detected. 9. DC machine with thyristors for commutation according to one of claims 1, 2, 4, 5, 6 or 8, characterized in that the inner spaces of the machine are filled with a liquid such as water or oil, which allows the machine to be operated in the submerged state. 25th 35