DE102018124588A1 - Power supply device with a lock switch - Google Patents

Abstract

The invention relates to an energization device (30) for energizing an excitation coil arrangement (25) of an in particular electronically commutated electric motor (13), in particular a machine tool, with excitation coils (EA, EB, EC) connected in a star point circuit, the energization device (30) for energizing the excitation coils (EA, EB, EC) has bridging strands which have two half branches (H1, H2) each with an electrical switch (SA1-SC2), the excitation coils (EA, EB, EC) with star point connections on one Star point (S) of the excitation coil arrangement (25) with the other excitation coils (EA, EB, EC) and with feed connections (A, B, C) with the associated bridge strand, which thus forms a feed bridge strand (BA, BB, BC ) forms, between whose half-branches (H1, H2) are electrically connected, the star point (S) connecting to another bridge strand of the current supply device (30), which thus forms a star-point bridge strand (BS) hen its half branches (H1, H2) are electrically connected, the switches (SA1-SC2) can be flowed through by currents for energizing the excitation coil arrangement (25) and by circulating currents (IKA, IKB, IKC) and by a control device (CO) of the energization device (30) can be controlled during a current supply phase (T1-T6) into a closed position provided for supplying current to an excitation coil (EA, EB, EC) connected to the bridge train. At least one switch (SA1-SC2) of the bridge strands is a blocking switch (SX) which blocks a flow of current in opposite current directions to block circulating currents (IKA, IKB, IKC) in a blocking position.

Description

The invention relates to an energization device for energizing an excitation coil arrangement of an in particular electronically commutated electric motor, in particular a machine tool, with excitation coils connected in a star point circuit, the energization device for energizing the excitation coils having bridging strands which have two half branches, each with an electrical switch, the Excitation coils with star point connections at a star point of the excitation coil arrangement with the other excitation coils and with feed connections with the associated bridge strand, which thus forms a feed bridge strand, are electrically connected between the half branches thereof, the star point being connected to a further bridge strand of the current supply device, which thus forms a star point bridge strand, between the half branches of which is electrically connected, the switches being energized by currents to energize the excitation coil arrangement and by circular str can flow through and can be controlled by a control device of the energization device during an energization phase into a closed position provided for energizing a respective excitation coil connected to the bridge strand.

Such a lighting device is in US 5,455,885 explained. This document explains how the feed connections of the excitation coils are each supplied with current via a feed bridge strand, whereby, unlike in typical star point bridge circuits, the star point is not connected, but is connected to a star point bridge strand. Thus, the feed current only flows through an excitation coil and the star point, unlike in typical bridge circuits, where the excitation current flows through not only one excitation coil but two excitation coils that are connected together at the star point. In practice, however, considerable problems have been shown in that the rotating rotor induces currents in the non-actively energized coils, which can lead to heating of the motor and to malfunction of the energizing device.

It is therefore the object of the present invention to provide an improved lighting device.

To achieve the object, it is provided in an energization device of the type mentioned at the outset that at least one switch of the bridge strands is a blocking switch which blocks a flow of current in opposite current directions in order to block circulating currents in a blocking position.

The invention further relates to a method for energizing an excitation coil arrangement according to the technical teaching of a further independent claim. The method relates to the operation of a lighting device according to the invention. In this case, switching at least one of the bridge branches configured as a blocking switch or the switch configured as a blocking switch into a blocking position is provided, in which the at least one switch blocks a current flow in the opposite current direction.

A preferred concept further provides that in the method, all switches are switched into the blocking position which do not follow the excitation coil in order to energize an excitation coil in the sense of feeding the excitation coil or to continue a current flow through the excitation coil in the sense of reducing a magnetic field their or their energization phase are provided. Thus, so to speak, all switches, in particular the feed bridge strands, are in the blocking position when they are not actively involved in energizing or de-energizing an excitation coil. This effectively prevents undesired circulating currents.

A preferred concept provides that the or all feed bridge strands each have blocking switches of this type. In particular, it is advantageous if at least one feed bridge branch, preferably all or more feed bridge branches in both half branches, have switches designed as blocking switches. Thus, those feed bridge strands that are not involved in active energization of an excitation coil can be actively switched off or blocked, so to speak.

A preferred concept further provides that all feed bridging strands in both half branches each have switches designed as blocking switches. Thus, each feed bridge strand can be blocked against circulating currents that are undesirable. For example, it is possible for three feeder bridging strands to be present in accordance with a connection of the motor to three excitation coils. Of course, further excitation coils can also be provided in the electric motor, in which case the energization device expediently has a feed bridge strand for each excitation coil.

The lock switch is preferably an ideal switch, so to speak. The blocking switch has, for example, a switching element which, in its open position, blocks in two current directions, that is to say opposite current directions. In particular, it is then possible to implement such a blocking switch if a semiconductor is provided which does not have an inverse diode or so to speak naturally existing diode. If such a semiconductor switch is available, it can form the blocking switch.

It is advantageously provided that at least one electrical switch is a field effect transistor, in particular a MosFET, or a bipolar transistor, in particular with an insulated gate electrode (insulated gate bipolar transistor or IGBT), or comprises such a transistor.

• Ein bevorzugtes Konzept sieht vor, dass der Sperrschalter ein erstes Schaltelement und ein zu dem ersten Schaltelement in Reihe geschaltetes zweites Schaltelement aufweist. Jedes Schaltelement weist eine parallele Diode auf, d.h. eine Diode, die zwischen dem Eingang und dem Ausgang des Schaltelementes geschaltet ist. Ein jeweiliges erstes oder zweites Schaltelement und dessen Diode können integrierte Bestandteile eines Halbleiterbausteins, beispielsweise eines Feldeffekttransistors, sein.

The invention can also be implemented with conventional semiconductor switches, for example MOSFETs or the like, for example on the basis of the following measure:

• A preferred concept provides that the blocking switch has a first switching element and a second switching element connected in series with the first switching element. Each switching element has a parallel diode, ie a diode which is connected between the input and the output of the switching element. A respective first or second switching element and its diode can be integrated components of a semiconductor module, for example a field effect transistor.

The switching elements are advantageously arranged such that their diodes have opposite blocking directions.

In the blocking position of the blocking switch, both switching elements are switched to an electrical open position, the diodes blocking current flows through the blocking switch in opposite current directions. Because of the and opposite blocking directions of the diodes, which are indeed connected in series, the blocking switch for currents in opposite current directions is blocking when it assumes its blocking position. For example, both switching elements are switched to their open position or non-conductive position in this situation.

The two switching elements and / or their diodes of a blocking switch are, for example, connected in anti-series.

Furthermore, it is possible for the blocking switch to have two semiconductor switching elements connected in series and blocking in opposite current directions. For example, the drain connections or source connections of semiconductor blocking switches, in particular MOSFETs or bipolar transistors, which are connected in series to form the blocking switch, are connected to one another. The switching elements are, for example, MOSFETs (metal oxide semiconductor field effect transistor), IGBTs (= insulated-gate bipolar transistor) or the like.

The invention can be implemented without further ado if the neutral point bridge strand has only one or no blocking switch blocking the opposite current direction. In particular, it is therefore possible that only the feed bridge strands contain or have blocking switches according to the invention.

Switches of conventional type, for example bipolar transistors, field effect transistors or the like, which have a built-in diode or inverse diode, so to speak, can be used in the neutral point bridge strand.

The at least one electrical switch or all electrical switches of the neutral point bridge strand each have or have a diode, for example a diode forming an integral part of the switch or an inverse diode, which enables current to flow through the switch even when it is open in one direction of current (and blocked in the opposite current direction), so that the half-branch of the star point bridge strand which has at least one electrical switch is conductive in one current direction when the switch is open, or is blocking or blocking in the opposite current direction.

The at least one electrical switch of the star point bridge strand or a half branch of the star point bridge strand is, for example, a field effect transistor, in particular a MOSFET, a bipolar transistor with an insulated gate electrode (IGBT) or has such a transistor. Of course, such field-effect transistors, bipolar transistors or the like can also be used in the switching elements of the blocking switch if they are connected in series with the opposite natural blocking direction, so to speak.

The energization device is preferably designed in such a way that in a first operating mode the control device controls the switches of the feed bridge strands and the star point bridge strand in such a way that in each case one excitation coil is energized. During the energization of this excitation coil, for example, a switch of a feed bridge branch and a switch of the neutral point bridge branch, to which the excitation coil is connected, conduct. Thus, the feed bridge strand to which the excitation coil is connected and the star point bridge strand are involved in each energization phase of an excitation coil.

Furthermore, it is advantageous if the energization device is designed such that the control device is designed in a second operating mode for energizing two excitation coils connected to the star point. In this second In the operating mode, for example, both switches of the neutral point bridge branch are open.

It is advantageously provided that the control device for energizing two excitation coils connected to the star point controls the switches of the star point bridge strand in an open position or blocking position, and switches of the feed bridge strands to which the excitation coils are connected, for energizing them, in particular pulsed or even with a single pulse. During an energization phase of the excitation coils, the excitation current can therefore be switched off one or more times, so that pulses are generated. However, it is also possible for the excitation coils to be energized permanently or non-pulsed during the entire energization phase.

The control device is preferably designed to control the switches of the feed bridge branches and the star point bridge branch in such a way that in each case one half branch of the star point bridge branch is conductive, i. H. one switch of this half branch is in the open position, while the other half branch of the star point bridging line is not conducting. In order to energize a single coil of the excitation coil arrangement, a half branch of the feed bridge strand to which the respective coil is connected is then active. It is advantageous that if the upper, so to speak. H. half branch connected to a supply potential, the feed bridge strand is conductive, the upper half branch of the neutral bridge branch is not conductive, but the lower half branch of the neutral bridge branch is conductive. If the lower half branch of the feed bridge strand is conductive, the upper half branch of the star point bridge strand is conductive.

A preferred concept provides that the energization device has a control circuit that is galvanically isolated from the at least one blocking switch for controlling the at least one blocking switch or at least one switching element of the blocking switch. The control circuit includes, for example, an optocoupler, a transformer, or both. The control circuit is connected between the control device and the switch to be controlled. It is preferred if such a control circuit is assigned to each blocking switch. It is possible for one and the same control circuit to control two switching elements of a blocking switch, which are to be switched synchronously into their closed position or open position or conductive position or transmitting position. The galvanic isolation means that potentials, which can occur, for example, when circuit currents are blocked by switching the blocking switch into the blocking circuit, cannot pass to the control side, i.e. the control device.

Although this concept is also possible with the star point bridge branch or the switches of the star point bridge branch, it is not absolutely necessary. With the neutral point bridge branch or its switches, simple wiring with conventional control is possible. The switches of the neutral point bridge strand are expediently controlled by the control device without galvanic isolation and / or without optocouplers and / or with the galvanic potential of the switches. For example, a typical driver circuit with a switching transistor, in particular a bipolar transistor, is readily possible for actuating the switch or the switches of the neutral point bridge strand. Such a circuit also has the advantage that the switches of the star point bridging line can be controlled particularly quickly and effectively, so that there is no need to fear any delays that may occur due to galvanically isolated control. For example, it is possible that the switches of the star point bridge strand are pulsed when energizing a respective excitation coil, i.e. be switched on and off once or several times while the switch of the feed bridge line involved in the current supply is permanently switched to the closed position or the conductive position.

This is because the control device is preferably designed in such a way that during a respective energization phase of an excitation coil for setting a current flowing through the excitation coil, a switch of a feed bridge branch and a switch of the neutral point bridge branch are driven into the closed position or the conductive position.

It is possible that both switches are permanently in the closed position or conductive position or that one of the switches is pulsed, i.e. for example, switched on and off once or several times during the energization phase in order to influence the current level.

A preferred concept provides that the control device switches the switch of the feed bridge strand permanently into the closed position during the energization phase and switches the switch of the neutral point bridge strand on or off once or several times during the energization phase to set a respective effective current level of the current flowing through the excitation coil . For example, pulse width modulation can be provided.

The energizing device is preferably designed such that in each case one excitation coil is fed by an excitation current, the excitation current flowing through a half branch of a feed bridge branch and a half branch of the neutral point bridge branch. To the extent that currents still flow in one or more of the other excitation coils, they are circular currents or currents generated or induced by the rotor, for example.

• Bevorzugt ist vorgesehen, dass die Steuerungseinrichtung zu einem Weiterführen eines Stromflusses durch eine Erregerspule im Sinne eines Abbauens eines Magnetfeldes der Erregerspule nach ihrer Bestromungsphase mindestens einen Schalter, insbesondere den Sperrschalter oder einen als Sperrschalter ausgestalteten Schalter, in eine Schließstellung oder leitende Stellung schaltet. Somit kann derjenige Sperrschalter, welcher gezielt den Strom der Erregerspule, der ja noch durch deren Magnetfeld nach der aktiven Bestromung fließt, leiten. Die Bestromungsvorrichtung ist also zu einem sozusagen aktiven Entstromen einer Erregerspule nach deren Bestromungsphase ausgestaltet. Andere Schalter der Brückenstränge, die nicht zu einem Entstromen oder Abbauen des Magnetfeldes der Erregerspule vorgesehen sind, werden durch die Steuerungseinrichtung in der Sperrstellung oder in beide Stromrichtungen blockierende Stellung geschaltet.

The following measure is particularly advantageous if one or more switches of the current supply device are configured as blocking switches:

• It is preferably provided that the control device switches at least one switch, in particular the blocking switch or a switch designed as a blocking switch, into a closed position or a conductive position in order to continue a current flow through an excitation coil in the sense of reducing a magnetic field of the excitation coil. Thus, the blocking switch which specifically conducts the current of the excitation coil, which still flows through its magnetic field after the active current supply, can be conducted. The energizing device is thus designed to, so to speak, actively de-energize an excitation coil after its energizing phase. Other switches of the bridge strands that are not provided for de-energizing or reducing the magnetic field of the excitation coil are switched by the control device in the blocking position or in the blocking position in both current directions.

In principle, it is possible for the circuit current or the current breaking down the magnetic field to flow through a diode of a semiconductor switch, for example an inverse diode, to break down a magnetic field of an excitation coil. The active de-energization, so to speak, that is, switching the switch into its open position or closed position or conductive position results in significantly less electrical losses, for example heat. In addition, the components of the energization device are less stressed, in particular thermally less stressed.

It is a basic idea that the electrical loss that can arise as a result of a diode or the like of another component is minimized. The control device actively switches the switch to the closed position, so to speak.

The control device is expediently designed to switch the at least one switch, which conducts the current which dissipates the magnetic field of the first excitation coil, into the closed position, this taking place immediately after the current has been switched from a first excitation coil to a second excitation coil of the excitation coil arrangement. So when switching from the first excitation coil to the second excitation coil, i.e. the first excitation coil is not to be energized per se, but the second excitation coil is fed, the current which is still driven by the first excitation coil is further dissipated via the switch switched to the closed position.

The at least one switch, which conducts the current breaking down the magnetic field of an excitation coil after its energization phase, and the switch, which previously conducted the current flowing through the excitation coil during this energization phase, expediently form components of different half branches of the same bridge strand. One switch thus initially energizes the excitation coil, while the other, so to speak, de-energizes or demagnetizes the excitation coil after this active energization.

The control device preferably opens the switch which conducts the current which degrades the magnetic field of the excitation coil before this current crosses zero or changes direction. It is advantageous if the control device opens the switch immediately before the zero crossing or immediately before or after a change in current direction, i.e. blocking the flow of electricity. If, for example, the current becomes zero from its maximum or undergoes a change of direction during a given period of time, the control device switches the switch into the open position or non-conductive position, in the last 2-5% of the given period of time. As a result of this measure, voltages are low which can be applied to the switch when switching to the open position or non-conductive position.

the control device switches the switch only at low voltages.

In the energizing device, it is advantageous if it has a measuring device for measuring the current which degrades the magnetic field of the excitation coil. The measuring device can be, for example, a resistance measuring device. However, it is also possible for the measuring device to be designed to extrapolate or predict the current, for example using a simulation device or simulation software.

The measuring device preferably detects the current on the basis of an internal resistance of the at least one switch, for example an internal resistance of a field effect transistor or Bipolar transistor. However, it is also possible for the current to be measured using a measuring resistor outside the switching element, that is to say a so-called shunt. It is also advantageous if the measuring device calculates a course of the current on the basis of at least one or more measurements. For example, based on an initial course of the current after the switch, which conducts the current for demagnetizing or de-energizing the excitation coil, is closed, it can be measured and then extrapolated. Typically, the current has an e-function.

It is furthermore advantageous if the measuring device detects or determines the current on the basis of several measurements in the sense of a scanning.

The invention is preferably implemented in the case of an electrical device in the form of a machine tool, in particular a screwing machine or drilling machine. The machine tool is preferably a hand-held machine tool or a semi-stationary machine tool, for example a saw, which can be set up at the place of use, e.g. a chop saw, construction site saw or the like. However, the energization device can also be easily implemented in a vacuum cleaner.

• 1 eine Seitenansicht einer Werkzeugmaschine mit einer Bestromungseinrichtung, von der in
• 2 ein Schaltbild dargestellt ist,
• 3 ein vereinfachtes Schaltbild der Bestromungseinrichtung gemäß 2,
• 4 ein zeitliches Bestromungsdiagramm, welches den Betrieb der Bestromungseinrichtung gemäß 2, 3 darstellt,
• 5 die Bestromungseinrichtung mit eingezeichneten Strömen während einer Bestromungsphase einer ersten Erregerspule,
• 6 die Schaltung gemäß 5, bei Beginn einer Bestromungsphase einer nachfolgenden Erregerspule, wobei ein Kreisstrom eingezeichnet ist,
• 7 die Schaltung gemäß 5 und 6 bei der Bestromung der nachfolgenden Erregerspule,
• 8 ein schematischer Verlauf eines eine Erregerspule durchfließenden Stromes während einer Entstromungsphase,
• 9 eine Ansteuerschaltung für einen Schalter eines Speise-Brückenstrangs der Schaltung gemäß 2,
• 10 eine Schaltung zur Ansteuerung eines Schalters eines Sternpunkt-Brückenstrang der Schalter gemäß 2,
• 11 eine weitere Bestromungseinrichtung mit einem Elektromotor in Sternpunkt-Schaltung, dessen Sternpunkt nicht an einen Brückenstrang angeschlossen ist, und
• 12 ein Bestromungsdiagramm für die Schaltung gemäß 11.

Exemplary embodiments of the invention are explained below with reference to the drawing. Show it:

• 1 a side view of a machine tool with a lighting device, of which in
• 2nd a circuit diagram is shown
• 3rd a simplified circuit diagram of the energization device according to 2nd ,
• 4th a temporal energization diagram, which according to the operation of the energization device 2nd , 3rd represents
• 5 the energization device with drawn currents during an energization phase of a first excitation coil,
• 6 the circuit according to 5 at the beginning of a current supply phase of a subsequent excitation coil, a circulating current being drawn in,
• 7 the circuit according to 5 and 6 when energizing the subsequent excitation coil,
• 8th 1 shows a schematic course of a current flowing through an excitation coil during a de-energization phase,
• 9 a control circuit for a switch of a feed bridge strand according to the circuit 2nd ,
• 10th a circuit for controlling a switch of a neutral point bridge strand of the switch according to 2nd ,
• 11 a further energization device with an electric motor in star point connection, the star point of which is not connected to a bridge strand, and
• 12th a lighting diagram for the circuit according to 11 .

An electrical device 10th in the form of a hand machine tool 11 has a housing 12th on in which an electric motor 13 is recorded. The electric motor 13 drives directly or via a gear 14 a tool holder 15 for a work tool 16 , for example a drilling tool, a sawing tool or the like. In the specific case is the electrical device or the hand machine tool 11 designed as a screwdriver or drill, so that the work tool 16 represents a drill or screwdriver.

The electric motor 13 and the transmission 14 form components of a drive train in a drive section 17th of the housing 12th is recorded. From the drive section 17th there is a handle section 18th at an angle, which is provided for gripping by an operator, that is to say has a handle, for example, or is designed as such. On the handle section 18th there are controls for operating the electrical device 10th , for example an operating switch 19th with which an operator uses the hand machine tool 11 switch on and off and in particular also a speed of the electric motor 13 can influence. The control switch 19th can thus directly to set a speed of the electric motor 13 serve. But it is also possible that a desired or maximum speed of the electric motor 13 on a speed control element 20th is adjustable. Furthermore is on the housing 12th a direction switch 21 provided with which a direction of rotation of the electric motor 13 can be switched.

For the electrical power supply of the device 10th serves, for example, an energy store 22 , especially a battery pack. This can be the supply potential V1 as well as the basic potential V0 deploy immediately. However, operation using a power supply network is also possible, for example using an electrical connecting line 23 with which the device 10th can be connected to a power supply network, for example an AC voltage network with 110V or 230V. In this case, the lighting device 30th for example, a rectifier or a rectifier circuit upstream to a supply potential V1 and a basic potential V0 to provide a DC voltage potential.

The specifications of the operating switch 19th , the speed control element 20th as well as the direction switch 21 sets a lighting device 30th so to speak. The lighting device 30th serves to energize an excitation coil arrangement 25th of the electric motor 13 . The excitation coil arrangement 25th includes excitation coils EA , EB and EC which are interconnected in a star point interconnection, ie at a star point S are electrically connected to each other. The excitation coils are on the outside of the star EA , EB and EC with their food connections A , B and C. with bridging strands BA , BB and BC a bridge circuit of the bridge lighting device 30th connected. The bridge strands BA , BB and BC are at the supply potential V1 and the basic potential V0 connected or extend between these two potentials. Every bridge strand BA , BB and BC includes a half branch H1 and H2 , taking the half branches H1 and H2 can also be referred to as upper or lower half branches. In the half branches H1 of the bridge strands BA , BB and BC are switches SA1 , SB1 , SC1 arranged in the half-branches H2 counter SA2 , SB2 and SC2 .

The food connections A , B and C. the excitation coils EA , EB and EC are between the half branches H1 and H2 of a respective bridge strand BA , BB and BC connected to the bridge strand, these connections to the bridge strand also being shown in the drawing for simplification and clarification A , B and C. are designated.

The lighting device 30th has another bridge strand, the one with the star point S is connected, namely between its half-branches H1 and H2 . This bridge strand, the one star point bridge strand BS forms, points in its half-branches H1 and H2 counter SS1 and SS2 on and is also with the potential V1 and V2 connected or extends between the same.

With the lighting device 30th so it is possible to use any excitation coil EA , EB and EC to energize individually, the respective excitation current via the coil EA , EB or EC and the star point S flows. The current is through one of the half branches H1 and H2 the bridge of the neutral point bridge strand BS guided.

The switches SA1 , SB1 and SC1 and SA2 , SB2 and SC2 such as SS1 , SS2 are controlled by a control device CO the lighting device 30th controlled. This is shown schematically by dashed lines, which, however, for simplicity and clarity in the 5 , 6 and 7 are omitted.

• Während einer Bestromungsphase T1 wird die Erregerspule EC aktiv bestromt, um einen Rotor RO des Elektromotors 13 anzutreiben. Während der Bestromungsphase T1 fließt ein Erregerstrom IEC für die Erregerspule EX vom Versorgungspotenzial V1 über den Schalter SC1 des Brückenstrangs B1 und eine Anschlussleitung LC zu dem Speise-Anschluss C der Erregerspule EA und von dort über den Sternpunkt S und den ebenfalls geschlossenen Schalter SS2 des Sternpunkt-Brückenstrangs BS zum Basispotenzial V0. Der Schalter SC1 ist dabei vorzugsweise dauerhaft in seiner Schließstellung oder elektrisch leitenden Stellung, während der Schalter SS2 zwar ebenfalls dauerhaft geschlossen sein kann, so dass der Erregerstrom IEC maximal ist, aber auch pulsweitenmoduliert oder in sonstiger Weise gepulst sein kann, was im Bestromungsdiagramm gemäß 4 als Pulsweitenansteuerung PWM dargestellt ist. Somit kann also durch ein Einschalten und Ausschalten des Schalters SS2 die Stromhöhe des Stromes IEC beeinflusst sein.

From the current supply diagram according to 4th goes a lighting scheme of the lighting device 30th out which by the control device CO is controlled. Based on 5 , 6 and 7 this becomes clearer:

• During an energization phase T1 becomes the excitation coil EC actively energized to a rotor RO of the electric motor 13 to drive. During the energization phase T1 an excitation current flows IEC for the excitation coil EX of the supply potential V1 over the switch SC1 of the bridge strand B1 and a connecting line LC to the feed connection C. the excitation coil EA and from there over the star point S and the switch, which is also closed SS2 of the neutral point bridge strand BS to the base potential V0 . The desk SC1 is preferably permanently in its closed position or electrically conductive position during the switch SS2 can also be permanently closed, so that the excitation current IEC is maximum, but can also be pulse-width modulated or pulsed in some other way, as shown in the current flow diagram 4th as pulse width control PWM is shown. Thus, by turning the switch on and off SS2 the current level of the current IEC to be influenced by.

In 6 is the energization phase T2 shown in which now instead of the excitation coil EC the excitation coil EA is energized. The control device controls accordingly CO the switch SA2 in the closed position or electrically conductive position while the switch SC1 is now open. The the coil EA exciting excitation current IEA flows from the supply potential V1 over the switch SS1 , which can be permanently closed / electrically conductive or pulsed with a PWM signal and switched off, to the star point S , from there over the coil EA and a connecting line LA the between their half branches H1 and H2 to the bridge strand BA is connected to the switch SA2 and finally to the basic potential V0 .

At the beginning of the energization phase T2 is however still a magnetic field in the excitation coil EC available, which in itself after the end of the energization phase T1 switched off current drives even further. This current is a circular current IKC , which is specifically broken down to the magnetic field of the coil EC to reduce. The circular current IKC therefore flows from the coil EC over the coil EA and the closed switch SA2 of the bridge strand BA as well as the closed switch SC2 of the bridge strand BC , i.e. the lower switch of the Bridge strand BC , back to the coil EC . The active downdraft, so to speak, via the closed switch SC2 is in 4th with a switch-on signal E shown.

If the excitation coil EC their magnetic field has broken down, i.e. the circulating current IKC is zero or almost zero, the control device opens CO the switch SC2 again what in 7 is shown. Then only the excitation current flows IEA to excite or energize the excitation coil EA .

The aforementioned procedure is also used in the sequential subsequent energization of the excitation coil B and subsequently C. applied what is shown in the current flow diagram 4th is indicated schematically. Each time an excitation coil is no longer actively energized, it is actively de-energized, so to speak, by closing the other switch in the previously actively energizing bridge strand to de-energize, which is shown in 4th with control blocks E is indicated.

• Jeder Schalter SA1, SA2, SB1, SB2, SC1, SC2 weist nämlich Schaltelemente S1 und S2 auf, die sozusagen gegensinnig oder antiseriell geschaltet sind. Die Schaltelemente S1 und S2 sind beispielsweise Bipolar-Transistoren, Feldeffekt-Transistoren, insbesondere MosFETs, deren jeweilige an sich vorhandene Inversdiode D1 und E2 in unterschiedliche Stromrichtungen sperrt. Somit können die Schaltelemente SA1-SC2 dann, wenn sie ihre Sperrstellung einnehmen (die Schaltelemente S1 und S2 sind dabei geöffnet bzw. elektrisch nicht leitend), in einander entgegengesetzte Stromrichtungen sperren. Somit können Kreisströme in der Art der Kreisströme IKA und IKB nur dann fließen, wenn eines der Schaltelemente SA1, SA2, SB1, SB2, SC1 oder SC2 geschlossen bzw. nicht in seiner Sperrstellung ist. Wenn jedoch wie in 6 dargestellt eine gewünschte oder aktiv gewollte Bestromungssituation besteht, d.h. die Steuerungseinrichtung CO den Schalter SA2 aus seiner Sperrstellung in seiner leitende oder Schließstellung verstellt, kann das aktive Entstromen der Erregerspule EC stattfinden.

The lighting device 30th prevents unwanted circular currents, ie currents caused, for example, by the rotation of the rotor RO in one of the non-actively energized coils EA , EB or EC the excitation coil arrangement 25th be induced. In the embodiment according to 5 are such, from the lighting device 30th prevented circulating currents IKA and IKB when energizing the excitation coil EC marked ( 5 ). If the switches SA2 or SB2 , unlike the lighting device 30th the case, so to speak, conventional switches KA2 or KB2 were what is indicated schematically in the drawing, such currents could flow. For example, bipolar field-effect transistors or bipolar transistors are typically provided as switching elements which have such an inverse diode DI. The as a lock switch SX designed switch SA1 , SB1 and SC1 and SA2 , SB2 and SC2 the lighting device 30th prevent such undesirable circulating currents IKA and IKB :

• Any switch SA1 , SA2 , SB1 , SB2 , SC1 , SC2 namely has switching elements S1 and S2 on, which are, so to speak, connected in opposite directions or anti-serial. The switching elements S1 and S2 are, for example, bipolar transistors, field effect transistors, in particular MosFETs, their respective inverse diodes D1 and E2 blocks in different current directions. Thus, the switching elements SA1-SC2 when they are in their locked position (the switching elements S1 and S2 are open or electrically non-conductive), block in opposite directions of current. Thus, circulating currents can be of the type of circulating currents IKA and IKB flow only when one of the switching elements SA1 , SA2 , SB1 , SB2 , SC1 or SC2 is closed or not in its locked position. However, if as in 6 shown there is a desired or actively wanted current supply situation, ie the control device CO the switch SA2 adjusted from its locked position in its conducting or closed position, the active de-energization of the excitation coil EC occur.

However, this active dehumidification should end if possible when the magnetic field of the respective excitation coil EA , EB and EC degrading electricity, such as electricity IKC , is zero or changes its current direction. According to the current flow 8th this is shown schematically where this change of current direction or zero crossing takes place at a time te. The control device CO controls the switch SC2 at time te from its closed position or managerial position ( 6 ) in its open position or electrically non-conductive position ( 7 ) at.

To detect the current flowing out of an excitation coil, for example, the current IKC , is a measuring device M intended. The measuring device M can, for example, the internal resistance of one or more switching elements S1 , S2 capture. It is also possible that the measuring device M for example, comprises a measuring resistor or a plurality of measuring resistors which is tensioned in a line carrying the respective circulating current.

It is advantageous if the measuring device M the respective circulating current or the excitation coil demagnetizing current is recorded at several points in time, for example at points in time ta , tb and tc . Close monitoring or monitoring of the current IKC at short intervals allows the measuring device M the zero crossing of the current IKC can capture optimally, so that the control device CO the "actively flowing" switch SA1-SC1 opens at the right time, namely at the respective zero crossing, of the respective current demagnetizing the excitation coil.

The switches SS1 and SS2 of the neutral point bridge strand BS are semiconductor switches HS , for example MOSFETS, IGBTs or the like, which have an inverse diode D exhibit.

To control the switches SA1-SC2 serves as a control circuit CX , in the 9 is shown schematically. The control circuit CX comprises an optocoupler, for example a gate driver optocoupler, with control connections S1 and S2 that to the control device CO are connected. A diode DX of the optocoupler OP generates appropriate control signals when they are on the Control connections S1 and DS2 is driven, making a transistor TX or an output stage of the optocoupler OP can be activated. The transistor TX controls via a resistance bridge R1 , R2 , between which, for example, the switching element S1 or the switching element S2 is switched, the respective switching element S1 or S2 on. Of course, both switching elements can S1 and S2 between the resistors R1 and R2 be switched. Such a potential-free or galvanically isolated control, however, is only for the feed bridge lines BA , BB and BC provided, but not for the neutral point bridge branch BS . This is a control circuit CS completely sufficient, for example one based on a control connection S3 by the control device CO controllable transistor TS comprises of a resistance bridge R3 , R4 between which the switch SS1 or SS2 is switched on, the respective switch SS1 or SS2 controls. The control circuit CS is significantly more responsive, which is why it uses pulsed control (pulse width control PWM please refer 4th ) can be advantageously implemented.

However, the so-called active de-energization by closing switches of a bridge circuit or energization device is not only advantageous in the case of energization devices that have a bridging branch for the star point, but also in such bridging circuits that do not have such a bridging branch, based on an energization device 130 in 11 is indicated schematically. The star point S of the electric motor 13 in this case is not connected and only connects the coils EA , EB and EC star-shaped.

In the current supply diagram according to 12th it becomes clear that, for example, two of the bridge strands BA , BB or BC together, so to speak, energizing a pair of excitation coils EA , EB and EC Afford. For example, during the energization phase t1, the excitation coil EC to be without power. The desk SA2 is from the control device CO initially closed while the switches SB1 and SB2 clocked with pulses PW switched on and off. By appropriate switch-on and switch-off times of the switches SB1 and SB2 can be the current level of the current, which in this case is via the coils EA and EB flows, be adjustable. Following this energization phase t2, an active de-energization takes place, so to speak, in that the switch SA1 from the control device CO for a drainage phase E is closed or switched on while the excitation coils are already energized EC and EB takes place. If the excitation coil EA is de-energized, so to speak, that is, its magnetic field is reduced, the energizing pulse ends E for the switch SA1 . Analogously, this method is used sequentially for the other excitation coils EB and EC applied, see 12th .

It is understood that the lighting device 30th like the lighting device 130 can be operated by, for example, the switches SS1 and SS2 of the neutral point bridge strand are each in the open position or electrically non-conductive position, d. h that the food bridge strands BA , BB and BC for energizing the excitation coil arrangement 25th serve. The control device can thus CO for example the electric motor 13 operate in a conventional star-point circuit, so to speak, resulting in a higher torque output at a lower speed of the electric motor 13 is feasible. However, if the speed is to be higher, the control device controls CO the lighting device 30th according to the current supply diagram according to 4th .

QUOTES INCLUDE IN THE DESCRIPTION

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Patent literature cited

• US 5455885 [0002]

Claims (24)

Energizing device for energizing an excitation coil arrangement (25) of an in particular electronically commutated electric motor (13), in particular a machine tool (11), with excitation coils (EA, EB, EC) connected in a star point circuit, the energizing device (30) for energizing the excitation coils (EA, EB, EC) has bridging strands which have two half branches (H1, H2) each with an electrical switch (SA1-SC2), the excitation coils (EA, EB, EC) with star point connections at a star point (S) the excitation coil arrangement (25) with the other excitation coils (EA, EB, EC) and with feed connections (A, B, C) with the associated bridge strand, which thus forms a feed bridge strand (BA, BB, BC) between whose half-branches (H1, H2) are electrically connected, the star point (S) being connected to a further bridge strand of the lighting device (30), which thus forms a star-point bridge strand (BS), between the half branches (H1, H2) is electrically connected, the switches (SA1-SC2) being able to be flowed through by currents for energizing the excitation coil arrangement (25) and by circulating currents (IKA, IKB, IKC) and by a control device (CO) of the energization device (30) during an energization phase (T1-T6) can be controlled in a closed position provided for energizing a respective excitation coil (EA, EB, EC) connected to the bridge strand, characterized in that at least one switch (SA1-SC2) of the bridge strands is a blocking switch (SX) which to block circulating currents (IKA, IKB, IKC) in a blocking position blocks a flow of current in opposite current directions. Current supply device after Claim 1 , characterized in that at least one feed bridge strand (BA, BB, BC) in both half branches (H1, H2) has switches (SA1-SC2) designed as blocking switches (SX). Current supply device after Claim 1 or 2nd , characterized in that all feed bridging strands in both half branches (H1, H2) each have switches (SA1-SC2) designed as blocking switches (SX). Current supply device according to one of the preceding claims, characterized in that the blocking switch (SX) has a first switching element (S1) and a second switching element (S2) connected in series with the first switching element (S1), each switching element (S1, S2) having one has parallel diode (D1, D2). Current supply device after Claim 4 , characterized in that the switching elements (S1, S2) are arranged such that their diodes (D1, D2) have opposite blocking directions, with both switching elements (S1, S2) switched into an electrical open position in the blocking position of the blocking switch (SX) and the diodes (D1, D2) block current flows through the blocking switch (SX) in opposite current directions. Current supply device according to one of the preceding claims, characterized in that the blocking switch (SX) has two semiconductor switching elements which are connected in series and block in opposite directions of the current. Current supply device according to one of the preceding claims, characterized in that the neutral point bridge strand (BS) has only one or no blocking switch (SX) which blocks in opposite current directions. Current supply device according to one of the preceding claims, characterized in that at least one electrical switch or all electrical switches of the star point bridge strand (BS) each have a diode, in particular an integral part of the switch and / or inverse diode, which have a current flow enabled by the switch even when it is open in a current direction, so that the half-branch (H1, H2) of the star point bridge strand (BS) having the at least one electrical switch is conductive in a current direction when the switch is open. Current supply device according to one of the preceding claims, characterized in that at least one electrical switch (SA1-SC2) is a field effect transistor, in particular a MosFET, or a bipolar transistor, in particular with an insulated gate electrode (insulated gate bipolar transistor or IGBT) includes such transistor. Current supply device according to one of the preceding claims, characterized in that it has a control circuit, in particular at least one optocoupler, which is electrically isolated from the at least one blocking switch (SX), for controlling the at least one blocking switch (SX) or at least one switching element of the blocking switch (SX). Current supply device according to one of the preceding claims, characterized in that the switches of the star point bridge branch (BS) are controlled by the control device (CO) without electrical isolation and / or without optocouplers and / or with the electrical potential of the switches. Current supply device according to one of the preceding claims, characterized in that the control device (CO) in a first operating mode controls the switches (SA1-SC2) of the feed bridge branches and the star point bridge branch (BS) in such a way that in each case one excitation coil (EA, EB , EC) is energized, and / or that the control device (CO) is designed in a second operating mode for energizing two excitation coils (EA, EB, EC) connected to the star point (S). Energizing device according to one of the preceding claims, characterized in that the control device (CO) for energizing two excitation coils (EA, EB, EC) connected to the star point (S) controls the switches of the star point bridge strand (BS) into an open position or a blocking position , and switches (SA1-SC2) of the feed bridge strings to which the excitation coils (EA, EB, EC) are connected, for their energization, in particular pulsed, switches on. Current supply device according to one of the preceding claims, characterized in that the control device (CO) during a respective current supply phase (T1-T6) of an excitation coil (EA, EB, EC) for setting a current flowing through the excitation coil (EA, EB, EC) in each case one Controls switch (SA1-SC2) of a feed bridge line (BA, BB, BC) and a switch of the star point bridge line (BS) to the closed position. Current supply device after Claim 14 , characterized in that the control device (CO) during the energization phase (T1-T6) the switch (SA1-SC2) of the feed bridge line (BA, BB, BC) permanently in the closed position and for setting a respective effective current level of the excitation coil (EA, EB, EC) current flowing through the switch of the star point bridge branch (BS), in particular several times, switches on and off during the energization phase (T1-T6). Energizing device according to one of the preceding claims, characterized in that the control device (CO) for continuing a current flow through an excitation coil (EA, EB, EC) in the sense of breaking down a magnetic field of the excitation coil (EA, EB, EC) after its energization phase ( T1-T6) switches at least one switch, in particular the or a blocking switch (SX), into a closed position. Current supply device after Claim 16 , characterized in that the control device (CO) immediately after switching the current from a first excitation coil (EA, EB, EC) to a second excitation coil (EA, EB, EC) of the excitation coil arrangement (25) switches the at least one switch (SA1- SC2), which conducts the current reducing the magnetic field of the first excitation coil (EA, EB, EC), into the closed position. Current supply device after Claim 16 or 17th , characterized in that the at least one switch (SA1-SC2), which conducts the current reducing the magnetic field of an excitation coil (EA, EB, EC) after its energization phase (T1-T6), and the switch which previously the excitation coil ( EA, EB, EC) passed through the current during this energization phase (T1-T6), form components of different half-branches (H1, H2) of the same bridge strand. Lighting device according to one of the Claims 16 to 18th , characterized in that the control device (CO) opens the switch (SA1-SC2), which conducts the current breaking down the magnetic field of the excitation coil (EA, EB, EC), before a zero crossing or change of current direction. Lighting device according to one of the Claims 16 to 19th , characterized in that it has a measuring device (M) for measuring the current breaking down the magnetic field of the excitation coil (EA, EB, EC). Current supply device after Claim 20 , characterized in that the measuring device (M) detects the current on the basis of an internal resistance of the at least one switch (SA1-SC2), in particular an internal resistance of a field effect transistor, and / or calculates and / or calculates a profile of the current on the basis of at least one or more measurements Determination of the current carries out several measurements in the sense of a scan. Electrical device in the form of a machine tool (11), in particular a hand machine tool (11), or a vacuum cleaner, with a lighting device according to one of the preceding claims. Method for energizing an excitation coil arrangement (25) of an in particular electronically commutated electric motor (13), in particular a machine tool (11), with excitation coils (EA, EB, EC) connected in a star point circuit using an energization device (30) which is used to energize the Excitation coils (EA, EB, EC) has bridging strands which have two half branches (H1, H2), each with an electrical switch (SA1-SC2), the excitation coils (EA, EB, EC) with star point connections at a star point (p ) of the excitation coil arrangement (25) with the other excitation coils (EA, EB, EC) and with feed connections (A, B, C) with the associated bridging section, which thus forms a bridging section (BA, BB, BC), between its half-branches (H1, H2) are electrically connected, the star point being electrically connected to another bridge strand of the lighting device (30), which thus forms a star point bridge strand (BS), between the half branches (H1, H2) thereof, the switches (SA1-SC2) by currents for energizing the excitation coil arrangement (25) and through circulating currents (IKA, IKB, IKC) and through a control device (CO) of the energization device (30) during an energization phase (T1-T6) in a for energizing a respective excitation coil connected to the bridge strand (EA, EB, EC) are intended to be actuated, characterized by switching at least one switch (SA1-SC2) of the bridge strands configured as a blocking switch (SX) into a blocking block In which the at least one switch (SA1-SC2) blocks a current flow in opposite current directions. Procedure according to Claim 23 , characterized by switching all switches into the blocking position that do not result in the energization of an excitation coil (EA, EB, EC) in the sense of feeding the excitation coil (EA, EB, EC) or in the continuation of a current flow through an excitation coil (EA, EB , EC) in the sense of breaking down a magnetic field of the excitation coil (EA, EB, EC) after its energization phase (T1-T6).

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