DE102022000172A1 - circuit unit and drive unit - Google Patents

Abstract

The invention relates to a circuit unit (10) for supplying a three-phase electric motor (50), comprising an inverter (20) which can be connected to a DC circuit on the input side and which can be connected on the output side to a first phase conductor (51), a second phase conductor (52) and a third phase conductor (53) for connecting the three-phase electric motor (50), the circuit unit (10) having a first switch (S1) for connecting the first phase conductor (51) to a star point (55), a second switch (S2) for connecting the second phase conductor (52) to the neutral point (55) and a third switch (S3) for connecting the third phase conductor (53) to the neutral point (55), the switches (S1, S2, S3) being self-conducting field effect transistors are executed. The invention also relates to a drive unit, in particular for a driverless transport vehicle, comprising at least one circuit unit (10) according to the invention and at least one three-phase electric motor (50) which is connected to the first phase conductor (51), to the second phase conductor (52) and to the third Phase conductor (53) is connected to the at least one circuit unit (10).

Description

The invention relates to a circuit unit for supplying a three-phase electric motor, comprising an inverter which can be connected to a DC circuit on the input side and which is connected on the output side to a first phase conductor, a second phase conductor and a third phase conductor for connecting the three-phase electric motor. The invention also relates to a drive unit, in particular for a driverless transport vehicle, which comprises at least one circuit unit according to the invention.

From the DE 10 2018 005 575 A1 a drive is known which has a synchronous motor and a converter. The motor phases of the synchronous motor can be supplied from the AC voltage-side connection of the inverter. The three-phase motor voltage of the synchronous motor can be fed to a neutral point via respective first resistors by means of a controllable switch.

From the DE 10 2012 012 048 A1 a multi-phase inverter bridge is known which comprises a combination of normally-on power transistors and normally-off power transistors. An output short circuit can be generated between at least two phases of the inverter bridge by means of the self-conducting power transistors.

From the U.S. 2015/0263650 A1 a system is known which has a three-phase electric motor which is connected to an inverter. The phases of the electric motor can be short-circuited using a switch.

From the EP 3 272 002 B1 a robotic system having a motor assembly for driving an articulated joint is known. The motor assembly includes a three-phase motor and a drive circuit.

From the DE 10 2012 012 047 A1 a technical system is known which has a three-phase electric motor. The phases of the electric motor can be short-circuited using several switching contacts.

The invention is based on the object of further developing a circuit unit for supplying a three-phase electric motor and a drive unit of the type mentioned at the outset.

The object is achieved according to the invention by a circuit unit for supplying a three-phase electric motor with the features specified in claim 1. Advantageous refinements and developments are the subject of the dependent claims. The object is also achieved by a drive unit having the features specified in claim 11.

A circuit unit according to the invention for supplying a three-phase electric motor includes an inverter which can be connected to a DC circuit on the input side and which is connected on the output side to a first phase conductor, a second phase conductor and a third phase conductor for connecting the three-phase electric motor. The circuit unit has a first switch for connecting the first phase conductor to a neutral point, a second switch for connecting the second phase conductor to the neutral point and a third switch for connecting the third phase conductor to the neutral point. The switches are designed as self-conducting field effect transistors.

During operation of the switching unit and the electric motor, a control voltage is applied to the control inputs of the switches. As a result, the switches are electrically high-impedance. In the absence of the control voltage at the control inputs, the switches become electrically conductive and thus each form a short circuit between one of the phase conductors and the neutral point. If the control voltage fails, the electric motor is automatically short-circuited and thus braked. If the control voltage fails, especially if there is a power failure, the electric motor will automatically come to a standstill.

According to an advantageous embodiment of the invention, the inverter has a negative terminal for connection to a negative pole of the DC circuit and a positive terminal for connection to a positive pole of the DC circuit. Said DC circuit is, for example, an intermediate circuit of a converter. The circuit unit can thus be used advantageously in a converter which also includes a rectifier for rectifying a single-phase or three-phase mains voltage.

According to an advantageous development of the invention, the star point is connected to the negative terminal of the inverter.

According to another advantageous development of the invention, the star point is connected to the positive terminal of the inverter.

According to another advantageous development of the invention, the star point is isolated, ie connected neither to the negative terminal nor to the positive terminal of the inverter.

According to a preferred embodiment of the invention, the inverter has a first switching transistor for connecting the positive terminal to the first phase conductor, a second switching transistor for connecting the positive terminal to the second phase conductor, a third switching transistor for connecting the positive terminal to the third phase conductor, a fourth switching transistor for connecting the negative terminal to the first phase conductor, a fifth switching transistor for connecting the negative terminal to the second phase conductor and a sixth switching transistor for connecting the negative terminal to the third phase conductor.

During operation of the circuit unit and the electric motor, high-frequency control voltages are applied to the control inputs of the switching transistors. As a result, the switches are alternately electrically high-impedance and electrically conductive. In the absence of the control voltages at the control inputs, the switching transistors become electrically highly resistive. To brake the electric motor, the control voltages are switched off from the control inputs of the switching transistors and from the control inputs of the switches. The electric motor is thereby automatically short-circuited and thus slowed down. There is no short circuit between the positive terminal and the negative terminal.

According to an advantageous embodiment of the invention, at least one of the switches is designed as a metal-oxide-semiconductor field-effect transistor. In this case, all switches are preferably designed as metal-oxide-semiconductor field-effect transistors.

According to an advantageous embodiment of the invention, at least one of the switches is designed as a junction field effect transistor. In this case, all switches are preferably designed as junction field effect transistors.

According to an advantageous embodiment of the invention, at least one of the switches is designed as a metal-semiconductor field-effect transistor. In this case, all switches are preferably designed as metal-semiconductor field-effect transistors.

According to an advantageous development of the invention, a switching element is connected in series with the switches in each case, which has a parallel connection of a fuse and a braking resistor. In the event of a short-circuit between the phase conductors and the neutral point, a short-circuit current with a relatively high amperage flows through the switches and the fuses. If the current exceeds a specified maximum value, the fuses in the switching elements will trip. The current then flows through the switches and through the braking resistors connected in parallel with the fuses. This reduces the current strength. This protects the switches from excessive short-circuit currents.

A drive unit according to the invention, in particular for a driverless transport vehicle, comprises at least one circuit unit according to the invention and at least one three-phase electric motor which is connected to the first phase conductor, the second phase conductor and the third phase conductor of the at least one circuit unit. The driverless transport vehicle preferably also includes an electrical energy store which is connected to the DC circuit to which the inverter of the circuit unit is connected on the input side.

The invention is not limited to the combination of features of the claims. For the person skilled in the art, there are further meaningful combinations of claims and/or individual claim features and/or features of the description and/or the figures, in particular from the task and/or the task arising from comparison with the prior art.

• 1: eine schematische Darstellung einer Antriebseinheit für ein fahrerloses Transportfahrzeug mit einer Schaltungseinheit gemäß einer ersten Ausführungsform und
• 2: eine schematische Darstellung einer Antriebseinheit für ein fahrerloses Transportfahrzeug mit einer Schaltungseinheit gemäß einer zweiten Ausführungsform.

The invention will now be explained in more detail with reference to figures. The invention is not limited to the exemplary embodiments shown in the figures. The figures represent the subject matter of the invention only schematically. It shows:

• 1 : a schematic representation of a drive unit for a driverless transport vehicle with a circuit unit according to a first embodiment and
• 2 1: a schematic representation of a drive unit for a driverless transport vehicle with a circuit unit according to a second embodiment.

1 shows a schematic representation of a drive unit for a driverless transport vehicle with a circuit unit 10 according to a first embodiment. In addition to said switching unit 10, the drive unit includes a three-phase electric motor 50, which is designed, for example, as a synchronous motor.

The circuit unit 10 is used to supply the three-phase electric motor 50 and includes an inverter 20, a first phase conductor 51, a second phase conductor 52 and a third phase conductor 53. The inverter 20 is connected to the first phase conductor 51, the second phase conductor 52 and the third phase conductor 53 on the output side. The electric motor 50 is also connected to the first phase conductor 51, to the second phase conductor 52 and to the third phase conductor 53 of the circuit unit 10.

The inverter 20 is connected to a DC circuit on the input side. For this purpose, the inverter 20 has a negative terminal 27 for connection to a negative pole of the DC circuit and a positive terminal 28 for connection to a positive pole of the DC circuit. Said DC circuit is, for example, an intermediate circuit of a converter and has an intermediate circuit capacitor which is connected between the negative terminal 27 and the positive terminal 28 .

The inverter 20 has a first switching transistor 21 for connecting the positive terminal 22 to the first phase conductor 51, a second switching transistor 22 for connecting the positive terminal 22 to the second phase conductor 52, a third switching transistor 23 for connecting the positive terminal 22 to the third phase conductor 53, a fourth switching transistor 24 for connecting the negative terminal 21 to the first phase conductor 51, a fifth switching transistor 25 for connecting the negative terminal 21 to the second phase conductor 52, and a sixth switching transistor 26 for connecting the negative terminal 21 to the third phase conductor 53 . The switching transistors 21, 22, 23, 24, 25, 26 are designed, for example, as normally-off metal-oxide-semiconductor field-effect transistors.

The switching transistors 21, 22, 23, 24, 25, 26 each have a control input 40 which is connected to a GATE connection of the respective switching transistor 21, 22, 23, 24, 25, 26. By applying a control voltage to the respective control input 40, the corresponding switching transistor 21, 22, 23, 24, 25, 26 becomes electrically conductive. In the absence of a control voltage at the respective control input 40, the corresponding switching transistor 21, 22, 23, 24, 25, 26 has a high electrical resistance.

Circuit unit 10 also has a first switch S1 for connecting first phase conductor 51 to a neutral point 55, a second switch S2 for connecting second phase conductor 52 to neutral point 55, and a third switch S3 for connecting third phase conductor 53 to neutral point 55 . Said switches S1, S2, S3 are designed as self-conducting field effect transistors.

The switches S1, S2, S3 are designed, for example, as metal-oxide-semiconductor field effect transistors, ie as MOSFETs. The switches S1, S2, S3 are designed, for example, as a junction field effect transistor, ie as an SFET or as a JFET. The switches S1, S2, S3 are designed, for example, as metal-semiconductor field-effect transistors, ie as MESFETs. All switches S1, S2, S3 are preferably designed in the same way.

The switches S1, S2, S3 each have a control input 40 which is connected to a GATE connection of the respective switch S1, S2, S3. By applying a control voltage to the respective control input 40, the corresponding switch S1, S2, S3 becomes electrically high-impedance. In the absence of a control voltage at the respective control input 40, the corresponding switch S1, S2, S3 is electrically conductive and thus forms a short circuit between one of the phase conductors 51, 52, 53 and the neutral point 55.

The star point 55 is isolated in the present case. In particular, the star point 55 therefore has no direct electrical connection to the negative terminal 27 or to the positive terminal 28 .

2 shows a schematic representation of a drive unit for a driverless transport vehicle with a circuit unit 10 according to a second embodiment. In addition to said switching unit 10, the drive unit includes a three-phase electric motor 50, which is designed, for example, as a synchronous motor.

The circuit unit 10 according to the second embodiment is largely the same as that in FIG 1 shown circuit unit 10 formed according to the first embodiment. Deviating from the circuit unit 10 according to the first embodiment, the star point 55 is connected to the negative terminal 27 of the inverter 20 in the circuit unit 10 shown here according to the second embodiment.

Reference List

10

circuit unit

20

inverter

21

first switching transistor

22

second switching transistor

23

third switching transistor

24

fourth switching transistor

25

fifth switching transistor

26

sixth switching transistor

27

negative terminal

28

positive terminal

40

control input

50

electric motor

51

first phase conductor

52

second phase conductor

53

third phase conductor

55

star point

S1

first switch

S2

second switch

S3

third switch

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018005575 A1 [0002]
• DE 102012012048 A1 [0003]
• US 2015/0263650 A1 [0004]
• EP 3272002 B1 [0005]
• DE 102012012047 A1 [0006]

Claims (11)

Circuit unit (10) for supplying a three-phase electric motor (50), comprising an inverter (20) which can be connected to a DC circuit on the input side and which on the output side can be connected to a first phase conductor (51), a second phase conductor (52) and a third phase conductor ( 53) for connecting the three-phase electric motor (50), characterized in that the circuit unit (10) has a first switch (S1) for connecting the first phase conductor (51) to a star point (55), a second switch (S2) for connection of the second phase conductor (52) to the neutral point (55) and a third switch (S3) for connecting the third phase conductor (53) to the neutral point (55), the switches (S1, S2, S3) being designed as self-conducting field effect transistors are. Circuit unit (10) after claim 1 , characterized in that the inverter (20) has a negative terminal (27) for connection to a negative pole of the direct current circuit and a positive terminal (28) for connection to a positive pole of the direct current circuit. Circuit unit (10) after claim 2 , characterized in that the neutral point (55) is connected to the negative terminal (27) of the inverter (20). Circuit unit (10) after claim 2 , characterized in that the neutral point (55) is connected to the positive terminal (28) of the inverter (20). Circuit unit (10) according to one of Claims 1 until 2 , characterized in that the star point (55) is isolated. Circuit unit (10) according to one of claims 2 until 5 , characterized in that the inverter (20) has a first switching transistor (21) for connecting the positive terminal (22) to the first phase conductor (51), a second switching transistor (22) for connecting the positive terminal (22) to the second phase conductor (52), a third switching transistor (23) for connecting the positive terminal (22) to the third phase conductor (53), a fourth switching transistor (24) for connecting the negative terminal (21) to the first phase conductor (51), a fifth switching transistor (25) for connecting the negative terminal (21) to the second phase conductor (52) and a sixth switching transistor (26) for connecting the negative terminal (21) to the third phase conductor (53). Circuit unit (10) according to one of the preceding claims, characterized in that at least one of the switches (S1, S2, S3) is designed as a metal-oxide-semiconductor field-effect transistor. Circuit unit (10) according to one of the preceding claims, characterized in that at least one of the switches (S1, S2, S3) is designed as a junction field effect transistor. Circuit unit (10) according to one of the preceding claims, characterized in that at least one of the switches (S1, S2, S3) is designed as a metal-semiconductor field-effect transistor. Circuit unit (10) according to one of the preceding claims, characterized in that a switching element is connected in series with each of the switches (S1, S2, S3) and has a parallel connection of a fuse and a braking resistor. Drive unit, in particular for a driverless transport vehicle, comprising at least one circuit unit (10) according to one of the preceding claims and at least one three-phase electric motor (50) which is connected to the first phase conductor (51), to the second phase conductor (52) and to the third phase conductor (53) is connected to the at least one circuit unit (10).

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