Drive system

Abstract

The invention relates to a drive system, the drive system comprising an electric motor and an inverter which feeds the electric motor, a cable electrically connecting the electric motor to the inverter, the cable comprising - first electrical lines, - a second electrical line, and - third electrical lines, a voltage detection means located at the first cable end detecting a voltage that is present between the second electrical line and another electrical line, in particular a measuring line, the other electrical line being one of the first electrical lines or one of the third electrical lines, the other electrical line being electrically connected to the second electrical line at the second cable end, the current that flows through the other electrical line being detected by a current detection means, and a resistance value being determined from the detected voltage and the detected current, said resistance value being supplied to a closed-loop control unit of the inverter.

Description

[0001] drive system

[0002] Description:

[0003] The invention relates to a drive system.

[0004] It is common knowledge that a drive system includes an electric motor.

[0005] From US 2010 / 0 194 329 A1, a drive system is known as the closest prior art.

[0006] A method for operating a drive system is known from DE 10 2011 014 753 A1.

[0007] A cable system is known from DE 199 08 045 A1.

[0008] A drive system with a hybrid cable is known from DE 10 2011 100 361 A1.

[0009] The invention is therefore based on the object of developing a drive system, wherein

[0010] According to the invention, the object is achieved in the drive system according to the features specified in claim 1.

[0011] Important features of the invention in the drive system are that the drive system comprises an electric motor and a converter which feeds the electric motor, wherein a cable, in particular a hybrid cable, electrically connects the electric motor to the converter, wherein the cable comprises first electrical lines, a second electrical line and third electrical lines, wherein a voltage detection means arranged at the first cable end detects a voltage present between the second electrical line and another electrical line, in particular a measuring line, wherein the other electrical line is one of the first electrical lines or one of the third electrical lines, wherein the other electrical line is electrically connected, in particular directly connected, to the second electrical line at the second, in particular other, cable end,wherein the current flowing through the other electrical line is detected by a current detection means, wherein a resistance value is determined from the detected voltage and the detected current, which resistance value is fed to a control unit of the converter, in particular for use in a stator flux-oriented control of the electric motor.

[0012] The advantage here is that the voltage drop across a measuring line can be determined using the second line. By determining the voltage drop across the measuring line and the current flowing through the measuring line, the cable resistance can be determined, which is attributable to the cable connecting the inverter to the electric motor. When controlling the electric motor, improved control can be achieved by repeatedly updating the cable resistance. This improves the control quality. It is not necessary for the measuring line to carry the motor current itself; it is also possible for the measuring line to carry another current that is recorded, in particular, for example, the current supplied to a brake.It is then important, however, that the measuring line is connected to the line carrying the motor current in such a thermally conductive manner that the temperature of the measuring line is equal to the temperature of the line carrying the motor current, particularly within a permissible deviation. In an advantageous embodiment, all first electrical lines have the same cross-section. It is advantageous if the first electrical lines can serve to supply a brake or can be designed as sensor lines.

[0013] In an advantageous embodiment, all third electrical lines have the same cross-section. It is advantageous that the third electrical lines carry the motor current, i.e., they are particularly high-voltage lines.

[0014] In an advantageous embodiment, the second electrical line has the same cross-section as the third electrical lines. This is advantageous in that the second line requires very little installation space within the cable. Furthermore, the cable can be used in various designs, in particular with a motor-side control unit for the brake, so that only the control unit needs to be supplied via the third electrical lines, or with an inverter-side control unit, which supplies the brake via the third electrical lines, so that a split brake coil with a center tap can be controlled by the control unit.

[0015] In an advantageous embodiment, the first electrical lines, the third electrical lines, and the second electrical line are connected to one another in a thermally conductive manner, in particular wherein the heat transfer resistance between these lines is lower than the heat transfer resistance from one of these lines to the environment. The advantage here is that the cable resistance can also be determined indirectly by determining the ohmic resistance of a third electrical line and using this to determine the cable resistance of the first electrical lines. This allows, in particular, a simple conversion of the resistances using the ratio of the line cross-sections. This is because all lines are designed as copper wires. In particular, the electrical lines differ only in their cable resistances.

[0016] In an advantageous embodiment, the first cable end is located on the converter side and the second cable end on the motor side, in particular with the voltage detection means and the current detection means located in the converter. This is advantageous because the cable can be used in both directions. If the voltage is detected on the converter side, the voltage detection can be implemented integrated into the converter's electronics, eliminating the need for data transmission of measured values ​​detected at the other cable end.

[0017] In an alternative advantageous embodiment, the first cable end is arranged on the motor side and the second cable end on the converter side, in particular wherein the voltage detection means and the current detection means are arranged on the electric motor or on a brake of the electric motor, in particular in a control unit. Advantageously, the current detection and the voltage detection do not have to be carried out on a first electrical line that has a current driven by a pulse-width-modulated voltage, but rather, detection can be carried out on a measuring line that has a sinusoidal current.

[0018] In an advantageous embodiment, the first electrical lines, the second electrical line, and the third electrical lines are each embodied as copper wire. This is advantageous in that different wire cross-sections can be used, and the voltage and current measurement on a measuring line, with the resulting ohmic resistance of the measuring line, is proportional to the cable resistance of a respective first electrical line through which the converter supplies the electric motor, in particular so that this line carries one phase of the motor current.

[0019] In an advantageous embodiment, the converter provides a three-phase voltage, in particular a three-phase voltage, to the electric motor, in particular the stator of the electric motor, via the first electrical lines. This voltage generates, in particular drives, a motor current. The converter, in particular the control unit of the converter, adjusts the motor voltage in such a way that the detected motor current is regulated to a target motor current, in particular one that is predetermined such that the electric motor achieves a target speed or a target torque. It is advantageous that the control unit enables stator-flux-oriented control.In an advantageous embodiment, the converter has an inverter, wherein the inverter has three series circuits connected in parallel and supplied from a direct voltage, in particular intermediate circuit voltage, wherein each of the series circuits has two controllable semiconductor switches connected in series with one another, for which the control unit generates pulse-width modulated control signals, in particular wherein the center taps of the series circuits form the AC voltage side connection of the inverter, wherein the voltage at the DC voltage side connection of the inverter is detected and fed to the control unit for consideration when determining the pulse width modulation ratio of the pulse-width modulated control signals.The advantage here is that when the control unit generates the control signals according to a control-engineering machine model, in particular according to a stator flux-oriented control, the cable resistance of the first electrical lines connecting the converter to the electric motor can be updated periodically, thus improving the control. The converter provides the electric motor with a three-phase voltage system via the first three electrical lines, in particular one that drives the motor current as three-phase current.

[0020] In an advantageous embodiment, the control unit takes the cable resistance into account when determining the pulse-width modulated control signals of the inverter. This improves control quality because the parameters used in the control are constantly updated.

[0021] In an advantageous embodiment, a control unit is arranged at the first cable end, which is powered by an AC power supply network and supplies a brake via the third electrical lines. The advantage here is that the voltage measurement is integrated into the converter, thus eliminating the need for direct data transmission of the current values ​​to the converter.

[0022] In an alternative advantageous embodiment, a control unit is arranged at the first cable end, which is supplied from an AC power supply network via the third electrical lines and electrically supplies, in particular, and controls, a brake arranged on the electric motor. Advantageously, the current measurement can be determined independently of the current fluctuations of the high-voltage current flowing through the first electrical lines.

[0023] In an advantageous embodiment, the control unit is connected to sensors, with the sensor signals being fed to the control unit. This is advantageous because the control unit also functions to evaluate sensor signals and / or as a data node. The values ​​recorded by the sensors can be forwarded via the control unit to the converter's signal electronics or to an industrial plant control system.

[0024] In an advantageous embodiment, a data transmission channel is provided between the converter and the control unit, in particular by modulating high-frequency voltage or current components onto one or more of the electrical lines, in particular onto first electrical lines or third electrical lines. Advantageously, a data stream can be transmitted via current and voltage components modulated onto these lines, wherein the components have a higher frequency than the three-phase voltage system provided by the converter to the electric motor.

[0025] In an advantageous embodiment, the determined resistance value is multiplied by the ratio, in particular the quotient, of the cross-section of the first lines to the cross-section of the third lines and used by the control unit, in particular for stator flux-oriented control of the electric motor. This is advantageous because an indirect and thus galvanically isolated determination of the resistance is possible, and a simple, in particular computationally inexpensive, conversion is sufficient to determine the cable resistance of the first electrical lines.

[0026] In an advantageous embodiment, the cable is a hybrid cable, in particular wherein the third electrical lines are low-voltage lines and the first lines are high-voltage lines or wherein the third electrical lines have a smaller line cross-section than the first electrical lines.

[0027] The advantage here is that a determination of the resistance of the third electrical lines can be carried out galvanically isolated from the first electrical lines via which the converter supplies the electric motor.

[0028] In an advantageous embodiment, the converter is powered by one or the AC power supply network, in particular the three-phase network. It is advantageous that the converter can preferably be supplied with a three-phase power supply, and that the control unit and the brake can be supplied from two lines of this three-phase supply.

[0029] The control unit controls or regulates the voltage provided to the brake coil and / or the current supplied to the brake coil.

[0030] Further advantages emerge from the dependent claims. The invention is not limited to the combination of features in the claims. Further possible combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent to those skilled in the art, particularly from the problem and / or the problem posed by comparison with the prior art.

[0031] The invention will now be explained in more detail using schematic illustrations:

[0032] Figure 1 shows a schematic diagram of a first drive system according to the invention.

[0033] Figure 2 shows a schematic diagram of a second drive system according to the invention.

[0034] Figure 3 shows a schematic diagram of a third drive system according to the invention.

[0035] As shown in Figure 1, the drive system has a converter which is electrically supplied from an alternating voltage supply network 5, in particular a three-phase network, in particular with three-phase current.

[0036] An electric motor 4, in particular a three-phase motor, is powered by the converter 1. For this purpose, first electrical lines 6 are routed from the converter 1 to the electric motor 4.

[0037] Preferably, the first electrical lines 6 are arranged and / or combined together with a second electrical line 7 and third electrical lines 8 in a hybrid cable 2.

[0038] In this way, wiring can be created quickly and easily.

[0039] The cable cross-section of the first electrical cables is preferably larger than the cable cross-section of the second electrical cable 7 and also larger than the cable cross-section of the third electrical cables 8.

[0040] Preferably, the cable cross-section of the second electrical cable 7 and the third electrical cable 8 is the same.

[0041] Preferably, the converter 1 is arranged in a control cabinet of an industrial plant or machine and the electric motor 4 is arranged in the plant or in a machine of the plant.

[0042] As shown in Figure 1, an electromagnetically actuated brake is mounted or integrated on the electric motor 4. This brake has an energizable coil with a center tap, so that the coil is formed from a series circuit of a first coil winding and a second coil winding, in particular concentric therewith.

[0043] By energizing the first coil winding, a magnetic field can be quickly built up, so that when a predetermined magnetic field strength is reached, the entire coil can be energized instead of just the first coil winding. This allows for energy-saving brake holding.

[0044] The coil, in particular the two coil windings arranged concentrically to one another, is accommodated in a recess of a magnetic body which is connected in a rotationally fixed manner to the stator housing of the electric motor 4.

[0045] A ring-like driver is connected to the rotor shaft of the electric motor in a rotationally fixed manner, whereby the driver is attached to the rotor shaft and has an external toothing.

[0046] A disc-shaped brake pad carrier has internal teeth, with which the brake pad carrier is attached to the external teeth of the driver, so that the internal teeth of the brake pad carrier engage with the external teeth of the driver. As a result, the brake pad carrier is connected to the driver in a rotationally fixed manner, but is displaceable relative to the driver in the axial direction, i.e., in the direction of the rotational axis of the rotor shaft.

[0047] The brake pad carrier has brake pads axially on both sides.

[0048] A ferromagnetic armature disk is arranged axially between the magnetic body and the brake pad carrier. This armature disk is connected to the magnetic body in a rotationally fixed manner, in particular by bolts extending through recesses in the armature disk, and these bolts are inserted into the magnetic body and / or are particularly firmly connected to the magnetic body. The bolts are aligned in the axial direction.

[0049] Spring elements supported on the magnet body press against the armature disk. When the coil is de-energized, these spring elements push the armature disk away from the magnet body toward the brake pad carrier, causing the brake pad carrier to contact a finely machined braking surface formed on a bearing plate of the electric motor or a friction plate that is non-rotatably connected to the stator housing of the electric motor.

[0050] When the coil is energized, however, the armature disc is attracted to the magnetic body against the spring force generated by the spring elements, so that the brake pad carrier is released from the armature disc and the braking force of the brake disappears.

[0051] When the coil is energized, only the first coil winding is energized in a first time period and then the second coil winding is also energized in a subsequent time period.

[0052] The control unit 3 is supplied, in particular, from two phases of the AC voltage supply network 5, in particular a three-phase network, and controls the current supplied to the brake, in particular to the brake coil or the brake coil windings. Preferably, however, the voltage applied to the coil or the coil windings can also be detected, in particular by a voltage detection means of the control unit 3.

[0053] In order to supply the brake, in particular the coil of the brake or the coil windings of the brake, with current and / or voltage, the third electrical lines 8 electrically connect the terminals of the control unit 3 to the terminals of the brake, in particular the coil of the brake or the coil windings of the brake.

[0054] The second electrical line 7 has the same cross-section as each of the third electrical lines 8.

[0055] However, the second electrical line 7 is led from a connection of the converter 1 to a connection of the electric motor 4, to which a first of the first electrical lines 6 is also led, in particular which has a larger line cross-section than the second electrical line 7. A means for detecting the voltage between the first of the first electrical lines 6 and the second electrical line 7 is arranged in the converter 1, wherein the value of this detected voltage is forwarded to signal electronics of the converter 1, which generates control signals for semiconductor switches of an inverter of the converter 1.

[0056] The inverter is preferably constructed from three series circuits connected in parallel, each of which has two semiconductor switches connected in series. The electric motor 4 is supplied from the center taps of the inverter.

[0057] The signal electronics comprises a control unit that preferably executes a stator flux-oriented control method. The current supplied by the inverter to the electric motor via the first electrical lines 6 is detected, in particular by a current sensor of the converter 1, and fed to the control unit.

[0058] In addition, the DC voltage supplying the three parallel series circuits of the inverter is recorded and also fed to the control unit.

[0059] The control unit determines an actual value of a speed and / or a torque of the electric motor 4 from the detected current curve, in particular taking into account the detected DC voltage.

[0060] This actual value is regulated to a setpoint by providing a three-phase voltage to the electric motor 4 from the control unit 3 through appropriate pulse-width modulated control of the semiconductor switches.

[0061] This three-phase voltage serves as the control variable of the controller unit.

[0062] When determining the resistance, the control unit uses a parameter representing the cable resistance of the first electrical lines 1. The cable resistance is temperature-dependent. To determine this parameter with high accuracy and, if possible, with constant updates, the voltage U occurring between the first of the first electrical lines 6 and the second electrical line 7 is repeatedly recorded in the converter 1.

[0063] This first of the first electrical lines 6 is electrically connected to the second electrical line 7 at the connection of the electric motor 4. In this way, the voltage U drop across the first of the first electrical lines, which occurs when the current flows through, can be determined.

[0064] From the detected voltage drop and the also detected current flowing through the first of the first electrical lines 6, the ohmic resistance of this first of the first electrical lines 6 can be determined and used as cable resistance by the control unit.

[0065] This improves the control unit's control performance. Overall, this also improves the control quality.

[0066] The control unit 3 can be arranged together with the converter in a control cabinet or together with or on the converter 1 in an industrial system or machine. The electric motor 4, including the brake 9, is arranged spatially separated from the converter, but in particular also in the system or on the machine.

[0067] From the electric motor 4, the electrical lines 6, 7, and 8 are led either individually or preferably together in a hybrid cable 2 to the converter 1 with the control unit 3.

[0068] As shown in Figure 2, in contrast to Figure 1, the control unit 3 is arranged on the electric motor 4 together with the brake 9.

[0069] Thus, the third electrical lines 8, which supply electrical power to the control unit 3, are again arranged individually, separately, or preferably in a hybrid cable 2, together with the second electrical line 7. However, the voltage U dropped across a first of the third electrical lines 8 is detected by a voltage detection means arranged in the control unit 3. For this purpose, the second electrical line 7 is electrically connected on the mains side to the first of the third electrical lines 8. The voltage detection means thus detects the voltage U dropped across the first of the third electrical lines 8 on the motor side and determines the ohmic resistance of the first of the third electrical lines 8 from the current flowing through the first of the third electrical lines 8, which current is also determined by the control unit.

[0070] Since the first electrical lines 6 in the hybrid cable are arranged together with the third electrical lines 8 and thus thermally connected, the temperature of all these lines 6 and 8 is essentially identical. Thus, the ohmic resistance of the respective first electrical line 6 can be determined very precisely from the determined ohmic resistance.

[0071] The control unit 3 transmits the detected value to the converter 1 via a data transmission channel. This data transmission channel is designed either as a data bus line, which is preferably also carried in the hybrid cable, in particular as a shielded cable, or by higher-frequency modulation, in particular onto the first electrical lines 6. This even makes it possible to save on additional lines.

[0072] This indirect, but very precise, determination allows the cable resistance of the cable running from inverter 1 to electric motor 4 to be used as a parameter in the control system. This also improves the control system.

[0073] Additionally, sensors for detecting physical variables, in particular temperature, speed, and torque, are also arranged in the electric motor 4 and / or the brake 9. The sensor signals are fed to the control unit 3, where they are evaluated and / or forwarded via the third electrical lines 8.

[0074] As shown in Figure 3, in contrast to the embodiment according to Figure 2, one of the third electrical lines, which functions as a measuring line, is additionally present and is connected to the second electrical line 7 at the end of the cable 2 facing away from the control unit 3. A voltage U applied by the control unit 3 between the two lines, i.e., between the second electrical line 7 and the third electrical line functioning as a measuring line, drives a current I through the third electrical line functioning as a measuring line. From this, the ohmic resistance can then be determined undisturbed and galvanically isolated.

[0075] In further embodiments according to the invention, in contrast to the aforementioned embodiments, an electric motor 4 without a brake 9 is used. The control unit 3 is then designed to evaluate and / or forward the sensor signals from sensors arranged in the electric motor 4, in particular for detecting values ​​of physical variables, in particular temperature, speed, torque.

[0076] List of reference symbols

[0077] 1 inverter 2 hybrid cables

[0078] 3 Control unit

[0079] 4 Electric motor, especially three-phase motor

[0080] 5 AC power supply network, especially three-phase network

[0081] 6 first line 7 second line

[0082] 8 third line

[0083] 9 Brake

Claims

Patent claims:

1. Drive system, wherein the drive system comprises an electric motor and an inverter which supplies the electric motor, wherein a cable, in particular a hybrid cable, electrically connects the electric motor to the inverter, wherein the cable comprises first electrical conductors, a second electrical conductor and a third electrical conductor, wherein a voltage sensing means arranged at the first cable end detects a voltage present between the second electrical conductor and another electrical conductor, in particular a measuring conductor, wherein the other electrical conductor is one of the first electrical conductors or one of the third electrical conductors, wherein the other electrical conductor is electrically connected to the second electrical conductor at the second, in particular other, cable end, in particular directly connected, wherein the current flowing through the other electrical conductor is detected by a current sensing means.wherein a resistance value is determined from the measured voltage and current, which is fed to a control unit of the inverter, in particular for use in stator flux-oriented control of the electric motor.

2. Drive system according to claim 1, characterized in that all first electrical conductors each have the same conductor cross-section and / or that all third electrical conductors each have the same conductor cross-section and / or that the second electrical conductor has the same conductor cross-section as the third electrical conductors.

3. Drive system according to one of the preceding claims, characterized in that the first electrical conductors, the third electrical conductors and the second electrical conductor are thermally connected to each other, in particular wherein the thermal resistance between these conductors is lower than the thermal resistance of one of these conductors to the environment.

4. Drive system according to one of the preceding claims, characterized in that the first cable end is arranged on the inverter side and the second cable end on the motor side, in particular wherein the voltage sensing means and the current sensing means are arranged in the inverter, or that the first cable end is arranged on the motor side and the second cable end on the inverter side, in particular wherein the voltage sensing means and the current sensing means are arranged on the electric motor or on a brake of the electric motor, in particular in a control unit.

5. Drive system according to one of the preceding claims, characterized in that the first electrical lines, the second electrical line and the third electrical lines are each designed as copper wire lines.

6. Drive system according to one of the preceding claims, characterized in that the converter provides a three-phase voltage, in particular a three-phase voltage, to the electric motor, in particular to the stator of the electric motor, via the first electrical lines, which causes a motor current, in particular drives, wherein the converter, in particular the control unit of the converter, sets the motor voltage such that the detected motor current is regulated to a target motor current, in particular which is specified such that the electric motor reaches a target speed or a target torque.

7. Drive system according to one of the preceding claims, characterized in that the converter has an inverter, wherein the inverter has three series circuits connected in parallel, supplied by a DC voltage, in particular an intermediate circuit voltage, wherein each of the series circuits has two controllable semiconductor switches connected in series with each other, the pulse-width modulated control signals of which are generated by the control unit, in particular wherein the center taps of the series circuits form the AC-side connection of the inverter, wherein the voltage at the DC-side connection of the inverter is detected and supplied to the control unit for consideration in determining the pulse-width modulation ratio of the pulse-width modulated control signals.

8. Drive system according to one of the preceding claims, characterized in that the control unit takes the cable resistance into account when determining the pulse width modulated control signals of the inverter.

9. Drive system according to one of the preceding claims, characterized in that a control unit is arranged at the first cable end, which consists of a supplied by an AC power supply network and supplies a brake via the third electrical lines, or that a control unit is arranged at the first cable end, which is supplied by an AC power supply network via the third electrical lines and supplies a brake arranged on the electric motor electrically, in particular and controls it.

10. Drive system according to one of the preceding claims, characterized in that the control unit is connected to sensors, wherein the sensor signals of the sensors are fed to the control unit.

11. Drive system according to one of the preceding claims, characterized in that a data transmission channel is provided between the converter and the control unit, in particular by modulating especially high-frequency voltage or current components onto one or more of the electrical lines, in particular onto first electrical lines or third electrical lines.

12. Drive system according to one of the preceding claims, characterized in that the determined resistance value is multiplied by the ratio, in particular quotient, of the conductor cross-section of the first conductors to the conductor cross-section of the third conductors and is used by the control unit, in particular for a stator flux-oriented control of the electric motor.

13. Drive system according to one of the preceding claims, characterized in that the cable is a hybrid cable, in particular - wherein the third electrical lines are low-voltage lines and the first lines are high-voltage lines, or wherein the third electrical lines have a smaller cross-sectional area than the first electrical lines.

14. Drive system according to one of the preceding claims, characterized in that the converter is supplied from an AC power supply network, in particular a three-phase network.

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