WO2009098143A2

WO2009098143A2 - Electric machine excited by permanent magnets for a domestic appliance and circuit arrangement comprising a machine excited by permanent magnets

Info

Publication number: WO2009098143A2
Application number: PCT/EP2009/050874
Authority: WO
Inventors: Hasan Gökcer ALBAYRAK; Falk Laube; Jörg SKRIPPEK
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2008-02-04
Filing date: 2009-01-27
Publication date: 2009-08-13
Also published as: DE102008007402A1; WO2009098143A3

Abstract

The invention relates to a machine (2) excited by permanent magnets for a domestic appliance, in particular for treating laundry items, said machine comprising a stator with a primary winding (3) for generating a magnetic field, a rotor with at least one permanent magnet that is mounted to rotate in relation to the stator and a measuring device for determining a speed and/or angular position of the rotor in relation to the stator. The measuring device has a separate measuring winding (21) positioned on the stator.

Description

Permanent magnet excited electric machine for a domestic appliance and circuit arrangement with a permanent magnet excited

machine

The present invention relates to a permanent magnet electric machine for a domestic appliance, in particular for the care of laundry, with a stator having a main winding for generating a magnetic field, with a rotor having at least one permanent magnet and is rotatably mounted relative to the stator , And with a measuring device for determining a rotational speed and / or an angular position of the rotor relative to the stator. Moreover, the present invention relates to a circuit arrangement with such a permanent-magnet-excited electric machine.

The term domestic appliance is understood in particular to mean a washing machine, a dryer or a washer-dryer.

In a classical control of a permanent magnet synchronous machine, or a so-called brushless DC machine, a generated by three Hall sensors usually speed signal is used to control the motor. In the case of a fault, for example in the case of a power electronics defect, a winding short-circuit, a cable break or the like, the rotational speed is nevertheless detected further via the sensor and evaluated via separate electronics. This ensures that additional required safety functions, such as a door lock in a rotating drum, are guaranteed.

In a sensorless operation of the brushless DC motor no sensor signal is required for operation, so that a speed detection takes place via the evaluation of an induced voltage of a machine winding in a current zero crossing. In other words, a voltage is thus induced according to the generator principle in the machine winding even during a motor operation, which is poled as the operating voltage and therefore counteracts the rotor current. This so-called counter voltage makes it possible to determine an idle speed. However, doing so in one Fault, the speed detection required for safety reasons are not ensured, so that an additional, independent speed detection must be provided. A remedy here creates, for example, an additional speed sensor, as usually a tachometer.

The object of the present invention is to ensure a speed detection in a permanent magnet excited electrical machine, in particular a redundant speed detection.

This object is achieved by a permanent magnet electric machine and by a circuit arrangement with the features according to the respective independent claim. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

A permanent magnet-excited electric machine according to the invention for a domestic appliance, in particular for the care of laundry items, comprises a stator which has a main winding for generating a magnetic field, and a

Rotor, which has at least one permanent magnet. In this case, the rotor is mounted rotatably movable relative to the stator. The electric machine includes a

Measuring device for determining a rotational speed and / or an angular position of the rotor relative to the stator, wherein the measuring device has a separate measuring winding, which is arranged on the stator.

Thus, a basic idea of the present invention is that the current rotational speed and / or the current angular position of the rotor relative to the stator can be determined by means of a separate measuring winding arranged on the stator. The invention is based on the finding that the rotor inherently carries a permanent magnet, which ensures upon rotation of the rotor that in the measurement winding in the frequency and amplitude speed-proportional voltage is induced, which in particular via a special electronics in a similar manner as a signal a Hall sensor can be evaluated. By means of the electric machine according to the invention it is achieved that the rotational speed or the relative angular position of the rotor can be determined in a low-cost manner on the basis of an analogue signal. By saving a conventional speed sensor is also created a cost-reduced and component-reduced electrical machine with regard to the production.

Preferably, the electrical machine is designed as an internal rotor.

In one embodiment, the machine is designed as a sensorless controlled electric machine, wherein the measuring device is preferably designed for redundant speed detection. In this way, with regard to safety, it is achieved that the rotational speed can be detected by the measuring winding even in the event of a fault, for example in the case of a power electronics defect, winding short circuit, cable breakage or the like, and thus additional required safety functions, such as, for example, a door lock Drum rotation, can be ensured.

Preferably, the stator has a group of teeth, which are arranged radially spaced from a rotation axis, wherein the main winding is formed as a tooth coil. In one embodiment, the measurement winding may be formed as a tooth coil. In particular, the wrapping of an arbitrary tooth is sufficient for speed detection, wherein for rotor position detection preferably a plurality of teeth, in particular two or three, are wound.

It can be provided that a ratio of a number of turns of the main winding to a number of turns of the measuring winding is in a value range between 80 and 120, in particular 100. Preferably, the measurement winding may be formed of a thinner wire compared to the main winding. Since only a small measuring current and a lower measuring voltage are required, the measuring winding can be formed from very few turns and very thin wire, so that a portion of a groove area formed between two teeth required for the execution is small, and thus only very little space for the main winding is lost.

Preferably, the main winding is wound over the measuring winding, wherein the main winding and the measuring winding are preferably wound by means of a Nadelwicklers. In particular, the measuring winding is introduced before the main winding and may preferably be provided with an additional phase insulation. Because of that Main winding is wound over the measuring winding, it is achieved that an additional mechanical protection of the measuring winding is ensured. Moreover, by winding both the main winding and the measuring winding by means of the needle winder in terms of manufacturing, it is achieved that the measuring winding can be introduced to the stator in the same way and with the same wire thickness as the main winding.

Preferably, the main winding on three coil strands, which are designed for operation with three-phase current.

A circuit arrangement according to the invention is designed for operating a domestic appliance, in particular for the care of laundry items. The circuit arrangement comprises the permanent magnet excited electric machine according to the invention.

Preferably, the measuring winding is coupled to a test input of a control unit for controlling processes of the domestic appliance. This ensures that the rotational speed and / or the relative angular position of the rotor can be detected particularly reliably by means of the control unit. In particular, the control unit may be designed as a microcontroller.

In one embodiment, the main winding on three coil strands, which are designed for operation with three-phase current, and are coupled to a voltage converter, in particular a converter. Preferably, the voltage converter is coupled to the control unit and controlled by this. In particular, the voltage converter is able to convert an AC voltage or a rectified voltage into a three-phase current, with which the electric machine can be supplied. The voltage converter may preferably have a bridge circuit with a plurality of transistors, in particular field-effect transistors. In particular, the electric machine can thus be commutated electronically. In particular, the rectifier thus constitutes a three-phase current regulator. The skillful coupling of the voltage converter to the control unit ensures that the rotational speed of the rotor detected by means of the measuring winding can be used to control and thus regulate the electrical machine. Preferably, the voltage converter is coupled to a rectifier, in particular a bridge rectifier, which is coupled to an input of the circuit arrangement. This ensures that an AC voltage from the side of a supply network can be rectified, and thus the voltage converter must be formed only for operation with DC voltage. Preferably, the rectifier is coupled to the input via an EMC filter. This ensures that no interference signals can be transmitted from the electrical machine in the supply network.

Preferably, a DC link capacitor is connected in parallel to the rectifier and the voltage converter, wherein a voltage divider is preferably connected in parallel to the rectifier and the voltage converter, and between two resistors of the voltage divider a voltage detection is formed, which is coupled to a measuring input of the control unit. In particular, the intermediate circuit capacitor is an energy store and preferably has the task of smoothing a DC link voltage having a ripple. Moreover, the use of the voltage divider with the two resistors ensures that the intermediate circuit voltage can be detected by the control unit. Preferably, a DC link resistor for absorbing a DC link voltage is connected in parallel to the rectifier or the voltage converter, wherein an electronic control element, in particular a transistor, is connected in series with the DC link resistor, which is controllable by the control unit. This ensures that an excessive DC link voltage can be absorbed and reduced by the DC link resistance.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing.

The single FIGURE shows a circuit arrangement for operating a household appliance with a permanent magnet-excited electric machine. A circuit arrangement 1 shown in the figure is designed for operating a household appliance for the care of laundry items, in the present case a washing machine. The home appliance can also be a dryer or a washer-dryer.

The circuit arrangement 1 comprises a permanent magnet-excited electric machine 2, which in turn has a stator and a rotor rotatably mounted relative to the stator rotatably mounted. In this case, the rotor comprises permanent magnets, wherein the stator is associated with a main winding 3, which in the present case has three coil strands 3a, 3b, 3c. In the present case, the permanent-magnet-excited electric machine 2 is designed for operation with three-phase current.

In the present example, the three coil strands 3a, 3b, 3c are coupled to a voltage converter 4, which in the present case is designed in the form of a bridge circuit and has the task of an inverter. The circuit arrangement 1 further comprises a control unit 5, which is coupled to the voltage converter 4 via a driver device 6, which provides in favor of safety for a level adjustment of control signals of the control unit 5. The control unit 5 is presently designed as a microcontroller. At this point, it should be mentioned that the voltage converter 4 comprises a plurality of transistors, in the present case field effect transistors, via which the three coil sections 3a, 3b, 3c of the electric machine 2 are commutated. In other words, the three coil strands 3a, 3b, 3c in the present case are commutated electronically, wherein the voltage converter 4 is a three-phase regulator.

The circuit arrangement 1 also has an input 7, on which an EMC filter 8 is arranged, which has the task of preventing a transmission of interference signals of the circuit arrangement 1 in a supply network, and thus the supply network and other devices connected to the supply network devices protect. The EMC filter 8 is coupled to a rectifier 9, which is designed here as a bridge rectifier with four diodes. The rectifier 9 is also coupled to the voltage converter 4 via intermediate poles 10, 11. By using the rectifier 9 ensures that the voltage converter 4 is supplied with a rectified voltage. Between the two DC link poles 10, 1 1, a DC link capacitor 12 is parallel to the rectifier 9 and the Voltage transformer 4 connected. This DC link capacitor 12 has to ensure that the rectifier 9 and the voltage converter 4 energetically couple with each other on a common DC voltage level. Thus, the intermediate circuit capacitor 12 is an energy storage, by means of which a ripple of an AC voltage to be smoothed by the supply network.

In addition, a voltage divider 13 is connected in parallel with the intermediate circuit capacitor 12 between the two intermediate circuit poles 10, 11. The voltage divider 13 comprises two voltage divider resistors 13a, 13b, between which a voltage detection pole 14 is formed. In the present case, the voltage detection pole 14 is coupled to a measuring input 15 of the control unit 5 of the circuit arrangement 1. In this way, a voltage applied between the two DC link poles 10, 11 can be detected and evaluated by means of the control unit 5. For this purpose, a DC link resistor 16 is also provided, which is connected in parallel with the DC link capacitor 12 between the two DC link poles 10, 11. In addition, a transistor 17 is connected in series with the intermediate circuit resistor 16, whose control terminal 18 is coupled to an output 19 of the control unit 5. In this case, the DC link resistor 16 has the task of optionally absorbing a voltage applied between the two DC link poles 10, 11 voltage and thus to destroy. The serial connection of the DC link resistor 16 to the transistor 17 ensures that a current flowing through the DC link resistor 16 and the transistor 17 can be regulated by the control unit 5 by driving the transistor 17. If the voltage present between the intermediate circuit poles 10, 11 is too great, which can be detected by the control unit 5 via the voltage divider 13, then the transistor 17 is driven, so that current flows via the intermediate circuit resistance 16.

At this point, it should be mentioned that the three coil strands 3a, 3b, 3c of the main winding 3 of the stator of the electric machine 2 are coupled to a device 20 for detecting a countervoltage of the electric machine 2. This device 20 is coupled to the control unit 5. According to a generator principle, a voltage is induced in the main winding 3 even with a motor operation of the electric machine 2. This induced voltage represents the reverse voltage of the electric machine 2. The device 20 is thus capable of an idling speed of the permanent magnet excited electric machine 2 and to detect the current position of the rotor relative to the stator. Usually, such a rotor position or speed detection is used to drive a sensorless controlled electric machine. However, a speed detection required for safety reasons can not be ensured in the event of a fault, so that an additional, independent speed detection must be provided. For this purpose, the stator of the electric machine 2 comprises a separate measuring winding 21, which in the present case are inserted in grooves of three coil strands 3a, 3b, 3c of the stator in favor of a reliable rotor position detection. These are grooves of the stator, which are formed between each two teeth of the stator. In comparison with the main winding 3, the measuring winding 21 is formed from a few turns, so that the proportion of the groove area required for the execution is very small and thus only very little space for the main winding 3 is lost. In the present example, the measuring winding 21 is introduced in front of the main winding 3 and comprises an additional phase insulation, not shown, wherein the main winding 3 is wound in the present case over the measuring winding 21, whereby an additional mechanical protection of the measuring winding is ensured. The measuring winding 21 is also coupled to a measuring device 22, which is designed to detect the rotational speed and the position of the rotor with respect to the stator of the electric machine 2. This measuring device 22 is also coupled to the control unit 5. Thus, the possibility is given to regulate the rotational speed of the electric machine 2 on the part of the control unit 5 as a function of signals of the measuring device 22. In addition, this ensures that in an error case the speed detection required for safety reasons due to the measuring winding 21 and the additional speed detection is ensured. A door lock on a rotating drum is thereby ensured. Another advantage of the measuring winding 21 in the present case is that no additional speed sensor, such as a Hall sensor, is required, whereby a cost-reduced circuit 1 is provided.

Claims

claims

A permanent magnet excited electric machine (2) for a domestic appliance, in particular for the care of laundry, comprising a stator which has a main winding (3) for generating a magnetic field with a rotor having at least one permanent magnet and rotational relative to the stator is movably mounted, and with a measuring device for determining a rotational speed and / or an angular position of the rotor relative to the stator, characterized in that the measuring device has a separate measuring winding (21) which is arranged on the stator.

2. Electrical machine (2) according to claim 1, characterized in that the machine (2) is designed as an internal rotor.

3. Electrical machine (2) according to claim 1 or 2, characterized in that the machine (2) is designed as a sensorless controlled electric machine.

4. Electrical machine (2) according to claim 3, characterized in that the measuring winding (21) is designed for redundant speed detection.

5. Electrical machine (2) according to any one of the preceding claims, characterized in that the stator comprises a group of teeth which are arranged radially spaced from a rotation axis, wherein the main winding (3) is formed as a toothed winding.

6. Electrical machine (2) according to claim 5, characterized in that the measuring winding (21) is designed as a toothed winding.

7. Electrical machine (2) according to one of the preceding claims, characterized in that a ratio of a number of turns of the main winding (3) to a number of turns of the measuring winding (21) in a value range between 80 and

120, in particular 100 is.

8. Electrical machine (2) according to one of the preceding claims, characterized in that the measuring winding (21) is formed of a compared to the main winding (3) thinner wire.

9. Electrical machine (2) according to any one of the preceding claims, characterized in that the main winding (3) over the measuring winding (21) is wound.

10. Electrical machine (2) according to one of the preceding claims, characterized in that the main winding (3) and the measuring winding (21) are wound by means of a Nadelwicklers.

1 1. Circuit arrangement (1) for operating a domestic appliance, in particular for the care of laundry, with a permanent magnet electric machine (2) according to one of claims 1 to 10.

12. Circuit arrangement (1) according to claim 1 1, characterized in that the measuring winding (21) is coupled to a test input of a control unit (5) for controlling processes of the domestic appliance.

13. Circuit arrangement (1) according to claim 1 1 or 12, characterized in that the main winding (3) has three coil strands (3a, 3b, 3c), which are designed for operation with three-phase current, and with a voltage converter (4), in particular a converter are coupled.

14. Circuit arrangement (1) according to claim 12 and 13, characterized in that the voltage converter (4) is coupled to the control unit (3) and can be controlled by the latter.

15. Circuit arrangement (1) according to any one of claims 13 or 14, characterized in that the voltage converter (4) is coupled to a rectifier (9), in particular a bridge rectifier, which is coupled to an input (7) of the circuit arrangement (1) is.

16. Circuit arrangement (1) according to claim 15, characterized in that the rectifier (9) is coupled to the input (7) via an EMC filter (8).

17. Circuit arrangement (1) according to claim 15 or 16, characterized in that an intermediate circuit capacitor (12) is connected in parallel to the rectifier (9) and the voltage converter (4).

18. Circuit arrangement (1) according to one of claims 15 to 17, characterized in that a voltage divider (13) is connected in parallel to the rectifier (9) and the voltage converter (4), and between two resistors (13a, 13b) of the voltage divider (13) a Spannungserfassungspol (14) is formed, which is coupled to a measuring input (15) of the control unit (5).

19. Circuit arrangement (1) according to one of claims 15 to 18, characterized in that a DC link resistor (16) for absorbing a DC link voltage in parallel with the rectifier (9) and the

Voltage converter (4) is connected, and an electronic control element (17), in particular a transistor, in series with the intermediate circuit resistor (16) is connected, which is controllable by the control unit (5).