WO2008064791A2

WO2008064791A2 - Electric drive device

Info

Publication number: WO2008064791A2
Application number: PCT/EP2007/009965
Authority: WO
Inventors: André Fella; Bernd Spatz
Original assignee: Robert Bosch Gmbh
Priority date: 2006-12-01
Filing date: 2007-11-17
Publication date: 2008-06-05
Also published as: WO2008064791A3; DE102006057213A1

Abstract

The invention relates to an electric drive device that is equipped with a brushless electric motor that can be controlled with a frequency-variable alternating current on its supply connection. A direct current source is also provided. The invention is characterised in that the electric motor is configured as a permanently excited synchronous motor, that a mechanic commutator that is coupled to a rotor of the synchronous motor and that connects a pol of the direct current source to one of its outlet conductors in accordance with an angular position of the rotor is provided, and that a switch via which the outlet conductor of the commutator can be connected to the supply connection of the synchronous motor is provided.

Description

description

Electric drive device

The invention relates to an electric drive device according to the preamble of patent claim 1.

In a large number of industrial plants, electric drives are used for moving and positioning machine elements. In wind power plants with pitch control, rotor blades are rotatably mounted on a rotor hub. The angle of attack of the rotor blades is adjusted continuously for the purpose of power regulation during operation. In addition to hydraulic drives are increasingly used electric drives. A proven concept is the use of DC motors. In the event of a breakdown, these can be connected directly to a DC source, e.g. Accumulators are connected to rotate the rotor blades in a flag position. A disadvantage of such DC motors is the use of a commutator and brushes that wear out quickly in normal operation. The brushes must be replaced at regular intervals and thus increase the maintenance considerably.

By using brushless motors one tries to achieve a higher wear resistance. Such a drive concept for blade pitching of wind turbines shows e.g. DE 103 35 575 B4. Here, an asynchronous motor is controlled by means of an inverter. An electric note energy storage supports the voltage of the DC link if one

Mains supply fails.

The disadvantage is that, in principle, an electronic drive controller is required for brushless drives. The power semiconductors of the drive controller may fail or be damaged by overvoltage, for example. It is therefore the object of the present invention to provide a low-wear and reliable electric drive.

This object is achieved by an electric drive unit having the features of patent claim 1.

According to the present invention, the electric drive device is equipped with a brushless electric motor which can be driven at its supply connection with a frequency-variable alternating current. In addition, a DC power source is available. The special feature of the present invention is that the electric motor is designed as a permanently excited synchronous motor, that a mechanical commutator is present, which is coupled to a rotor of the synchronous motor and which depending on an angular position of the rotor one pole of the DC power source with one of his Output conductor connects, and that a switch is provided, via which the output conductor of the commutator can be connected to the supply terminal of the synchronous motor. In this way, the synchronous motor on the one hand by controlling its

On the other hand - in emergency operation - be driven by supplying a direct current from the DC power source. The mechanical commutator is an extremely robust component which is not damaged by overvoltages - eg lightning strikes in the wind turbine. The control of emergency operation is extremely simple and reliable. It is merely made the connection between the commutator and the supply terminal of the synchronous motor via the switch. The use of the permanently excited synchronous motor and the coupling of the commutator to the rotor ensures a start-up of the rotor as soon as there is an electrical connection between the DC power source via the commutator to the supply terminal of the synchronous motor. In normal operation, the commutator does not carry any current. Therefore, the wear of the brushes over a conventional DC motor is greatly reduced. The wear can be even further reduced by the commutator is switched mechanically ineffective. Further, advantageous embodiments of the present invention are in the

Subclaims specified.

A high level of safety and reliability when starting up a safe position can be achieved if the switch is electrically controllable and if it is disconnected when a drive current is applied. Conversely, this means that in case of failure of a drive current, the connection between the

Commutator and the supply terminal of the synchronous motor is manufactured and the synchronous motor is a driven machine element -. a rotor blade - moves into a safe position.

A drive unit with high efficiency and sophisticated, inexpensive technology is obtained by using a three-phase AC motor in

Connection with a commutator with three output conductors.

Preferably, by the arrangement of commutator and rotor, a direction of rotation in DC operation can be predetermined. This allows the direction of movement to be set reliably in emergency mode. For this purpose, the commutator is coupled to the rotor so that the rotating field generated in the stator of the angular position of the rotor in the respective direction of movement with a certain offset but at the same speed ahead. The sign of the offset and thus the direction of rotation can be determined by the polarity of the direct current supplied to the commutator. In order to minimize the wear on the brushes, these are preferably lifted by means of a device of a slip ring of the commutator. Such lifting may e.g. be accomplished by means of a solenoid. Alternatively, the commutator can also be decoupled via a switchable coupling from the rotor of the synchronous motor. However, it should be noted here that the coupling ensures a predetermined angular position between the rotor and the slip ring during coupling.

Hereinafter, the present invention and its advantages will be explained with reference to the embodiment shown in the figure. Figure 1 illustrates the basic structure of the electric drive unit. FIG. 1 shows an electrical drive device 1. With this electric drive device 1, a machine component is moved or positioned. In particular, the electric drive device 1 is suitable for rotating a rotor blade of a wind power plant about its axis. In this way, the blade pitch of the rotor blade for controlling the operating state of the wind turbine can be changed.

The electric drive device 1 is fed from an AC network 3 in normal operation. Furthermore, an additional energy source, the accumulator unit 5, is present in order to operate the electric drive device 1 even in the event of a failure of the AC mains 3. This allows you to drive the corresponding machine component in a safe position.

Thus, e.g. brought the rotor blades of a wind turbine in case of failure of the AC mains 3 in the flag position.

The electric drive device 1 has an electric motor 7. This is designed as a permanently excited synchronous motor. The drive of the electric motor 7 via a drive controller 9. The drive controller 9 generates a variable three-phase AC voltage by means of an angle sensor 1 1, which is coupled to the motor shaft 12. About a contactor 14, the output terminals of the drive controller 9 are connected to the supply terminal 16 of the motor. Furthermore, the motor shaft 12 is coupled to an electrically drivable brake 18 and to a commutator unit 20.

The commutator 20 consists of a slip ring carrier 21 on a slip ring pattern is applied. Furthermore, a plurality of brushes for contacting the slip ring carrier 21 are present. Two brushes 23 and 24 are connected to the poles of the accumulator unit 5 and serve to apply a DC voltage to two mutually insulated, annular strip conductors 30 and 31 of the slip ring pattern. With this DC voltage alternately the output terminals U, V and W of the commutator 20 are acted upon. The brushes 25, 26 and 27 connected to these terminals run on a path between the two interconnects 30 and 31. Alternatively, projections of the tracks 30 and 31 protrude into the path of the track

Brushes 25, 26 and 27 in and thus periodically establish an electrical contact between the poles of the accumulator unit 5 and the outputs U, V and W of the commutator.

With such a commutator unit 20, the circulating magnetic field, which is usually generated in the synchronous motor 7 during control with three-phase current, can be represented in 6 discrete steps per period. The development of the peripheral surface of the slip ring carrier 21 is shown schematically in FIG. The brushes 25, 26 and 27 are arranged circumferentially around the slip ring carrier 21. The number of projections is matched to the number of poles of the synchronous motor 7. The total number of projections corresponds to the number of magnetic poles of the synchronous motor. The more pairs of poles the synchronous motor 7 has, the more often the energization of the terminals U ₁ V and W must change during one revolution of the rotor of the synchronous motor 7. In the example shown in FIG. 1, the commutator unit 20 is designed for a four-pole synchronous motor 7. Accordingly, each conductor 30 and 31 each have two projections. For a two-pole engine one projection would suffice. The rotor of the synchronous motor 7 and the slip ring carrier 21 are coupled so that the magnetic field currently generated in the synchronous motor 7 is offset in the switching positions of the commutator by about one step to the angular position of the rotor.

Further components of the electric drive device 1 are a safety controller 35 and another isolating contactor 15. Via the isolating contactor 15, a connection between the output connections U, V and W of the commutator unit 20 with the supply connection 16 of the electric motor 7 can be established. The safety controller 35 is connected via control lines to the separating contactors 14 and 15 and to the brake 18. Furthermore, the safety controller 35 can be used to control electromechanical actuators 36 with which the brushes 23, 24, 25, 26 and 27 can be lifted off the slip ring carrier 21. The safety controller 35 receives a status signal from the drive controller 9 on the signal line 40.

This status signal is generated by a conventional internal monitoring Circuit of the drive controller 9 generates and indicates whether the drive controller 9 is working properly. In particular, a proper function of the power semiconductors of the drive controller 9 is displayed.

In normal operation, the safety controller 35 supplies the contactor 14 with a drive current. The contactor 15 is not activated. Thereby, the contactor 14 is held in the closed position and the contactor 15 in the open position, as shown in the figure 1. In addition, the brake 18 is supplied with a drive current which causes a release of the brake 18. Another drive current is supplied to the electromechanical actuators 36 of the brushes. This drive current ensures that the

Brushes are lifted from the slip ring carrier 21. In this normal operation, the synchronous motor 7 is supplied by the drive controller 9 with electrical energy. The brake 18 is released (the electrical connection to the

Commutator 20 via the contactor 15 is disconnected. The electric motor 7 can thus be controlled within a position control or a speed control according to a default signal.

In particular, in normal operation no current flow takes place via the contact points at which the brushes 23, 24, 25, 26 and 27 touch the conductor track pattern of the slip ring carrier 21. Even if the brushes were not lifted, so the wear alone would be greatly reduced. Because the

Brushes 23, 24, 25, 26 and 27 are additionally lifted off the slip ring carrier 21 according to this embodiment, no mechanical wear takes place in normal operation.

If the safety controller 35 detects the failure of the drive controller 9 by the status signal supplied to it by the drive controller 9 on the signal line 40, it initiates an emergency operation, in which the motor 7 is moved to a safe position. When Blattverstellantrieb a wind turbine this is typically the flag position of the rotor blade. In emergency operation, the separation contactor 15 is supplied with a drive current. Isolating contactor 14 is not activated. As a result, the contactor 14 separates the electrical Connection between the drive controller 9 and the supply input 16 of the electric motor 7. The isolation contactor 15 establishes a connection between the supply connection 16 and the outputs U, V and W of the commutator unit 20. In addition, the energization of the electromechanical actuator 36 is eliminated, so that the brushes 23, 24, 25, 26 and 27 with the grinding ring pattern on the slip ring carrier 21 come into contact. The brake 18 remains initially solved.

By the commutator 20 15 stator windings of the synchronous motor 7 are connected to the DC voltage of the accumulator unit 5 with closed contactor. The rotor of the synchronous motor 7 and the stator magnetic field have an angular offset, which causes a start-up of the rotor. The rotor takes the slip ring carrier 21 of the commutator 20 with it during its rotational movement. In the synchronous motor 7, as the rotor rotates, a stepwise switched magnetic rotating field advancing the rotor in the respective direction of rotation is generated. The direction of rotation can be predetermined by the polarity of the accumulator unit 5.

In emergency operation, therefore, the electric motor 7 is supplied by the accumulator unit 5 via the commutator 20. The electric motor 7 drives the motor shaft 12 in the direction of reaching a safe position. Upon reaching the safe position switching off the electric drive device 1 can be done easily by a limit switch. After reaching the safe position, the brake 18 is brought into engagement with the motor shaft 12. Thereby, the motor shaft 12 is fixed in the safe position.

The brake 18 is initially kept open after the start of emergency operation. Only when the safe position - the flag position in the example of Windkraft- anläge - is reached, the brake is brought into engagement. Reaching the safe position is signaled by a limit switch to the safety controller 35, which then opens the contactor 15 and the brake 18 is engaged. The safety controller 35 could also be the connection between the accumulator unit 5 and the commutator 20 via a disconnect suitable contactor or the brushes 23 and 24 or 25, 26 and

27 lift off the slip ring carrier 21.

The emergency operation is terminated when the safety controller 35 detects a faultless drive controller 9 after the fault has been eliminated. As a result, the state described for the normal operation of the contactors 14 and 15, the brake 18 and the electromechanical actuator 36 is restored.

Thus, the electric motor 7 is again controlled from the drive controller 9.

The safety controller 35 can be designed as a separate electronic or electromechanical module. This is controlled by means of the status signal of the drive controller 9. However, the safety controller can also be integrated into the drive controller 9.

Instead of the contactor 15, which closes in the driven state, a contactor can be used, which is open in the activated state. This isolating contactor would be energized during normal operation and kept open. Such an isolating contactor would reliably establish the connection between the commutator 20 and the synchronous motor 7 in the event of emergency, even in the absence of a power supply for the safety controller 35.

The present invention provides an electric drive device equipped with a brushless permanent magnet synchronous motor. The permanently excited synchronous motor is controlled by a drive controller with a variable frequency alternating current. In addition, the possibility was created to drive the electric motor from a battery unit directly with direct current. For this purpose, a mechanical commutator is coupled to the rotor of the synchronous motor and a switch is provided, through which the output conductor of the commutator can be connected to the supply terminal of the synchronous motor. The present invention thus enables a reliable emergency operation of the electric drive device in a safe position using a DC power source and simplest, electromechanical switching means. LIST OF REFERENCE NUMBERS

1 Electric drive unit

3 AC mains

5 accumulator unit

7 electric motor

9 drive controller

11 rotation angle sensor

12 motor shaft

14 isolating contactor

15 isolating contactor

16 supply connection

18 brake

20 commutator unit

21 slip ring carriers

23 brush

24 brush

25 brush

26 brush

27 brush

30 trace

31 trace

35 safety control

36 electromechanical actuators

40 status signal line

U output conductor

V output conductor

W output conductor

Claims

claims

1. Electric drive device, in particular for adjusting a Blattanstellwinkels a wind turbine, with a brushless electric motor (7) which is controllable at its supply terminal (16) with a variable frequency alternating current, and with an additional DC power source (5), characterized in that the electric motor (7) is designed as a permanently excited synchronous motor, that a mechanical commutator (20) is present, which with a

Rotor of the motor (7) is coupled and which, depending on an angular position of the rotor, a pole of the DC power source (5) with one of its output conductor (U, V, W) connects, and in that a switch (15) is provided, over which the Output conductor (U, V, W) of the commutator (20) to the supply terminal (16) of the

Motors (7) are connectable.

2. Electric drive device according to claim 1, characterized in that the switch (15) is electrically controllable and that the switch (15) separates upon application of a drive current.

3. Electrical drive device according to claim 1 or 2, characterized in that the motor (7) is designed as a three-phase AC motor, and that the commutator (20) has three output conductors.

4. The method according to claim 3, characterized in that the arrangement of commutator (20) and rotor defines a direction of rotation in DC operation.

5. Electrical drive device according to one of claims 1 to 4, characterized in that a device is provided, with the Brushes (23, 24, 25, 26, 27) of the commutator (20) of a slip ring (21) of the commutator (20) are liftable.