DE102006036986A1 - Electric synchronous motor with field suppressor e.g. for hybrid-drive motor vehicle, has axially movable stator so that active length of coil in magnetic exciter-field can be varied - Google Patents

Abstract

A synchronous electric motor (1) has a stator (5) provided with at least one coil (7) and at least one rotor (10) for generating a magnetic exciter-field, in which the coil (7) is arranged at least partly in the exciter-field and during action of the coil (7) with a coil current, a torque is generated in the rotor (10). The stator (5) is axially movable, so that the active conductor length of the coil (7) located in the magnetic exciter-field of the rotor (10) is variable. An independent claim is given for a method for operating an electric synchronous motor with field-suppressor.

Description

The The invention relates to a synchronous electric motor with field weakening device according to the generic term of claim 1 and an associated method for operating an electric synchronous motor with field weakening device according to the generic term of claim 11.

regulated Drives with high required rated speeds are usually with asynchronous machines and the associated possibility a comfortable electric field weakening by means of a regulated Magnetization current component realized. This can be over a wide speed range a constant power at the motor shaft be delivered. In synchronous electric motors, although Have advantages in terms of efficiency, but depending on Design a rather narrow speed range. however, is the realization of a field weakening for development a broader speed range associated with loss of efficiency, because of the usually excited by permanent magnets main field by Generation of opposing fields, if necessary by means of an additional winding, electrically counteracted must become.

For example, from the EP 0622266 B1 a method and a device for controlling a converter-fed permanent-magnet synchronous motor in the base speed range with subsequent switching to field weakening to increase the speed range known, the motor current in the base speed range depending on a predetermined motor current setpoint and a determined motor current and in the field weakening depending on a detected pilot angle is regulated.

From the DE 4408719 C1 For example, a generator-electric motor combination is known which can be used as an electromagnetic torque converter or large-spread electromagnetic transmission, for example, in a motor vehicle having a hybrid drive structure. In this case, the generator-electric motor combination has a fixed to an input shaft hollow cylindrical generator rotor and a hollow shaft mounted on an output shaft motor rotor, the rotors are axially behind each other and distributed on its inner side in the circumferential direction permanent magnets are provided with alternating polarity , In addition, an axially displaceably arranged hollow cylindrical stator is provided with at least one short-circuit winding, which, depending on the position of the permanent magnets of the two rotors to each other, is switched. However, this is not an electric synchronous motor in the true sense, but rather a so-called electrical transmission, ie an electromagnetic torque converter.

Of the The invention is therefore based on the technical problem of providing an improved synchronous electric motor and an improved method for its To create operation, wherein the electric synchronous motor over a preferably wide speed range with possible low losses should work.

The solution the technical problem results according to the invention by things the claims 1 and 11. Further advantageous embodiments of the invention result from the dependent claims.

The invention is based on the finding that the basic principle of an electromagnetic torque converter can also be transferred to a synchronous electric motor. In the course of this occurs the surprising effect of days, that also by mechanical means, if necessary, a field weakening can be achieved, which, unlike the previously known electrical procedures, is particularly low loss executable. This is inventively achieved by an electric synchronous motor with field weakening device and a method for its operation are proposed, comprising at least one stator, which has at least one winding, and at least one rotor for generating a magnetic field exciter, wherein the winding is at least partially disposed in the exciter field and upon application of the winding with a winding current, a torque can be generated in the rotor and the stator is arranged to be axially displaceable, so that the active conductor length L _{T of} the winding, which is located in the exciting field of the rotor, is variable. It may also be a relative movement of the stator, ie, the stator is fixed and the rotor is moved. In this way, the machine geometry of an electric synchronous motor, in particular in speed-controlled operation, can be mechanically changed so that its efficiency advantages can be combined with the requirement for low-loss field weakening. In addition to the active field weakening, which allows a higher speed with the same power, a reduction of sheet metal losses at high speeds is achieved by the axial displacement of the stator and thus shortening the active conductor length of the winding. In speed-controlled operation, for example, for rotational speeds n> 0, an axial displacement of the stator can be performed. The displacement leads to a varying active coverage area of permanent magnet and winding and thus causes a weakening of the machine field, since the integrally effective magnetic flux is continuously changed depending on the stator. Thereby both the generation of the torque and the voltage formation of the motor is affected. This results in an adaptation of the voltage requirement of the electric motor over the entire operating range. Thus, the best possible utilization of the power supply unit with respect to the available currents and voltages is possible. Furthermore, when the stator is pulled out of the exciting field, the iron volume interspersed with eddy currents is reduced, since a higher frequency of the magnetic flux change causes a higher eddy current formation, especially at high rotational speeds by reducing the active iron volume by shifting the In summary, the electric synchronous motor with mechanical field weakening device according to the invention offers a plurality of advantages: a comparatively high torque, for example for starting the motor, can be achieved when the stator is fully immersed in the excitation field, while in field weakening operation - ie at mechanically pulled out of the exciting field stator - at the same power a comparatively high (rated) speed can be achieved, which is above the rated speed of the synchronous motor with fully immersed Sta Furthermore, due to the mechanical stator displacement at high rotational speeds, the iron losses due to eddy currents can be reduced, resulting in a high degree of efficiency over a wide operating range. In addition, an active power adjustment of the synchronous motor to the power supply device is possible by means of the mechanical stator displacement, without having to resort to the conventional control technique with lossy electrical, field weakening or Polumschaltungen. The control of the synchronous motor can be done via conventional power supplies. The electric synchronous motor with mechanical field weakening device according to the invention can preferably be used in all areas in which both a high starting torque and at the same time a high rated speed is required.

In an advantageous embodiment is the electric synchronous motor as a permanent-magnet brushless DC motor ("brushless DC motor ") educated. This is a commutatorless drive with the operating behavior a direct current machine, which is one with permanent magnets excited synchronous machine which is e.g. is driven with block-shaped currents. These are particularly advantageous as an electric drive in hybrid vehicles or e.g. can be used as servomotors.

In In a further advantageous embodiment, the rotor is as internal rotor or designed as an external rotor. The electric synchronous motor then comprises a device for axial displacement of the located in the inner or outer part of the synchronous motor Stators out of the excitation field of the rotor. Both are Rotor and stator preferably formed as a hollow cylinder. in principle is conceivable in the same way that instead of the stator of the Rotor has at least one winding and vice versa, the stator Permanent magnets for generating a magnetic exciter field having. Likewise is basically conceivable that instead of the stator and the rotor (or both) are formed axially displaceable.

In Another advantageous embodiment is an additional one Windungsumschaltung provided. In this way, the Possibilities of a improved adaptation to a power supply device yet be extended.

In a further advantageous embodiment, in a high-torque operation at a rotational speed n which is between 0 and a nominal rotational speed n ₁ and a nominal torque M _{n of} the synchronous motor, the stator with the maximum active conductor length L _{T_max of} the winding is immersed in the exciting field of the rotor. The synchronous motor is thus operated in the speed range between 0 and n _1, preferably with fully immersed in the rotor stator. Here, the maximum flux linkage Φ _nominal acts, and the voltage requirement of the synchronous motor increases approximately linearly with the motor speed n. With motor _rated current, the motor develops its rated torque M _n . In this way, in (speed) controlled operation, a (partial) operating strategy for high-torque operation, eg for starting, can be realized.

In a further advantageous embodiment, in a high speed operation at a speed n, which is between the rated speed n ₁ and a maximum speed n ₂ , and a torque M ~ 1 / n, the active conductor length L _{T of} the winding by axial displacement of the stator of the Shortened exciter field. In other words, in the speed range between n ₁ and n ₂ , the stator is "pulled out" axially from the rotor and the immersion depth L _T is thus reduced The flux linkage Φ decreases in such a way that the motor voltage U _KL remains constant ) the motor torque with 1 / n, whereby the power remains constant, because nominal voltage U _rated and nominal current are applied, in this way a (partial) operating strategy for the high-speed operation can be realized in speed-controlled operation.

In a further advantageous embodiment, the axial displacement of the stator is position-controlled via an actuator, the actuator preferably is formed electrically or hydraulically. However, it is also conceivable that any other forms of actuators are used, eg pneumatic actuators or combinations of the aforementioned. Further preferably, a position setpoint L _{T_soll of} the stator can be determined as a function of the current operating state of the motor. However, it is also preferably conceivable that the position setpoint L _{T_soll of} the stator can also be determined as a function of the current and / or the current voltage of the power supply _device . Thus, in the speed-controlled operation by means of the actuators, in each case that stator position that best suits the desired operating state of the synchronous motor and / or the power supply device and / or the entire system in which the synchronous motor acts as a drive unit with respect to speed, torque, power, motor voltage, motor current or efficiency corresponds to be adjusted. The supply of the synchronous motor can preferably be effected via known self-commutated power converters. The control of the power converter can then be made preferably further by a higher-level current, speed and position control.

The Invention will be described below with reference to a preferred embodiment explained in more detail. in the associated Drawings show

1 a schematic representation of the arrangement of a stator and a rotor of an electric synchronous motor according to the invention with mechanical field weakening,

2a , b, c is a schematic representation of the process of active mechanical field weakening by stator displacement and

3a , b the working range of the electric synchronous motor according to the invention with mechanical field weakening in terms of flux linkage, speed, immersion depth, motor voltage and torque.

1 schematically shows a synchronous electric motor 1 with mechanical field weakening. The electric synchronous motor 1 is designed as a permanent magnet brushless DC motor ("brushless DC motor") and includes a stator 5 which is a winding 7 has, and a rotor 10 for generating a means of permanent magnets 12 excited magnetic excitation field. The rotor 10 For example, it is designed as an external rotor, ie both rotor 10 as well as stator 5 are hollow cylindrical, wherein the rotor 10 a larger diameter than the stator 5 has and concentric to this on an axis 14 is arranged. The winding 7 is in the operating state of the synchronous motor 1 at least partially in the excitation field of the rotor 10 arranged and upon application of the winding 7 with a winding current is a torque in the rotor 10 producible, so that the rotor 10 around the axis 14 on which it is arranged, can turn what is in the 1 . 2a . 2 B and 2c through an arrow 15 is indicated. The electric synchronous motor 1 comprises a device for the axial displacement of, for example, in the inner part of the synchronous motor 1 located stator 5 from the exciting field of the rotor 10 out, with the stator 5 is arranged so axially displaceable that it is in the direction of displacement 8th can be moved. As a result, an active conductor length L _{T of} the winding 7 located in the excitation field of the rotor 10 is changeable and thus depends directly on the immersion depth of the stator 5 into the exciting field of the rotor 10 from. The axial displacement of the stator 5 is preferably position-controlled via an actuator system (not shown), wherein the actuator system can be designed, for example, electrically or hydraulically. The control of the synchronous motor 1 can be done via conventional power supply devices, for example, preferably via known self-commutated power converter (not shown). The control of the power converter can then be made preferably by a higher-level current, speed and position control (also not shown).

2a . 2 B and 2c schematically show the process of active mechanical field weakening by stator displacement. It shows 2a the stator 5 in one fully in the excitation field of the rotor 10 immersed state, 2 B the stator 5 in about halfway out of the excitation field of the rotor 10 pulled out state, ie with slight field weakening, and 2c the stator 5 in a nearly completely out of the exciting field of the rotor 10 pulled out state, ie with strong field weakening. For example, in speed-controlled operation, for example for rotational speeds n> 0, an axial displacement of the stator 5 in the direction of displacement 8th performed, the shift leads to a lower active coverage area of permanent magnets 12 and winding 7 and thus causes a weakening of the machine field of the synchronous motor 1 , As a result, both the generation of the torque and the voltage formation of the synchronous motor 1 affected. This results in an adaptation of the voltage requirement of the synchronous motor 1 over the entire operating range. Thus, the best possible utilization of the power supply unit with respect to the available currents and voltages is possible. In addition to the active field weakening, which allows a higher speed and lower torque with the same power, is due to the axial displacement of the stator 5 and thus shortening the active conductor length L _{T of} the winding, a reduction of sheet metal losses at high speeds he enough. When pulling out the stator 5 From the excitation field, the volume of iron interspersed with eddy currents is reduced. Since a higher frequency of the magnetic flux change entails a higher formation of eddy currents, especially at high rotational speeds by reducing the active iron volume by moving the stator 5 a reduction of sheet metal losses and thus a loss of field weakening can be achieved.

3a and 3b shows the operation of the electric synchronous motor according to the invention 1 (see. 1 . 2a . 2 B . 2c ) with mechanical field weakening. Saturation influences and voltage drops on windings and the like are not taken into account. In high-torque operation, ie, for example, when starting the synchronous motor 1 , is the stator 5 at a speed n, which is between 0 and a rated speed (without field weakening) n ₁ , and a nominal torque (without field weakening) M _{n of} the synchronous motor 1 with the maximum active conductor length L _{T_max of} the winding 7 into the exciting field of the rotor 10 immersed (cf. 2a ). The synchronous motor 1 So is in the speed range between 0 and n _1, preferably in completely in the exciter field of the rotor 10 immersed stator 5 operated. Here acts a maximum flux linkage, namely the nominal flux linkage Φ _nominal (see. 3a ), and the voltage requirement of the synchronous motor 1 , that is, the motor voltage U _KL , increases approximately linearly with the motor speed n. At rated motor current, the motor then develops its nominal torque M _n (see. 3b ). A high speed operation can then by axial displacement of the stator 5 from the exciting field of the rotor 10 out (cf. 2 B and 2c ) be achieved. At a speed n, which is between the rated speed (without field weakening) n ₁ and a maximum speed (= rated speed with field weakening) n ₂ , and a torque M ~ 1 / n, the active conductor length L- of the winding is shortened by stator displacement. That is, in the speed range between n ₁ and n ₂ , the stator 5 in the direction of displacement 8th axially from the field of excitation of the rotor 10 pulled out ( 2 B and 2c ) and the immersion depth or the active conductor length L _T is thus reduced ( 3a ). The flux linkage Φ decreases in such a way that the motor voltage U _KL remains constant. Thus, the motor torque M (at rated current) drops with 1 / n, whereby the power remains constant, since rated voltage U _rated and rated current applied ( 3b ). So can with fully immersed in the excitation field stator 5 a comparatively high torque, for example for starting the engine, can be achieved while in field weakening operation - ie when the stator is pulled out mechanically from the exciter field 5 - With the same power a comparatively high (rated) speed n can be achieved, which is above the rated speed n _{1 of} the synchronous motor 1 with fully immersed stator 5 lies. For controlling the Hochdrehmoment- or high-speed operation of the synchronous motor 1 can eg a position setpoint L _{T_soll} (not shown) of the stator 5 depending on the current operating state of the synchronous motor 1 and / or in dependence on the current and / or the current voltage of the power supply device (not shown) and used for control purposes.

1

synchronous motor

5

stator

7

winding

8th

shift direction

10

rotor

12

permanent magnet

14

axis

15

arrow

Φ

flux linkage

Φ _nominal

Nominal flux linkage

L _T

active conductor length

L _{T_max}

maximum active conductor length

M

engine torque (at rated current)

M _n

rated torque (without field weakening)

n

Engine speed

n ₁

Rated speed (without field weakening)

n ₂

maximum Speed (rated speed with field weakening)

U _KL

motor voltage

U _nominal

nominal voltage

Claims (13)

Electric synchronous motor ( 1 ) with field weakening device, comprising at least one stator ( 5 ), which has at least one winding ( 7 ), and at least one rotor ( 10 ) for generating a magnetic exciter field, wherein the winding ( 7 ) is at least partially arranged in the excitation field and when the winding ( 7 ) with a winding current a torque in the rotor ( 10 ), characterized in that the stator ( 5 ) is arranged axially displaceable, so that the active conductor length L _{T of} the winding ( 7 ), which are located in the exciting field of the rotor ( 10 ) is changeable. Electric synchronous motor ( 1 ) according to claim 1, characterized in that the electric synchronous motor ( 1 ) is designed as a permanent-magnet brushless DC motor. Electric synchronous motor ( 1 ) according to one of the preceding claims, characterized in that the rotor ( 10 ) is designed as an internal rotor or as an external rotor. Electric synchronous motor ( 1 ) after one the said claims, characterized in that an additional turn switching is provided. Electric synchronous motor ( 1 ) according to any one of the preceding claims, characterized in that in a high-torque operation at a speed n, which is between 0 and a rated speed n ₁ , and a nominal torque M _{n of} the synchronous motor ( 1 ) the stator ( 5 ) with the maximum active conductor length L _{T_max of} the winding ( 7 ) in the exciting field of the rotor ( 10 ) is immersed. Electric synchronous motor ( 1 ) according to one of the preceding claims, characterized in that in a high-speed operation at a speed n which is between the rated speed n ₁ and a maximum speed n ₂ , and a torque M ~ 1 / n, the active conductor length L _{T of} the winding ( 7 ) by axial displacement of the stator ( 5 ) is shortened from the excitation field out. Electric synchronous motor ( 1 ) according to one of the preceding claims, characterized in that the axial displacement of the stator ( 5 ) is position-controlled via an actuator system. Electric synchronous motor ( 1 ) according to claim 7, characterized in that the actuator is electrically or hydraulically formed. Electric synchronous motor ( 1 ) according to one of the preceding claims, characterized in that a position setpoint L _{T_soll of} the stator ( 5 ) can be determined as a function of the current operating state of the engine. Electric synchronous motor ( 1 ) according to one of the preceding claims, characterized in that the position setpoint value L _{T_soll of} the stator ( 5 ) can be determined as a function of the current and / or the current voltage of the power supply device. Method for operating an electric synchronous motor ( 1 ) with field weakening device, comprising at least one stator ( 5 ), which has at least one winding ( 7 ), and at least one rotor ( 10 ) for generating a magnetic exciter field, wherein the winding ( 7 ) is at least partially arranged in the excitation field and when the winding ( 7 ) with a winding current a torque in the rotor ( 10 ), characterized in that the stator ( 5 ) for changing the active conductor length L _{T of} the winding ( 7 ), which are located in the exciting field of the rotor ( 10 ) is moved axially. A method according to claim 11, characterized in that for achieving a Hochdrehmomentbetriebs at a speed n, which is between 0 and a rated speed n ₁ , and a nominal torque M _{n of} the synchronous motor ( 1 ) the stator ( 5 ) with the maximum active conductor length L _{T_max of} the winding ( 7 ) in the exciting field of the rotor ( 10 ) is positioned. Method according to one of claims 11 or 12, characterized in that to achieve a high speed operation at a speed n, which is between the rated speed n ₁ and a maximum speed n ₂ , and a torque M ~ 1 / n, the active conductor length L _T of Winding ( 7 ) by axial displacement of the stator ( 5 ) is shortened from the exciter field out.