DE102016218324A1 - Electric machine and method for operating an electric machine - Google Patents

Abstract

The invention relates to an electrical machine and a method for operating an electrical machine, wherein the electric machine (1) comprises a stator (2) and a rotor (3), wherein the stator (2) has at least three stator teeth (SZ1, ... , SZ6), wherein each stator tooth (SZ1, ..., SZ6) is wound with a phase windings (PW1, ..., PW6), the phase windings (PW1, ..., PW6) being wound in a neutral point (S) are electrically connected, wherein the rotor (3) has at least one rotor tooth (RZ1, RZ2), wherein the at least one rotor tooth (RZ1, RZ2) is formed such that in a energized state of the electric machine (1) has a magnetic resistance of a magnetic Circle (M) which closes via the rotor tooth (RZ1) and a stator tooth (SZ1, ..., SZ6) with an energized phase winding (PW1, ..., PW6), then is minimal when the magnetic circuit ( M) via a stator tooth (SZ1, ..., SZ6) adjacent to this stator tooth (SZ1, ..., SZ6) an energized phase winding (PW1, ..., PW6) closes.

Description

The invention relates to an electrical machine and a method for operating an electrical machine.

• a) geringes Gewicht,
• b) geringe Fertigungskosten,
• c) eine hohe Drehmomentdichte und damit geringe Getriebeuntersetzung,
• d) eine hohe Leistungsdichte,
• e) einen geringen Verschleiß sowie
• f) ein geringes Schleppmoment auf, wodurch keine Notwendigkeit von Freilauf oder Kupplung besteht.

To drive electric vehicles usually permanent magnet synchronous machines with electronic three-phase sine commutation serve. Such machines have in particular a comparison

• a) low weight,
• b) low production costs,
• c) a high torque density and thus low gear reduction,
• d) a high power density,
• e) low wear as well
• f) a low drag torque, whereby there is no need for freewheel or clutch.

• 1) eine Begrenzung des Drehzahlbereiches und der Leistung erfolgt,
• 2) eine verminderte Eigensicherheit der elektrischen Maschine besteht,
• 3) permanente Ummagnetisierungsverluste erzeugt werden und
• 4) eine Abhängigkeit von der Verfügbarkeit von Rohstoffen für die Herstellung starker Permanentmagnete besteht.

A disadvantage is the existing so-called counter electromotive force by the

• 1) there is a limitation of the speed range and the power,
• 2) a reduced intrinsic safety of the electrical machine exists,
• 3) permanent Ummagnetisierungsverluste be generated and
• 4) there is a dependency on the availability of raw materials for the production of strong permanent magnets.

• I. eine geringere Kupfer-Ausnutzung als permanenterregte Maschine, daher geringere gravimetrische und volumetrische Drehmomentdichte, Bauraumprobleme im Fahrzeug,
• II. geringere Ausnutzung des Luftspaltes im Vergleich mit einer permanenterregten Maschine,
• III. im Allgemeinen höhere Lärmentwicklung aufgrund der üblichen Block-Kommutierung,
• IV. geringere Induktivität im unausgerichteten Zustand „unaligned“, erhöhter schaltungstechnischer Aufwand zur Vermeidung von EMV-Problemen,
• V. höhere Zahl von Phasenleitungen im Vergleich mit anderen Motorkonzepten (6 statt 3 Phasenleitungen).

Further known are switched reluctance motors. These have, inter alia, the following properties:

• I. a lower copper utilization as a permanently excited machine, therefore lower gravimetric and volumetric torque density, space problems in the vehicle,
• II. Lower utilization of the air gap in comparison with a permanent-magnet machine,
• III. generally higher noise due to the usual block commutation,
• IV. Lower inductance in the unaligned state "unaligned", increased circuit complexity to avoid EMC problems,
• V. Higher number of phase lines compared to other motor concepts (6 instead of 3 phase lines).

The DE 38 131 30 C2 describes a switched reluctance motor having a plurality of independent stator phases and a rotor with a power converter to which the stator phases are connected.

The JP 2011-035995 A describes a motor controller that can operate an SR motor.

The US 2002/0125783 discloses the physical principles of an SR motor capable of providing a constant torque when operated with three sinusoidal voltages.

The JP 2003-180 059 A discloses a switched reluctance generator which may also be used as a reluctance motor. This has a star-shaped so-called armature winding and a field winding. The field winding is mandatory for magnetization of the rotor and thus required for the operation of the reluctance generator. Only by this magnetization of the rotor can be achieved in the rotation of the rotor then a change in the magnetic field in the machine, which then induces an electric field in the stator tooth windings. The document does not disclose complete coverage of adjacent stator teeth by a rotor tooth.

The technical problem arises of providing an electrical machine and a method for operating an electrical machine, which increases a gravimetric and / or volumetric torque density and reduces a circuit complexity.

The solution of the technical problem results from the objects with the features of claims 1 and 10. Further advantageous embodiments of the invention will become apparent from the dependent claims.

It proposes an electric machine. The electric machine comprises a stator and a rotor. The stator has at least three stator teeth. A stator tooth can in this case have or form a pole piece.

The stator may, for example, be substantially hollow-cylindrical, with at least three, preferably more than three, stator teeth being provided along an inner circumference of the stator. Two Stator teeth can limit at least one stator slot. Also, a stator tooth may be limited by two stator slots. These stator teeth can protrude, for example, from an inner circumferential surface of the hollow cylindrical stator. The stator may in particular be designed as a stator of a so-called salient pole machine, wherein a salient pole corresponds to a stator tooth.

Each stator tooth is wrapped in a phase winding. Thus, the electric machine comprises phase windings. In particular, the electric machine comprises at least three mutually different phase windings. The electric machine can in this case be an m-phase machine, where m is greater than or equal to 3 and wherein each phase is associated with at least one phase windings.

The stator tooth associated with a phase may thus designate a stator tooth wound with a phase winding associated with the corresponding phase. One phase may also be associated with more than one phase winding, each of these phase windings wrapping stator teeth different from each other. Also, a phase winding can wrap over more than one stator tooth.

The phase windings can be electrically connected in a neutral point. The phase windings can in this case in particular be electrically connected such that the phases are electrically connected in a neutral point. In other words, the phase windings or the phases are connected in a star connection.

In particular, adjacent phase windings can be arranged offset from one another by 360 ° / m / n. Here, n may denote the number of stator teeth per phase. A stator tooth can form a pole. Thus, the total number of stator poles can be m × n. Adjacent phase windings may be arranged in particular adjacent to each other along the inner circumference. Thus, stator teeth wrapped by these adjacent stator windings may also be arranged at 360 ° / m / n adjacent each other. Neighboring phase windings may in particular be phase windings which are assigned to different phases from one another. In particular, phase windings can be arranged along the inner circumference such that m phase windings that follow one another along the inner circumference are each assigned to one of the m phases.

The phase windings may be arranged according to a winding scheme of a permanent magnet synchronous machine.

The rotor has at least one rotor tooth. Preferably, the rotor has more than one rotor tooth. The rotor may e.g. be formed substantially cylindrical, wherein along an outer circumference of the rotor, the at least one rotor tooth is provided. The rotor tooth can e.g. protrude from an outer surface of the rotor. In this case, one rotor tooth or several rotor teeth can limit at least one rotor groove. Also, a rotor tooth may be limited by two rotor grooves. However, this is not mandatory. The rotor tooth may also be formed as a portion of the rotor whose surface forms part of the outer surface of the rotor, the portion having a predetermined magnetic conductivity. This may in particular be higher than the magnetic conductivity of a central portion of the rotor.

The rotor, in particular the rotor tooth, may be formed from a non-permanent magnetic material. The rotor tooth can preferably be formed from a magnetically conductive material. A rotor tooth can form a rotor pole.

The electrical machine can be designed as an internal rotor machine. However, it is also conceivable to design the electrical machine as an external rotor machine. Both stator and rotor may be laminated.

Next, the at least one rotor tooth is formed such that in a current-fed state of the electric machine, a magnetic resistance of a magnetic circuit which closes on the rotor tooth and a stator tooth with a current-carrying phase winding, then is minimal when the magnetic circuit via a to this stator tooth adjacent stator tooth with a (also) energized phase winding closes. This minimum magnetic resistance can arise in particular when the rotor is in a first angular position. The magnetic circuit closes here via no other rotor tooth.

The magnetic circuit may denote a closed path, in particular the course of a field line, wherein at least a portion of the path is arranged respectively in the stator teeth and in the rotor tooth. Further sections of the path can be arranged in the air gap and in the stator body.

The energized state of a phase winding may indicate a state in which a current flows through the phase winding. Also, the energized state may indicate a state in which a current flows through the phase winding whose amplitude is larger than a predetermined threshold. Specifically, the energized state may designate a state that sets at a timing of a block commutation operation of the electric machine.

In particular, if the electric machine is a three-phase machine, the block commutation mode may be a so-called 120 ° rectangular commutation mode. In this case, a current flows through phase windings associated with two of the three phases, while the phase windings associated with the remaining phase are de-energized. After every 60 ° (electrical), the current flow is switched to the next phase pair.

In this case, different energization states can exist. In different energizing conditions, e.g. each different phase windings are energized. As a result, different stator teeth are also wound with current-carrying phase windings depending on the state of energization.

Thus, an energization state may be associated with an angular position of the rotor in which previously explained minimum magnetic resistance of the magnetic circuit, which closes via the rotor tooth and the stator teeth with a current-carrying phase winding, is provided.

The first angular position may be associated with a first energizing state. Further angular positions can be assigned to further energization states.

In other words, the at least one rotor tooth is designed such that the rotor tooth, in particular in the first angular position, minimizes the magnetic resistance of the magnetic circuit, which in the energized state via two adjacent stator teeth each with energized phase windings and the at least one rotor tooth , Thus, in the first angular position of the rotor, the magnetic resistances of all the different magnetic circuits closing in the energized one over the first energized stator tooth may be larger.

Thus, in the first angular position, the rotor tooth magnetically short-circuits the energized phase windings of the adjacent stator teeth or maximizes their magnetic coupling or minimizes the reluctance between them.

In yet other words, the at least one rotor tooth is designed such that a state of minimal reluctance is achieved in the first angular position.

If the electric machine comprises a plurality of rotor teeth, the magnetic resistances of a plurality of corresponding magnetic circuits may be minimal in the first angular position of the rotor.

The magnetic resistances of other magnetic circuits, which close over a rotor tooth or a portion of a rotor tooth and a stator tooth not covered by the rotor tooth or a portion of such an uncovered stator tooth, may hereby be greater than the magnetic resistance of the magnetic circuit via the rotor tooth, the first stator tooth and the stator tooth adjacent to the first stator tooth. In particular, the magnetic resistances of other magnetic circuits, which close over a first stator tooth, a counter to the direction of rotation to the first stator tooth immediately adjacent stator tooth and a rotor tooth, may be greater than the magnetic resistance of the magnetic circuit extending over the rotor tooth, the first Statorzahn and in the direction of rotation to the first stator tooth immediately adjacent stator tooth closes. In particular, the magnetic resistances of these other magnetic circuits can be maximum precisely if the magnetic resistance of the magnetic circuit, which closes via the rotor tooth, the first stator tooth and a stator tooth immediately adjacent to the first stator tooth in the direction of rotation, is minimal.

The electric machine differs from a permanently excited synchronous machine in that no rotor made of permanent magnetic material is needed. From a switched Reluctance machine, the electrical machine differs in that less phase cables are needed to operate. In a three-phase machine, for example, only three phase lines are required instead of the four or six phase lines required in a three-phase reluctance machine. As will be explained in more detail below, the proposed machine allows a higher gravimetric and volumetric torque density with a comparable space than the switched reluctance machine.

The proposed machine may also be referred to as a switched reluctance motor in star connection (SRS).

According to the invention, a surface of the at least one rotor tooth completely covers the pole faces of the adjacent stator teeth with current-fed phase windings. Thus, a first part of the surface of the rotor tooth covers the entire pole face of the first stator tooth with energized phase winding and another part of the surface of the rotor tooth, the entire pole face of the adjacent stator tooth with energized phase winding. Thus, a rotor pole may be formed with respect to a stator pole as a double pole.

This may be the case, in particular in the first angular position.

A hidden portion of the pole face of a stator tooth may denote a portion opposite to which a portion of the surface of the rotor tooth is located relative to the air gap between stator and rotor. Thus, an air gap width between the hidden portion of the pole face of the stator tooth and the rotor may be minimal, the air gap width being e.g. is measured along a normal to the hidden portion of the pole face.

The feature that a surface of the at least one rotor tooth completely covers the pole faces of the adjacent stator teeth with energized phase windings may hereby be equivalent to the feature that the at least one rotor tooth is designed such that in a energized state of the electrical machine a magnetic resistance of a magnetic circuit, which closes via the rotor tooth and a first stator tooth with a current-carrying phase winding, then is minimal, when the magnetic circuit closes over a stator tooth adjacent to the stator tooth with a current-fed phase winding.

This results in an advantageous manner a simple production of the electric machine.

In a preferred embodiment, an angle between a tangent at a point, in particular at any point or point, an outer circumferential surface of a stator tooth and a radial groove centerline of the stator groove defined by the outer circumferential surface has a value between 0 (inclusive) and π / 8 (inclusive). The angle may in particular be the angle in a cross-sectional plane which is oriented perpendicular to the axis of rotation of the rotor.

In other words, the stator tooth can thus be arranged and / or formed such that the angle between the tangent and the radial groove center line has a value between 0 and π / 8. The tangent and the radial groove center line can be arranged or run in the illustrated cross-sectional plane.

A tangent may in this case be a straight line which touches the outer lateral surface at least, but not necessarily exclusively, in the point of the outer lateral surface. Furthermore, the tangent can be oriented perpendicular to a surface normal of the outer lateral surface at the contact point.

A stator tooth can in this case have a pole core section. Furthermore, a stator tooth can also have or form a pole shoe section. However, this is not mandatory. A pole piece section may e.g. designate a portion of the stator tooth in which a width of the stator tooth increases in the illustrated cross-sectional plane toward the axis of rotation of the rotor. The width may be a width along a circumferential direction.

The outer surface of the stator tooth may denote a surface defining a stator slot. In other words, the outer circumferential surface may be part of a wall surface of a side wall of the stator groove. The stator is in this case arranged between two adjacent stator teeth.

The radial groove center line of the stator groove bounded by the outer lateral surface may in this case denote a line which extends in the radial direction from the axis of rotation of the rotor to a stator yoke section, wherein the stator yoke section likewise delimits the stator slot, in particular in the cross-sectional plane explained above. For example, the radial groove centerline may extend from a center of the stator yoke portion between the two adjacent stator teeth to the axis of rotation of the rotor, particularly in the cross-sectional plane previously discussed.

Thus, therefore, the angle between a tangent at any point of the outer circumferential surface of the stator tooth and the radial groove center line of the limited by the outer circumferential surface Statornut have a value between 0 and π / 8.

In this way, the lowest possible magnetic resistance of the magnetic circuit can be achieved in an advantageous manner, which closes on the rotor tooth, the first stator tooth and the stator tooth adjacent to the first stator tooth. This in turn advantageously enables a uniform development of the torque or a reduction of torque fluctuations and the provision of a high efficiency.

In a further embodiment, the phase windings are electrically connected in a neutral point. This has already been explained above. The connection of the phase windings in a star point advantageously allows the operation of a multi-pole electric machine with a minimum number of phase lines. Thus, e.g. an electric machine with six stator poles are operated with 3 phase cables.

In a further embodiment, the stator 3 × n stator teeth, wherein the rotor has n rotor teeth. Here, n can be an integer positive number, ie n = 1, 2, .... In this case, the electric machine may be, in particular, a three-phase machine (m = 3). For example, the stator 6 Stator teeth and the rotor 2 Have rotor teeth.

This advantageously results in a higher gravimetric and volumetric torque density than in a switched reluctance machine according to the prior art and a higher gravimetric volumetric power density.

In a further embodiment, one of the 1 × n rotor teeth each covers an angular segment of 4π / (3 × n) of the air gap and one of the 3 × n stator teeth each covers an angular segment of π / (3 × n) of the air gap. A covered portion of the air gap between the stator and the rotor may denote a portion interposed between the respective stator tooth and rotor and the opposite portion of the surface of the rotor and the stator, respectively. This results in an advantageous manner a low, in particular a lowest possible, magnetic resistance and thus a high efficiency.

In a further embodiment, the stator teeth each form a pole piece. This may mean that a width of the stator tooth increases towards the free end of the stator tooth and / or is maximum at the free end. The width may be along the circumference, e.g. along an inner circumference of the stator in an inner rotor machine or along an outer circumference of the stator in an external rotor machine are detected.

This results in an advantageous manner, a higher efficiency due to the lower magnetic resistance.

In an alternative embodiment, the stator 3 × n stator teeth, with the rotor 2 × n rotor teeth. For example, the stator 6 Stator teeth and the rotor 4 Have rotor teeth. Here, n can be an integer positive number, ie n = 1, 2, ....

This results in an advantageous manner, a further increase in the torque density, in particular in comparison to the previously explained embodiment.

In a further embodiment, each one of the 2 × n rotor teeth covers an angular segment of 2π / (2 × n) of the air gap and each of the 3 × n stator teeth an angular segment of 2π / (6 × n) of the air gap. This results in an advantageous manner a high, in particular the highest possible, torque density. This can be 50% higher compared to a switched reluctance motor with the same number of slots.

In a further embodiment, the stator teeth do not form a pole piece. This may mean that a width of the stator tooth towards the free end of the stator tooth is reduced or remains constant. Alternatively or cumulatively, the width at the free end may be minimal.

This results in an advantageous manner a more compact design.

Further proposed is a method for operating an electrical machine according to one of the embodiments described in this disclosure, wherein the phase windings of the electrical machines are energized in a commutation mode. Preferably, the commutation operation is a block commutation operation. In block commutation mode, the phase windings can be supplied with time-varying voltage blocks. Alternatively, the commutation operation may be a sine commutation operation.

In block commutation mode, depending on the time, the phase windings are energized by different stator teeth. In different energization states, the magnetic resistance is minimal for different magnetic circuits, with the various magnetic circuits closing via the at least one rotor tooth and the stator teeth with the correspondingly energized phase windings. If different energization states follow one another in time, the rotor will change the angular position in order to minimize the reluctance. Thus, the rotor is rotated from a first angular position in the first Bestromungszustand in a further angular position when the Bestromungs state changes to another Bestromungszustand, which is assigned to this further angular position. In other words, the rotor will rotate to an energized state dependent angular position, the angular positions of different energization states being different from each other.

Some technical explanations are given below, in particular also for comparing a permanent-magnet synchronous machine (PMSM), a switched reluctance machine (S / R) and a proposed electric machine (SRS).

The following explanations relate to an analytical model that can be used to compare the achievable torque and power density of the various types of machines.

First, the power and torque density of a permanent-magnet synchronous motor (PMSM) can be determined. The maximum power output of an electric motor with permanent excitation results at a certain maximum speed ω _m and a maximum torque M, which can apply the engine at this speed. P (ω) = π M _m (1.1)

For the sake of simplification, it is assumed that the maximum rotational speed ω _{m is} reached when the electromagnetic opposing force of the motor is the same as the intermediate circuit voltage U _ZK . The mutual induction U _EMK generally results U _EMK = dΦ / dt (1.2) where Φ denotes the flow.

N_Z

... die Zahl der Windungen auf dem einzelnen Statorzahn,

A_Core

... den magnetisch wirksamer Querschnitt des Eisenkerns

bezeichnet. Die Zahl der betroffenen Windungen und damit die Konstante c_w hängen vom Wicklungsschema und von der Schaltung der elektrischen Maschine (z.B. Stern/Dreieck) ab. Bei einem PMSM-Motor mit sechs Nuten und konzentrierten Wicklungen in Sternschaltung beispielsweise gilt: c_w = 4. In a phase winding one can generally assume that applies Φ = BA _Core c _w N _Z (1.3) in which

N _Z

... the number of turns on the single stator tooth,

A _core

... the magnetically effective cross section of the iron core

designated. The number of windings affected and thus the constant c _w depend on the winding scheme and on the circuit of the electrical machine (eg star / delta). For example, in a PMSM motor with six slots and concentrated star-connected windings, c _w = 4.

The time for the change in the magnetic flux density from B _max to -B _max results from the Ummagnetisierungfrequenz. This can be calculated from the speed of the machine and the number of poles N _{P of} the pole wheel approximately as follows:

d.h. für die maximale Drehzahl gilt:

Inserting equations (1.4) and (1.3) in (1.2) yields the following approximation formula:

ie for the maximum speed applies:

wobei I den Phasenstrom bezeichnet. For the sake of simplification, the torque constant that results from the design of the PMSM is to be calculated for the torque. The derivation of an analytic expression for k _i is omitted. The maximum power of the machine then results in:

where I denotes the phase current.

Before considering the conditions in the switched reluctance motor, this section will consider the maximum possible current in the motor. The same applies to the electrical circuit:

Here, V _m denotes the so-called magnetic stress and R _m the magnetic resistance. It generally applies: Φ = BA _Core

mit

l_air

... Breite des Luftspalts,

N_w

... Zahl der Windungen im magnetischen Kreis,

A_Pole

... Polfläche,

µ₀

... Permeabilität des Vakuums,

µ_r

... relative Permeabilität des Statorzahnmaterials.

And especially when the magnetic circuit saturates: Φ = B _max A _core (2.2) V _m = NI (2.3) and, under the simplifying assumption that only the air gap is decisive for the magnetic resistance, applies

With

l _air

... width of the air gap,

N _w

... number of turns in the magnetic circuit,

A _pole

... pole surface,

μ ₀

... permeability of the vacuum,

μ _r

... relative permeability of the stator tooth material.

In a switched reluctance motor, the pole face is exactly as large as the magnetically effective cross section of the stator tooth. This is generally not the case with a machine with pole pieces. Therefore, a factor C _{m is} introduced which determines the relationship between the area of the pole piece and the magnetically active area A _core .

Equations (2.2), (2.3) and (2.4) inserted in (2.1) show:

Equation (2.5) allows the pole face and the magnetically effective cross section to be eliminated from the equation:

Switching to the electromagnetic voltage results in the maximum possible magnetic tension:

Considered below is the switched reluctance motor, which may also be referred to as a switched reluctance machine. In particular, the calculation for the maximum torque and the maximum speed for a switched reluctance motor is derived.

wobei L die Induktivität, N_N die Zahl der Nuten und dφ die Änderung des Rotorwinkels/Arbeitsschritt bezeichnen. Die Zahl der Nuten kann gleich der Zahl der Statorzähne sein. For the torque applies because of the conservation of the magnetic co-energy:

where L is the inductance, N _{N is} the number of slots, and dφ is the change in rotor angle / operation. The number of grooves can be equal to the number of stator teeth.

As an approximation, that

Where the symbol "aligned" designates the condition of the closed magnetic circuit and "unaligned" the condition of the open magnetic circuit. N _Z is the number of stator teeth, R _mSR is the magnetic resistance of the S / R motor in the aligned state, and φ _SR is the rotor angle of the S / R motor.

Substituting equation (3.4) into equation (3.3) yields:

Substituting equation (3.5) into equation (3.2) and (3.1)

Taking into account equation (2.6), the maximum torque of the machine follows:

A more compact representation of equation (3.7) can be derived by using equation (2.4):

It is based on the idealized assumption that the pole face covers the entire angle segment. Therefore:

Where r _{ls is} the radius of the air gap and l _{s is} the length of the stator.

Furthermore, applies

Inserted in (3.8) follows

The following applies: C _mSR = 1, so that the following expression results after shortening:

To calculate the maximum speed, equations (1.2) and (1.3) are again assumed. Instead of (1.4), there is another expression for an S / R engine. It should be noted that with the S / R motor, the number of slots and not the pole is decisive for the re-magnetization speed. Whenever a phase winding is energized, the rotor continues to move ^-1 revolutions about (2N _N). This happens within a time Δt and the faster, the higher the speed of the motor is. Instead of (1.4), therefore, the time for the remagnetization from 0 to B _max applies:

Since, in contrast to equation (1.5) in an S / R motor, the magnetic flux density of not -B _max and B _max increases but only from 0 to B _max, following instead of Equation (1.5):

For the maximum speed of the motor, instead of equation (1.6):

Equation (3.14) can be further simplified by expressing the magnetically effective cross-section A _core by equation (3.9):

For the maximum power, taking into account equation (3.11)

Aus Gleichung (3.15) ist ersichtlich, dass die Möglichkeiten zur Leistungssteigerung eines S/R Motors ganz allgemein begrenzt sind. Konstruktive Maßnahmen wie eine Vergrößerung der Statortiefe, eine Erhöhung der Zahl der Nuten oder des Luftspaltradius sind allein geeignet das maximale Drehmoment, nicht jedoch die Leistung zu erhöhen. Die Möglichkeiten zur Erhöhung der Leistung beschränken sich auf:

• 1. Eine Vergrößerung des Luftspaltes, was mit einer Verringerung des Wirkungsgrades einhergeht,
• 2. eine Erhöhung der Zwischenkreisspannung,
• 3. eine Änderung des Wickelschemas (Beeinflussung von c_wSR und/oder N_Z) und entsprechend Verwendung eines Umrichters, der größere Phasenströme liefern kann.

In practice, N _N and c _{wSR are} related. Since the maximum current supplied by the inverter is limited, the winding scheme usually provides for connecting all tooth coils of a phase in series, so that:

It can be seen from equation (3.15) that the possibilities for increasing the performance of an S / R engine are generally limited. Constructive measures such as increasing the depth of the stator, increasing the number of slots or the air gap radius alone are capable of increasing the maximum torque, but not the power. The possibilities to increase the performance are limited to:

• 1. An enlargement of the air gap, which is associated with a reduction in the efficiency,
• 2. an increase in the intermediate circuit voltage,
• 3. A change in the winding _scheme (influencing c _wSR and / or N _Z ) and according to the use of an inverter that can deliver larger phase _currents .

• – In Kombination mit großen Stromstärken sind EMV-Probleme zu erwarten.
• – Ein Tiefsetzsteller eine Anordnung zur Spannungswandlung, welche die Drossel als Energiespeicher nutzt. Ist die Induktivität der Spule zu gering um die notwendige Energie zu speichern, so erfordert es das Wirkprinzip des Tiefsetzstellers, die Schaltfrequenz zu erhöhen, was die zu erwartenden EMV-Probleme verstärkt. Zudem sinkt der Wirkungsgrad des Tiefsetzstellers, da jeder Schaltvorgang Schaltverluste im Umrichter erzeugt.

With regard to 3, note that the inverter and motor coil form a buck converter. Its choke has an extremely low inductance in the case of the S / R motor in the state "unaligned", which entails the following:

• - In combination with high currents, EMC problems are to be expected.
• - A buck converter an arrangement for voltage conversion, which uses the throttle as energy storage. If the inductance of the coil is too low to store the necessary energy, it requires the operating principle of the step-down converter to increase the switching frequency, which amplifies the expected EMC problems. In addition, the efficiency of the step-down converter decreases because each switching process generates switching losses in the converter.

Another implication of Equation (3.15) is that, for example, the length of the stator and thus the weight of the motor does not directly affect the maximum power output of the motor. Thus, the gravimetric power density can be increased by reducing the length of the stator, with the motor delivering less torque each but achieving a higher speed. The possibilities here are limited by the fact that the re-magnetization losses increase disproportionately with increasing speed and that the reduction ratio can not be chosen arbitrarily large in practice.

wobei

f_core

... Ummagnetisierungsfrequenz

In order to be able to take the magnetization losses into account, the following approximation formula is assumed:

in which

f _core

... re-magnetization frequency

wobei

m_Fe

... Masse des Kernmaterials, welches von der Ummagnetisierung betroffen ist

k_1,5T

... Verlustziffer des verwendeten Kernmaterials bei 1,5 Tesla

The Ummagnetisierungsfrequenz increases with the number of poles and the speed of the motor

in which

m _Fe

... mass of the core material, which is affected by the magnetization reversal

k _1.5T

... Loss number of the core material used at 1.5 Tesla

r_A

... Außendurchmesser des Stators

The following estimation formula is used for the mass of the core material: m _Fe ≈ A _Core (r _A - r _ls ) N _N ρ _{F e}

r _A

... outer diameter of the stator

The magnetically active cross section A _core or the iron cross section can in turn be expressed by (3.9):

Substituted in equation (3.16) we get:

Now consider an SRS engine with six slots and two double poles. The rotor double pole conceals two adjacent stator teeth of the stator in the SRS principle.

Since two magnetic circuits are closed simultaneously in the SRS motor, equation (4.1) and equation (3.1) differ by a factor of two.

With the same number of slots, the following applies:

In order to determine L _unaligned , the magnetic circuits belonging to the phase windings of the adjacent stator teeth (winding A and winding C) are considered separately. This results in subsystem 1 (winding A) and subsystem 2 (winding C).

Subsystem 1 and subsystem 2 are electrically connected in series and magnetically connected in parallel. Due to the electrical series connection results in:

Equation (3.12) and Equation (3.9) used in Equation (3.8) gives:

Equation (4.6) inserted in equation (4.1) yields:

In order to be able to achieve a more compact form by means of equation (2.6), we have to shorten it and expand it by a factor of 4/4:

Due to the approximately twice the pole surface, it is assumed:

By means of equations (4.3) and (4.9), equation (4.8) can be brought into a form which allows the direct comparison with the S / R motor:

A more compact representation of Equation (4.8) can again be obtained by means of Equation (2.4):

weiterhin gilt

It is based on the idealized assumption that the pole face covers the entire angle segment. Therefore:

continues to apply

Substituted in equation (4.11) follows

Shortening yields:

L_unaligned2 = 0 (4.17) If one compares equations (3.11) and (4.14) one recognizes that the torque of the SRS with the same number of slots is higher than the torque of the S / R engine, as long as

L _unaligned2 = 0 (4.17)

A suitable choice is, for example, C _mSRS = 0.9. The maximum value is C _mSRS = 1. With a suitable choice of C _mSRS = 0.9 a 21.5% higher torque is generated than with the S / R motor with the same number of slots. At the maximum value C = 1 _MSRS to an increase of up to 50% yields.

To calculate the maximum speed, the equation (1.2) and (1.3) are used again. Instead of equation (1.4), another expression results for an SRS engine. It must be remembered that the number of slots in the SRS motor and not the pole is decisive for the rate of magnet reversal.

Whenever a motor coil is energized, the rotor moves to N ^-1 _N turns on, that is to say twice as fast as the S / R motor. In turn

this happens within a time Δt and the faster, the higher the speed of the motor:

Now, in phase connection, two phase windings of different phases flow through the phase current in series. Their electromagnetic counterforce is therefore to sum. Again, the previously discussed subsystem 1 and subsystem 2 are considered. The magnetic flux density increases in subsystem 1 from B _max / 2 to B _max , while in subsystem 2 it increases from 0 to B _max . For a SRS motor with six slots or six stator teeth, the result is: c _wSRS64 = 4, because the electromagnetic counterforce is induced in four teeth. Since in the two of the four stator teeth - those assigned to subsystem 1 - the magnetic flux density increases only half as fast as in the other two Stator teeth, which are assigned to subsystem 2, an additional correction factor of ¾ must be introduced. Instead of equation (3.13) follows

For the maximum speed of the motor, instead of (2.9):

• – aufgrund der Sternschaltung gilt: c_wSRS = 2c_wSR
• – für den magnetisch wirksamen Querschnitt gilt: A_CoreSRS = 2C_mA_CoreSR
• – der Luftspaltradius soll gleich bleiben (nach Optimierung ist der Luftspaltradius eines S/R Motors im Vergleich zu einem SRS-Motor größer, insbesondere bei kleiner Nutenzahl)

To allow a direct comparison between the maximum speed of the S / R and the SRS engine, the following assumptions are made:

• - due to the star connection: c _wSRS = 2c _wSR
• - for the magnetically effective cross section: A _CoreSRS = 2C _m A _CoreSR
• - The air gap radius should remain the same (after optimization, the air gap radius of an S / R engine is larger compared to an SRS engine, especially with a small number of slots)

The comparison of equations (4.20) and (3.9) yields

Equation (4.20) can be further simplified by _replacing the magnetically effective cross-section using (3.9) and the relationship A _CoreSRS = 2C _m A _CoreSR :

For the maximum power, equations (4.21) and (4.14) give the following expression

The direct comparison with equation (3.15) taking into account c _wSRS = 2c _wSR yields:

Equation (4.23) shows that an SRS engine outputs less maximum power than an S / R engine, depending on C _m .

Assuming that the increase in power density occurs by increasing the speed, it should be noted that the maximum power is delivered at a lower speed compared to the S / R motor. A lower speed leads to a lower Ummagnetisierungsfrequenz, wherein the proportionality factor is the number of poles. Due to the smaller number of poles, the magnetic reversal frequency is particularly low with the SRS 6x / 2x.

This gives a large margin for improving the power density, since the Ummagnetisierungsfrequenz enters disproportionately in the iron losses. Thus, with an SRS with 6 stator teeth and 4 rotor teeth (SRS 6/4), a higher power density can be achieved than with the S / R motor.

An increase in power density can be achieved by two measures that must be carried out simultaneously: using a converter with greater ampacity, reducing the number of turns per tooth (N _Z ).

In contrast to the S / R motor, the minimum inductance of the SRS is half of its maximum phase inductance. Compared to the S / R engine no EMC problems are to be expected.

With regard to the re-magnetization losses, again based on equation (3.16), an SRS with 6 stator teeth and 2 rotor teeth (SRS 6/2) operates at half as high a re-magnetization frequency due to the smaller number of poles. However, the pole face is twice as large. Thus, the mass of nuclear material affected by magnetic reversal is twice as large: m _Fe ≈ A _Core (r _A - r _ls ) N _N ρ _{F e}

The magnetically effective cross section, which can also be referred to as iron cross section, can be expressed by equation (3.9) and A _CoreSRS = 2C _m A _CoreSR :

Substituted in equation (3.16)

In the following a proposed electric machine with 6 stator teeth and 4 rotor teeth (SRS 6/4) is considered. With this design, as with the S / R motor, C _m = 1 can be selected, resulting in a 50% higher torque density and the same power density. However, as with the S / R motor, the reversal frequency is twice as high.

Again, it can be assumed from equation (4.8):

With the SRS 6/4, the magnetic resistance and the angle of rotation per work step change compared to the SRS 6/2: due to the smaller pole area, the magnetic resistance is doubled, due to half the step size, Δφ _{SRS is} halved.

Both effects compensate each other so that the maximum torque continues to be Equation (4.14). With C _m = 1, the maximum torque of an SRS 6/4 is exactly 50% higher than the maximum torque of an S / R 6/4 engine.

Since the SRS simultaneously closes two magnetic circuits whose induced voltage is added in series (c _wSRS = 2c _wSR ), the following equation (4.19) can be used for the calculation of the EMF equation (3.13):

Taking equation (3.9) into account, equation (4.21) yields:

For the maximum power follows from equations (4.14) and (5.1):

The maximum power is therefore the same for the SRS 6x / 4x with the same parameters as for the S / R motor.

Assuming that the increase in power density is achieved by increasing the speed, it should be noted that the maximum power compared to the S / R motor is delivered at a 1/3 lower speed. A lower speed and thus lower Ummagnetisierungsfrequenz give more scope to improve the power density, since the Ummagnetisierungsfrequenz enters disproportionately in the iron losses. Thus, with a SRS 6/4, a higher power density can be achieved than with the S / R motor, but less than with the SRS 6/2.

For the Ummagnetisierungsverluste is again assumed by equation (3.16). A count of the re-magnetization processes shows that the re-magnetization frequency is just as high as in the S / R engine, so that the corresponding iron losses are approximately equal:

In the following, motor designs in different technologies PMSM, S / R and SRS are compared.

• – Maximales Drehmoment: 40 Nm
• – Maximale Leistung: 7,5kW
• – Maximale Drehzahl: 1700/Min
• – Der Bauraum ist wie folgt festgelegt: Außendurchmesser Stator: 180mm; Länge Stator: 75mm
• – Die Motoren werden an einer Zwischenkreisspannung von 48V betrieben.
• – Der Umrichter liefert einen maximalen Phasenstrom von 240A.

Initial situation can form a drive solution for an electric vehicle based on a PMSM with the following parameters:

• - Maximum torque: 40 Nm
• - Maximum power: 7,5kW
• - Maximum speed: 1700 / min
• - The installation space is defined as follows: Outer diameter Stator: 180mm; Length of stator: 75mm
• - The motors are operated at a DC link voltage of 48V.
• - The inverter supplies a maximum phase current of 240A.

The design of the motors requires a suitable choice of the air gap radius. This should be chosen so that there is enough space in the slots for the phase windings. The air gap radius was approximately determined by means of a calculation table, which is not listed here. In addition, a buffer was included to ensure manufacturing feasibility. The result of the determination of r _ls is listed in the table, which makes the design computationally comprehensible. The maximum current of each design is adjusted in each case so that the saturation flux density B _max = 1.2T is reached. A reference design of a PMSM with 18 slots or 18 stator teeth and 16 poles or 16 rotor teeth is available.

Table 1 shows various engine types. The first number in the motor type designation denotes the number of stator teeth (number of slots) and the second number the number of rotor teeth (number of poles). Table 1: Torque and power of various motor designs description r _ls (m) c _w N _Z N _N C _m A _Core [m ^ 2] π _m [1 / min] M _max [Nm] P _max [kW] PMSM 18/16 0.05 12 3 18 0.9 0.00118 1768 40.0 7.4 S / R 18/15 0.05 6 4 18 1 0.00065 4244 12.9 5.7 SRS 18/6 0.05 12 4 18 0.9 0.00118 3144 15.7 5.2 SRS 18/12 0.05 12 4 18 1 0.00065 2829 19.3 5.7 S / R 42/35 0.053 14 4 42 1 0.00030 1716 31.8 3.3 SRS 27/18 0.053 18 4 27 1 0.00046 1780 30.7 5.7 SRS 30/10 0.053 20 4 30 0.9 0.00075 1780 27.3 5.1 SRS 36/10 0.053 24 4 36 0.9 0.00062 1483 33.2 5.2 SRS 36/20 0.053 24 4 36 1 0.00035 1335 40.9 5.7

• – S/R Motor: 42 Nuten
• – SRS 6/2: 30 Nuten
• – SRS 6/4: 27 Nuten

Table 1 shows that the distance between PMSM and switched reluctance motor is reduced with respect to the torque density by means of the SRS principle. An 18-slot S / R motor achieves 32% of the torque of a PMSM, and an SRS 18/12 achieves 48% of the torque of a comparable PMSM. The maximum speeds are higher than the comparable PMSM. At comparable maximum speed, a maximum reluctance motor (S / R or SRS) achieves a maximum torque of 75% compared to the PMSM. With the SRS 6x / 2x the maximum torque is lower, since the following applies: C _m <1. The following key numbers must be realized in each case:

• - S / R engine: 42 slots
• - SRS 6/2: 30 slots
• - SRS 6/4: 27 slots

An SRS 36/24 achieves the same volumetric torque density as the 18-slot reference motor in PMSM technology. The expected gravimetric torque density is lower than with a PMSM, since twice as many copper windings must be provided.

To replace the reference motor, increase the power density of the drive solution. This is possible by using an inverter with increased current carrying capacity (see Table 2).

Table 2 Modifying the winding scheme on the SRS 36/20 and increasing the current carrying capacity results in the same level of power and torque as PMSM 18/16 description r _ls (m) c _w N _Z N _N C _m A _Core [m ^ 2] π _m [1 / min] M _max [Nm] P _max [kW] PMSM 18/16 0.05 12 3 18 0.9 0.00118 1768 40.0 7.4 SRS 36/20 @ 320A 0.053 24 3 36 1 0.00035 1780 40.9 7.6

• – Um das Zieldrehmoment zu erreichen soll ein Untersetzungsgetriebe Verwendung finden.
• – Die maximale Drehzahl des Motors soll 15000/Min nicht überschreiten, um die zusätzlichen Aufwände für Lagerung und Lüftung gering zu halten.
• – Aufgrund des passiven Kühlungskonzeptes sollen die Eisenverluste im Motor 4% der Maximalleistung des Motors nicht überschreiten.
• – Damit alle betrachteten Varianten dasselbe Leistungsniveau erreichen, wird für alle S/R und SRS ein Umrichter mit erhöhter Stromtragfähigkeit verwendet. Die Zahl der Wicklungen beträgt damit bei PMSM, SRS und S/R N_Z = 3.

For the given engine in PMSM technology, the power density should be increased. Due to installation space and cooling, the following boundary conditions may apply: the stator diameter should remain the same, but the length of the stator alone should be changed.

• - To achieve the target torque to find a reduction gear use.
• - The maximum speed of the motor should not exceed 15000 / min in order to keep the additional costs for storage and ventilation low.
• - Due to the passive cooling concept, the iron losses in the motor should not exceed 4% of the maximum power of the motor.
• - For all S / R and SRS, a converter with increased current carrying capacity is used to ensure that all variants considered achieve the same level of performance. The number of windings is thus at PMSM, SRS and S / RN _Z = 3.

Table 3 lists motor design recommendations in PMSM, S / R, and SRS technology, as well as possible increases in power density. As an estimate of the increase in power density, the stator length is used. Thus, for example, a possible shortening of the stator by a factor of two is evaluated as a possible doubling of the gravimetric and volumetric power density of the engine. Table 3: Increase in gravimetric and volumetric power density

In Table 3 it can be seen that under the given boundary conditions the possibilities for increasing the power density for a PMSM engine are> 800%, for an S / R engine only 20%. An SRS 6/2 engine (SRS 36/12) achieves potential increases of 600% and is therefore a promising approach for increasing the power density of switched reluctance motors.

The invention will be explained in more detail with reference to exemplary embodiments. The figures show:

1a a schematic cross section through an electrical machine according to the invention in a first energizing state and a schematic current flow plan,

1b a schematic cross section through an electrical machine according to the invention in a second Bestromungszustand and a schematic Stromflussplan,

1c a schematic cross section through an electrical machine according to the invention in a third Bestromungszustand and a schematic Stromflussplan,

1d a schematic cross section through an electric machine according to the invention in a fourth Bestromungszustand and a schematic Stromflussplan,

1e a schematic cross section through an electrical machine according to the invention in a fifth Bestromungszustand and a schematic Stromflussplan,

1f a schematic cross section through an electrical machine according to the invention in a sixth Bestromungszustand and a schematic Stromflussplan,

2a a schematic cross section through another electrical machine according to the invention in a first energized state and a schematic current flow plan,

2 B a schematic cross section through the further electrical machine according to the invention in a second state of energization and a schematic current flow plan,

2c a schematic cross section through the further electrical machine according to the invention in a third state of energization and a schematic current flow plan,

3 a schematic circuit diagram of the different energizing states,

4 a schematic cross section through an electric machine in a further embodiment and

5 a schematic cross section through an electric machine in another embodiment.

Hereinafter, like reference numerals designate elements having the same or similar technical features.

1a shows a schematic cross section through an electrical machine 1 , The electric machine 1 includes a stator 2 and a rotor 3 , The stator 2 has six stator teeth SZ1, SZ2, SZ3, SZ4, SZ5, SZ6. The stator teeth SZ1, ..., SZ6 each have a pole piece or form such a pole piece. The rotor 3 has two rotor teeth RZ1, RZ2. A first phase winding P1 surrounds the first stator tooth SZ1. A first phase winding PW1 surrounds the first stator tooth SZ1. A second phase winding PW2 wraps around the second stator tooth SZ2. A third phase winding PW3 surrounds the third stator tooth SZ3. A fourth phase winding PW4 wraps around the fourth stator tooth SZ4. A fifth phase winding PW5 surrounds the first stator tooth SZ5. A sixth phase winding PW6 wraps around the sixth stator tooth SZ6. Thus, in 1a a SRS 6/2 shown.

The first phase winding PW1 and the fourth phase winding PW4 are assigned to a first phase P1. The second phase winding PW2 and the fifth phase winding PW5 are associated with a second phase P2. The third phase winding PW3 and the sixth phase winding PW6 are assigned to a third phase P3.

The phases P1, P2, P3 and their associated phase windings PW1, ..., PW6 are electrically connected in a neutral point S.

In 1a is the electric machine 1 shown in a first Bestromungszustand. In this first Bestromungszustand the first phase P1 and thus its associated phase windings PW1, PW4 is energized. Next, the third phase P3 and thus its associated phase windings PW3, PW6 is energized. The current flow and its direction are indicated by arrows I. The second phase P2 and thus its associated phase windings PW2, PW5 are not energized.

The rotor 3 is in a first angular position. In this angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the first stator tooth SZ1 and the pole face of the sixth stator tooth SZ6. Further, a surface of the second rotor tooth RZ2 covers the pole faces of the third stator tooth SZ3 and the pole face of the fourth stator tooth SZ4.

In 1a schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the first angular position and the first current state of the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the first stator tooth SZ1 with an energized phase winding PW1, then is minimal, when the magnetic circuit M via the adjacent to the first stator tooth SZ1 sixth stator tooth SZ6 with a energized phase winding PW6 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes on the second rotor tooth RZ2 and the fourth stator tooth SZ4 with a current-fed phase winding PW4, then minimal when the magnetic Circle over the adjacent to the fourth stator tooth SZ4 third stator tooth SZ3 with an energized phase winding PW3 closes.

Next are in 1a a supply potential VP is shown, to which phase lines of the phases P1, P2, P3 via an inverter, which is represented by switches, are connected.

The energized phases P1, P3 form two subsystems. These are electrically connected in series and magnetically connected in parallel. The first magnetic subsystem includes magnetic circuits that close over the first stator tooth SZ1 and the sixth stator tooth SZ6, and magnetic circuits that close over the first stator tooth SZ1 and the second stator tooth SZ2. Which of these magnetic circuits comprises the first subsystem depends on the angular position of the rotor 3 from. Will the rotor 3 from the sixth angular position, which will be explained in more detail below, into the first angular position, the first magnetic subsystem first comprises the magnetic circuit which closes via the first stator tooth SZ1 and the second stator tooth SZ2 and later in the course of the rotation then the magnetic circuit closes over the first stator tooth SZ1 and the sixth stator tooth SZ6. Correspondingly, the second subsystem first comprises the magnetic circuit which closes via the first stator tooth SZ1 and the sixth stator tooth SZ6 and later in the course of the rotation then the magnetic circuit which closes via the sixth stator tooth SZ6 and the fifth stator tooth SZ5.

The second magnetic subsystem includes magnetic circuits that close over the sixth stator tooth SZ6 and the first stator tooth SZ1, and magnetic circuits that close over the sixth stator tooth SZ6 and the fifth stator tooth SZ5.

1b shows a schematic cross section through the in 1a illustrated electrical machine 1 in a second energizing state, in a block commutation mode of the electric machine 1 temporally follows the first Bestromungszustand.

In this second Bestromungszustand the second phase P2 and thus its associated phase windings PW2, PW5 is energized. Next, the third phase P3 and thus its associated phase windings PW3, PW6 is energized. The current flow and its direction is indicated by arrows I. The first phase P1 and thus its associated phase windings PW1, PW4 are not energized.

The rotor 3 moves from the first angular position to a second angular position during the transition from the first energizing state to the second energizing state. In this second angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the sixth stator tooth SZ6 and the pole face of the fifth stator tooth SZ5. Further, a surface of the second rotor tooth RZ2 covers the pole faces of the third stator tooth SZ3 and the pole face of the second stator tooth SZ2.

In 1b schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the second angular position and the second Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the sixth stator tooth SZ6 with an energized phase winding PW6, then is minimal, when the magnetic circuit M via the adjacent to the sixth stator tooth SZ6 fifth stator tooth SZ5 with a energized PW5 phase winding closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes on the second rotor tooth RZ2 and the third stator tooth SZ3 with a current-fed phase winding PW3, then minimal, when the magnetic circuit on the adjacent to the third stator tooth SZ3 second stator tooth SZ2 with an energized PW2 phase winding closes.

1c shows a schematic cross section through the in 1a illustrated electrical machine 1 in a third energizing state, in a block commutation mode of the electric machine 1 temporally follows the second Bestromungszustand.

In this third Bestromungszustand the second phase P2 and thus its associated phase windings PW2, PW5 is energized. Furthermore, the first phase P1 and thus the phase windings PW1, PW4 assigned to it are energized. The current flow and its direction is indicated by arrows I. The third phase P3 and thus its associated phase windings PW3, PW6 are not energized.

The rotor 3 moves from the second angular position to a third angular position during the transition from the second energizing state to the third energizing state. In this third angular position A surface of the first rotor tooth RZ1 covers the pole faces of the fifth stator tooth SZ5 and the pole face of the fourth stator tooth SZ4. Furthermore, a surface of the second rotor tooth RZ2 covers the pole faces of the second stator tooth SZ2 and the pole face of the first stator tooth SZ1.

In 1c schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the third angular position and the third Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the fifth stator tooth SZ5 with an energized phase winding PW5, then is minimal, when the magnetic circuit M via the adjacent to the fifth stator tooth SZ5 fourth stator tooth SZ4 with a energized phase winding PW4 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes on the second rotor tooth RZ2 and the second stator tooth SZ2 with a current-carrying phase winding PW2, then minimal, when the magnetic circuit on the adjacent to the second stator tooth SZ2 first stator tooth SZ1 with an energized phase winding PW1 closes.

1d shows a schematic cross section through the in 1a illustrated electrical machine 1 in a fourth lighting state, which is in a block commutation mode of the electric machine 1 time follows the third Bestromungszustand.

In this fourth Bestromungszustand the third phase P3 and thus its associated phase windings PW3, PW6 is energized. Furthermore, the first phase P1 and thus the phase windings PW1, PW4 assigned to it are energized. The current flow and its direction is indicated by arrows I. The second phase P2 and thus its associated phase windings PW2, PW5 are not energized.

The rotor 3 moves from the third angular position to a fourth angular position during the transition from the third current state to the fourth state of current. In this fourth angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the fourth stator tooth SZ4 and the pole face of the third stator tooth SZ3. Further, a surface of the second rotor tooth RZ2 hides the pole faces of the first stator tooth SZ1 and the pole face of the sixth stator tooth SZ6.

In 1d schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus formed such that in the fourth angular position and the fourth Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the fourth stator tooth SZ4 with an energized phase winding PW4, then is minimal, when the magnetic circuit M via the adjacent to the fourth stator tooth SZ4 third stator tooth SZ3 with a energized phase winding PW3 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes via the second rotor tooth RZ2 and the first stator tooth SZ1 with a current-carrying phase winding PW1, then minimal, when the magnetic circuit on the adjacent to the first stator tooth SZ1 sixth stator tooth SZ6 with an energized PW6 phase winding closes.

1e shows a schematic cross section through the in 1a illustrated electrical machine 1 in a fifth lighting state, which is in a block commutation operation of the electric machine 1 temporally follows the fourth Bestromungszustand.

In this fifth Bestromungszustand the third phase P3 and thus its associated phase windings PW3, PW6 is energized. Furthermore, the second phase P2 and thus the phase windings PW2, PW5 assigned to it are energized. The current flow and its direction is indicated by arrows I. The first phase P1 and thus its associated phase windings PW1, PW4 are not energized.

The rotor 3 At the transition from the fourth energizing state to the fifth energizing state, it moves from the fourth angular position to a fifth angular position. In this fifth angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the second stator tooth SZ2 and the pole face of the third stator tooth SZ3. Further, a surface of the second rotor tooth RZ2 hides the pole faces of the fifth stator tooth SZ5 and the pole face of the sixth stator tooth SZ6.

In 1e schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the fifth angular position and the fifth current state of the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the second stator tooth SZ2 with an energized phase winding PW2, then is minimal, when the magnetic circuit M via the adjacent to the second stator tooth SZ2 third stator tooth SZ3 closes with an energized phase winding PW3. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes via the second rotor tooth RZ2 and the sixth stator tooth SZ6 with a current-fed phase winding PW6, then minimal, when the magnetic circuit on the adjacent to the sixth stator tooth SZ6 fifth stator tooth SZ5 with an energized PW5 phase winding closes.

1f shows a schematic cross section through the in 1a illustrated electrical machine 1 in a sixth energization state, which is in a block commutation mode of the electric machine 1 time follows the fifth Bestromungszustand.

In this sixth Bestromungszustand the first phase P1 and thus its associated phase windings PW1, PW4 is energized. Furthermore, the second phase P2 and thus the phase windings PW2, PW5 assigned to it are energized. The current flow and its direction is indicated by arrows I. The third phase P3 and thus its associated phase windings PW3, PW6 are not energized.

The rotor 3 In the transition from the fifth energizing state to the sixth energizing state, it moves from the fifth angular position to a sixth angular position. In this sixth angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the second stator tooth SZ2 and the pole face of the first stator tooth SZ1. Further, a surface of the second rotor tooth RZ2 hides the pole faces of the fifth stator tooth SZ5 and the pole face of the fourth stator tooth SZ4.

In 1f schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus formed such that in the sixth angular position and the sixth Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the second stator tooth SZ2 with an energized phase winding PW2, then is minimal, when the magnetic circuit M via the adjacent to the second stator tooth SZ2 first stator tooth SZ1 with a energized phase winding PW1 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes via the second rotor tooth RZ2 and the fourth stator tooth SZ4 with a current-fed phase winding PW4, then minimal, when the magnetic circuit on the adjacent to the fourth stator tooth SZ4 fifth stator tooth SZ5 with an energized PW5 phase winding closes.

Time after the sixth Bestromungszustand can the electric machine 1 be energized again in the first Bestromungszustand. In the successive energization states, the current I can each have a phase angle from the intervals of [0 ° -60 °], [60 ° -120 °], [120 ° -180 °], [180 ° -240 °], [240 ° -300 °], [300 ° -360 °].

When transitioning from one angular position to the next angular position of the rotor 3 perform a rotation of 60 ° in the present embodiment.

2a shows a schematic cross section through an electrical machine 1 in a further embodiment. The electric machine 1 includes a stator 2 and a rotor 3 , The stator 2 has six stator teeth SZ1, SZ2, SZ3, SZ4, SZ5, SZ6. The stator teeth SZ1, ..., SZ6 each have no pole piece or form no such pole piece made. The rotor 3 has four rotor teeth RZ1, RZ2, RZ3, RZ4. A first phase winding P1 surrounds the first stator tooth SZ1. A second phase winding PW2 wraps around the second stator tooth SZ2. A third phase winding PW3 surrounds the third stator tooth SZ3. A fourth phase winding PW4 wraps around the fourth stator tooth SZ4. A fifth phase winding PW5 surrounds the first stator tooth SZ5. A sixth phase winding PW6 wraps around the sixth stator tooth SZ6. Thus, in 1a a SRS 6/4 shown.

The rotor 3 is an inner section 4 which is formed of a magnetically non-conductive material. The outer portions that form the rotor teeth RZ1, ..., RZ4 are formed of magnetically conductive material. The inner section 4 is here designed such that four rotor teeth RZ1, ..., RZ4 are formed. The second rotor tooth RZ2 is located opposite the first rotor tooth RZ1. Likewise, the fourth rotor tooth RZ4 faces the third rotor tooth RZ3.

The first phase winding PW1 and the fourth phase winding PW4 are assigned to a first phase P1. The second phase winding PW2 and the fourth fifth phase winding PW5 are a second phase P2 assigned. The third phase winding PW3 and the sixth phase winding PW6 are assigned to a third phase P3.

The phases P1, P2, P3 and their associated phase windings PW1, ..., PW6 are electrically connected in a neutral point S.

In 2a is the electric machine 1 shown in a first Bestromungszustand. In this first Bestromungszustand the first phase P1 and thus its associated phase windings PW1, PW4 is energized. Next, the third phase P3 and thus its associated phase windings PW3, PW6 is energized. The current flow and its direction is indicated by arrows I. The second phase P2 and thus its associated phase windings PW2, PW5 are not energized.

The rotor 3 is in a first angular position. In this angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the first stator tooth SZ1 and the pole face of the sixth stator tooth SZ6. Further, a surface of the second rotor tooth RZ2 covers the pole faces of the third stator tooth SZ3 and the pole face of the fourth stator tooth SZ4. Further, a surface of the third rotor tooth RZ3 hides the pole face of the fifth stator tooth SZ5 and the slots between the fifth stator tooth SZ5 and the sixth stator tooth SZ6 and the fourth stator tooth SZ4. Further, a surface of the fourth rotor tooth RZ4 hides the pole face of the second stator tooth SZ2 and the grooves between the second stator tooth SZ2 and the first stator tooth SZ1 and the third stator tooth SZ3.

In 2a schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the first angular position and the first current state of the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the first stator tooth SZ1 with an energized phase winding PW1, then is minimal, when the magnetic circuit M via the adjacent to the first stator tooth SZ1 sixth stator tooth SZ6 with a energized phase winding PW6 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes via the second rotor tooth RZ2 and the fourth stator tooth SZ4 with a current-fed phase winding PW4, then minimal, when the magnetic circuit on the adjacent to the fourth stator tooth SZ4 third stator tooth SZ3 with an energized phase winding PW3 closes.

Next are in 1a a supply potential VP is shown, to which phase lines of the phases P1, P2, P3 via an inverter, which is represented by switches, are connected.

2 B shows a schematic cross section through the in 2a illustrated electrical machine 1 in a second energizing state, in a block commutation mode of the electric machine 1 temporally follows the first Bestromungszustand.

In this second Bestromungszustand the second phase P2 and thus its associated phase windings PW2, PW5 is energized. Next, the third phase P3 and thus its associated phase windings PW3, PW6 is energized. The current flow and its direction is indicated by arrows I. The first phase P1 and thus its associated phase windings PW1, PW4 are not energized.

The rotor 3 moves from the first angular position to a second angular position during the transition from the first energizing state to the second energizing state. In this second angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the sixth stator tooth SZ6 and the pole face of the fifth stator tooth SZ5. Further, a surface of the second rotor tooth RZ2 covers the pole faces of the third stator tooth SZ3 and the pole face of the second stator tooth SZ2. Further, a surface of the third rotor tooth RZ3 conceals the pole face of the fourth stator tooth SZ4 and the slots between the fourth stator tooth SZ4 and the fifth stator tooth SZ5 and the third stator tooth SZ3. Further, a surface of the fourth rotor tooth RZ4 hides the pole face of the first stator tooth SZ1 and the slots between the first stator tooth SZ1 and the sixth stator tooth SZ1 and the second stator tooth SZ2.

In 2 B schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the second angular position and the second Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the sixth stator tooth SZ6 with an energized phase winding PW6, then is minimal, when the magnetic circuit M via the adjacent to the sixth stator tooth SZ6 fifth stator tooth SZ5 with a energized PW5 phase winding closes. Next is also a magnetic Resistance of the magnetic circuit, not shown, which closes via the second rotor tooth RZ2 and the third stator tooth SZ3 with an energized phase winding PW3, then minimal, when the magnetic circuit via the adjacent to the third stator tooth SZ3 second stator tooth SZ2 with an energized phase winding PW2 closes.

2c shows a schematic cross section through the in 2a illustrated electrical machine 1 in a third energizing state, in a block commutation mode of the electric machine 1 temporally follows the second Bestromungszustand.

In this third Bestromungszustand the second phase P2 and thus its associated phase windings PW2, PW5 is energized. Furthermore, the first phase P1 and thus the phase windings PW1, PW4 assigned to it are energized. The current flow and its direction is indicated by arrows I. The third phase P3 and thus its associated phase windings PW3, PW6 are not energized.

The rotor 3 moves in the transition from the second Bestromungszustand in the third Bestromungszustand in from the second angular position to a third angular position. In this third angular position, a surface of the first rotor tooth RZ1 covers the pole faces of the fifth stator tooth SZ5 and the pole face of the fourth stator tooth SZ4. Furthermore, a surface of the second rotor tooth RZ2 covers the pole faces of the second stator tooth SZ2 and the pole face of the first stator tooth SZ1. Further, a surface of the third rotor tooth RZ3 hides the pole face of the third stator tooth SZ3 and the grooves between the third stator tooth SZ3 and the fourth stator tooth SZ4 and the second stator tooth SZ2. Further, a surface of the fourth rotor tooth RZ4 hides the pole face of the sixth stator tooth SZ6 and the slots between the sixth stator tooth SZ6 and the first stator tooth SZ1 and the fifth stator tooth SZ5.

In 2c schematically a magnetic circuit M is shown. The rotor teeth RZ1, RZ2 are thus designed such that in the third angular position and the third Bestromungszustand the electric machine 1 a magnetic resistance of the magnetic circuit M, which closes via the first rotor tooth RZ1 and the fifth stator tooth SZ5 with an energized phase winding PW5, then is minimal, when the magnetic circuit M via the adjacent to the fifth stator tooth SZ5 fourth stator tooth SZ4 with a energized phase winding PW4 closes. Next is also a magnetic resistance of the magnetic circuit, not shown, which closes on the second rotor tooth RZ2 and the second stator tooth SZ2 with a current-carrying phase winding PW2, then minimal, when the magnetic circuit on the adjacent to the second stator tooth SZ2 first stator tooth SZ1 with an energized phase winding PW1 closes.

Time after the third Bestromungszustand can the electric machine 1 be energized in a fourth, fifth and sixth energizing state, not shown. In the successive energization states, the current I can have phase angles from the intervals of [0 ° -60 °], [60 ° -120 °], [120 ° -180 °], [180 ° -240 °], [240 ° 300 °], [300 ° -360 °].

When transitioning from one angular position to the next angular position of the rotor 3 perform a rotation of 60 ° in the present embodiment.

3 shows a schematic circuit diagram of the different energization states. Here, the currents I in the different phases P1, P2, P3 are shown for different time intervals in a block commutation mode. The first current state is set between 0 ° (electrical) and 60 ° (electrical). The second current state is set between 60 ° (electrical) and 120 ° (electrical). The third energizing state is set between 120 ° (electric) and 180 ° (electric). The fourth current state is set between 180 ° (electrical) and 240 ° (electrical). The fifth current state is set between 240 ° (electric) and 300 ° (electric). The sixth current state is set between 300 ° (electrical) and 360 ° (electric). The currents I can be provided for example by an inverter, wherein switching elements of the inverter are controlled in a corresponding manner.

The proposed electric machine 1 has a stator 2 on, which is comparable to the stator of a permanent-magnet synchronous machine. The pole shoes of the stator teeth SZ1,... SZ6, in contrast to the PMSM, can be designed such that they do not saturate when they transition from the state "unaligned" to "aligned". The stator 2 can be provided with a single tooth winding, comparable to the stator of a permanent magnet synchronous machine. The phases P1, P2, P3 and the phase windings PW1, ..., PW6 of the proposed electric machine 1 are operated in star connection, comparable to the stator of a permanent magnet synchronous machine. Next, the electric machine 1 a rotor 3 With Have double poles. A double pole covers in each case the stator teeth SZ1,..., SZ6 of two adjacent, different phases P1, P2, P3 of associated phase windings PW1,..., PW6 and closes them magnetically short in the state "aligned". The phase windings PW1,... PW6 belonging to the respective remaining phase are magnetically isolated if the illustrated phase windings PW1,..., PW6 are magnetically short-circuited. During the rotation, for example, in each case the phase windings PW1,..., PW6 of the phases P1-P2, then P2-P3 and then P3-P1 can be magnetically short-circuited in succession, the rotor 3 performs a rotational movement and outputs a drive torque.

4 shows a schematic cross section through an electrical machine 1 in a further embodiment, wherein the electric machine 1 essentially like those in the 1a to 1f illustrated electrical machine 1 is trained. Shown are a stator 2 and a rotor 3 the electric machine 1 in a cross-sectional plane, wherein the cross-sectional plane perpendicular to a rotational axis RA of the rotor 3 is oriented. The stator 2 has six stator teeth SZ1, SZ2, SZ3, SZ4, SZ5, SZ6. The rotor 3 has two rotor teeth RZ1, RZ2. For clarity, not shown are phase windings of the stator 2 ,

Each of the stator teeth SZ1, ..., SZ6 has or forms a pole piece. In particular, each stator tooth SZ1,..., SZ6 has a pole core section 5 and a pole piece section 6 on. In the pole piece portion, a width of a stator tooth SZ1,..., SZ6 increases along the radial direction toward the rotation axis RA, wherein the width along a circumferential direction may be a circle about the rotation axis RA.

Further illustrated are outer lateral surfaces 7 the stator teeth SZ1, ..., SZ6, which has a stator groove 8th between adjacent stator teeth SZ1, ..., SZ6 limit. The outer lateral surfaces 7 in this case outer lateral surfaces of both the Polkernabschnitts 5 as well as the pole piece section 6 be. Also shown is a stator yoke 9 , where sections 10 of the stator yoke 9 each also the stator groove 8th limit.

Also shown is a point P of the outer surface 7 of the first stator tooth SZ1, wherein the point P is a point of the outer circumferential surface 7 of the pole piece section 6 of the first stator tooth SZ1. Also shown is a tangent T to the outer surface 7 at this point P. The tangent T corresponds to that in 4 illustrated embodiment, tangents in other points of the outer lateral surface 7 of the pole piece section 6 of the first stator tooth SZ1. Also shown is a radial groove center line ML of the outer circumferential surface 7 of the first stator tooth SZ1 limited stator 8th , wherein the stator groove 8th is arranged between the first stator tooth SZ1 and the second stator tooth SZ2. The radial groove center line ML intersects both the axis of rotation RA of the rotor 3 and also the center point or a center line of the section parallel to the axis of rotation RA 10 of the Stator yoke 9 which is disposed between the first and second stator teeth SZ1, SZ2. Also shown is an angle α between the tangent T and the radial center line ML, where the angle α in the in 4 illustrated embodiment has a value of π / 8. Both the tangent T and the groove center line ML are arranged in a cross-sectional plane which is oriented orthogonal to the axis of rotation RA.

5 shows a schematic cross section through an electrical machine 1 in a further embodiment, wherein the electric machine 1 essentially like those in the 2a to 2f illustrated electrical machine 1 is formed .. Shown are a stator 2 and a rotor 3 the electric machine 1 in a cross-sectional plane, wherein the cross-sectional plane perpendicular to a rotational axis RA of the rotor 3 is oriented. The stator 2 has six stator teeth SZ1, SZ2, SZ3, SZ4, SZ5, SZ6. The rotor 3 has four rotor teeth RZ1, RZ2, RZ3, RZ4. For clarity, not shown are phase windings of the stator 2 ,

In the in 5 illustrated embodiment, the stator teeth SZ1, ..., SZ6 no pole piece or forms no pole piece. In particular, each stator tooth SZ1,..., SZ6 thus has only one pole core section 5 and no pole piece section 6 on.

Further illustrated are outer lateral surfaces 7 the stator teeth SZ1, ..., SZ6, which has a stator groove 8th between adjacent stator teeth SZ1, ..., SZ6 limit. Also shown is a stator yoke 9 , where sections 10 of the stator yoke 9 each also the stator groove 8th limit.

Also shown is a point P of the outer surface 7 of the first stator tooth SZ1. Also shown is a tangent T to the outer surface 7 in this point P.

The tangent T corresponds to the in 5 illustrated embodiment, tangents in other points of the outer lateral surface 7 of the first stator tooth SZ1. Also shown is a radial groove center line ML of the outer circumferential surface 7 of the first stator tooth SZ1 limited stator 8th , wherein the stator groove 8th is arranged between the first stator tooth SZ1 and the second stator tooth SZ2. The radial groove center line ML intersects both the axis of rotation RA of the rotor 3 and also the center point or a center line of the section parallel to the axis of rotation RA 10 of the Stator yoke 9 which is disposed between the first and second stator teeth SZ1, SZ2. Also shown is an angle α between the tangent T and the radial center line ML, where the angle α in the in 5 illustrated embodiment has a value of π / 12. Both the tangent T and the groove center line ML are arranged in a cross-sectional plane which is oriented orthogonal to the axis of rotation RA.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 3813130 C2 [0005]
• JP 2011-035995 A [0006]
• US 2002/0125783 [0007]
• JP 2003-180059 A [0008]

Claims (10)

Electric machine, the electric machine ( 1 ) a stator ( 2 ) and a rotor ( 3 ), wherein the stator ( 2 ) has at least three stator teeth (SZ1, ..., SZ6), wherein each stator tooth (SZ1, ..., SZ6) is wound with a phase windings (PW1, ..., PW6), wherein the rotor ( 3 ) has at least one rotor tooth (RZ1, RZ2), wherein the at least one rotor tooth (RZ1, RZ2) is designed such that in an energized state of the electric machine ( 1 ) a magnetic resistance of a magnetic circuit (M), which closes via the rotor tooth (RZ1, RZ2) and a stator tooth (SZ1, ..., SZ6) with a current-energized phase winding (PW1, ..., PW6), then minimal is when the magnetic circuit (M) closes with a stator tooth (SZ1, ..., SZ6) adjacent to this stator tooth (SZ1, ..., SZ6) with an energized phase winding (PW1, ..., PW6), characterized in that a surface of the at least one rotor tooth (RZ1, RZ2) completely covers the pole faces of the adjacent stator teeth (SZ1, ..., SZ6) with respective energized phase windings (PW1, ..., PW6). Electrical machine according to claim 1, characterized in that an angle between a tangent at a point of an outer circumferential surface of a stator tooth and a radial groove center line of the outer circumferential surface bounded by the stator has a value between 0 and π / 8. Electrical machine according to claim 1 or 2, characterized in that the phase windings (PW1, ..., PW6) are electrically connected in a neutral point. Electrical machine according to one of the preceding claims, characterized in that the stator ( 2 ) 3 × n stator teeth (SZ1, ..., SZ6), wherein the rotor ( 3 ) 1 × n rotor teeth (RZ1, RZ2). Electrical machine according to claim 4, characterized in that each one of the 1 × n rotor teeth (RZ1, RZ2) covers an angular segment of 4π / (3 × n) of the air gap, wherein each one of the 3 × n stator teeth (SZ1, ... , SZ6) covers an angular segment of π / (3 × n) of the air gap. Electrical machine according to claim 4 or 5, characterized in that the stator teeth (SZ1, ..., SZ6) each form a pole piece. Electrical machine according to one of claims 1 to 3, characterized in that the stator ( 2 ) 3 × n stator teeth (SZ1, ..., SZ6), wherein the rotor ( 3 ) 2 × n rotor teeth (RZ1, ..., RZ4). Electrical machines according to claim 7, characterized in that in each case one of the 2 × n rotor teeth (RZ1, RZ2) covers an angular segment of 2π / (2 × n) of the air gap, one of the 3 × n stator teeth (SZ1, ... , SZ6) covers an angular segment of 2π / (6 × n) of the air gap. Electrical machine according to claim 7 or 8, characterized in that the stator teeth (SZ1, ..., SZ6) form no pole piece. Method for operating an electrical machine according to one of Claims 1 to 9, the phase windings (PW1,..., PW6) of the electric machine ( 1 ) are energized in a Kommutierungsbetrieb.

Images