NL2025517B1

NL2025517B1 - Electric motor and primary part

Info

Publication number: NL2025517B1
Application number: NL2025517A
Authority: NL
Inventors: León Van Vuure Thorwald
Original assignee: Tecnotion Assets B V
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2021-11-23

Abstract

The present invention relates to an electric motor of either the synchronous or the asynchronous type. It particularly relates to an alternating current, ‘AC’ synchronous motor. The 5 motor may be a linear motor or may have the more common rotating form. The present invention further relates to a primary part of an electric motor, the part being either a stator or a rotor. According to the present invention, the pole shoes of the teeth of the primary part of the motor are made from electrical steel of Which the silicon content is lower than that of the remainder of the teeth. In this manner, the adverse effects on the overall performance of the motor 10 of stamping damage associated With the manufacture of the pole shoes can be mitigated. Fig. 3 15

Description

Electric motor and primary part The present invention relates to an electric motor of either the synchronous or the asynchronous type. It particularly relates to an alternating current, ‘AC’ synchronous motor. The motor may be a linear motor or may have the more common rotating form. The present invention further relates to a primary part of an electric motor, the part being either a stator or a rotor.

Electric motors as defined by the preamble of claim 1 are known in the art and typically comprise a primary part that comprises a yoke, a plurality of teeth connected to the yoke, and a plurality of electrical coils. The known electric motor further comprises a secondary part typically comprising a plurality of magnets, such as permanent magnets. The primary part and secondary part are configured to mutually move when energizing the plurality of electrical coils. Each tooth among the plurality of teeth comprises a first member that extends from the yoke towards the secondary part and a second member that forms a pole shoe connected to an end of the first member. Each coil is wound around the first member of one or more teeth among the plurality of teeth.

Adjacent tecth are typically surrounded by an electrical coil that is driven using a different phase. For example, in a three-phase system, three coil groups can be identified that each comprise a plurality of coils. The coils in each coil group are driven by the same phase, whereas coils from different coil groups are driven by different phases.

By energizing the coils, a force will be generated that causes a relative movement between the primary and secondary parts. Here, one of the primary part and secondary part is typically kept stationary thereby acting as the stator, whereas the other of the primary part and secondary part is allowed to move thereby acting as the rotor.

It should be noted that the invention equally relates to electric motors in which the secondary part does not comprise permanent magnets but only comprises soft magnetic or non- magnetic material such as for example used in induction motors. In another embodiment, the secondary part is a squirrel cage rotor.

Important parameters of an electric motor are the maximum force that can be generated at a given current level through the coils and the energy loss within the motor and in particular in the teeth. To this end, cold-rolled non-grain-oriented (CRNGO) electrical steel is preferably used for manufacturing the teeth. Additional benefits conferred by alternative electrical steels are offset by greater difficulties in manufacturability and higher cost. Electrical steel is distinguished from ordinary steels by the addition of silicon to the alloy, and displays a high permeability, has a narrow hysteresis curve, and increased electrical resistance, thereby reducing energy loss in the teeth.

Typically, the teeth are formed using a laminated structure comprising a plurality of layers that are stacked. Each of these layers may be coated by an insulator to reduce Eddy current losses. The layers are typically made using a stamping process in which the layers are stamped from a sheet of electrical steel. The stamping process, through extreme local plastic deformation, introduces a narrow area of reduced magnetic performance located near the perimeter of the stamped part. Alternative manufacturing processes, such as laser cutting, do not necessarily lead to smaller areas of reduced magnetic performance.

An object of the present invention is to provide an improvement to the abovementioned electric motor in which a higher force can be generated using the same current through the IO electrical coils.

According to a first aspect of the invention, this object has been achieved using the electric motor of claim 1 that is characterized in that the second member is manufactured from silicon steel having a second silicon content being lower than the first silicon content.

In the prior art electric motor, for each tooth, the second member is integrally connected to the first member and/or the second member and the first member are made from the same material, typically electrical steel.

According to the present invention, the second member and the first member are made from different materials. More in particular, the second member is made using electrical steel having a lower silicon content than the electrical steel of the first member.

The Applicant has found that during the stamping process of relatively small parts from electrical steel, such as the pole shoe, considerable stamping damage may be generated that deteriorates the magnetic performance to such an extent that if this same part was made from electrical steel having a lower silicon content, the positive effects associated with the reduction in stamping damage will outweigh the reduced magnetic performance of the electrical steel itself. The Applicant has found that stamping damage will increase with increasing silicon content, as at increased silicon levels, the steel will become more brittle.

The Applicant further found that, using the primary part of the invention, a higher maximum force can be reached for a given current through the electrical coils, than using a primary part in which the first and second members are made from the same electrical steel.

The first and/or second member can be made from grain oriented electrical steel or cold- rolled non-grain-oriented electrical steel. In an embodiment, the second member is made from cold-rolled non-grain-oriented electrical steel and the first member from grain oriented electrical steel. In another embodiment, both the first and second members are made from cold-rolled non- grain-oriented electrical steel.

The second silicon content in percent by weight can be lower than the first silicon content in percent by weight. For example, the second silicon content in percent by weight can be at least two percent smaller than the first silicon content in percent by weight. Additionally or alternatively, the first silicon content in percent by weight may lie in a range extending from 0.5 to

6.5 percent, more preferably from to 2 to 3 percent, and the second silicon content in percent by weight may lie in a range extending from 0 to 2 percent, more preferably from 0.5 to 1 percent. In an extreme case, the second silicon steel content is zero rendering the electrical steel equivalent to regular steel. Therefore, the present invention equally relates to embodiments in which electrical steel is used for the first member and regular steel is used for the second member.

The primary and secondary parts may be configured for performing a mutual rotational or linear movement.

Each first member may extend along a respective first direction from the yoke towards the secondary part, and the corresponding second member may be elongated in a second direction that is substantially perpendicular to the first direction. For example, in a rotary motor, the yoke may have a hollow cylindrical shape from which the teeth extend radially inward. In such a motor, the secondary part is arranged inside the yoke. This part may also have a cylindrical shape consisting of a steel or iron cylinder on which permanent magnets are arranged with the magnetic polarization typically oriented in the radial direction. Alternatively, the motor may be of the asynchronous type, in which case the secondary part can be embodied as a “squirrel cage”.

In a linear motor, the primary part and secondary part can each be elongated along the direction of mutual movement and may have a beam or bar shape. The permanent magnets of the secondary part are typically arranged such that the magnetic polarization is oriented perpendicular to the direction of mutual movement. The teeth of the primary part are directed towards the permanent magnets.

The primary part can be a laminated structure comprising a plurality of layers stacked in a third direction. This third direction can be perpendicular to the first and second directions. For example, in the abovementioned rotary motor, the third direction corresponds to the axis of the cylindrical yoke. In the abovementioned linear motor, the third direction is sometimes referred to as “port” and “starboard” in analogy to a moving ship.

Each of the layers may comprise an insulation layer for electrically isolating that layer from adjacent layers. In this manner, Eddy current losses can be minimized.

Each layer in the stack of layers may comprise an integrally formed first part for forming the yoke and the first members of the teeth, and a plurality of second parts for forming the second members of the teeth, wherein the second parts are connected to the first part. Furthermore, the integrally formed first part may comprise a plurality of first coupling structures and each of the second parts may comprise a second coupling structure for coupling with a respective first coupling structure for the purpose of coupling that second part to the first part.

Alternatively, each layer in the stack of layers may comprise a first part for forming the yoke, a plurality of third parts for forming the first members of the teeth, and a plurality of second parts for forming the second members of the teeth, wherein the third parts are connected to the first part and wherein each second part is connected to a respective third part. In this case, the first part may comprise a plurality of third coupling structures, the third parts may each comprise a fourth and a fifth coupling structure, and the second parts may each comprise a sixth coupling structure. The third coupling structures and the fourth coupling stractures may be configured for coupling the third parts to the first part, and the fifth coupling structures and the sixth coupling structures may be configured for coupling the second parts to the third parts.

Each pair among the first and second coupling structures, the third and fourth coupling structures, and the fifth and sixth coupling structures, may comprise a recess and a corresponding protrusion that can be inserted into the recess for coupling the relevant coupling structures. Corresponding recesses in the layers of the stack of layers may be aligned in the third direction thereby forming a groove that extends along the third direction and in which groove the {5 corresponding protrusions are arranged.

For example, for manufacturing the primary part, as a first step, the abovementioned first parts may be stacked for forming the yoke and the first members. Each first part may have a plurality of recesses, and the recesses of different layers may be aligned such that grooves are formed. As a second step, the second parts for forming the second members, e.g. pole shoes, are inserted one after another in the grooves to couple each first part to a plurality of second parts. In this case, each second part is provided with a protrusion that cooperates with a recess in the first part. This coupling should provide a coupling in at least one, and preferably two different directions perpendicular to the third direction.

Alternatively, for manufacturing the primary part, as a first step, the abovementioned first parts may be stacked for forming the yoke. Each first part may have a plurality of recesses, and the recesses of different layers may be aligned such that grooves are formed. As a second step, the third parts for forming the first members are inserted one after another in the grooves to couple each first part to a plurality of third parts. In this case, each third part is provided with a protrusion that cooperates with a recess in the first part and each third part is provided with a recess. After having arranged the third parts in the grooves formed by the recesses of the first part, further grooves are formed by the recesses of the third parts in which the second parts are arranged one after another for forming the second members. In this case, each second part is provided with a protrusion that cooperates with a recess in a respective third part. Similar to the embodiment above, the coupling between the first parts and third parts and between the third parts and second parts should provide a coupling at least one, and preferably two different directions perpendicular to the third direction.

Alternatively or alternatively, corresponding protrusions in the layers of the stack of layers may be aligned in the third direction thereby forming a ridge that extends along the third direction and to which ridge the corresponding recesses are coupled. For example, each first part may comprise a plurality of protrusions, and by stacking the first parts ridges are formed that extend 5 along the third direction and to which ridges the second parts forming the pole shoes can be coupled or to which ridges the third parts can be coupled for forming the first members. In this later case, the coupling between the third parts and the second parts can be identical in the sense that first a ridge is formed after which the recesses of the second parts are coupled to the third parts.

According to a second aspect, the present invention provides a primary part for an electric motor, said motor further comprising a secondary part preferably comprising a plurality of magnets, such as permanent magnets. According to this second aspect of the invention, the primary part comprises a yoke, a plurality of teeth connected to the yoke, and a plurality of electrical coils. Each tooth among the plurality of teeth comprises a first member that extends from the yoke towards the secondary part and a second member that forms a pole shoe connected to an end of the first member, each coil being wound around the first member of one or more teeth among the plurality of teeth.

The first member is manufactured from electrical steel having a first silicon content. Moreover, the primary part is configured, when installed in the electric motor, to perform a mutual movement relative to the secondary part when energizing the plurality of electrical coils.

The primary part is characterized in that the second part is manufactured from silicon steel having a second silicon content being lower than the first silicon content.

The primary part according to the second aspect of the invention may be identical to the primary part according to the first aspect of the invention.

Next, the present invention will be described in more detail referring to the appended drawings, wherein: Figure 1 illustrates an embodiment of a rotary synchronous motor in accordance with the present invention; Figure 2 illustrates a primary part of the motor of figure 1 in which some of the electrical coils are omitted for illustrative purposes; Figure 3 illustrates a layer among the stack of layers for forming the primary part of figure 2; and Figure 4 illustrates two examples for coupling the various parts of the layer shown in figure 3.

Figure 1 illustrates an embodiment of a rotary permanent magnet synchronous motor 100 in accordance with the present invention. Motor 100 comprises a primary part 10 that comprises a yoke 11 made of steel, cobalt steel or electrical steel. As shown in more detail in figure 2, primary part 10 further comprises a plurality of teeth that extend radially inward from yoke 11. The teeth each comprise a first member 12 and a second member 13, wherein the second member 13 forms a so-called pole shoe for guiding magnetic flux.

Primary part 10 also comprises a plurality of electrical coils 14 that, in figure 1, are each wound around a respective tooth, more in particular around first member 12 of a respective tooth. This arrangement is known as “concentrated winding” in the art. Typically, electrical coils 14 are driven using a three-phase electrical system. In such case, the coils are divided into three equal groups, each corresponding to a different electrical phase. 1t is noted that the present invention is not limited to this embodiment and that other embodiments are envisaged in which electrical coils 14 are wound around the first member of a plurality of teeth and/or that the first member of at least one tooth is surrounded by parts of different coils 14, which is referred to as “distributed winding” in the art.

Secondary part 20 comprises a cylindrical back plate 21 made of steel or electrical steel.

On back plate 21 a plurality of permanent magnets 22 are arranged of which the magnetic polarization is oriented in the radial direction. It is noted that the present invention is not limited to this embodiment and that other embodiments are envisaged. For example, permanent magnets may be absent or largely absent from a secondary part of the reluctance motor type. In another example, the secondary part may consist of a cylinder made from a non-magnetic material such as copper or aleminum, preferably provided with periodic gaps to create a “squirrel cage” type rotor of a motor of the asynchronous type.

Motor 100 can be actuated by energizing electrical coils 14 in a manner known in the art. Typically, primary part 10 is kept stationary and secondary part 20 is allowed to rotate. However, the opposite is equally possible.

Now referring to figure 2, in which some electrical coils 14 are omitted for illustrative purposes, yoke 11 is integrally connected to the plurality of first members 12. However, second members 13 are not integrally connected to first members 12 as will be explained later. More in particular, first members 12 are made from a different material than second members 13. More in particular, first members 12 are made of non-grain oriented silicon steel having a higher silicon content than the electrical steel of which second members 13 are made. For example, the silicon content in percent by weight of the first member lies in a range extending from 0.5 to 6.5 percent, more preferably from 2 to 3 percent, and the silicon content in percent by weight of the second member lies in a range extending from Ô to 2 percent, more preferably from 0.5 to 1 percent.

Now referring to figure 3, primary part 10 is made using a stacking of layers IOA. The stacking direction of layers 10A corresponds to the axial direction in figure 1.

In the embodiment of figure 3, each layer 10A comprises a single first part 30 for forming yoke 11 and first members 12, and a plurality of second parts 31 for forming second members 13. Figure 4 illustrates two examples of how second parts 31 can be connected to first part 30 although other means of connecting second parts 31 to first part 30, such as welding, are not excluded.

As illustrated in figure 4, first part 30 comprises a plurality of protrusions 30A and second parts 31 each comprise a recess 31 A. During manufacturing of primary part 10, first parts 30 will be stacked and aligned thereby forming a plurality of ridges associated with protrusions 30A. Thereafter, second parts 31 will be coupled to those ridges, for example by sliding recesses 31A over the formed ridges. Alternatively, first part 30 may comprise recesses allowing grooves to be formed when stacking first parts 30. In such case, each second part may comprise a protrusion that can be inserted into the formed groove for coupling second parts 31 to first parts 30.

After coupling second parts 31 to first parts 30 a consolidating step may be performed in which the various layers and parts thereof become fixedly attached. For example, the entire primary part may be cast in a synthetic resin.

Figures 3 and 4 illustrate how layer IOA comprises a first part 30 and a second part 31. Alternatively, layer 10A may comprise a first part for forming yoke 11, a plurality of second parts for forming second members 13, and a plurality of third parts for forming first members 12. In this case, the coupling between the second parts and the third parts and between the first part and the third parts may be similar to that described in conjunction with figures 3 and 4. In such case, the first parts will be stacked first after which the third parts are coupled to the first parts. As a final step, the second parts will be coupled to the third parts.

By using a laminated structure for primary part 10, Eddy current losses in primary part 10 can be minimized. This can be achieved in particular when each layer 10A, or the parts thereof, is covered with an insulating layer for electrically isolating layer 10A from adjacent layers 10A or parts thereof.

The embodiments shown in figures 4 show a possible way in which second members 13 can be connected to first members 12 allowing these members to be made from different material. The Applicant has found that when second members 13 are made from the same electrical steel as first members 12, for example by using a stacking of layers of which each layer comprises a single part for simultaneously forming yoke 11, first member 12, and second member 13, a degraded performance is obtained when compared to motors in which second members 13 are made from silicon steel having a lower silicon content than the silicon steel of which first members 12 are made. This effect is attributed to the stamping damage that occurs when forming second members

12. This damage degrades the magnetic performance to such an extent that the overall losses in the motor are worse than if the second members 12 would have been made using electrical steel having a lower silicon content. More in particular, the Applicant has found that the increased stamping damage associated with electrical steel having a higher silicon content, due to the increased brittleness, has a more degrading effect on motor performance than the associated improving effect associated with using the higher silicon content. This particularly holds for second member 13, which is a relatively small and of which the volume in which stamping damage will occur will form a considerable part of the total volume of second member 13.

Although the invention has been explained using a rotary motor it should be apparent to the skilled person that the invention can be equally applied to linear motors. Farthermore, the embodiments shown for explaining the invention should not be construed as limiting the invention to only those embodiments. Rather, various modifications could be implemented without departing from the scope of invention which is defined in the appended claims.

Claims

MODIFIED CONCLUSIONS I.

Electric motor (100) comprising: a primary part (10) comprising: a Yoke (11); a plurality of teeth connected to the yoke; a plurality of electrical coils (14); a secondary part (20) preferably comprising a plurality of magnets, such as permanent magnets (22);

wherein the primary part and secondary part are arranged to move relative to each other when energizing the plurality of electric coils:

wherein each prong among the plurality of prongs comprises a first portion (12) extending from the yoke toward the secondary portion and a second portion (13) forming a pole shoe connected to one end of the first portion wherein each coil is wound around the first portion of one or more teeth among the plurality of teeth;

the first portion being fabricated from electrical steel having a first silicon content;

the second portion being fabricated from electrical steel having a second silicon content lower than the first silicon content;

wherein the primary member is a laminated structure comprising a plurality of layers (10a) stacked in a third direction, each layer preferably being covered by an insulating layer for electrically insulating that layer from adjacent layers in the stack of layers:

characterized in that the first and/or second part is made of grain-oriented electrical steel or cold-rolled non-grain-oriented electrical steel:

wherein each layer in the stack of layers comprises an integrally formed first portion (30) for forming the yoke and the first portions of the teeth, and a plurality of second portions (31) for forming the second portions of the teeth wherein the second portions are joined to the first portion, the integrally formed first portion including a plurality of first coupling structures (30A) and wherein each of the second portions includes a second coupling structure (31A) for coupling to a respective first coupling structure so as to coupling said second portion to the first portion: or wherein each layer in the stack of layers comprises a first portion for forming the Yoke, a plurality of third portions for forming the first portions of the teeth, and a plurality of second portions portions for forming the second portions of the teeth, the third portions being joined to the first portion and each second portion being joined having a respective third portion, the first portion including a plurality of third coupling structures, the third portions each comprising a fourth and a fifth coupling structure, and the second portions each including a sixth coupling structure, the third coupling structures and the fourth coupling structures being arranged to coupling the third portions to the first portion, and wherein the fifth coupling structures and the sixth coupling structures are arranged to couple the second portions to the third portions.

An electric motor according to claim 1, wherein the second part is made of cold-rolled non-grain-oriented electrical steel and the first part is made of grain-oriented electrical steel.

An electric motor according to any one of the preceding claims, wherein the second silicon content in weight percent is lower than the first silicon content in weight percent.

The electric motor of claim 3, wherein the second silicon content in weight percent is at least two percent less than the first silicon content in weight percent.

An electric motor according to claim 1 or 2, wherein the first silicon content in weight percent is in a range from 0.5 to 6.5 percent, more preferably from 2 to 3 percent, and wherein the second silicon content in weight percent is in a range from 0 to 2 percent more preferably from 0.5 to 1 percent.

An electric motor according to any preceding claim, wherein each first portion extends along a respective first direction from the yoke toward the secondary part, and wherein the corresponding second portion is elongated in a second direction substantially perpendicular to the first direction .

An electric motor according to any one of the preceding claims, wherein the primary and secondary parts are oriented to perform a mutually rotating movement.

An electric motor according to any one of claims 1-6, wherein the primary and secondary part are designed to perform a mutual linear movement.

An electric motor according to claim 6, wherein the third direction is perpendicular to the first and second directions.

An electric motor according to any preceding claim, wherein each pair among the first and second coupling structures, the third and fourth coupling structures, and the fifth and sixth coupling structures, comprises a recess and a corresponding protrusion insertable into the recess for coupling of the relevant coupling structures.

An electric motor according to claim 10, wherein corresponding recesses in the layers of the stack of layers are aligned in the third direction and thereby form a groove extending along the third direction and in which groove the corresponding projections are placed and/or wherein corresponding protrusions in the layers of the stack of layers aligned in the third direction thereby forming a ridge extending along the third direction and to which ridge the corresponding recesses are coupled.

A primary part (10) for an electric motor (100), the motor further comprising a secondary part (20) which preferably comprises a plurality of magnets, such as permanent magnets (22), the primary part comprising: a yoke (11 ); a plurality of teeth connected to the yoke: a plurality of electrical coils (14); wherein each prong among the plurality of prongs comprises a first portion (12) extending from the yoke toward the secondary portion and a second portion (13) forming a pole shoe connected to one end of the first portion wherein each coil is wound around the first portion of one or more teeth among the plurality of teeth; the first portion being fabricated from electrical steel having a first silicon content; wherein the primary member is arranged, when installed in the electric motor, to perform relative movement relative to the secondary member upon energization of the plurality of electric coils; the second portion being fabricated from electrical steel having a second silicon content lower than the first silicon content; wherein the primary member is a laminated structure comprising a plurality of layers (10a) stacked in a third direction, each layer preferably being covered by an insulating layer for electrically insulating that layer from adjacent layers in the stack of layers; characterized in that the first and/or second part is made of grain-oriented electrical steel or cold-rolled non-grain-oriented electrical steel; wherein each layer in the stack of layers comprises an integrally formed first portion (30) for forming the yoke and the first portions of the teeth, and a plurality of second portions (31) for forming the second portions of the teeth wherein the second portions are joined to the first portion, the integrally formed first portion comprises a plurality of first coupling structures (30A) and wherein each of the second portions comprises a second coupling structure (3 1A) for coupling to a respective first coupling structure to couple said second portion to the first portion: or wherein each layer in the stack of layers comprises a first portion for forming the yoke, a plurality of third portions for forming the first portions of the teeth and a plurality of second portions for forming the second portions of the teeth, the third portions being connected to the first portion and each second portion being connected having a respective third portion, the first portion including a plurality of third coupling structures, the third portions each comprising a fourth and a fifth coupling structure, and the second portions each including a sixth coupling structure, the third coupling structures and the fourth coupling structures being arranged to coupling the third portions to the first portion, and wherein the fifth coupling structures and the sixth coupling structures are arranged to couple the second portions to the third portions.