NL2017031A

NL2017031A - A brushless electric motor system having integrated power stages, a corresponding method as well as a motorized vehicle comprising such a brushless electric motor.

Info

Publication number: NL2017031A
Application number: NL2017031A
Authority: NL
Inventors: Henricus Renier Klomp Martinus
Original assignee: Saluqi Holding B V
Priority date: 2016-06-23
Filing date: 2016-06-23
Publication date: 2018-01-08
Also published as: NL2017031B1

Abstract

A brushless electric motor system having integrated power stages, said electric motor system comprising a rotor, a stator, a plurality of power stages, and a cooling system comprising a substantially flat hollow main cool body arranged to support the flowing of a cooling medium inside said hollow main cool body for cooling said main cool body, a base cooling plate connected to a first flat surface of said hollow main cool body and to said plurality of power stages for transferring heat between said plurality of power stages and said base cool plate, heat resistance inserts connected to said base cooling plate and said plurality of electrically excitable coils for transferring heat between said plurality of coils and said base cooling plate wherein said heat resistance inserts provide for a thermal conductivity, thereby creating a thermal buffer such that said electrically excitable coils are cooled less compared to said power stages, by said cooling system.

Description

The present invention is related to brushless electric motor systems, more specifically to brushless electric motor systems comprising a stator having electrically excitable coils, and a rotor having a plurality of permanent magnets, which rotor is arranged to rotate with respect to the stator.

In general, a brushless electric motor refers to a Direct Current, DC, motor wherein a mechanical brush and a commutator have been modified into electric means. Accordingly, since such a brushless electric motor does not generate abrasion, dust and electric noise, and has good output and efficiency, it is appropriate for, for example, a high-speed rotation type motor, so that various researches and developments have been conducted on the next generation motor.

However, in case of the brushless electric motor, a rotor of a DC motor, around which coils are wound, is substituted with a permanent magnet, and a method of controlling the speed is switched from a voltage control type into an excitation phase control type, so that a driving circuit, in the form of power control means, is required.

In general, a brushless electric motor comprises a rotor comprising a plurality of permanent magnets, and a stator comprising a plurality of electrically excitable coils for generating an induction field for interaction with said plurality of permanent magnets to cause said rotor to rotate with respect to said stator.

One of the drawbacks of the known brushless electric motor systems is that they require an intensive cooling system for cooling, amongst other, the electrical excitable coils as well as the power stages that drive those coils.

It is therefore an object of the present invention to provide for a brushless electric motor system with a cooling system which is more efficient and simpler compared to the prior art.

In order to achieve that object, the invention provides, in a first aspect thereof, in a brushless electric motor system having integrated power stages, said electric motor system comprising:

a rotor comprising a plurality of permanent magnets;

a stator comprising a plurality of teeth placed adjacently to each other, wherein electrically excitable coils are winded on each of said teeth, respectively, for generating an induction field for interaction with said plurality of permanent magnets to cause said rotor to rotate with respect to said stator, a plurality of power stages, such as half H-bridges, wherein each power stage is arranged to drive a single pair of two coils of said coils winded on said plurality of teeth;

a cooling system comprising:

a substantially flat hollow main cool body arranged to support the flowing of a cooling medium inside said hollow main cool body for cooling said main cool body;

a base cooling plate connected to a first flat surface of said hollow main cool body and to said plurality of power stages for transferring heat between said plurality of power stages and said base cool plate;

heat resistance inserts connected to said base cooling plate and said plurality of electrically excitable coils for transferring heat between said plurality of coils and said base cooling plate, wherein said heat resistance inserts provide for a thermal conductivity, thereby creating a thermal buffer such that said electrically excitable coils are cooled less compared to said power stages, by said cooling system.

It was the insight of the inventor to provide a cooling system with a single substantially flat hollow main cool body, which is used to cool the electrically excitable coils as well as the power stages. As such, one cooling system is provided to cool both the electrically excitable coils and the power stages.

The inventor noted that, typically, the operating temperature of the electrically excitable coils is much higher compared to the operating temperature of the power stages. As such, in the prior, two cooling systems are used. One cooling system for cooling the power stages and one cooling system for cooling the electrically excitable coils.

The inventor noted that two cooling systems is not desired as in such a case also two pumps for pumping the cooling medium, two piping systems for transporting the cooling medium, two cool bodies, two cooling plates, etc., are required. All these aspects require space which is usually of the essence in a brushless electric motor system. By using a single cooling system, the weight of the electric motor system, and thus also its efficiency, is further improved.

One of the aspects of the invention is that heat resistance inserts are provided between the electrically excitable coils and the base cool plate for amending the thermal conductivity between the coils and the base plate. The advantage hereof is that the electrically excitable coils, having a different desired operating temperature, can be cooled from the same main cool body as compared to the power stages. As such, using a single cooling system, the operating temperature of the electrically excitable coils and the operating temperature of the power stages can be controlled at the same time, even if these operating temperatures differ.

In accordance with the present invention, a single power stage may comprise a half H-bridge composed of two Field Effect Transistors, wherein the output of the half H-bridge is directly connected to the pair of electrically excitable coils.

A brushless electric motor is also known as an electronically commutated motor, which is a synchronous motor that is powered by a Direct Current, DC, electric source via power stages, which produce an AC electric signal to drive the coils and thus the motor. In this context, AC, alternating current, does not imply a sinusoidal waveform, but rather a bi-directional current with no restriction on waveform. Additional sensors and electronics eventually control the outputs of the power stages in their amplitude, waveform and frequency, i.e. rotor speed.

The rotor typically comprises a plurality of permanent magnets which are each placed adjacently to each other along said circumference of said rotor, wherein said permanent magnets are ordered in such a way that there is an alternating order of the north and south poles facing the electrically excitable coils. That is, for example, the first permanent magnet produces a north pole facing the coils, the permanent magnet placed directly adjacent thereto produces a south pole facing the coils, etc.

Further, the invention is directed to a brushless electric motor system. In accordance with the present invention, the brushless electric motor system may also be used as a generator for generating electrical power. The brushless electric motor system may also be used as a combined motor and generator in one.

In an example, the stator comprising said plurality of teeth has a predefined radius, wherein said heat resistance inserts are connected to said base cooling plate in a circular manner having a substantially same predefined radius as said stator, wherein the number of heat resistance inserts equals the number of electrically excitable coils, respectively.

A single heat resistance insert is thus used per electrically excitable coil, such that each electrically excitable coil has its own insert via which the heat is transferred to the base cooling plate.

Here, the plurality of power stages may be connected to the base cooling plate via a surface area inside a circle spanned by said plurality of heat resistance inserts.

As such, the power stages are situated in such a way that they are comprised within the circle spanned by the coils, i.e. in the middle of the coils. This proved to be an efficient way of placing the power stages. The advantage hereof is that the brushless electric motor system is compact. Further, the use of a single cooling system is here even more beneficial as the power stages are spaced closed to the electrically excitable coils. This makes the manufacturing of the inserts even more simple, as the cooling plate can be placed adjacent to the power stages as well as adjacent to the electrically excitable coils.

The concept is new and inventive compared to the prior art as in the prior art the power stages are not placed within the vicinity of the coils, thereby making the use of a single cooling system more difficult. The inventor found that the power stages can be placed close to the electrically excitable coils, such that the cooling plate can cool the coils as well as the power stages at the same time. In order to get to the coils, and to amend the amount of cooling of the coils, inserts are used which are placed against the coils as well as against the cooling plate.

In an example, the heat resistance inserts comprise solid spacing blocks of a material comprising any of aluminium, stainless steel, etc.

Here, the solid spacing blocks may be provided with through holes for reducing the thermal conductivity thereof.

The inventor has found that the type of material used for the heat resistance inserts does not need to be a thermal isolator. The key aspect of the invention is that a thermal bridge is obtained between the coils and the cooling plate such that the coils are cooled less compared to the power stages. Depending on the length of the inserts and the type of material of the inserts, different operating temperatures of the coils can be obtained.

In another example, the substantially flat hollow main cool body comprises an inlet and an outlet, both provided at a second flat surface of said hollow main cool body, for inputting and outputting said medium, respectively.

The advantage of this example is that the risk of a leak, for example when using water as a cooling medium, in the inlet or outlet will not affect the power stages and/or electronics provided to control the power stages as these are connected to the base cooling plate which is connected to the main cool body at a first flat surface thereof.

The risk of water getting to the power stages and/or the electronics provided to control the power stages, in case of a leak in the inlet and/or outlet, is thus reduced significantly in case the inlet and the outlet are provided another flat side of the hollow main cool body as compared to the case cooling plate.

It is noted that the inlet may be provided in substantially a centre point of said circle. That is, the inlet may be provided in substantially the middle of the circle spanned by the coils I the inserts.

In a detailed example here, the substantially flat hollow main cool body comprises flow channels for supporting the flow of said cooling medium between said inlet and said outlet, wherein said flow channels originate from said inlet and extend radially outwardly.

The advantage hereof is explained as follows. The cooling medium enters the substantially flat hollow main cool body at the centre point thereof and then flows radially outwardly. This means that the cooling medium first encounters the power stages as the power stages are placed within the circle spanned by the inserts. This is beneficial as the power stages need to be cooled more compared to the coils, i.e. the operating temperature of the power stages is lower then the operating temperature of the coils. The cooling medium will, of course, be warmed up by the power stages to a higher temperature. This is, however, not an issue as the warmed up cooling medium is still able to cool the coils as the coils are operating at a higher temperature then the power stages.

It is thus advantageous in case the cooling medium first encounters the power stages and, subsequently, encounters the coils.

The cooling system may comprise said cooling medium, wherein said cooling medium is any of air and water.

According to the present invention, the cooling medium may be a gas or a liquid.

The advantage of a gas medium is that only a few components are required and that it is therefore very cost effective to implement. No pump, control unit, pipes and a dispensing system are required for cooling the electric motor system. Further, there is no risk on leakage as no liquid is present in the cooling system. A further advantage is that the amount of maintenance to be performed is reduced due to the absence of moving parts in the cooling system.

The advantage of a liquid medium is that less volume, compared to a gaseous medium, is required to obtain the same level of cooling. A liquid medium is further less depending on, for example, the ambient temperature.

In an example, the electric motor system comprises thirty-six electrically excitable coils and eighteen power stages.

In another example, the cooling plate is connected to said main cool body via a pasta, wherein said base cooling plate is connected to said plurality of power stages via a paste, wherein said heat resistance inserts are connected to said base cooling plate via a paste and wherein said plurality of electrically excitable coils are connected to said heat resistance inserts via a pasta.

In a detailed example, the base cooling plate comprises a heat sink.

In an example, each of the power stages comprises a single half Hbridge for driving the electrically excitable coils.

An H-bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. These circuits are used in different types of fields to allow electric motors to run forwards and backwards. A variation of this electronic circuit uses just the two FET’s or transistors on one side of the load, in this example the load is a pair of two coils, similar to a class AB amplifier. Such a configuration is also called a half bridge.

A half H-bridge is a practical implementation for driving the electrically excitable coils wounded around the teeth of the stator.

In yet another example, the rotor surrounds said stator.

In a second aspect, the invention provides in a method of operating a brushless electric motor system according to any of the examples provided above.

In a third aspect, the invention provides in a motorized electrical vehicle comprising a brushless electric motor system according to any of the examples as provided above.

The expressions, i.e. the wording, of the different aspects comprised by the brushless electric motor system, the method and the motorized electrical vehicle according to the present invention should not be taken literally. The wording of the aspects is merely chosen to accurately express the rationale behind the actual function of the aspects.

In accordance with the present invention, different aspects applicable to the above mentioned examples of the brushless electric motor system, including the advantages thereof, correspond to the aspects which are applicable to method and/or the motorized electrical vehicle according to the present invention.

The above-mentioned and other features and advantages of the invention will be best understood from the following description referring to the attached drawings. In the drawings, like reference numerals denote identical parts or parts performing an identical or comparable function or operation.

Brief description of the drawings

Figure 1 is a schematic diagram illustrating a particular embodiment of the brushless electric motor system in an example.

Figure 2 is a schematic figure illustrating a stator and power stages in an example.

Figure 3 is a schematic diagram of a rotor in an example, which rotor is suitable to surround a stator shown in figure 2.

Figure 4 is a schematic diagram of a brushless electric motor system according to the present invention.

Figure 5 is a schematic layout of a brushless electric motor system according to the present invention.

Detailed description

Figure 1 is a schematic diagram illustrating a particular example of a brushless electric motor system 1 to be used according to the present invention. The actual stator and rotor of the system 1 are not shown, there aspects are shown in figure 2 and figure 3, respectively. Figure 1 thus displays the electronic circuitry including the power stages 2-7 and the electrically excitable coils which are winded on each of the teeth of the stator.

According to the example shown in figure 1, a single master control unit 18 is provided which is arranged for controlling three sub control units 11, 12, 13 based on inputs 17 in said master control unit related to any of speed, torque, accelerator and brake signals. It may be advantageous in case such a master control unit 18 is implemented in such a way that it is capable of detecting any form of malfunctioning in the master control unit 18 itself, and, preferably, is able to repair and/or recover from any error or malfunctioning detected. This improved the reliability and the safety aspects of the motor system 1. The functionality of the master control unit 18 may also be implemented redundantly so that in case of an error or malfunctioning in a part of the system, the remainder of the system 1 is able to take over the corresponding functionality thereby increasing the reliability of the system 1 as a whole.

The brushless electric motor system 1 further comprises three sub control units 11, 12, 13, each operating one power electronic means 20. Each sub control unit 11, 12, 13 is coupled to its own rotor position sensor, not shown, via inputs 14, 15, 16, respectively, for determining a position of the rotor with respect to said stator. This aspect further improves the reliability of the system 1 as a whole, as even in case one of the rotor position sensors fails, the motor 1 is still able to function properly. That is, a malfunctioning in one of the rotor position sensors will lead to a sub control unit 11, 12, 13 to malfunction, i.e. to function improperly. As this specific motor 1 comprises three sub control units 11, 12, 13, the remaining two sub control units 11, 12, 13, i.e. the sub control units 11, 12, 13 which are operating properly, will make sure that the motor 1 is at least functioning correctly. This does mean that the motor 1 has a reduced available power as one of the sub control units 11, 12, 13 is not contributing thereto.

The rotor position sensors are typically comprised of hall sensors or rotary encoders. Rotary encoders along with their controllers could be used to exactly what the angle of the rotor is with respect to the stator. A Hall sensor is, for example, placed in an appropriate position. It can sense if in front of it is the North or the South pole. Each of the Hall sensors will then transmit this signal to its corresponding sub control unit 11, 12, 13. The sub control units 11, 12, 13 will, subsequently, then switch on or off the appropriate drivers 8, 9, 10, needed in order to provide the torque.

Each of the power electronic means 20 comprises a first driver 8 for driving two of the eighteen power stages, i.e. the power stages referred to with reference numerals 4 and 7, and comprises a second driver 9 for driving another two of said eighteen power stages, i.e. the power stages referred to with reference numerals 3 and 6, and further comprises a third driver 10 for driving yet another two of said eighteen power stages, i.e. the power stages referred to with reference numerals 2 and 5.

The above is explained with reference to one of the sub control units 11, i.e. only the sub control unit referred to with reference numeral 11. It is to be understood that both of the other two sub control units 12, 13 are coupled to a power electronic means, and that these power electronic means each are coupled to six power stages, etc. This adds up to a total of eighteen power stages, divided over nine drivers, three sub control units and a single master control unit. Such a implementation is beneficial for the reliability of the brushless electric motor system as a whole.

The power stages 2-7 and the coils which are winded around the teeth of the stator tend to breakdown the most. As such, the brushless electric motor system 1 is designed in such a way that a failure occurring in these components is not destructive for the functioning in the system 1 as a whole. This is accomplished, amongst other, by the redundancy aspects of the present example.

As such, it was the insight of the inventor to couple one power stage to each pair of coils. For example, power stage indicated with reference numeral 7 is coupled to the pair of coils A.1, A.2 which are controlled using the phase A.

Each power stage 2-7 comprises a half H-bridge for driving a pair of coils. A half H-bridge is an electronic circuit comprising two transistors or two Field Effect Transistors, FET, which are controlled by a control signal in such a way that in case a high control signal is supplied a load is coupled to a high input voltage, and in case a low control signal is supplied the load is coupled to a low input voltage. Each of the driver 8, 9, 10 should be designed in such a way that it is not possible to drive the half H-bridge in such a way that both of the two FET’s are in their conductive state such that a short circuit between the high input voltage and the low input voltage occurs.

So, following the reasoning provided above, only one pair of coils are affected in case a single half H-bridge, for example a particular FET thereof, breaks down. The remaining of the pairs of coils still function properly thereby contributing to the reliability of the system 1.

Each of the two coils of a pair are driven such that the induction field of a first coil A.1, B.1, C.1 of the pair is directed oppositely to an induction field of a second coil A.2, B.2, C.2 of the pair.

This aspect may be accomplished by connecting each of the two coils of a pair, for example coils referred to with reference numeral A.1 and A.2,, in parallel, wherein each of the two coils of the pair are winded differently. That is, a first coil, for example coil referred to with reference numeral A.1, is winded clockwise and the second coil, i.e. the coil referred to with reference numeral A.2, is winded anticlockwise. This accomplishes that, when the half H-bridge 7 drives the coils A.1 and A.2, the produced induction fields of these two coils are oppositely directed. Effectively, a magnetic north pole and a magnetic south pole are created in such a way.

In this example the coils are placed adjacently to each other in the order of A.1-A.2-B.2-B.1-C.1-C.2 or A.2-A.1-B.1-B.2-C.2-C.1. Here, the number following the letter A, B or C indicates the direction of the magnetic induction field. So, coils referred to with letters having a same number produce a magnetic induction field in the same direction. This means that, when actuated, the coil A.2 produces a magnetic induction field in the same direction as the coils B.2 and C.2. Accordingly, when actuated, the coil A.1 produces a magnetic induction field in the same direction as the coils B.1 and C.1.

Further, the rotor comprises permanent magnets which have either a magnetic north pole or a magnetic south pole directed to the coils of the stator. The permanent magnets are oriented in such a way the magnetic poles are alternately ordered, i.e. first a magnetic north pole directed to the coils, then a magnetic south pole directed to the coils, then again a magnetic north pole directed to the coils, etc. The above ensures that the rotor rotates smoothly with respect to the stator.

The outputs of the coils in ach group of three pairs of coils 19 are connected to each other in order to further improve the reliability of the system 1.

Based on the above, the brushless electric motor system 1 comprises thirty-six electrically excitable coils winded on the teeth of the stator, and forty-two permanent magnets comprised by the rotor.

Figure 2 is a schematic figure illustrating a stator 51 and combined power stages, i.e. referred to with reference H, according to the present example.

In this particular example, the stator 51 is designed in such a way that a rotor is to surround the stator 51. The stator 51 comprises a plurality of teeth 52, wherein electrically excitable coils are winded on each of those teeth 52. Here, the stator 51 comprises exactly thirty-six teeth 52, divided in to six groups 53 of six teeth 52 each. The groups, and thus also the teeth 52 comprised by the groups 53, are placed, i.e. oriented, adjacently to each other along a circumference of the rotor 51. The electrically excitable coils, i.e. the ones referred to with references A.1-A.2B.2-B.1-C.1-C.2 or A.2-A.1-B.1-B.2-C.2-C.1, are to generate magnetic induction fields for interaction with a plurality of permanent magnets comprised by the rotor (not shown). This causes the rotor to rotate with respect to the stator 51.

The teeth 52 may comprise a magnetic core for enhancing the produced magnetic field. The shape of any tooth 52 is such that a magnetic field produced by a coil winded on such a tooth 52 is directed radially with respect to an inner axis of the stator 51, i.e. towards the permanent magnets comprised by the rotor.

Figure 3 is a schematic diagram of a rotor 81 according to the present example, which rotor 81 is suitable to surround a stator shown in figure 2. Here, the rotor comprises forty-two recesses 82, which recesses 82 are used to accommodate the permanent magnets (not shown). The recesses are spaced 83 with respect to each other such that the magnets do not, or minimally, influence each other. The stator 51 of figure 2 is to be placed inside the rotor 81 shown in figure 3. The rotor 81 is further rotatably mounted to the stator 51 such that the rotor 81 is able to rotate with respect to the stator 51.

In accordance with the present example, the rotor 81 may also be implemented as a shaft or the like, wherein the stator 51 surround the rotor 81.

Figure 4 is a schematic layout of a brushless electric motor system according to the present invention.

Here, a brushless electric motor system 101 having integrated power stages is shown. The invention is displayed as a schematic diagram as to explain the functionality. The actual stator and rotor of the system 101 are not shown.

The electric motor system comprise a rotor comprising a plurality of permanent magnets and a stator comprising a plurality of teeth placed adjacently to each other, wherein electrically excitable coils are winded on each of said teeth, respectively, for generating an induction field for interaction with said plurality of permanent magnets to cause said rotor to rotate with respect to said stator.

Further, a plurality of power stages 106, such as half H-bridges, are provided, wherein each power stage is arranged to drive a single pair of two coils of said coils winded on said plurality of teeth. In the present example, the electric motor system 101 comprises thirtysix electrically excitable coils, eighteen power stages 106, wherein each power stage comprises a single H-bridge and thus two Metal Oxide Semiconductor, MOS, Field Effect Transistor’s, FETs. It are these MOSFET’s that need to be cooled efficiently by the cooling system according to the present invention.

In figure 4 is the cooling system shown, which comprises a substantially flat hollow main cool body 110 arranged to support the flowing of a cooling medium inside said hollow main cool body for cooling said main cool body, a base cooling plate 108 connected to a first flat surface of said hollow main cool body and to said plurality of power stages for transferring heat between said plurality of power stages and said base cool plate, heat resistance inserts 104 connected to said base cooling plate and said plurality of electrically excitable coils 102 for transferring heat between said plurality of coils and said base cooling plate 108,

The heat resistance inserts 104 provide for a thermal conductivity, thereby creating a thermal buffer such that said electrically excitable coils 102 are cooled less compared to said power stages 106, by said cooling system.

In the present example, the cooling medium is of a temperature close to about 50 degrees Celsius. The operating temperature of the MOSFET’s is about 60 degrees Celsius. The MOSFET’s are directly connected to the base cooling plate 108 in order to obtain sufficient cooling for the MOSFET’s to their operating temperature. The operating temperature of the coils is about 90 degrees Celsius, i.e. much higher compared to the operating temperature of the MOSFET’s. As such, the inventor has found to provide inserts 104 between the coils 102 and the base cooling plate 108, such that a single cooling system can be used for cooling the MOSFET’s to about 60 degrees Celsius and the coils 102 to about 90 degrees Celsius. The inserts 104 thus provide for a thermal conductivity, thereby creating a thermal buffer such that the electrically excitable coils 102 are cooled less compared to the power stages 106, by the cooling system.

Pasta’s 103, 105, 109, 107 may be used to connect each of the above mentioned elements firmly to each other, such that heat transfer between these elements is improved.

Figure 5 is a schematic layout of a brushless electric motor system 201 according to the present invention. Here, the hollow main cool body 202, the base cooling plate 204, the heat resistance inserts 203, the electrically excitable coils 206, the power stages 205 are indicated in a layout position so that it is clear how the elements are oriented with respect to each other.

The power stages 205, i.e. the MOSFET’s as indicated above, are placed on a printed circuit board, PCB, 209, which further comprises the control logic for controlling the MOSFET’s. The coils 206 are winded on the teeth 210 of the stator for generating an induction field for interaction with the plurality of permanent magnets 208 to cause the rotor to rotate with respect to the stator.

The present invention is not limited to the embodiments as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present invention as disclosed in the appended claims without having to apply inventive skills.

Claims

CONCLUSIONS

A brushless electric motor system with integrated power stages, the electric motor system comprising:

- a rotor comprising a plurality of permanent magnets;

- a stator comprising a plurality of teeth disposed adjacent to each other, in which electrically excitable coils are wound on each of the teeth, respectively, to generate an induction field for interaction with the plurality of permanent magnets to cause the rotor to rotate relative to the stator,

a plurality of power stages, such as half H-bridges, wherein each power stage is adapted to control a single pair of two coils from the coils wound on the plurality of teeth;

- a cooling system comprising:

- a substantially flat hollow main cooling body adapted to support the flow of a cooling medium into the hollow main cooling body for cooling the main cooling body;

a base cooling plate connected to a first flat surface of the main hollow cooling body and to the plurality of power stages for transferring heat between the plurality of power stages and the base cooling plate;

heat resistance inserts connected to the base cooling plate and the plurality of electrically excitable coils for transferring heat between the plurality of coils and the base cooling plate, wherein the heat resistance inserts provide a thermal conductivity, thereby creating a thermal buffer such that the electrically excitable coils be cooled less compared to the power stages by the cooling system.

A brushless electric motor system according to claim 1, wherein the stator comprising the plurality of teeth has a predetermined radius, wherein the heat resistance inserts are connected to the base cooling plate in a circular fashion with a substantially the same predetermined radius as the stator, wherein the number of heat resistance inserts is equal to the number of electrically excitable coils, respectively.

The brushless electric motor system of claim 2, wherein the plurality of power stages are connected to the base cooling plate via a surface area in a circle spanned by the plurality of the heat resistance inserts.

A brushless electric motor system according to any of the preceding claims, wherein the heat resistance inserts comprise fixed spacer blocks of a material comprising one of aluminum and stainless steel.

The brushless electric motor system of claim 4, wherein the fixed spacer blocks are provided with holes for reducing their thermal conductivity.

A brushless electric motor system according to any one of the preceding claims, wherein the substantial planes hollow main cooling body comprises an inlet and an outlet, both provided at a second flat surface of the hollow main cooling body, for inputting and outputting the medium, respectively.

A brushless electric motor system according to claims 6 and 3, wherein the input is provided in substantially a center point of the circle.

A brushless electric motor system according to claim 7, wherein the substantial planar main hollow heat sink comprises flow channels for supporting the flow of the heat sink between the inlet and the outlet, wherein the flow channels descend from the inlet and extend radially outward.

A brushless electric motor system according to any one of the preceding claims, wherein the cooling system comprises the cooling medium, wherein the cooling medium is one of air and water.

The brushless electric motor system according to any of the preceding claims, wherein the electric motor system comprises thirty-six electrically excitable coils and eighteen power stages.

A brushless electric motor system according to any one of the preceding claims, wherein the base cooling plate is connected to main cooling body via a paste, wherein the base cooling plate is connected to the plurality of power stages via a paste, wherein the heat resistance inserts are connected to the base cooling plate via a paste and wherein the plurality of the electrically excitable coils are connected to the heat resistance inserts via a paste.

A brushless electric motor system according to any one of the preceding claims, wherein the base cooling plate comprises a cooling body.

A brushless electric motor system according to any one of the preceding claims, wherein the rotor surrounds the stator.

5

A method of operating a brushless electric motor system according to any of the preceding claims.

A motorized electric vehicle comprising a brushless electric motor system according to any one of claims 1 to 13.