SHIELDING STRUCTURE FOR POWER CONVERSION SYSTEM AND METHOD THEREOF

An electromagnetic shielding structure includes a first shielding material disposed at a first location with respect to at least one radiation source and a second shielding material attached with the first shielding material by fastening means. The second shielding material is disposed at a second location with respect to the at least one electromagnetic radiation source so as to define a predetermined gap between the first shielding material and the second shielding material. The first shielding material shields at least part of first frequency electromagnetic radiations generated from the at least one electromagnetic radiation source and penetrating through the second shielding material and the predetermined gap. The second shielding material shields at least part of second frequency electromagnetic radiations generated from the at least one electromagnetic radiation source.

DETAILED DESCRIPTION

Embodiments disclosed herein generally relate to improved electromagnetic shielding structures for power converters (or shortly referred to as converters) for purpose of electromagnetic radiation shielding or suppression. As a general rule, the improved electromagnetic shielding structure provided by the present disclosure can be used in a wide range of applications for shielding electromagnetic radiations generated from one or more electromagnetic radiation sources in association with the converters. For example, the improved electromagnetic shielding structures can be used in association with converters for driving electric machines or AC electric motors at a fixed speed or a variable/adjustable speed. The improved electromagnetic shielding structure can also be used in association with power converters for supplying AC electric power or DC electric power for transmission and distribution. The electromagnetic shielding structures provided by the present disclosure may be combined or integrated with a conventional cabinet to make the cabinet achieve at least dual functions of accommodating the converters therein as well as suppressing or shielding electromagnetic radiations generated from at least one radiation source in association with the operation of the converter. As used herein, the terms “suppress” and “shield” being used interchangeably throughout the description refer to the use of any appropriate material for at least partially absorbing the energy of electromagnetic radiations/waves, or at least partially reflecting the energy of electromagnetic radiations/waves, or at least partially canceling the energy of electromagnetic radiations/waves, or any other mechanism for reducing the intensity or magnitude of the electromagnetic radiations/waves.

In some embodiments, the present disclosure proposes a bi-layer, double-layer, or dual-layer electromagnetic shielding structure that can achieve the function of shielding electromagnetic radiations in a wide radiation frequency spectrum or frequency range. As used herein, “bi-material,” “double-material,” and “dual-material” electromagnetic shielding structures are not intended to encompass shielding structures only having two shielding materials with the capability of electromagnetic radiation shielding, but rather, are intended to cover shielding structures having at least two shielding materials or multiple shielding materials with the capability of the electromagnetic radiations shielding. In a particular embodiment, the bi-material shielding structure may comprise a first shielding material for example a first shielding metal such as steel for effectively shielding first frequency radiations such as low frequency electromagnetic radiations generated from the at least one radiation source in association with the converter. The bi-material electromagnetic shielding structure may also comprise a second shielding material for example second shielding metal such as copper, aluminum, and/or a combination thereof for effectively shielding second frequency radiations such as high frequency electromagnetic radiations generated from the at least one radiation source in association with the converter.

In some embodiments, the first shielding material and the second shielding material may be mechanically coupled or connected together in a detachable/removable manner by appropriate fastening means. With this detachable/removable configuration, a flexible shielding solution can be selected depending on the frequency of the electromagnetic radiations. For example, the electromagnetic radiations only contain low frequency components, for example, the converter may be commanded to provide low frequency current output to an AC electric motor for low rotation speed operation. In this case, the second shielding material may be removed from the cabinet. In another condition, when the electromagnetic radiations contain high frequency and low frequency components, the second shielding material and the first shielding material can be assembled together at the cabinet. In some embodiments, when the first shielding material and the second shielding material are assembled together, a predetermined gap may be formed between the two shielding materials. In this manner, the second shielding material can be placed nearer to the one or more electromagnetic radiation source for absorbing the high frequency components first.

Still in some embodiments, in addition to using the proposed bi-material electromagnetic shielding structure to suppress electromagnetic radiation in a manner to prevent electromagnetic radiations transmitted in an inside-to-outside direction, the bi-material electromagnetic shielding structure proposed herein can also be applied to shield electromagnetic radiations in a manner to prevent electromagnetic radiations transmitted in an outside-to-inside direction. For example, the bi-material electromagnetic shielding structure may be combined with or integrated with a protective cover/casing for an electrical component such as a processor and a controller, such that electromagnetic interference with one or more electrical or electronic components located inside of the cabinet can be prevented. Consequently, device failures of the processor and controller caused by the electromagnetic interferences can be avoided.

With the proposed electromagnetic shielding structure disclosed herein, the present disclosure can achieve a plurality of technical effects or benefits, one of which is electromagnetic radiations in a wide frequency spectrum or frequency range generated in association with the operation of the converter can be suppressed, such that the system can pass the safety standard in relation to electromagnetic radiations. Another technical effect or benefit is that by employing the proposed bi-layer shielding structure, at least one side of the cabinet for accommodating the converter therein can be maintained at a low temperature for preventing thermal damage to an operator even the radiation source contains high frequency components and/or high current. Other technical effects or benefits will be apparent to those skilled in the art by referring to the detailed descriptions provided below and the accompanying the drawings.

FIG. 1illustrates a block diagram of a system10in accordance with an exemplary embodiment of the present disclosure. The system10may be any appropriate converter based system capable of being configured to perform power conversion in a wide range of applications such as a vehicle, a pump, a wind turbine generator, a solar panel, a fan, a compressor, a mixer, a mill, a conveyor, and so on. In one non-limiting example, the system10can be a medium voltage drive system which is configured to drive one or more AC electric motors operating at a fixed speed or a variable speed.

As illustrated inFIG. 1, the system10includes a converter126which is capable of being housed or accommodated in a cabinet or enclosure100. In general, the converter126is configured to convert a first electric power124provided from an upstream power source122to a second electric power128for a downstream power destination136. Each of the first electric power124and the second electric power128can be DC power and AC power. As used herein, “DC” refers to an electric parameter that has a constant value/level or an electric parameter formed by superimposing noise signals or ripples with a constant value/level. As used herein, “AC” refers to an electric parameter varying as a function of time in a periodic manner and may contain fundamental components as well as harmonic components. In one embodiment, the converter126may comprise a DC-to-AC converter such as a multi-level inverter for converting first electric power124having a DC form to second electric power128having an AC form. In another embodiment, the converter126may comprise a DC-to-DC converter such as a single-active-bridge converter and a dual-active-bridge converter for converting first electric power124having a DC form to second electric power128also having a DC form. Still in another embodiment, the converter126may comprise an AC-to-DC converter such as a multi-level rectifier for converting first electric power124having an AC form to second electric power128having a DC form. Yet in another embodiment, the converter126may comprise an AC-to-AC converter such as a matrix converter for converting first electric power124having an AC form to second electric power128also having an AC form. In one embodiment, the upstream power source122may be at least part of a power grid for supplying AC electric power or DC power to the converter126. The upstream power source122may also be a power generation device such as a wind turbine or a solar panel for supplying AC power or DC power to the converter126. In one embodiment, the second electric power128may be directly supplied to a downstream power destination136which may be a power grid for power transmission and distribution. In another embodiment, the second electric power128may be transformed by a transformer to have a voltage matched with the downstream power destination136such as power grid. In some embodiments, the downstream power destination136may be a load such as an AC electric motor which is capable of being driven by the second electric power128.

With continuing reference toFIG. 1, the converter126may be in communication with a controller102for receiving one or more control signals104from the controller102. In response to the control signals104, the converter126can be controlled to provide an output having desired parameters such as voltage, current, frequency, and phase. The controller40may include any suitable programmable circuits or devices such as a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic controller (PLC), and an application specific integrated circuit (ASIC). The converter126may include a plurality of switching elements/devices such as IGBT and IGCT (not shown) arranged in a predetermined topology, including but not limited to, a diode clamped topology, a flying capacitor clamped topology, and an H-bridge topology. The plurality of switching elements/devices can be switched on and off according to the control signals104such as pulse signals and/or gating signals provided from the controller102in a predefined pattern or sequence.

Further referring toFIG. 1, during normal operation, the system10typically will emit electromagnetic radiations from one or more electromagnetic radiation sources in association with the converter126due to the switching operations of the plurality switching elements/devices in the converter126. As shown inFIG. 1, in one embodiment, one or more conduction paths coupled between the converter126and the downstream power destination136for transporting the second electric power128may become one or more electromagnetic radiation sources. In one embodiment, bus-bars used as the conduction path are capable of emitting one or more electromagnetic radiations when alternating current as well as harmonic components contained in the second electric power128are transmitted through the one or more conduction paths. In some embodiments, the electromagnetic radiations can be very strong when the converter126is commanded to provide the alternating current with a high frequency and/or a high current. For example, the alternating current provided from the converter126may be several hundred Hertz and several thousand Amperes when an AC electric motor is desired to operate at a high rotation speed. As a non-limiting example, the converter126may be instructed to provide an alternating current output having a frequency of about 467 Hz and current amplitude of about 1000 A. In one embodiment, to prevent the electromagnetic radiations generated from the one or more electromagnetic radiation sources from being transmitted to the outside of the cabinet100to satisfy at least some electromagnetic emission requirements, at least one side of the cabinet100may be provided with an electromagnetic shielding structure for shielding the electromagnetic radiations.

Further referring toFIG. 1, in one embodiment, the cabinet100at least includes a front side112, a left side114, a right side116, and a back side118that are sequentially connected to form a structure for accommodating the converter126therein. As shown inFIG. 1, the cabinet100may also be configured to accommodate one or more other components, such as the controller102and transformer132therein. In one embodiment, all of the four cabinet sides112,114,116,118may be provided with a respective electromagnetic shielding structure for shielding electromagnetic radiations generated within the cabinet110. In another embodiment, a single-piece shielding structure may be attached to the four cabinet sides112,114,116,118for shielding the electromagnetic radiations. In some embodiments, one or more electromagnetic shielding structures may be particularly disposed on a cabinet side that is located closer with respect to the one or more electromagnetic radiation sources. That is to say, for the cabinet side that is located farther away from the one or more electromagnetic radiation source, in some occasions, it may be not necessary to the provide the electromagnetic shielding structures thereon, because the electromagnetic radiations arriving at the cabinet side may be attenuated to an acceptable level. The electromagnetic radiations emitted from the electromagnetic radiation source can be expressed by the following equations:

where Ėx(0) and is the magnitude of the electric field generated at the radiation source, {dot over (H)}y(0) is the magnitude of the magnetic field generated at the radiation source, z is certain position in the space that the electric field or the magnetic field may arrive at, δ is the skin depth. According to equation (2), the magnitude of the magnetic field at a distance tdcan be expressed by the following equation:

It can be seen from equation (3) that when the distance is larger than 3 δ, the magnetic radiation can be substantially attenuated to zero.

In one embodiment, as shown inFIG. 1, an electromagnetic shielding structure140may be particularly provided at the front side112of the cabinet100. In some embodiments, the front side112may be arranged with a door structure that can be opened or closed to allow an operator20to access one or more components such as the converter126located inside of the cabinet100. As will be described in more detail below, providing the electromagnetic shielding structure140at the front side112of the cabinet100is advantageous not only because electromagnetic radiations can be effectively suppressed by the electromagnetic shielding structure140, but also the front side112can be maintained at a low temperature. As a result, when the operator20is instructed to perform maintenance operations with respect to one or more components located inside of the cabinet100, potential thermal damages to the operator20can be avoided. One example of the electromagnetic shielding structure will be described with reference toFIG. 2.

Referring toFIG. 2, a perspective view of an electromagnetic shielding structure150in accordance with one exemplary embodiment of the present disclosure is illustrated. The electromagnetic shielding structure150may be used as the electromagnetic shielding structure140shown inFIG. 1. In one embodiment, the electromagnetic shielding structure150is constructed to have a bi-layer, double-layer, or dual-layer electromagnetic shielding structure. For example, in one embodiment, the electromagnetic shielding structure150may include at least a first shielding member152. In one embodiment, the first shielding member152can be integrally formed as part of the front side112(shown inFIG. 1) for at least accommodating the converter126therein. In other embodiments, the first shielding member152can be separately formed and be attached to the front side112of the cabinet100by one or more fastening means. In the illustrated embodiment, the first shielding member152is arranged to have a generally flat plate structure having a predetermined thickness. In some embodiments, the first shielding member152can be constructed to have other structures. For example, the first shielding member152can be defined with a plurality of through holes/openings having any appropriate shapes, such as circular, elliptical, square, rectangular, and polygonal, to form a mesh structure. A mesh structure can allow heat generated at the first shielding member152or the front side112of the cabinet100to be more easily dissipated to the environment while the normal electromagnetic shielding function performed by the first shielding member152can still be retained. In one embodiment, the first shielding member152may be made from a first type of metal shielding material, such as steel for effectively shielding or suppressing first electromagnetic radiations having a frequency located in a first frequency spectrum or frequency range. In one embodiment, the first frequency spectrum may range from about 0 Hz to about 100 Hz. In other embodiments, any appropriate material either commercially available in the market or developed in the future that has similar shielding characteristics such as skin depth, conductivity, and/or permeability as steel capable of shielding electromagnetic radiations in a low frequency range can be used in the present disclosure.

With continuing reference toFIG. 2, in one embodiment, the bi-layer electromagnetic shielding structure150further include a second shielding member154. In one embodiment, the second shielding member154is similarly arranged to have a generally flat plate structure having a predetermined thickness. The second shielding member154is shaped to have a smaller overall size than the first shielding member154for purpose of being assembled with the first shielding member154. In other embodiment, similar to the first shielding member152, the second shielding member154can also be constructed to have other structures. For example, the second shielding member154can also be defined with a plurality of holes/opening having any appropriate shapes, such as circular, elliptical, square, rectangular, and polygonal to form a mesh structure for facilitating thermal dissipation without substantially sacrificing the electromagnetic radiation shielding function. In one embodiment, the second shielding member154may be made from a second type of metal shielding material, such as copper or aluminum for effectively shielding second electromagnetic radiations having frequency value located in a second frequency spectrum or frequency range. In a particular embodiment, the second frequency range may be from about 100 Hz to about 1000 Hz. In other embodiments, any appropriate material either commercially available in the market or developed in the future that has similar characteristics such as skin depth, conductivity, and permeability as copper and aluminum can be used in the present disclosure. Still in some embodiments, the second shielding member154may be made from a combination of the copper, aluminum, and any other appropriate material.

With continuing reference toFIG. 2, in one embodiment, the first shielding member152is coupled to the second shielding member154in a detachable or removable manner. The detachable or removable configuration has the benefit of allowing the second shielding member154to be removed from the first shielding member154. In some embodiments, the second shielding member154may be replaced with a new one or with different physical configurations such as size, shape, and thickness. More specifically, in one embodiment, one side or an inner side153of the first shielding member152is provided with at least one coupling member for coupling the second shielding member154with the first shielding member152. In one embodiment, two coupling members155,156are provided at the inner side of the first shielding member152for firmly securing the second shielding member154thereto. The first coupling member155is disposed adjacent to an upper end of the first shielding member152and the second coupling member156is disposed adjacent to a lower end of the first shielding member152. The first and second coupling members155,156may be defined with one or more openings or holes such that one or more screws157can be used to secure the second shielding member154and the first shielding member152together. In alternative embodiment, the first shielding member152and the second shielding member154can be firmly secured together by other means, such as wielding.

With continuing reference toFIG. 2, in one embodiment, the first and second coupling members155,156placed at the inner side of the first shielding member152is particularly designed to have a predetermined height. Thus, when the second shielding member154is secured to the first shielding member152via the first and second coupling members155,156, a gap or an intermediate layer is defined between the first shielding member152and the second shielding member154. In one embodiment, as shown inFIG. 2, the gap or the intermediate layer is filled with atmosphere therein. In other embodiments, the gap or the intermediate layer may be filled with other insulated materials. Due to this gap or intermediate layer, when the electromagnetic shielding structure150is provided at the front side112of the cabinet100, the second shielding member154is positioned nearer to the one or more electromagnetic radiation source than the first shielding member152. With this configuration, when one or more electromagnetic radiations are emitting from the one or more electromagnetic radiation sources in association with the converter26, the second shielding member154will receive the electromagnetic radiations first, such that high frequency electromagnetic radiations will be shielded first by the second shielding member154.

As is known, a skin depth of a material for purpose of electromagnetic radiation shielding can be expressed by the following equation:

where δ is the skin depth, f is the frequency of the electromagnetic radiations, σ is the conductivity of the shielding material, μ0is the permeability of free space, μris the relative permeability of the shielding material. According to equation (4), since the copper and aluminum has a smaller relative permeability than the steel, the skin depth of the second shielding member154which is made from copper or aluminum is larger than that made from steel. Comparing to using steel material for shielding the high frequency electromagnetic radiations, using the copper and aluminum material can significantly reduce thermal loss due to a larger skin depth of the copper and aluminum. Consequently, the front side of the cabinet100can be maintained at a relatively low temperature. Table-1 shows typical skin depth data of copper, aluminum, and steel at different electromagnetic radiation frequencies. For electromagnetic radiations having high frequency components, the copper and aluminum has larger skin depth than the steel. For example, at a first high frequency of 467 Hz, the skin depth of the aluminum and copper are 3.97 and 3.06 respectively, which are both larger than steel having a skin depth of 0.42. Increasing the frequency can reduce the skin depth. For example, at a second high frequency value of 567 Hz, the skin depth of the aluminum and copper are reduced to 3.60 and 2.78 respectively, which are still larger than steel material having a skin depth of 0.38.

Further referring toFIG. 2, the second shielding member154can be particularly designed with a predetermined thickness to allow high frequency components to be shielded or suppressed and let low frequency components to pass through. More specifically, the low frequency components contained in the electromagnetic radiations penetrating through the second shielding member154will further propagate through the gap defined between the first shielding member152and the second shielding member154and arrive at the first shielding member152. The low frequency electromagnetic radiations are further shielded or suppressed by the first shielding member152made of steel. As shown in table-1 above, at low frequency, for example at 50 Hz, the steel shielding material has a thin skin depth of 1.29. The thin skin depth still can allow the low frequency electromagnetic radiations absorbed by the first shielding member152while the thermal loss generated at the first shielding member152is low.

FIG. 3illustrates a top view of an electromagnetic shielding structure160in accordance with another embodiment of the present disclosure. The electromagnetic shielding structure160shown inFIG. 3can be used as the electromagnetic shielding structure140shown inFIG. 1. More particularly, the electromagnetic shielding structure160is suitable for being attached to one side for example the front side112of the cabinet100which has a double door structure. In the illustrated embodiment, the electromagnetic shielding structure160is similarly arranged to have a dual-layer shielding structure. For example, the electromagnetic shielding structure160may include a first shielding layer161and a second shielding layer163. Different than the electromagnetic shielding structure150shown inFIG. 2, the first shielding layer161includes a pair of first shielding members162,164. Each of the pair of first shielding members162,164may be integrally formed as part of a respective door portion of the front side112of the cabinet100. In other embodiments, each of the pair of first shielding members162,164may be detachably/removably attached to the respective door portion of the front side112of the cabinet100. In one embodiment, the pair of first shielding members162,164may be made from a first type of metal shielding material, such as steel for effectively shielding first electromagnetic radiations having a frequency located in a first frequency spectrum or frequency range. In other embodiments, any appropriate material either commercially available in the market or developed in the future that has similar shielding characteristics such as skin depth, conductivity, and permeability as steel capable of shielding electromagnetic radiations in a low frequency range can be used in the present disclosure. Still in some embodiments, the first shielding layer161may comprise more than two shielding members.

With continuing reference toFIG. 3, in one embodiment, the second shielding layer163includes a pair of second shielding members166,168. In one embodiment, the pair of second shielding members166,168may be made from a second type of metal shielding material, such as copper and aluminum for effectively shielding second electromagnetic radiations having frequency value located in a second frequency spectrum or frequency range. In other embodiments, any appropriate material either commercially available in the market or developed in the future that has similar characteristics such as skin depth, conductivity, and permeability as copper and aluminum can be used in the present disclosure. Still in some embodiments, more than two metal materials having high conductivity and low permeability such as copper and aluminum can be combined to form the second shielding members166,168.

With continuing reference toFIG. 3, in some embodiments, the electromagnetic shielding structure160may be configured to shield electromagnetic radiations generated from at least first, second, and third electromagnetic radiation source172,174,176. In the illustrated embodiment, the three electromagnetic radiation sources172,174,176are configured for transmitting converter outputs provided from the converter126to the load such as a three-phase AC electric motor. More specifically, the first electromagnetic radiations source172may be a first bus-bar conduction path for transmitting first phase current provided from the converter126to a first winding of the AC electric motor. The second electromagnetic radiation source174may be a second bus-bar conduction path for transmitting a second phase current provided from the converter126to a second winding of the AC electric motor. The third electromagnetic radiation source176may be a third bus-bar conduction path for transmitting third phase current provided from the converter126to a third winding of the AC electric motor.

As can be seen inFIG. 3, the first shielding layer161or the pair of first shielding members162,165are positioned at a first distance d1relative to the three radiations sources172,174,176. The second shielding layer163or the pair of second shielding members166,168are positioned at a second distance d2which is smaller than the first distance d1relative to the three radiation sources172,174,176. Thus, a gap or intermediate layer178is defined between the first shielding layer161and the second shielding layer163. In one embodiment, the gap or intermediate layer178is filled with atmosphere. In other embodiments, the gap or intermediate layer178may be filled with other materials such as insulated material therein. With this configuration, when the three radiation sources172,174,176emit radiations inside of the cabinet, the pair of second shielding members166,168will function to the shield or suppress high frequency component contained in the electromagnetic radiations. The low frequency part of the electromagnetic radiations penetrating through the pair of second shielding members166,168and the gap178will be suppressed or shielded by the pair of first shielding members162,164. Thus, by providing the electromagnetic shielding structure160on at least one cabinet side of the cabinet100, a wide frequency range electromagnetic radiations generated from one or more electromagnetic radiations sources within the cabinet can be well suppressed or shielded. The electromagnetic shielding effect can be better seen by referring to a couple of diagrams shown inFIGS. 4-6.

FIG. 4illustrates low frequency electromagnetic radiation shielding result210of a conventional solution using steel shielding material and proposed solutions of using bi-layer shielding materials. More specifically,FIG. 4illustrates a magnetic field intensity of the electromagnetic radiations as a function of distance at a frequency of 50 Hz. In the illustrated diagram, a first curve202represents the magnetic intensity of the electromagnetic radiations as a function of distance in which a combination of steel and copper are used for shielding the electromagnetic radiations. A second curve204represents the magnetic intensity of the electromagnetic radiations as a function of distance in which a combination of steel and aluminum are used for shielding the electromagnetic radiations. A third curve206represents the magnetic intensity of the electromagnetic radiations as a function of distance in which steel material is used for shielding the electromagnetic radiations. As shown in these curves202,204,206, in a first range212, starting from a first position where the electromagnetic radiation source for example a bus-bar is located to a second position where the shielding material is located, the steel and copper combination shielding structure and the steel and aluminum combination shielding structure can cause less magnetic attenuation than the steel shielding structure. Further as shown inFIG. 4, in a second range214, starting from the second position where the shielding material is located to an outside of the cabinet, using the steel and copper combination shielding structure and the steel and aluminum combination shielding structure can cause the magnetic intensity substantially reduced to zero, which is better than the steel shielding structure.

FIG. 5illustrates high frequency electromagnetic radiations shielding result220using the electromagnetic shielding structure160shown inFIG. 3in accordance with an exemplary embodiment of the present disclosure. More specifically, the electromagnetic shielding structure160is used for shielding the electromagnetic radiations at a frequency of 467 Hz. As shown inFIG. 5, first curve226represents the magnetic intensity of the electromagnetic radiations as a function of distance in which steel and copper combined shielding structure is used for shielding the electromagnetic radiations. Further as shown inFIG. 5, a second curve228represents the magnetic intensity of the electromagnetic radiations as a function of distance in which steel shielding material is used for shielding the electromagnetic radiations. It can be seen that, in a first range222, starting from a first position where the electromagnetic radiation source is located to a second position where the shielding structure is positioned, the steel and copper combined shielding structure causes the magnetic intensity to have less magnetic attenuations than the steel shielding structure. Further as shown inFIG. 5, in a second range224, starting from the second position where the shielding structure is positioned to the outside of the cabinet, the magnetic intensity is substantially reduced to zero. Thus, in some aspects, using the newly proposed shielding structure of a combination of copper and steel can have comparable shielding effect as the conventional shielding structure using steel material for shielding for example.

FIG. 6illustrates high frequency electromagnetic radiations shielding result230using the electromagnetic shielding structure160shown inFIG. 3in accordance with another exemplary embodiment of the present disclosure. More specifically, the electromagnetic shielding structure160is used for shielding the electromagnetic radiations at frequency of 567 Hz. Similar toFIG. 5, in a first range222, the steel and copper combined shielding structure can also cause the magnetic intensity to have less magnetic attenuations than the steel shielding structure. Further as shown inFIG. 6, in a second range234, the magnetic intensity is substantially reduced to zero. Thus, in some aspects, using the newly proposed shielding structure at least a combination of copper and steel can have comparable shielding effect as the conventional shielding structure using steel material for shielding for example.

FIG. 7illustrates the total thermal loss240generated at the shielding structure for shielding electromagnetic radiations having different frequencies in accordance with an exemplary embodiment of the present disclosure. Referring toFIG. 7, a first group242shows the total thermal loss generated by using the conventional shielding structure and the newly proposed shielding structure for shielding electromagnetic radiations having a low frequency of 50 Hz. As shown in the bars, for shielding electromagnetic radiations having low frequency value, using the newly proposed shielding structures (the steel plus copper and steel plus aluminum, shown in254,256) generate substantially small thermal loss as the conventional electromagnetic shielding structure (the steel shielding structure, shown in252).

Further referring toFIG. 7, a second group244and a third group246shows the generated total thermal loss for shielding a first high frequency electromagnetic radiations of 467 Hz and a second high frequency electromagnetic radiations of 567 Hz. As shown in bars, using the newly proposed electromagnetic shielding structures (steel plus copper and steel plus aluminum, shown in264,266,274,276) can generate much less thermal loss than by using the conventional electromagnetic shielding structure (the steel shielding structure, shown in262,272).

FIG. 8illustrates a flowchart of a method400of using electromagnetic shielding structures for shielding or suppressing electromagnetic radiations generated within a cabinet in accordance with an exemplary embodiment. In some embodiments, the method400can also be implemented for maintaining at least one side of a cabinet at low temperature.

In one implementation, the method400may start to implement from block402. At block402, a first shielding member may be provided for purpose of shielding or suppressing low frequency electromagnetic radiations. In one embodiment, the first shielding member may be provided on at least one side of a cabinet for example the cabinet100shown inFIG. 1. In one embodiment, the first shielding member may comprise steel material or any other material having similar characteristics as steel particularly designed for shielding electromagnetic radiations having low frequency components. In some embodiments, the first shielding material may integrally formed as part of a side of the cabinet for accommodating one or more components such as a converter therein. In another embodiment, the first shielding material may be detachably or removably attached to one side of the cabinet. In some embodiments, the first shielding material is particularly being provided at the side of the cabinet that is located nearer to the one or more electromagnetic radiations sources.

At block404, a second shielding member is provided for purpose of shielding or suppressing high frequency electromagnetic radiations. In one embodiment, the second shielding member may comprise copper and aluminum material or any other material that has similar characteristics as copper and aluminum for shielding or suppressing electromagnetic radiations having high frequency components. In some embodiments, the second shielding material may be coupled to the first shielding member in a detachable or removable manner. More specifically, in some embodiments, a predetermined gap or an intermediate layer may be defined between the first shielding member and the second shielding member, such that the second shielding member can be placed closer to the one or more electromagnetic radiations sources than the first shielding member. Thus, high frequency electromagnetic radiations generated from the one or more electromagnetic sources can be first suppressed by the second shielding member. Because high conductivity and low permeability material are used by the second shielding member for shielding or suppressing the high frequency electromagnetic radiations, less thermal loss are generated at the cabinet side that is attached with the shielding structure, and as a result the cabinet can be maintained at a low temperature.

The method400described with reference toFIG. 10may be modified in various ways in accordance with certain embodiments of the present disclosure. For example, the operations performed at blocks402and404can exchange order in some embodiments. In some embodiments, the second shielding member can be provided prior to providing the first shielding member. In other embodiment, the method404may comprise additional operations. In some implementation, after block, the method400may further include a block for securing the first shielding member and the second shielding member together. For example, the first shielding member and the second shielding member may be secured together by screws.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional assemblies and techniques in accordance with principles of this disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.