CN106300746A - Change the rotor radiator structure of channel-section steel mounting means - Google Patents

Abstract

The invention relates to a heat dissipation structure of a motor rotor which changes the installation mode of channel steel, mainly comprising radial ventilation grooves, rotor teeth, axial ventilation channels, rotor iron core and channel steel. The rotor core is evenly divided into several sections along the axial direction, and there is a certain gap between adjacent rotor cores to form a radial ventilation ditch. The rotor teeth of adjacent segmented rotor cores correspond to each other in the axial direction. In the ventilation ditch and distributed along the circumference, and installed between the rotor teeth of adjacent segmented rotor cores, two I-shaped cross-section streamlined channel steels are placed between each rotor tooth of adjacent segmented rotor cores, and the rotor core is close to The rotating shaft is slotted to form an axial ventilation channel to provide a passage for the flow of the cooling medium. The structure of the present invention can give full play to its fanning ability and fluid guiding effect, greatly improving the heat dissipation effect of the rotor, and thus improving the working efficiency of the motor.

Description

The heat dissipation structure of the motor rotor by changing the channel steel installation method

technical field

The invention relates to a heat dissipation structure of a motor rotor that changes the installation mode of channel steel, and belongs to the field of motor ventilation technology and design and manufacture.

Background technique

Inside the motor with high power density, the rotor core of the motor is segmented, and radial air passages are formed between the core segments, and channel steel is attached inside to play the role of supporting components. At the same time, during the rotation of the motor, the rotor ventilation channel steel can play the role of a fan to a certain extent, and can improve the flow characteristics of the cooling medium. Chinese Patent No. 201320330289.4 describes the I-shaped cross-section channel steel, which can effectively improve the strength, but does not fully consider the effect of the channel steel on changing the gas flow; The boundary layer between the cooling gas in the ditch increases the heat dissipation area, but the wind resistance at the connection is relatively large and it is easy to form eddy currents. Both of the above two channel steel structures fail to efficiently utilize the flow diversion performance and fan performance of the channel steel.

Contents of the invention

The technical problem of the present invention is: to overcome the problem of poor ventilation effect of the existing motor due to the low utilization rate of the rotor ventilation channel steel, and to propose a ventilation structure that effectively improves the wind driving capacity of the rotor, so that the flow efficiency of the cooling medium inside the motor is relatively improved , the cooling effect has been improved.

The technical solution of the present invention is: change the heat dissipation structure of the motor rotor in the channel steel installation mode, mainly including radial ventilation grooves (1), rotor teeth (2), axial ventilation channels (3), rotor core (4) and slots steel (5). The rotor core (4) is evenly divided into several sections along the axial direction, and the number n of sections is related to the axial length D of the motor rotor, that is, n=D/187˜D/210. A certain gap is left between the adjacent rotor cores ( ₄ ) to form a radial ventilation ditch ( ₁ ). The length D is related, that is, L=[D/14+(R ₂ -R ₁ )/4]/60～[D/14+(R ₂ -R ₁ )/4]/50. The rotor teeth (2) of the adjacent segmented rotor cores (4) correspond to each other in the axial direction, and the channel steel (5) is located in the radial ventilation groove (1) and distributed along the circumference, and is installed in the adjacent segment Between the rotor teeth (2) of the rotor core (4), two channel steels (5) are placed between each rotor tooth (2) of the adjacent segmented rotor core (4), and the rotor core (4) is close to the shaft Slots are made at the position to form an axial ventilation channel (3) to provide a passage for the flow of cooling medium. The cross section of the axial ventilation channel (3) is designed to be circular, and the diameter Φ is related to the inner diameter R ₁ of the motor rotor and the outer diameter R ₂ of the rotor , that is, Φ=0.12(R ₂ -R ₁ )～0.18(R ₂ -R ₁ ), the radial distance between the axial ventilation channel (3) closest to the rotating shaft and the inner circle of the iron core is W=1/2Φ, corresponding to The included angle α=18° between the center point of the adjacent two axial air ducts (3) and the origin of the rotor core (4).

The channel steel is streamlined with an I-shaped section, and the height L ₁ of the channel steel is related to the inner diameter R ₁ of the rotor, the outer diameter R ₂ of the rotor and the axial length D, that is, L ₁ =[D/14+(R ₂ -R ₁ ) /4]/60～[D/14+(R ₂ -R ₁ )/4]/50, channel steel section width W ₁ is designed according to channel steel height L ₁ , W ₁ =1/3L ₁ ～1/2L _1. The overall width W ₂ of streamlined channel steel with I-shaped cross-section is related to the cross-sectional width W ₁ of the channel steel, which is W ₂ = 1.84W ₁ to 1.88W ₁ times, and the radius R ₃ of the arc section is related to the height L ₁ of the channel steel, that is, R ₃ =4.3L ₁ ~4.6L ₁ , the straight line length L ₂ of one arc segment =1.95R ₃ , the structural dimensions of two adjacent arc segments are the same, and the directions are opposite. The streamlined channel steel with I-shaped cross-section is designed as long and short. The long channel steel is composed of 5 arc segments, and its length L ₃ =0.4(R ₂ -R ₁ )～0.45(R ₂ -R ₁ ); the short channel steel Composed of two arc segments, the length L ₄ =0.15(R ₂ -R ₁ )～0.2(R ₂ -R ₁ ), two I-shaped section streamlines placed between the corresponding rotor teeth in the two segmented rotor cores The channel steel is one long channel steel mentioned above and one short channel steel mentioned above. _The installation direction is along the radial direction. It is equal to the distance L ₅ from the proximal tooth edge and the distance L ₇ between the short channel steel and the proximal tooth edge, and is equal to the distance L ₆ between the centers of the two channel steels, that is, L ₅ =L ₆ =L ₇ . On the whole, the long channel steel and short channel steel are regularly distributed on the circumference, the channel steel corresponding to three adjacent rotor teeth is a group, and the channel steel installation method of any group is "long channel steel" in the clockwise direction. ", "short channel", "long channel", "short channel", "short channel", "long channel".

Three channel steels (5) can also be placed between each rotor tooth (2) of the adjacent segmented rotor core (4), one is designed as a long channel steel, and its length L ₃ =0.4(R ₂ - R ₁ )～0.45(R ₂ -R ₁ ), one is designed as short channel steel, length L ₄ =0.15(R ₂ -R ₁ )～0.2(R ₂ -R ₁ ), one is medium channel steel, The straight line length L ₈ of the middle channel steel is related to the inner diameter R ₁ of the motor rotor and the outer diameter R ₂ of the rotor, which is L ₈ =0.18(R ₂ -R ₁ )～0.19(R ₂ -R ₁ ). The distance W ₄ between the channel steel and the core edge is designed to be 4mm~5mm, the medium channel steel is installed between the long channel steel and the short channel steel, the center distance between the medium channel steel and the long channel steel is L ₁₀ and the center distance between the medium channel steel and the short channel steel L ₁₁ is equal, that is, L ₁₀ =L ₁₁ . The distance L ₉ between the center of the long channel steel and its proximal tooth edge is equal to the distance L ₁₂ between the center of the short channel steel and its proximal tooth edge, and equal to the distance between the center of the long channel steel and the middle channel steel and the distance between the centers of the medium channel steel and the short channel steel 3/4 of the sum of the distances, that is, L ₉ =L ₁₂ =3/4(L ₁₀ +L ₁₁ ). On the whole, the long channel steel, medium channel steel and short channel steel are regularly distributed on the circumference, the channel steel corresponding to three adjacent rotor teeth is a group, and the channel steel on the three teeth of any group is installed in the order of The clockwise direction is "long channel steel", "medium channel steel", "short channel steel", "long channel steel", "medium channel steel", "short channel steel", "short channel steel", "medium channel steel "," long channel steel ".

Compared with the prior art, the present invention has the advantages of adopting different structures and quantities of the motor rotor ventilation channel steel, changing the air volume flowing through the rotor to different degrees, enhancing the gas flow performance inside the motor, and achieving a better cooling effect, so that the motor is Lower temperature under the same operating conditions.

Description of drawings

Figure 1 is a schematic diagram of the motor rotor core ventilation structure;

Figure 2 is an enlarged view of part A in Figure 1;

Fig. 3 is the front view and the right view of the motor rotor core ventilation structure in Fig. 1, wherein Fig. 3a is the main view and Fig. 3b is the right view;

Fig. 4 is a schematic diagram and a top view of an I-shaped cross-section streamlined channel steel, Fig. 4a is a schematic diagram of an I-shaped cross-section streamlined channel steel, and Fig. 4b is a top view of an I-shaped cross-section streamlined channel steel;

Figure 5 is a cross-sectional view of a radial ventilation ditch of a rotor when the motor is installed with streamlined channel steel with an I-shaped cross-section;

Fig. 6 is an enlarged view of part B in Fig. 5;

Figure 7 is an enlarged view of part C in Figure 6;

Figure 8 is an enlarged view of part B in the case of changing the length of the I-shaped cross-section streamlined channel steel on the basis of Figure 5;

Fig. 9 is a cross-sectional view of a radial ventilation ditch of a rotor when the number of streamlined channel steels with an I-shaped cross-section is changed by the motor;

Figure 10 is an enlarged view of part D in Figure 9;

Fig. 11 is an enlarged view of part E in Fig. 10 .

detailed description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Fig. 1, Fig. 2 and Fig. 3 (Fig. 2 is an enlarged view of part A in Fig. 1, Fig. 3a is a front view of Fig. 1, and Fig. 3b is a right view of Fig. 1), the changing channel steel installation method described in the present invention The motor rotor cooling structure mainly includes radial ventilation grooves (1), rotor teeth (2), axial ventilation channels (3), rotor core (4) and channel steel (5). For a large motor with a capacity above 1MW, the rotor core (4) is evenly divided into several segments along the axial direction, and the number n of segments is related to the axial length D of the rotor of the motor, that is, n=D/187˜D/210. A certain gap is left between the adjacent rotor cores ( ₄ ) to form a radial ventilation ditch ( ₁ ). The length D is related, that is, L=[D/14+(R ₂ -R ₁ )/4]/60～[D/14+(R ₂ -R ₁ )/4]/50. The rotor teeth (2) of the adjacent segmented rotor cores (4) correspond to each other in the axial direction, and the channel steel (5) is located in the radial ventilation groove (1) and distributed along the circumference, and is installed in the adjacent segment Between the rotor teeth (2) of the rotor core (4), two channel steels (5) are placed between each rotor tooth (2) of the adjacent segmented rotor core (4), and the rotor core (4) is close to the shaft Slots are made at the position to form an axial ventilation channel (3) to provide a passage for the flow of cooling medium. The cross section of the axial ventilation channel (3) is designed to be circular, and the diameter Φ is related to the inner diameter R ₁ of the motor rotor and the outer diameter R ₂ of the rotor , that is, Φ=0.12(R ₂ -R ₁ )～0.18(R ₂ -R ₁ ), the radial distance between the axial ventilation channel (3) closest to the rotating shaft and the inner circle of the iron core is W=1/2Φ, corresponding to The included angle α=18° between the center point of the adjacent two axial air ducts (3) and the origin of the rotor core (4). In this embodiment, the inner diameter of the rotor of the motor is R ₁ =1800mm, the outer diameter of the rotor is R ₂ =2842mm, and the axial length of the rotor core (4) is D = 3570mm. After optimization design, the rotor core (4) can be segmented The number of segments n=18.8～16.9, preferably 18, the axial length L of the radial ventilation ditch (1)=8.58mm～11.3mm, preferably 10mm, the diameter of the axial ventilation channel Φ=125.1mm～187.6mm, preferably 166.7mm, W =83.35.

In order to better improve the ventilation effect, the channel steel (5) of the present invention takes the streamlined I-shaped cross-section, as shown in Figure 4 (Fig. ), whose cross-section is I-shaped and extends in a wave form (this figure only shows a section of the actual whole channel steel). Fig. 5, Fig. 6 and Fig. 7 are cross-sectional views of radial ventilation ditch of a rotor under the condition of installing I-shaped section streamlined channel steel (Fig. 6 is an enlarged view of part B in Fig. 5, and Fig. 7 is an enlarged view of part C in Fig. 6) . Among them, the height L ₁ of the channel steel is related to the inner diameter R ₁ of the rotor, the outer diameter R ₂ of the rotor and the axial length D, that is, L ₁ =[D/14+(R ₂ -R ₁ )/4]/60～[D/ 14+(R ₂ -R ₁ )/4]/50. In this embodiment, the inner diameter of the motor rotor is R ₁ =1800mm, the outer diameter of the rotor is R ₂ =2842mm, and the axial length of the rotor core D=3570mm, so L ₁ = 8.58 mm to 11.3 mm, preferably 10 mm. The section width W ₁ of the channel steel is designed according to the height L ₁ of the channel steel, and is W ₁ =1/3L ₁ ~1/2L ₁ , that is, 3.3mm~5mm, preferably 4mm here. The overall width W ₂ of the I-shaped streamlined channel steel is related to the cross-sectional width W ₁ of the channel steel, which is ₁ times W ₂ = 1.84W ₁ ~ 1.88W, where W ₂ = 3.31mm ~ 3.38mm, preferably 3.35mm. The top view of streamlined channel steel with I-shaped cross-section is shown in Figure 4b, where the radius R ₃ of the arc segment (the radius of the maximum bending point) is designed to be related to the height L ₁ of the channel steel, that is, R ₃ =4.3L ₁ ~4.6L ₁ , the radius of an arc segment The straight line length L ₂ =1.95R ₃ , the fan effect of this design is the most obvious. The structural dimensions of two adjacent arc segments are the same, and the directions are opposite. It can be seen from Figure ₆ that the streamlined channel steel with _{I -} shaped cross _- section of the motor is designed as long and short. R ₁ ), where L ₃ =260.5mm～281.3mm, preferably 275mm; the short steel is composed of 2 arc segments, and the length L ₄ =0.15(R ₂ -R ₁ )～0.2(R ₂ -R ₁ ), here At L ₄ =104.2 mm to 114.6 mm, preferably 110 mm. The two I-shaped cross-section streamlined channel steels placed between the corresponding rotor teeth in the two segmented rotor cores are the above-mentioned 275mm long channel steel and the above-mentioned 110mm short channel steel respectively, and the installation direction is along the radial direction. At the far-axis end of the channel steel, the distance between the channel steel and the edge of the iron core (W ₃ in Fig. 7 ) is 4 mm to 5 mm, preferably 4.5 mm. Figure 7 is an enlarged view of part C of tooth I in Figure 6, where the distance between the 275mm long channel steel and the proximal tooth edge (L ₅ in Figure 7) and the distance between the 110mm short channel steel and the proximal tooth edge (L _{7 in Figure 7} ) and the distance between the centers of the two channel steels (L ₆ in Fig. 7 ), that is, L ₅ =L ₆ =L ₇ . On the whole, long channel steels and short channel steels are regularly distributed on the circumference, the channel steels corresponding to three adjacent rotor teeth form a group, and the channel steels of any group (I, II, III in Figure 6) are installed In the clockwise direction, they are "275mm I-shaped section streamlined long channel steel", "110mm I-shaped section streamlined short channel steel", "275mm I-shaped section streamlined long channel steel", "110mm I-shaped section streamlined short channel steel", "110mm I-shaped cross-section streamlined short channel steel" and "275mm I-shaped cross-section streamlined long channel steel" divide all the rotor teeth of the motor into several groups that do not overlap with each other in counterclockwise order, and the rules of each group are the same. When the ventilation channel steel is designed as the streamlined structure of the I-shaped section, the flow direction and speed of the fluid entering the ventilation ditch can be significantly changed, which can effectively improve the flow performance. Due to the bending of the streamlined channel steel with the I-shaped section, the rotor rotation direction The difference will affect the flow rate and flow rate of the cooling medium flowing into the ventilation ditch. With this setting, when the motor rotates clockwise, the air volume can be increased by 16% to 23% at most.

On this basis, the length of the 110mm I-shaped cross-section streamlined short channel steel can be changed and increased to 275mm, that is, the lengths of the two channel steels are equal, as shown in Figure 8 (Figure 8 is based on Figure 4, adding 110mm work Enlarged view of part B when the length of streamlined channel steel with zigzag cross-section is 275mm). Such setting effectively suppresses the eddy current formed by the flow of the cooling medium in the ventilation ditch.

In order to further improve the ventilation effect of the rotor, three channel steels (5) can also be placed between each rotor tooth (2) of the adjacent segmented rotor core (4) of the present invention, as shown in Fig. 9, Fig. 10 and Fig. 11, where Figure 9 is a cross-sectional view of a rotor radial ventilation ditch, Figure 10 is an enlarged view of part D in Figure 9, and Figure 11 is an enlarged view of part E in Figure 10, in the original 275mm long channel steel and 110mm short channel steel Based on the design of channel steel. The straight line length of the channel steel (L ₈ in Figure 10) is related to the motor rotor inner diameter R ₁ and rotor outer diameter R ₂ , that is, L ₈ =0.18(R ₂ -R ₁ )～0.19(R ₂ -R ₁ ), in this In the embodiment, the inner diameter of the motor rotor R ₁ =1800mm, the outer diameter of the rotor R ₂ =2842mm, that is, L ₈ =187.5mm-197.9mm, preferably 195mm here. Each channel steel is installed in the ventilation ditch between the two rotor tooth axes, and three channel steels are installed on each tooth, which are one of the above-mentioned 275mm steel, one of the above-mentioned 195mm steel and one of the above-mentioned 110mm steel. The whole steel extends radially, and the direction of the axis coincides with the radial direction of the rotor. At the far-axis end of the channel steel, the distance W ₄ between the channel steel and the edge of the core is designed to be 4 mm to 5 mm, preferably 4.5 mm. In Figure 11, a, b and c represent "275mm I-shaped cross-section streamlined steel", "195mm I-shaped cross-section streamlined steel" and "110mm I-shaped cross-section streamlined steel", respectively, and b channel steel is installed between a and c channel steels, The center distance L ₁₀ between b channel steel and a channel steel is equal to the center distance L ₁₁ between b channel steel and c channel steel, that is, L ₁₀ =L ₁₁ . The distance L ₉ between the center of channel steel a and its proximal tooth edge is equal to the distance L ₁₂ between the center of channel steel c and its proximal tooth edge, and equal to the sum of the distance between the centers of channel steel a and b and the distance between the centers of channel steel b and c 3/4, that is, L ₉ =L ₁₂ =3/4(L ₁₀ +L ₁₁ ). On the whole, the long channel steel, medium channel steel and short channel steel are regularly distributed on the circumference, the channel steel corresponding to three adjacent rotor teeth is a group, and the channel steel on the three teeth of any group (Fig. 10 IV, V, VI) The preferred installation methods in the clockwise direction are "275mm I-shaped section streamlined long channel steel", "195mm I-shaped section streamlined medium channel steel", "110mm I-shaped section streamlined short channel steel", "275mm I-shaped section streamlined long channel steel", "195mm I-shaped section streamlined medium channel steel", "110mm I-shaped section streamlined short channel steel", "110mm I-shaped section streamlined short channel steel", "195mm I-shaped section streamlined medium channel Steel", "275mm I-shaped cross-section streamlined long channel steel". In the same way, all the teeth of the motor are divided into several groups that do not overlap with each other in counterclockwise order, and the rules of each group are the same.

The above is only a specific embodiment of the present invention, but the protection of the present invention is not limited thereto, and any improvement without substantial changes made by those skilled in the art without changing the principle should also be regarded as the present invention. protection scope of the invention.

The contents not described in detail in the description of the present invention belong to the prior art known to those skilled in the art.

Claims (2)

1. The heat dissipation structure of the motor rotor that changes the channel steel installation method is characterized in that it mainly includes radial ventilation grooves (1), rotor teeth (2), axial ventilation channels (3), rotor core (4) and channel steel ( 5). The rotor core (4) is evenly divided into several sections along the axial direction, and the number n of sections is related to the axial length D of the motor rotor, that is, n=D/187˜D/210. A certain gap is left between the adjacent rotor cores ( ₄ ) to form a radial ventilation ditch ( ₁ ). The length D is related, that is, L=[D/14+(R ₂ -R ₁ )/4]/60～[D/14+(R ₂ -R ₁ )/4]/50. The rotor teeth (2) of the adjacent segmented rotor cores (4) correspond to each other in the axial direction, and the channel steel (5) is located in the radial ventilation groove (1) and distributed along the circumference, and is installed in the adjacent segment Between the rotor teeth (2) of the rotor core (4), two channel steels (5) are placed between each rotor tooth (2) of the adjacent segmented rotor core (4), and the rotor core (4) is close to the shaft Slots are made at the position to form an axial ventilation channel (3) to provide a passage for the flow of cooling medium. The cross section of the axial ventilation channel (3) is designed to be circular, and the diameter Φ is related to the inner diameter R ₁ of the motor rotor and the outer diameter R ₂ of the rotor , that is, Φ=0.12(R ₂ -R ₁ )～0.18(R ₂ -R ₁ ), the radial distance between the axial ventilation channel (3) closest to the rotating shaft and the inner circle of the iron core is W=1/2Φ, corresponding to The included angle α=18° between the center point of the adjacent two axial air ducts (3) and the origin of the rotor core (4). The channel steel is streamlined with an I-shaped section, and the height L ₁ of the channel steel is related to the inner diameter R ₁ of the rotor, the outer diameter R ₂ of the rotor and the axial length D, that is, L ₁ =[D/14+(R ₂ -R ₁ ) /4]/60～[D/14+(R ₂ -R ₁ )/4]/50, channel steel section width W ₁ is designed according to channel steel height L ₁ , W ₁ =1/3L ₁ ～1/2L _1. The overall width W ₂ of streamlined channel steel with I-shaped cross-section is related to the cross-sectional width W ₁ of the channel steel, which is W ₂ = 1.84W ₁ to 1.88W ₁ times, and the radius R ₃ of the arc section is related to the height L ₁ of the channel steel, that is, R ₃ =4.3L ₁ ~4.6L ₁ , the straight line length L ₂ of one arc segment =1.95R ₃ , the structural dimensions of two adjacent arc segments are the same, and the directions are opposite. The streamlined channel steel with I-shaped cross-section is designed as long and short. The long channel steel is composed of 5 arc segments, and its length L ₃ =0.4(R ₂ -R ₁ )～0.45(R ₂ -R ₁ ); the short channel steel It consists of 2 arc segments, the length of which is L ₄ =0.15(R ₂ -R ₁ )～0.2(R ₂ -R ₁ ), and is placed between the corresponding rotor teeth in the two segmented rotor cores (4). The streamlined channel steel with zigzag cross _- section is one long channel steel mentioned above and one short channel steel mentioned above. The installation direction is along the radial direction. The distance L ₅ between the long channel steel and the proximal tooth edge is equal to the distance L ₇ between the short channel steel and the proximal tooth edge, and is equal to the distance L ₆ between the centers of the two channel steels, that is, L ₅ =L ₆ =L ₇ . On the whole, the long channel steel and short channel steel are regularly distributed on the circumference, the channel steel corresponding to three adjacent rotor teeth is a group, and the channel steel installation method of any group is "long channel steel" in the clockwise direction. ", "short channel", "long channel", "short channel", "short channel", "long channel". 2. The heat dissipation structure of the motor rotor according to claim 1, characterized in that: three channel steels are placed between each rotor tooth (2) of the adjacent segmented rotor cores (4) (5), one is designed as long channel steel, its length L ₃ =0.4(R ₂ -R ₁ )～0.45(R ₂ -R ₁ ), one is designed as short channel steel, its length L ₄ =0.15(R ₂ -R ₁ )～0.2(R ₂ -R ₁ ), one is the middle channel steel, the straight line length L ₈ of the middle channel steel is related to the inner diameter R ₁ of the motor rotor and the outer diameter R ₂ of the rotor, which is L ₈ =0.18(R ₂ -R ₁ )～0.19(R ₂ -R ₁ ), at the far-axis end of the channel steel, the distance W ₄ between the channel steel and the core edge is designed to be 4mm～5mm, and the middle channel steel is installed between the long channel steel and the short channel steel , the center distance L ₁₀ between the middle channel steel and the long channel steel is equal to the center distance L ₁₁ between the middle channel steel and the short channel steel, that is, L ₁₀ =L ₁₁ . The distance L ₉ between the center of the long channel steel and its proximal tooth edge is equal to the distance L ₁₂ between the center of the short channel steel and its proximal tooth edge, and equal to the distance between the center of the long channel steel and the middle channel steel and the distance between the centers of the medium channel steel and the short channel steel 3/4 of the sum of the distances, that is, L ₉ =L ₁₂ =3/4(L ₁₀ +L ₁₁ ). On the whole, the long channel steel, medium channel steel and short channel steel are regularly distributed on the circumference, the channel steel corresponding to three adjacent rotor teeth is a group, and the channel steel on the three teeth of any group is installed in the order of The clockwise direction is "long channel steel", "medium channel steel", "short channel steel", "long channel steel", "medium channel steel", "short channel steel", "short channel steel", "medium channel steel "," long channel steel ".