An oil-cooling and temperature-reducing unit for high-voltage frequency converters

Abstract

The present invention discloses an oil-cooling and temperature-reducing unit for a high-voltage frequency converter, which relates to the technical field of frequency converter heat dissipation and solves the problem of cooling oil solidification. It includes a frequency converter housing, and a transmission structure is connected to one side of the frequency converter housing. The transmission structure includes an oil pump, and the oil pump drives a suction fan and a transmission screw to rotate through transmission. The output end of the oil pump is connected to a diversion oil pipe, and an oil body crushing assembly is installed at the connection between the diversion oil pipe and the oil pump. Among them, the oil body crushing assembly includes a movable collar, and the movable collar is sleeved on one side of the diversion oil pipe. Crushing balls are arranged inside the movable collar, and the crushing balls crush the solidified oil body. A dredging insertion rod is installed on one side inside the movable collar, and the dredging insertion rod dredges the oil pipe; in the present invention, the problems of cooling oil solidification and volatilization in a low-temperature environment are effectively delayed through a mechanical transmission method.

Description

Technical Field

[0001] The present invention belongs to the technical field of frequency converter heat dissipation, and specifically relates to an oil-cooling and temperature-reducing unit for high-voltage frequency converters. Background Art

[0002] In gas-fired power plants, high-voltage frequency converters are key electrical equipment used to control and regulate the speed of motors, thereby optimizing the operating efficiency of gas turbines. However, when high-voltage frequency converters are operating, they generate a large amount of heat. If the heat is not dissipated in a timely manner, it may affect the performance and lifespan of the equipment.

[0003] The existing Chinese patent with the publication number discloses a heat dissipation device for a mine-used AC frequency converter, which belongs to the technical field of mine-used AC frequency converters. The technical problem to be solved is that the ventilation openings provided on the frequency converter may cause dust to enter and prevent heat from being dissipated. The adopted solution is that the heat dissipation device for the mine-used AC frequency converter includes a frequency converter body, through holes, mounting plates, fans, sealing plates, lifting devices, and sealing mechanisms. The heat dissipation device for the mine-used AC frequency converter provided by the present invention can blow the blowing frame through the fans, thereby canceling the sealing of the through holes by the sealing plates and realizing the dissipation of the temperature inside the frequency converter body. At the same time, the air and dust inside the frequency converter body can be blown out of the frequency converter body, further blowing out the heat and dust inside the frequency converter body, and solving the problem that a large amount of dust enters through the ventilation openings provided on the existing frequency converter and is not easily discharged.

[0004] However, the heat dissipation device for this AC frequency converter still has the following defects:

[0005] 1. The device uses air-cooling technology. After the device stops working, dust will accumulate in the dead corners inside the device. Traditional water-cooling can seal the frequency converter, but its structure is complex and the failure rate is high. Problems such as blockage of the water circulation system, pump failure, and thermostat failure are likely to occur. Moreover, if the water-cooling system leaks, it will directly lead to the scrapping of the frequency converter and the motor, resulting in large failure losses.

[0006] The present invention adopts an oil-cooling method instead of water-cooling. However, traditional oil-cooling has the problem of oil and gas leakage, which leads to the condensation of oil stains on the surface of the frequency converter. Because the frequency converter vibrates during operation, over time, the sealing performance of the frequency converter housing will be affected, resulting in the volatilization of the oil-cooling oil. The volatilization rate of engine oil is usually slow, but under specific conditions, such as heating or exposure to air, its volatility will increase. The volatilization rate is related to the quality of the engine oil.

[0007] 2. In addition, oil-cooling also has the problem of solidification of the cooling oil at low temperatures. Although the traditional method of adding pour point depressants has a pour point depressing effect, the cooling oil will still solidify at a certain temperature, and the pour point depressants will dilute the cooling oil and affect the cooling effect. Summary of the Invention

[0008] The object of the present invention is to provide an oil-cooling and temperature-reducing unit for a high-voltage frequency converter to solve the problems presented in the above-mentioned background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] An oil-cooling and temperature-reducing unit for a high-voltage frequency converter includes a frequency converter housing. One side of the frequency converter housing is connected with a transmission structure, and the transmission structure includes an oil pump, an extraction fan, and a reciprocating lead screw. The input end of the oil pump is connected with a diversion oil pipe, and an oil body crushing component is installed on the outer wall of the diversion oil pipe.

[0011] Among them, the oil body crushing component includes a movable collar, and the movable collar is sleeved on one side of the diversion oil pipe. The movable collar is composed of an inner ring and an outer ring. The inner ring is fixedly connected to the outer wall of the diversion oil pipe, and the outer ring is rotatably connected to the outer wall of the diversion oil pipe. A plurality of rolling balls are installed between the inner ring and the outer ring, and the rolling balls crush the solidified oil body. A dredging insertion rod is installed on one side inside the movable collar, and the dredging insertion rod dredges the oil pipe.

[0012] In a further technical solution, the outer wall of the movable collar is fixedly connected with a first transmission gear, and a second transmission gear is installed on one side of the first transmission gear. The second transmission gear and the first transmission gear are driven by a transmission chain.

[0013] Among them, the inner side of the second transmission gear is fixedly provided with a third transmission gear through a coupling shaft, and a fourth transmission gear is provided on one side of the third transmission gear, and a fifth transmission gear is provided on one side of the fourth transmission gear. The third transmission gear, the fourth transmission gear, and the fifth transmission gear are driven by gears.

[0014] In a further technical solution, a fan installation hole is inlaid on one side of the frequency converter housing.

[0015] Among them, one side of the fifth transmission gear is connected with an extraction fan, and the extraction fan is installed inside the fan installation hole.

[0016] In a further technical solution, one end of the coupling shaft inside the second transmission gear is fixedly connected with a reciprocating lead screw, and a movable scraper penetrates through the bottom end of the reciprocating lead screw. The movable scraper is installed on the outer wall of the reciprocating lead screw.

[0017] Among them, four groups of through grooves are provided on the movable scraper, and the oil body passes through the through grooves.

[0018] Among them, an inner interlayer of a cabinet is provided inside the frequency converter housing. The movable scraper moves in the cavity between the frequency converter housing and the inner interlayer of the cabinet, and the cooling oil body is also poured into the cavity.

[0019] Further technical solution: on one side of the connection between the diversion oil pipe and the movable collar, a first connection port is inlaid, and on the other side of the connection between the diversion oil pipe and the movable collar, a second connection port is inlaid.

[0020] Further technical solution: the interior of the movable collar is in a hollow ring shape, and the contact surfaces on both sides of the movable collar and the diversion oil pipe are sealed by a sealing ring.

[0021] Wherein, an oil passage plug is fixed at the middle position of the installation place of the diversion oil pipe and the movable collar.

[0022] Further technical solution: a connecting toothed ring is fixed on one side inside the movable collar, and cutting slope teeth are arranged on the inner side of the connecting toothed ring.

[0023] Further technical solution: on both sides of the top end of the second connection port, support frames are fixed, and elastic elements are sleeved on the support frames. The elastic elements have elasticity.

[0024] Wherein, the top end of the elastic element is connected with a movable strut, and through holes are arranged on both sides of the movable strut. The movable strut is slidably connected with the support frame, and a dredging insertion rod is fixed at the middle position of the support frame.

[0025] Further technical solution: the top end of the dredging insertion rod is spherical, the bottom end of the dredging insertion rod is sharp, and the dredging insertion rod is arranged at the middle position of the second connection port.

[0026] Further technical solution: a plurality of groups of rolling balls are arranged on the surface of the rolling ball, and the sliding friction is changed into rolling friction through the rolling balls.

[0027] Advantages of the present invention:

[0028] Firstly, select oils with lower pour point and cold filter plugging point to be used in combination with this device to ensure that the oil can still maintain fluidity at low temperatures. The device effectively delays the problem of the cooling oil solidifying in a low-temperature environment through a mechanical transmission method. Compared with the traditional method of heating the oil to improve fluidity, this mechanical transmission method has a better cooling effect, and the problem of oil volatilization is solved by an exhaust fan.

[0029] Cool the frequency converter by using an oil circulation method, extract the oil gas volatilized from the cooling oil inside the frequency converter cabinet by an exhaust fan, and use it in combination with the oil cooling system to effectively capture and recover the volatilized oil gas. In addition, it can also reduce the condensation of oil stains on the surface of the frequency converter and strengthen the external ventilation of the frequency converter, ensure the air circulation on the surface of the frequency converter, reduce the residence time of the oil gas in the air, thereby reducing the volatilization loss. In addition, the heat on the surface of the oil cooling system is taken away by the exhaust air to reduce the temperature of the oil gas, which can further reduce the oil gas volatilization.

[0030] Because the cooling oil solidifies when the temperature first approaches the solidification point of the cooling oil, and the flow rate of the oil slows down and stays in local areas of the circulation system for a long time and then solidifies. When the frequency converter works, the electrical components generate heat, and the inner temperature is higher than the outer temperature. Therefore, the cooling oil in the oil-cooled fuel tank solidifies gradually from the outside to the inside. Therefore, by driving the movable scraper through the reciprocating screw rod transmission to scrape the solidified oil body on the inner wall in time in the interlayer between the outer shell of the frequency converter and the inner layer of the cabinet, the solidification problem of the oil body can be delayed, and the overall practicability of the device is improved.

[0031] Other features and advantages of the present invention will be described in detail in the following specific implementation section. Brief Description of the Drawings

[0032] Figure 1 : The first three-dimensional external structure schematic diagram of the present invention.

[0033] Figure 2 : The first three-dimensional exploded structure schematic diagram of the present invention.

[0034] Figure 3 : The Figure 2 enlarged structure schematic diagram at A in the present invention.

[0035] Figure 4 : The second three-dimensional exploded structure schematic diagram of the present invention.

[0036] Figure 5 : The third three-dimensional exploded structure schematic diagram of the present invention.

[0037] Figure 6 : The Figure 6 enlarged structure schematic diagram at B in the present invention.

[0038] Figure 7 : The fourth three-dimensional exploded structure schematic diagram of the present invention.

[0039] Figure 8 : The three-dimensional sectional view schematic diagram of the oil crushing component of the present invention.

[0040] Figure 9 : The Figure 8 enlarged structure schematic diagram at C in the present invention.

[0041] Figure 10 : The three-dimensional enlarged schematic diagram of the connection between the dredging plug rod and the second connection port of the present invention.

[0042] Figure 11 : The top view sectional view schematic diagram of the present invention.

[0043] Figure 12 : The schematic diagram of the rolling ball structure of the present invention.

[0044] Figure 13:Schematic diagram of the prior art.

[0045] Reference numerals: 1, frequency converter housing; 2, transmission structure; 201, oil transfer pump; 202, diversion oil pipe; 203, first transmission gear; 204, transmission chain; 205, second transmission gear; 206, third transmission gear; 207, fourth transmission gear; 208, fifth transmission gear; 209, exhaust fan; 210, reciprocating lead screw; 211, moving scraper; 3, oil crushing assembly; 301, movable collar; 302, first connection port; 303, rolling ball; 304, connecting tooth ring; 305, oil passage plug; 306, support frame; 307, elastic element; 308, movable strut; 309, dredging plug; 310, second connection port; 4, fan mounting hole; 5, inner sandwich of the cabinet. Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0047] In the prior art, the air-cooling cooling method is relatively common. For example, in the published technical document "CN117750708A, an energy-saving temperature reduction system and usage method for a water source cooling unit of a high-voltage frequency converter", as Figure 13 shown, although cold air can be generated in its technical solution to cool the frequency converter unit, it overly relies on cooling water. The water needs to consume more additional electric energy to become cold, and the cooling effect is not very ideal. The present invention proposes a more efficient cooling unit to replace the above solution.

[0048] Embodiment 1

[0049] As Figures 1-12 shown in the figure, a high-voltage frequency converter oil-cooling temperature reduction unit includes a frequency converter housing 1. One side of the frequency converter housing 1 is connected with a transmission structure 2, and the transmission structure 2 includes an oil transfer pump 201, an exhaust fan 209 and a reciprocating lead screw 210. The input end of the oil transfer pump 201 is connected with a diversion oil pipe 202;

[0050] The device cools the frequency converter by using the oil circulation method, extracts the oil and gas volatilized from the cooling oil inside the frequency converter cabinet through the exhaust fan 209, and uses it in combination with the oil-cooling system, effectively capturing and recovering the volatilized oil and gas. In addition, it can also reduce the condensation of oil stains on the surface of the frequency converter and strengthen the external ventilation of the frequency converter, ensuring the air circulation on the surface of the frequency converter, reducing the residence time of oil and gas in the air, thereby reducing the volatilization loss. In addition, the heat on the surface of the oil-cooling system is taken away by the air extraction to reduce the temperature of the oil and gas, which can further reduce the oil and gas volatilization;

[0051] Embodiment 2

[0052] The outer wall of the movable collar 301 is fixedly connected with a first transmission gear 203, and a second transmission gear 205 is installed on one side of the first transmission gear 203. The second transmission gear 205 and the first transmission gear 203 are driven by a transmission chain 204.

[0053] Wherein, a third transmission gear 206 is fixedly installed inside the second transmission gear 205 through a coupling shaft. A fourth transmission gear 207 is arranged on one side of the third transmission gear 206. The fourth transmission gear 207 is rotationally connected to the frequency converter housing 1. A fifth transmission gear 208 is arranged on one side of the fourth transmission gear 207. The third transmission gear 206, the fourth transmission gear 207 and the fifth transmission gear 208 are driven by meshing teeth.

[0054] A fan mounting hole 4 is inlaid on one side of the frequency converter housing 1.

[0055] Wherein, one side of the fifth transmission gear 208 is connected with an exhaust fan 209, and the exhaust fan 209 is installed inside the fan mounting hole 4.

[0056] One end of the coupling shaft inside the second transmission gear 205 is fixedly connected with a reciprocating lead screw 210. The bottom end of the reciprocating lead screw 210 penetrates through a movable scraper 211, and the movable scraper 211 is installed on the outer wall of the reciprocating lead screw 210.

[0057] Wherein, four through grooves are arranged on the movable scraper 211, and the oil body passes through the through grooves.

[0058] Wherein, an inner sandwich layer 5 of the cabinet is arranged inside the frequency converter housing 1. The movable scraper 211 moves in the cavity between the frequency converter housing 1 and the inner sandwich layer 5 of the cabinet, and the cooling oil body is also poured into the cavity.

[0059] The output end of the oil pump 201 is communicated with the cavity between the frequency converter housing 1 and the inner sandwich layer 5 of the cabinet through a pipeline, so that the oil inside the cavity can circulate. The fifth transmission gear 208 is fixedly connected to the end of the fan blade shaft of the exhaust fan 209. When the exhaust fan 209 is composed of a fan housing, a driving motor and a fan blade shaft, when the exhaust fan 209 operates, it drives the fifth transmission gear 208 to rotate through the fan blade shaft, and then drives the third transmission gear 206 through the fourth transmission gear 207 to drive the reciprocating lead screw 210 to rotate synchronously with the second transmission gear 205. When the reciprocating lead screw 210 rotates, it drives the movable scraper 211 to reciprocate on the inner side of the inner sandwich layer 5 of the cabinet, so as to scrape the solidified oil body on the inner walls of the frequency converter housing 1 and the inner sandwich layer 5 of the cabinet, reduce the contact time of the oil with the inner walls of the frequency converter housing 1 and the inner sandwich layer 5 of the cabinet, and thus delay the solidification problem of the oil body, and further improve the overall practicability of the device.

[0060] Because the cooling oil solidifies when the temperature is close to the solidification point of the cooling oil, and the flow rate of the oil slows down and stays in a local area of the circulation system for a long time and then solidifies. When the frequency converter works, the electrical components generate heat, and the inner temperature is higher than the outer temperature. Therefore, the cooling oil in the oil-cooled fuel tank solidifies gradually from the outside to the inside. Therefore, the way of scraping by the moving scraper 211 can delay the solidified cooling oil on the side wall;

[0061] Embodiment 3

[0062] An oil body crushing component 3 is installed on the outer wall of the diversion oil pipe 202. Among them, the oil body crushing component 3 includes a movable collar 301, and the movable collar 301 is sleeved on one side of the diversion oil pipe 202. The movable collar 301 is composed of an inner ring and an outer ring. The inner ring is fixedly connected to the outer wall of the diversion oil pipe 202, and the outer ring is rotatably connected to the outer wall of the diversion oil pipe 202. A plurality of rolling balls 303 are installed between the inner ring and the outer ring, and the rolling balls 303 crush the solidified oil body. One side of the inside of the movable collar 301 is provided with a dredging rod 309, and the dredging rod 309 dredges the oil pipe. A first connection port 302 is inlaid on one side of the connection between the diversion oil pipe 202 and the movable collar 301, and a second connection port 310 is inlaid on the other side of the connection between the diversion oil pipe 202 and the movable collar 301. The inside of the movable collar 301 is a hollow ring shape. The contact surfaces on both sides of the movable collar 301 and the diversion oil pipe 202 are sealed by a sealing ring. Among them, an oil passage plug 305 is fixed at the middle position of the installation place of the diversion oil pipe 202 and the movable collar 301. A connecting toothed ring 304 is fixed on one side of the inside of the movable collar 301, and the inner side of the connecting toothed ring 304 is provided with cutting slope teeth. Support frames 306 are fixed on both sides of the top of the second connection port 310, and an elastic element 307 is sleeved on the support frames 306. The elastic element 307 has elasticity. Among them, the top of the elastic element 307 is connected with a movable support rod 308, and through holes are provided on both sides of the movable support rod 308. The movable support rod 308 is slidably connected with the support frames 306. A dredging rod 309 is fixed at the middle position of the support frames 306. The top of the dredging rod 309 is spherical, and the bottom of the dredging rod 309 is sharp. The dredging rod 309 is arranged at the middle position of the second connection port 310. Multiple groups of rolling beads are arranged on the surface of the rolling balls 303 to change the sliding friction into rolling friction through the rolling beads;

[0063] When the second transmission gear 205 rotates, it drives the first transmission gear 203 through the transmission chain 204 to drive the outer ring of the movable collar 301 to rotate, and then drives a plurality of rolling balls 303 to roll through friction. When the oil returns through the diversion oil pipe 202, the oil passes through the second connection port 310 and is rolled by a plurality of rolling balls 303 to crush the agglomerated oil, so as to ensure the subsequent flow effect of the oil. At the same time, the solidification of the oil is slowed down by the friction of the rolling balls 303, so as to improve the heat conduction effect of the oil, and further improve the cooling effect on the electrical components inside the frequency converter housing 1;

[0064] While the outer ring of the movable collar 301 rotates, it drives the connecting gear ring 304 to rotate. Due to the sloped groove inside the connecting gear ring 304, when the connecting gear ring 304 rotates, the sloped groove on the inner side will move the dredging rod 309 up and down reciprocally, performing reciprocating insertion and extraction on the inner side of the second connection port 310, which can further dredge the oil body in the channel, thus ensuring the fluidity during the oil circulation process, and further improving the overall practicality of the device.

[0065] In addition, by optimizing the design of the oil pipeline, the length of the oil pipeline is reduced to further prevent the cooling oil from solidifying. Moreover, heat insulation materials are used for components such as the oil tank, oil pipe, and cooling interlayer of the oil cooling oil circulation system, further reducing heat loss and keeping the temperature of the oil within an appropriate range.

[0066] The high-voltage inverter cooling system for a gas power plant adopts an oil-cooled heat dissipation technology. By pouring mineral oil into the body of the heat dissipation seat, the heat-conducting property of the oil is utilized to absorb and dissipate the heat generated by the inverter circuit board. The heat dissipation effect of oil cooling is better than that of air-cooled engines, and the failure rate is lower than that of water-cooled engines. Moreover, after a failure and leakage occur in oil cooling, it will not only not damage the inverter and the motor but also play a lubricating role, and also prevent the engine oil from becoming thinner due to excessive temperature.

[0067] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0068] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims

1. A high-voltage frequency converter oil-cooling and temperature-reducing unit, comprising a frequency converter housing (1), characterized in that: One side of the frequency converter housing (1) is connected with a transmission structure (2), and the transmission structure (2) includes an oil transfer pump (201), an exhaust fan (209) and a reciprocating lead screw (210). The input end of the oil transfer pump (201) is connected with a diversion oil pipe (202), and an oil body crushing assembly (3) is installed on the outer wall of the diversion oil pipe (202). Among them, the oil body crushing assembly (3) includes a movable collar (301), and the movable collar (301) is sleeved on one side of the diversion oil pipe (202). The movable collar (301) is composed of an inner ring and an outer ring. The inner ring is fixedly connected to the outer wall of the diversion oil pipe (202), and the outer ring is rotatably connected to the outer wall of the diversion oil pipe (202). A plurality of crushing balls (303) are installed between the inner ring and the outer ring, and the crushing balls (303) crush the solidified oil body. One side inside the movable collar (301) is installed with a dredging rod (309), and the dredging rod (309) dredges the oil pipe. The outer wall of the movable collar (301) is fixedly connected with a first transmission gear (203), and a second transmission gear (205) is installed on one side of the first transmission gear (203). The second transmission gear (205) and the first transmission gear (203) are driven by a transmission chain (204). Among them, a third transmission gear (206) is fixedly connected to the inner side of the second transmission gear (205) through a coupling shaft. A fourth transmission gear (207) is arranged on one side of the third transmission gear (206), and a fifth transmission gear (208) is arranged on one side of the fourth transmission gear (207). The third transmission gear (206), the fourth transmission gear (207) and the fifth transmission gear (208) are driven by meshing teeth. One end of the coupling shaft inside the second transmission gear (205) is fixedly connected with a reciprocating lead screw (210), and a movable scraper (211) penetrates through the bottom end of the reciprocating lead screw (210). The movable scraper (211) is installed on the outer wall of the reciprocating lead screw (210). Among them, four groups of through grooves are provided on the movable scraper (211), and the oil body passes through the through grooves. Among them, an inner sandwich (5) of the cabinet is arranged inside the frequency converter housing (1). The movable scraper (211) moves in the cavity between the frequency converter housing (1) and the inner sandwich (5) of the cabinet, and the cooling oil body is also poured into the cavity. One side of the connection between the diversion oil pipe (202) and the movable collar (301) is inlaid with a first connection port (302), and the other side of the connection between the diversion oil pipe (202) and the movable collar (301) is inlaid with a second connection port (310). The inside of the movable collar (301) is in a hollow ring shape, and the contact surfaces on both sides of the movable collar (301) and the diversion oil pipe (202) are sealed by a sealing ring. Among them, an oil passage plug (305) is fixed at the middle position of the installation place of the diversion oil pipe (202) and the movable collar (301).

2. The oil-cooling and temperature-reducing unit of a high-voltage frequency converter according to claim 1, characterized in that: A fan installation hole (4) is inlaid on one side of the frequency converter housing (1). Wherein, one side of the fifth transmission gear (208) is connected with an exhaust fan (209), and the exhaust fan (209) is installed inside the fan mounting hole (4).

3. The oil-cooling and temperature-reducing unit for high-voltage frequency converter according to claim 1, wherein: One side inside the movable collar (301) is fixed with a connecting gear ring (304), and the inner side of the connecting gear ring (304) is provided with slope-cut teeth.

4. A high-voltage frequency converter oil cooling and temperature reduction unit according to claim 1, characterized in that: Both sides of the top of the second connection port (310) are fixed with support frames (306), and an elastic element (307) is sleeved on the support frames (306), and the elastic element (307) has elasticity. Wherein, the top of the elastic element (307) is connected with a movable support rod (308), and through holes are provided on both sides of the movable support rod (308). The movable support rod (308) is slidably connected with the support frame (306), and a dredging plug rod (309) is fixed at the middle position of the support frame (306).

5. The oil-cooling and temperature-reducing unit for high-voltage frequency converter according to claim 4, characterized in that: The top of the dredging plug rod (309) is spherical, the bottom of the dredging plug rod (309) is sharp, and the dredging plug rod (309) is arranged at the middle position of the second connection port (310).

6. The oil-cooling and temperature-reducing unit for high-voltage frequency converter according to claim 1, wherein: Multiple groups of ball bearings are provided on the surface of the rolling ball (303), and the sliding friction is changed into rolling friction through the ball bearings.

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