Plateau electric machinery

What are the characteristics of plateau motor? Why can't GM be used in plateau areas?

Modified on 2016/07/1810: 40: 21traffic: 169.

Altitude has adverse effects on motor temperature rise, motor corona (high voltage motor) and DC motor commutation. Attention should be paid to the following three aspects:

? ( 1)? The higher the altitude, the greater the temperature rise of the motor and the smaller the output power. However, when the temperature decreases with the elevation to compensate for the influence of elevation on temperature rise, the rated output power of the motor can be unchanged; ?

(2)? Anti-corona measures should be taken when high voltage motor is used in plateau; ?

(3)? Altitude is not conducive to DC motor commutation, so we should pay attention to the selection of carbon brush materials.

Plateau motor is used above 1000 meters above sea level. According to the national industry standard: JB/T7573-94 "General Technical Conditions for Electrical Products in Plateau Environment", plateau motors are divided into several grades: no more than 2000m, 3000m, 4000m and 5000m respectively. ?

The main characteristics of the plateau area are:

1, the air pressure or air density is small. ?

2. The temperature is low and the temperature changes greatly. ?

The absolute humidity of the air is very small. ?

3. The solar radiation illumination is high. ?

5. Less precipitation. ?

There are many windy days every year. ?

7. The soil temperature is low and the freezing period is long. ?

Due to the above reasons, it will bring the following adverse effects to the motor operation, so corresponding measures should be taken in the design and manufacture:

1, which leads to the decrease of insulation strength: for every increase of 1000m, the insulation strength decreases by 8- 15%. ?

2. The breakdown voltage of the electric gap is reduced, so the electric gap should be increased according to the altitude. ?

3, corona starting voltage is reduced, anti-corona measures should be strengthened. ?

4. The cooling effect of air medium decreases, the heat dissipation capacity decreases, and the temperature rise increases. Every time 1000M is increased, the temperature rise will increase by 3- 10%, so the temperature rise limit should be revised.

The oxygen content in the air at an altitude of 5000 meters is only 53% of the sea level. ? 2.2? Temperature?

? The temperature is measured at a height of 1.5m above the ground. The biggest feature of the troposphere is that the temperature decreases with the elevation. In the free atmosphere, the average altitude increases by 100 m, and the temperature decreases by 0.65℃. In fact, the decline rate of troposphere height is different. ?

2.2. 1? The highest temperature at high altitude is within 2000 meters, generally between 30℃ and 40℃. The lowest value of the highest temperature appears in the Qinghai-Tibet Plateau, mostly within 30℃, or even less than 20℃. ? 2.2.2? The maximum daily average temperature is the highest value of the daily average temperature recorded in each year, taking the average value for many years. ?

? The maximum daily average temperature rises by about 100m, and the temperature drops by 0.5℃. ?

? The daily average maximum temperature of 1 km ~ 5 km is 30℃, 25℃, 20℃, 15℃ and 10℃ respectively. ? 2.2.3? The lowest annual average temperature appears in the northwest of Qinghai-Tibet Plateau, which has the highest terrain. The annual average temperature of 1 km ~ 5 km is 20℃, 15℃, 10℃, 5℃ and 0℃ respectively. With the increase of altitude, the annual average temperature decreases. ?

2.2.4? The daily range of maximum temperature is related to latitude, cloud cover, land and ocean distribution, topography, surface characteristics, altitude and season. According to statistics, the average daily variation of the annual maximum temperature is generally between 20℃ and 30℃. ?

2.2.5? The lowest temperature mainly depends on latitude and altitude. For the same latitude area, the lowest temperature is relatively low at higher altitudes, such as Yanchi at 1349m, with the lowest temperature of -28.5℃, while Dachaidan at the same latitude is at an altitude of 3 174m, with the lowest temperature of -33.6℃. ? 2.3? What is the maximum intensity of direct solar radiation?

? The fundamental reason for the different climate on the earth is solar radiation, and the strength of solar radiation determines the geographical latitude. However, with the increase of altitude, the thickness, air density, water vapor and suspended matter of sunlight passing through the atmosphere decrease accordingly. The greater the transmittance of sunlight, the stronger the radiation reaching the ground. Due to the large temperature difference in Xia Dong, the temperature is higher in summer. So the data of solar radiation is the maximum intensity of direct solar radiation from June to August in summer. ?

? 1 km to 5km, the maximum intensity of direct solar radiation is 10 1, 1064,118,1. As can be seen from the above data, with the increase of altitude, the intensity of direct solar radiation increases. When the altitude increases 1000m, the direct solar radiation intensity increases by about 54W/m2. ? 2.4? Frozen soil? Permafrost in China is mainly distributed in Daxinganling, western mountainous areas and Qinghai-Tibet Plateau. The topography of the frozen soil region in Northeast China is mainly hills and mountains. Although the altitude is not high, it is the coldest natural area in China because of its high latitude and the influence of Siberian high-pressure air. The western frozen soil region, although some latitudes are low, belongs to the alpine plateau region, with high terrain and deep inland, belonging to the alpine climate. Their common characteristics are low annual average temperature and long freezing period. The thickness of permafrost in Qinghai-Tibet Plateau is generally between 25m and 120m, even reaching 175m. ?

2.5? Dust? The dust in the northwest loess plateau and Qinghai-Tibet plateau is also quite serious. ?

? The number of sandstorm days in northwest China (visibility is only 10km) is 24 to 68 days. ? Rainstorm days (visibility is only 1km) 10d ~ 22d. The size of the dust is closely related to the wind speed. As the wind speed increases, the diameter of the blown dust particles increases. ?

2.6? Snow? The Qinghai-Tibet Plateau is surrounded by mountains and protected by Pamirs, Karakorum, Kunlun Mountains, Himalayas and Tanggula Mountains. The climate of the Arctic Ocean, the Pacific Ocean and the Indian Ocean can hardly have a significant impact on the climate inside the plateau, so the climate here is dry and cold, and the rainfall is scarce, especially in the northern Tibet Plateau. The annual maximum snowfall there is less than 10 cm. The heaviest snow in China occurs in Xinjiang and Northeast China. Altai Mountain, Tianshan Mountain, Himalayan Mountain, Qilian Mountain and Southwest Hengduan Mountain are snow-capped mountains in China, and the distribution of snow in most areas shows obvious regularity of thickening with the elevation. ?

3? The influence of plateau environment on mechanical and electrical products?

3. 1? The effect of low air pressure?

3. 1. 1? The combustion of internal combustion engine deteriorates, the power decreases obviously and the fuel consumption increases. ?

? The working volume of internal combustion engine is fixed. Because the air density changes with altitude, the amount of air entering the engine cylinder will also change. For a naturally aspirated diesel engine, if the oil supply of the oil pump remains unchanged, the fuel entering the cylinder can not be fully burned, which will make the exhaust smoke thicker, the exhaust temperature rise, and the combustion chamber parts overheat, leading to a decrease in power and a deterioration in economic indicators. According to the field test, the output of internal combustion engine decreases by 9% ~ 13% on average and the fuel consumption increases by about 6% every time the altitude rises1000 m. ?

? There are 420 construction machines and transportation machines at Longyangxia Hydropower Station at an altitude of 2,700 meters. The power loss reaches 37%. Domestic loaders can only be used in the construction site at an altitude of 2800m m, but not at the construction site at an altitude of 3300m m. When the ZL30 loader produced by a factory works in the field at an altitude of 3000m, the bucket lifting capacity is reduced by 50%. CX-80 locomotive produced by a factory. Three 50-ton wagons can be pulled in Xining, but only two wagons can be pulled in Xitieshan at an altitude of 3 173m?

3. 1.2? Deterioration of cooling system of internal combustion engine?

? With the increase of altitude, the atmospheric pressure decreases and the boiling point of cooling water also decreases. See Table 2 for the boiling points of water at different altitudes. ?

Table 2? What is the boiling point of water at different altitudes? Altitude (m)?

0? 1000? 2000? 3000? 4000?

Boiling point of cooling water (℃)? 100? 96.6? 93.3? 90.0? 86.9?

Every altitude 1000 meters, the boiling point of water drops by about 3.3℃. According to drivers working in plateau areas, the cooling water of internal combustion engines, especially diesel engines, often "boils". The solution is to stop cooling or turn off hot water and add cooling water. The former is delayed, and the latter is contradictory, because the plateau area is short of water and the water quality is poor. Due to the decrease of air density in plateau, although the volume flow rate of cooling fan remains unchanged, the weight flow rate is greatly reduced. Every altitude 1000 meters, the weight air volume decreases by 8%. In fact, the cooling effect of the fan and the cooling effect of the cooling water tank are reduced. However, the internal combustion engine burns badly when pulled out at high sea. When the exhaust temperature rises, the heat load of the parts increases. If the heat dissipation is not good, it will make the work abnormal, especially the cooling of the engine. Its maximum power is limited by the thermal load. When the cooling intensity is insufficient, the exhaust temperature rises sharply. The heat load is too high. There is even a cylinder pulling phenomenon. ?

? The above two points have such problems for cranes, truck cranes, construction machinery, trucks, piling machinery and other mechanical products powered by diesel engines and internal combustion engines. ? 3. 1.3? Air compressor discharge temperature rises?

? With the increase of height, the atmospheric pressure decreases, which leads to the decrease of weight displacement. The numerical value is that the average displacement decreases 1 1% ~ 12% with each elevation, and the volume displacement also decreases with the elevation. Every increase of 1000m decreases by 2% ~ 3% on average. Therefore, with the increase of altitude, the exhaust temperature of the compressor increases. ? 3. 1.4? Affect the breaking ability of low-voltage electrical appliances?

? With the increase of altitude, the air density decreases and the air heat dissipation ability weakens. When the contact breaks the current, the dielectric recovery strength decreases, and the arc is difficult to extinguish, which is easy to cause arc reignition, thus prolonging the arcing time and shortening the contact life. ?

? The plateau air is thin, the heat dissipation ability is weakened, and the action time of thermal relay is shortened? 3. 1.5? Is the corona starting voltage of high voltage motor reduced?

? Because the plateau air is thin, the intermolecular distance increases and the ion free path increases, the corona initial voltage decreases. For example, the 5# generator set (25,000 kW, 6.3kV) in Qiaotou Power Plant at high altitude began to hear the discharge sound when the voltage rose to 1.7kV, and the voltage rose to 2.5kV? When I started to see corona sparks, when the voltage rose to 3.6kV, I would see serious corona phenomenon. Under the rated voltage of 6.3kV,? Corona is serious and smells of ozone. ?

? In addition, low air pressure will reduce the external insulation strength of high-voltage electrical porcelain; Affecting the service life of the battery; It affects the commutation of DC motor and brush wear. ? 3.2? How does low temperature affect the operation of mechanical and electrical products? 3.2. 1? Is it difficult to start the internal combustion engine cold?

? Low temperature is a feature of plateau climate. With the increase of altitude, the temperature decreases linearly, and the lowest temperature in the Qinghai-Tibet Plateau is generally below -30℃. The low-temperature starting problem of internal combustion engine is basically similar to that in cold plain area, but the lack of oxygen and low air pressure in plateau area make the ignition starting performance of internal combustion engine worse than that in plain area. ?

3.2.2? Affect the performance of battery?

? Due to the low temperature, the viscosity of sulfuric acid electrolyte increases, and the negative active material is passivated prematurely, which affects the diffusion speed of electrolyte in the plate, so that the basic electrochemical reaction of lead storage battery can only be incomplete on the surface of the plate without electrolyte. Therefore, the capacity and start-up discharge performance of lead-acid batteries decrease with the decrease of temperature. ? 3.2.3? Affect the starting performance of the motor?

? Low temperature is beneficial to the heat dissipation of the motor, but it has some influence on the start-up of the small motor. Because of the low temperature, the consistency of grease increases or freezes, which leads to the increase of static resistance moment and the difficulty of starting. Grease freezes at low temperature and loses its lubricating ability. When starting, it rubs against the bearing and whistles, which accelerates the wear of the bearing. ?

3.2.4? Influence on instrument performance?

? Due to the low temperature and large temperature difference between day and night, the characteristics of linear components in the instrument change linearly, and the test instruments (including pressure gauges, pressure gauges, flow meters, etc.). ) General accuracy is low, repeatability is poor, and zero drift is serious. ? 3.2.5? It reflects that the asphalt thermal insulation adhesive cracked at low temperature, and the moisture affected the thermal insulation performance, and the mechanical properties of the thermal insulation material decreased, which obviously hardened and became brittle. Rubber and styrene-butadiene rubber-based natural rubber cable sheaths are easy to break and peel at -30℃. ?

? The choice of engine oil should also be cautious. The viscosity index of the existing low pour point hydraulic oil is still low. Although its pour point is below -40℃, as a medium for transmitting torque in hydraulic system, it has no good fluidity above 10 degrees above the pour point and cannot meet the requirements of working in low temperature areas. The low-temperature test of rubber seal shows that with the decrease of temperature, its hardness, breaking strength and elongation all show a downward trend in different degrees. ?

3.3? The influence of solar radiation on plateau mechanical and electrical products? 3.3. 1? Affect the mechanical properties of plastics?

? The damage of sunlight to organic substances is not only related to the energy of chemical bonds, but also related to the density of molecular bonds. The molecular bonds of thermosetting plastics have network structure and relatively high density, so photochemical cracking has little influence on their mechanical properties, but has great influence on the mechanical properties of thermoplastics. ?

3.3.2? Effect on paint coating?

? Strong sunlight cracking and large temperature difference in plateau areas will accelerate the aging and cracking of paint coatings. According to the analysis, the photoaging of paint coating is photooxidation aging, and its speed is not only related to radiation intensity and total sunlight, but also related to moisture, oxygen, temperature and humidity in the atmosphere. Although the intensity and total amount of solar radiation are relatively large in the plateau area, the climate is dry, the air is thin and the temperature is low, and the moisture, oxygen content and temperature in the atmosphere are not as high as those in the humid and hot zone, so the influence of plateau climate on paints and coatings is not as strong as that in the humid and hot zone. ? 3.3.3? Influence on motor operation?

? The motor used outdoors in the plateau area should exceed the temperature rise limit due to the heat generated during operation and the direct irradiation of the sun. However, according to the investigation, the overheating phenomenon of the motor is not obvious, because the low temperature in the plateau area has a certain offset effect on the temperature rise, so the problem is not big. ? 3.4? Influence of frozen soil on mechanical and electrical products? 3.4. 1? Influence on pile drivers and drilling machines?

? When piling in plateau permafrost regions, it is generally difficult to directly drive precast piles into permafrost layers without drilling holes first because the permafrost is hard. ?

? For example, in the construction of frozen soil at an altitude of 4470m along the Qingshui River in Qinghai, there is a melting layer in the frozen soil in this area, and serious hole collapse occurs during drilling. The construction season is in late July, and it is high-temperature frozen soil with ground temperature of -0.5℃ ~- 1℃. When the hole collapse is serious, a large amount of surface mud will enter the hole, melting the frozen soil on the hole wall and the frozen soil at the hole bottom. In addition, due to the hard frozen soil, the cemented carbide pieces and drill edges of drill pipes are much more seriously worn. Moreover, the power consumption of the drilling rig has also increased. ? 3.4.2? Impact on communication cables?

? The frost heaving, cracking and thawing settlement of soil layer caused by freezing and thawing of frozen soil have great influence on the bending and stretching of buried cables, which may cause lead cables to break. ?

? According to the investigation, the lowest temperature in frozen soil is generally not lower than-16℃, so when laying cables, 300×300mm salt sand medium is filled around the cables, on the one hand, the cables can be in unfrozen state, and on the other hand, the frozen layer can be relatively displaced in the case of frost heaving and cracking, thus reducing the tension on the cables. ? 3.5? Influence of dust on the operation of mechanical products?

? The loess plateau and Qinghai-Tibet plateau are relatively windy and dusty. The plateau area is dry with little rain and less vegetation on the ground. Coupled with strong winds, the harm of dust to internal combustion engines (including diesel-powered machinery, pile drivers, trucks, loaders, etc.) is obvious. ).？

? Users report that the air filter will be blocked soon when it is used in plateau area, and the dust leaking into the cylinder accelerates the wear of the moving parts of the engine. The cyclone paper filter screen should be maintained every 50 hours according to the instructions, but in Longyangxia construction site, it is full of dust in 1 ~ 2 hours. One shift needs to clean the air filter and pat the paper filter twice. ?

? Dust has different effects on motor bearings, low-voltage electrical contacts and switches. , omitted here. ?

4? Concluding remarks?

? China has a vast high altitude area. Due to various conditions, the development of industry and agriculture there is relatively slow. At present, automobile transportation is still the main means of transportation, and the power loss of diesel engines and internal combustion engines used in plateau areas is quite serious. Therefore, it is of great significance to study the power recovery technology of mechanical products. Tibet is of great strategic significance, where there are important mineral resources. It is of great significance to build the railway transportation system in Tibet as soon as possible to improve the life in people in Xizang. Fortunately, the country has made up its mind to extend the railway from Golmud, Qinghai to Lhasa, Tibet, and plans to open the Yunnan-Tibet Railway in Yunnan. It is conceivable that in the near future, the plateau area will get faster development. ?

? When the International Electrotechnical Commission (IEC) formulated relevant standards, there were almost no high-altitude areas in Europe. Its standard only considers below 3000m m, and at present, according to the domestic situation, the plateau environmental conditions and environmental technical requirements of mechanical industrial products are formulated. Two criteria of plateau environment. It provides a basis for designing and producing electromechanical products suitable for high altitude areas. This is of great value to improve the reliability of mechanical and electrical products and has practical significance to the development of national economy. ?

About the author: Liu Kuifang (1938-), male, from Tai Po, Guangdong, is a senior engineer. ? Author: (Guangzhou Electric Apparatus Research Institute,? Guangzhou? 5 10302)?

References:?

[ 1]? Environmental conditions of electrical products in high altitude areas. Kunming Institute of Electrical Apparatus Science? [2]? Investigation report on environmental adaptability of mechanical industry products. Guangzhou Electric Apparatus Research Institute, etc. 1992.

Plateau motor runs at high altitude because of low air pressure and poor heat dissipation conditions. And the operation efficiency will be reduced. So, is it the same? The rated electromagnetic load and heat dissipation design of motors running at different altitudes are different. It is better to run at reduced load than at high altitude. Otherwise, it will affect the life and performance of the motor, and even burn out in a short time.