SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING 惯性消 t Hydraulic motors possess an extremely high ratio of torque to inertia. Because of this, very little of the available torque is dissipated in accelerating the motor, most of the torque can be 除 applied directly to the load. Acceleration rates for unloaded hydraulic motors. for example, vary from about 0.3x105radians per second squared for larger sizes at 3000psi to 3. 4x10radians per second squared for smaller motors. No other transmission system produces motors having acceleration rates anywhere near these values. Higher supply pressures develop accordingly higher acceleration rates 加速度 Hydraulic motors develop no counter electro-motive force as do electrical motors There fore. the acceleration rate is essentially constant over their design speed ranges psi= pound per square inches每平方英寸磅
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic motors possess an extremely high ratio of torque to inertia. Because of this, very little of the available torque is dissipated in accelerating the motor; most of the torque can be applied directly to the load. Acceleration rates for unloaded hydraulic motors, for example, vary from about 0.3105 radians per second squared for larger sizes at 3000psi to 3.4105 radians per second squared for smaller motors. No other transmission system produces motors having acceleration rates anywhere near these values. Higher supply pressures develop accordingly higher acceleration rates. Hydraulic motors develop no counter electro-motive force as do electrical motors. Therefore, the acceleration rate is essentially constant over their design speed ranges. 惯 性 消 除 加速度 psi=pound per square inches 每平方英寸磅
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic devices can generate much more power in the same volume than can electrical devices The reason for this lies in the characteristics of the materials used in electrical equipment. The very best armature steels can develop only the equivalent of bout 200 psi in tractive power before they become saturated. By comparison, 3000 psi hydraulic equipment is very common and pressures up to 5000 psi are not rare 使饱和 电枢,转子 Because of the greater pressure density, hydraulic equipment in power sizes greater than I hp. tends to be mach smaller than electrical motors and somewhat smaller than pneumatic motors horsepower Hydraulic motors support heavy or springy loads much better than do electrical or pneumatic motors. Looking from the load back into the motors, electrical fields or compressed gasses are quite soft. The relatively incompressible oil is however. stiff
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic devices can generate much more power in the same volume than can electrical devices. The reason for this lies in the characteristics of the materials used in electrical equipment. The very best armature steels can develop only the equivalent of bout 200 psi in tractive power before they become saturated. By comparison, 3000 psi hydraulic equipment is very common and pressures up to 5000 psi are not rare. Because of the greater pressure density, hydraulic equipment in power sizes greater than l hp. tends to be mach smaller than electrical motors and somewhat smaller than pneumatic motors. Hydraulic motors support heavy or springy loads much better than do electrical or pneumatic motors. Looking from the load back into the motors, electrical fields or compressed gasses are quite soft. The relatively incompressible oil is, however, stiff. 使饱和 电枢，转子 horsepower
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic transmission systems efficiently transmit power farther than do mechanical systems, but not as far as electrical systems Hydraulic transmission systems may be less hazardous than electrical systems and are far safer than mechanical power transmission systems 危险的 Hydraulic oil is a good heat conductor so that the heavily loaded working area stays relatively cool. Heat generated at the working interface is conducted away rapidly. The working areas can therefore be made small because heat absorbing mass is not needed. Because of this and because of the high-pressure density, hydraulic motors weigh less than one pound per horsepower. Horsepower to weight ratios of up to 2.5 are not uncommon
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic transmission systems efficiently transmit power farther than do mechanical systems, but not as far as electrical systems. Hydraulic transmission systems may be less hazardous than electrical systems and are far safer than mechanical power transmission systems. Hydraulic oil is a good heat conductor so that the heavily loaded working area stays relatively cool. Heat generated at the working interface is conducted away rapidly. The working areas can therefore be made small because heat absorbing mass is not needed. Because of this and because of the high-pressure density, hydraulic motors weigh less than one pound per horsepower. Horsepower to weight ratios of up to 2.5 are not uncommon. 危险的
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic power systems al so have some drawbacks. Hydraulic oils are messy. Leaks drawback欠缺 are inevitable. The great lubricity of most hydraulic oils makes leaks and spillage very inevitable hazardous. Certain oils are excellent‖不可避免的 removers of paint and electrical insulation.spillage溢出 Hydraulic systems, particularly the high insulation绝缘 performance servo systems which use hydraulic power so efficiently, are extremelyvulnerable脆弱的 vulnerable to dirt and contamination. They contamination must constantly be watched to prevent the污染 addition or generation of contamination and hydraulic systems need expensive filtration filtration it rne to keep them clean
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic power systems also have some drawbacks. Hydraulic oils are messy. Leaks are inevitable. The great lubricity of most hydraulic oils makes leaks and spillage very hazardous. Certain oils are excellent removers of paint and electrical insulation. Hydraulic systems, particularly the high performance servo systems which use hydraulic power so efficiently, are extremely vulnerable to dirt and contamination. They must constantly be watched to prevent the addition or generation of contamination and hydraulic systems need expensive filtration to keep them clean. drawback 欠缺 inevitable 不可避免的 spillage 溢出 insulation 绝缘 vulnerable 脆弱的 contamination 污染 filtration 过滤
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING w A rupture or burst of an element of a high-pressure aL hydraulic system can be very dangerous. The high velocity streams of oil, which results can damage eyes, pierce skin, and harm other equipment. The author has seen a piece of tubing three feet long and 1.5 inches in diameter thrown whirling for more than fifty feet when a rupture occurred in a 3000 psi line.难燃工作液 Unless fire-resistant fluids are used, hydraulic leaks create B very real fire hazards. Most petroleum based fluids are highly ko: flammable. High temperatures can be generated where a high try velocity stream of oil from a rupture impacts on a flat surface 冲击 Finally, hydraulic power is so compact that developing and controlling fractional horsepower is difficult unless the pressure density is reduced to levels where electrical power is extremely competitive
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING A rupture or burst of an element of a high-pressure hydraulic system can be very dangerous. The high velocity streams of oil, which results can damage eyes, pierce skin, and harm other equipment. The author has seen a piece of tubing three feet long and 1.5 inches in diameter thrown whirling for more than fifty feet when a rupture occurred in a 3000 psi line. Unless fire-resistant fluids are used, hydraulic leaks create very real fire hazards. Most petroleum based fluids are highly flammable. High temperatures can be generated where a high velocity stream of oil from a rupture impacts on a flat surface. Finally, hydraulic power is so compact that developing and controlling fractional horsepower is difficult unless the pressure density is reduced to levels where electrical power is extremely competitive. 破 裂 难燃工作液 易 燃 的 冲 击