abb变频器计算公式.ppt

Technical guide No. 7 - Basic formulas基本公式 Road show 3 Jukka Juottonen Technical guide No. 7 - Basic formulas Purpose of the presentation 内容 Show the typical formulas used in basic dimensioning 说明基本选型公式 The targets of the presentation are that you:目的 Can do also manual calculations of basic dynamical systems (e.g. acceleration time) 动态系统的手工计算 Technical guide No. 7 - Basic formulas Motor’s mechanical output power can be calculated from speed and torque: 通过速度和力矩计算电机的输出功率 Technical guide No. 7 - Basic formulas Motor’s efficiency is output power divided by input power: 电机效率是输出功率/输入功率 Technical guide No. 7 - Basic formulas One of the fundamental equations for an electric motor is: 电机转子的加速规律 Technical guide No. 7 - Basic formulas Dynamic torque component changes the motor speed: 动态力矩分量影响电机转速 Technical guide No. 7 - Basic formulas Example: AC motor’s and load’s total moment of inertia is 3 kgm2. Constant load torque is 50 Nm. 举例：电机和负载的总转动惯量是3 kgm2 ，恒定负载力矩50 Nm A) What is the torque needed to accelerate the motor from 0 rpm to 1000 rpm speed in 10 seconds? 问题A)：电机转速在10秒内从0加速到1000rpm，需要多大力矩？ B) If the electric supply is switched off at 1000 rpm speed how fast will the motor decelerate to 0 rpm speed? 问题B)：如果电机运行在1000rpm时，停止供电， 那么电机减速至0rpm要多少时间？ Technical guide No. 7 - Basic formulas Technical guide No. 7 - Basic formulas ‘Inertia’ (moment of inertia) is important to know in many dimensioning cases. 选型时必须知道惯性(转动惯量)。 Generally J[kgm2] can be given by motor and machine manufacturers. 制造厂通常给出转动惯量：J[kgm2] Sometimes it can be calculated quite easily. For a cylinder shape the moment of inertia is proportional to mass and quadratically proportional to radius of the cylinder: J = m*r2. 转动惯量很容易计算。 圆筒型的转动惯量与其质量和半径的平方成正比：J = m*r2 Energy stored to a rotating mass is: E = 0.5*J*w2 旋转体储存的能量是：E = 0.5*J*w2 Technical guide No. 7 - Basic formulas When gear is used power, torque, mo