tailieunhanh - Industrial Brushless Servomotors Episode 7

Tham khảo tài liệu 'industrial brushless servomotors episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Motor and load dynamics IIS ms. Viscous damping and friction have been ignored and so the decay is the result of i2R loss in the stator winding. Figure Poles of an unloaded motor with Te 5rm Variation of load inertia Inclusion of a load inertia Jl increases the overall mechanical time constant to I M 1 d A An 7 m The ratio of electrical to mechanical time constant falls from Te rm to Te m- It is of interest to plot the locus of the poles on the s-plane as the ratio changes. The poles appear at the values of s which make the denominator of the transfer function for the motor-load unit equal to zero that is when 52 5 1 0 Te T e T M 116 Industrial Brushless Servomotors The roots of the quadratic are 2re y 4rị rerM When rM 4re there is no sinusoidal component and the two poles lie along the horizontal axis of the 5-plane. The physical interpretation of the two rates of exponential decay is that the transient response dies away relatively quickly at first and then more slowly as time goes on. When rM 4re the response is partly exponential and partly sinusoidal. The poles appear at 5 - cr JCJ - ----------r-z 2re y VM 4rễ For example when tm Te 5 j-v 3 2 T e . at the 60 position. When tm 4re both poles lie at Figure shows how the poles move as the ratio rises to make the value of the overall mechanical time constant change from one-fifth to more than four times the value of the electrical time constant. For the example of the unloaded motor with the poles shown in Figure this would mean increasing the load inertia from zero to greater than 19Jm. Overshoot Figure shows an exponential and oscillatory variation with time of the speed of an initially stationary motor-load unit following a step input of voltage. We know that 1 Ơ and U ------------ T 2re y TeTM 4rị Motor and load dynamics 117 Figure Movement of poles as load inertia is increased The response is shown as per-unit of a final steady-state speed and has a maximum value