本文主要讲的是电机转矩，在直接转矩控制中，电机转矩由变频直接控制，而在矢量控制中，电机转矩由电流和流量间接控制。该控制方法利用空间矢量的概念，分析了异步电动机定子坐标系下的数学模型，直接控制了异步电动机的磁通和转矩。在他的控制类型中没有复杂的坐标转换。与磁链矢量控制相比，直接转矩控制简单，转矩响应时间快。本篇代写论文价格文章由英国论文时Essay Times教育网整理，供大家参考阅读。
In direct torque control, motor torque is directly controlled by VFD, while in vector control, motor torque is indirectly controlled by current and flux. The concept of space vector is employed in this control method to analyze mathematic model of induction motor in stator coordinate, and directly control magnetic flux and torque of induction motor. There are no complicated coordinate transformations in his type of control. Compared with flux vector control, DTC is simple, and torque response time is very fast.
In a VFD constant pressure water supply application, varying the motor speed by changing the frequency of power supply to the motor can change the pump speed and operating condition to adapt the capacity and headof the pump to the change of the demand of water and keep the extreme pressure point pressure constant. Therefore, the electricity consumption is reduced.
Centrifugal pump is a type of quadratic torque load. The relationship between flow rate, shaft power and speed is: Q ∝ n, Ps∝ n3.Take for example a centrifugal pump with rated speed n1. The system curve is 1 when the pump runs at full load. The corresponding head and flow rate are H2 and Q1. Figure 2 represents the relationships between flow rate, speed and head.
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