Applied materials 0100-20213

Description

Applied materials 0100-20213

顺便说一句，如果电机中的电压真的降低了，电机确实会转得更慢，但这只是因为负载在交替后面拖着它。磁铁被极化，就好像电机以全速旋转一样，但因为它没有足够的扭矩来加快旋转，所以它的效率大大降低，如果负载增加，很可能会完全停止旋转。

VFD产生较低频率的方法是一个两步过程:将输入电压转换为DC总线电压，然后重新产生交流输出。

DC总线电压

首先，输入电压经过整流，这意味着它被转换为DC电压。这就是为什么一些较小的VFD可以用单相甚至DC电源供电。无论如何，他们可以把所有这些都转换成DC。

带PWM的交流波

为了将DC电压发送到电机，通过在正向和反向上开关MOSFETs来非常快速地对电流施加脉冲。这种速度脉冲或PWM信号，可以设计成很像交流波形。由于处理器负责晶体管的开关速度，因此创建低于60 Hz的频率非常简单。

Applied materials 0100-20213

By the way, if the voltage in the motor really decreases, the motor will indeed rotate slower, but this is only because the load drags it after alternating. The magnet is polarized, just like a motor rotating at full speed, but its efficiency is greatly reduced because it does not have enough torque to accelerate rotation. If the load increases, it is likely to completely stop rotating.

The method of generating lower frequencies in VFD is a two-step process: converting the input voltage to DC bus voltage, and then generating AC output again.

DC bus voltage

Firstly, the input voltage is rectified, which means it is converted into a DC voltage. That’s why some smaller VFDs can be powered by single-phase or even DC power sources. Anyway, they can convert all of this into DC.

AC wave with PWM

In order to send DC voltage to the motor, MOSFETs are switched in both forward and reverse directions to quickly apply pulses to the current. This type of speed pulse or PWM signal can be designed to resemble an AC waveform. Since the processor is responsible for the switching speed of the transistor, creating frequencies below 60 Hz is very simple.