频率固定 meaning in Chinese

frequency fixing

The steady frequency three - phase ac can be changed into the ac which frequency is continuously adjusted in the experiment unit composed of rectifier , inverter , control circuit , and relay safeguard circuit
Spwm三相变频实验单元能够把频率固定的三相交流电变换成频率连续可调的三相交流电，它主要包括交直变换、逆变、控制和继电保护电路。
This paper include the following parts . firstly the sine exciting - voltage is guaranteed by direct digital synthesize technology ; secondly the digital output of cos ( 9 ) and sin ( 9 ) are generated by microcontroller ; thirdly the two voltage signals which are the product of the two former signals gained by the multiplying d / a converter , being filtered and amplified , have constant frequency , and one amplitude has sine function relationship of with the input angle , and the other amplitude has cosine function relationship of with the input angle ; finally the two signals are acquired and analyzed by relative instrument and software
主要由以下几部分组成：用数字频率合成技术( dds )产生正弦激励电压信号u _ msin ( t ) ；用单片机产生幅度的数字量输出sin ( )和cos ( ) ；用乘法型d a转换器实现激励电压和幅度的乘积，并通过滤波器和功放后即得到频率固定，幅值随输入角成正余弦变化的电压信号；最后用数据采集卡采集输出信号，显示波形并进行频谱分析。