SPWM is a set of constant amplitude but unconstant width rectangular serial pulse produced by control return circuit to approximate sinusoidal voltage waves.

(正弦脉宽调制)是由控制回路产生一组等幅而不等宽的矩形脉冲列，用来近似正弦电压波。

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The structure substituted rectangular prism for common quarter wave, and improved the stability of the optical voltage transformer.

该结构用直角棱镜代替了普通的四分之一波片，提高了光学电压互感器的稳定性。

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The machine directly winds the primary coil on the rectangular enclosed voltage transformer core, which is originated by our institute.

该机可在矩形封闭的电压互感器铁芯上直接绕制一次线圈，为我所之首创。

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