本文介绍了采用新的脉宽调制原理和微电脑技术，研制出的25赫正弦波铃流源。

In this paper, using a new principle of PWM and the teehnique of storage system in a microcomputer are deseribed, and a 25Hz sinusidal bell current source has been developed.

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而SPWM（正弦波脉宽调制）波的产生和控制则是变频技术的核心之一。

The generating and controll of Sinusoidal Pulse-Width Modulation (SPWM) waveforms is one of the core technology of frequency conversion.

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