The carrier phase shift technique based parallel back-to-back PWM converter is used on the direct-drive wind power system, with a switching frequency as low as 1 kHz.
直驱型风力发电系统需要全功率变流器，在现有器件功率水平以及开关频率等诸多因素制约下，变流器直接并联的方式具备结构简单、模块化设计、易扩展的优点。
Also, a large frequency spectrum (698-806 MHz) was freed by switching over from analog TV to the digital one.
此外，从模拟电视信号到数字电视信号的切换也释放了广阔的频道(698 - 806mhz)。
A repetition rate, or operating frequency, lower than that allowed by the switching times is often specified for a relay.
继电器往往会以开关时间规定一个重复率，或者说是工作频率，使用时需低于该值。
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