YB560103-BR
如果谐波分量的均方根值已知，则可以通过以下公式轻松计算总均方根值：总谐波畸变THD总谐波畸变定义为：电流THD电压THD谐波畸变率是一个非常重要的参数，它提供了有关电压和电流波形的谐波含量以及这些值较高时应采取的必要措施的信息。对于THDi<10%和THDu<5%，谐波含量可忽略不计，因此无需任何规定。断路器的标准参考IEC 60947低压开关设备和控制设备标准IEC 60947-2（2003年第三版）的附录F提供了有关检查过电流脱扣器谐波抗扰度的试验的信息。特别是，它描述了试验电流的波形，在该波形下，根据注入电流的确定值，释放应具有符合本标准规定的行为。下文中，报告了试验电流波形的特征，其应交替形成如下：1）由基波分量和基波72%-88%之间的三次谐波变量构成，峰值因子等于2，或由基波45%-55%之间的五次谐波变量构成，峰值因子等于1.9或2）的基波分量和高于基波60%的三次谐波、高于基波14%的五次谐波和高于基波7%的七次谐波。该试验电流的峰值系数应大于2.1，并且每半个周期的给定时间应小于该周期的42%。

If the rms values of the harmonic components are known, the total rms value can be easily calculated by the following formula: Total harmonic distortion THD The total harmonic distortion is defined as: THD in current THD in voltage The harmonic distortion ratio is a very important parameter, which gives information about the harmonic content of the voltage and current waveforms and about the necessary measures to be taken should these values be high. For THDi < 10% and THDu < 5%, the harmonic content is considered negligible and such as not to require any provisions. Standard references for circuit-breakers IEC 60947 Low-voltage switchgear and controlgear Annex F of the Standard IEC 60947-2 (third edition 2003) gives information about the tests to check the immunity of the overcurrent releases against harmonics. In particular, it describes the waveform of the test current, at which, in correspondence with determinate values of injected current, the release shall have a behaviour complying with the prescriptions of this Standard. Hereunder, the characteristics of the waveform of the test current are reported, which shall be formed, in alternative, as follows: 1) by the fundamental component and by a 3rd harmonic variable between 72% and 88% of the fundamental, with peak factor equal to 2 or by a 5th harmonic variable between 45% and 55% of the fundamental, with peak factor equal to 1.9 or 2) by the fundamental component and by a 3rd harmonic higher than 60% of the fundamental, by a 5th harmonic higher than 14% of the fundamental and by a 7th harmonic higher than 7% of the fundamental. This test current shall have a peak factor > 2.1 and shall flow for a given time < 42% of the period for each half period.