变频器输出电抗器感量计算

<p><span style="font-size:13px">变频器的输出是经</span><span style="font-size: 13px;font-family:&#39;ˎ̥&#39;,serif">PWM</span><span style="font-size:13px">调制的电压波，由于电动机绕组的电感性质能使电流连续，因此电流基本上是正弦形的，脉冲宽度调制</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">(PWM)</span><span style="font-size:13px">有着陡峭的电压上升和下降的前后沿，即</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">dv/dt</span><span style="font-size:13px">很大，使得输出引线向外界发射含量极大的电磁干扰，并且在引出线对地、电机绕组匝间、绕组对地间都产生很大的脉冲电流，附图</span><span style="font-size:13px">表示</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">SPWM</span><span style="font-size:13px">电压，电流的波形。</span></p><p><span style="font-size:13px"><img src="/upload/article/20231030/1698672632263954.png" title="1698672632263954.png" alt="image.png"/></span></p><p></p><p><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&nbsp;</span><span style="font-size:13px">为了减轻变频器输出</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">dv/dt</span><span style="font-size:13px">对外界的干扰，降低输出波形畸变，达到环保标准，减少对电机绕组的电压冲击造成绝缘损坏，降低电机的温升和噪音，避免在变频器输出功率管上因</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">dv/dt</span><span style="font-size:13px">和流过过大的脉冲冲击电流使功率管损坏，以及降低负载短路造成对变频器的损伤，有必要在变频器输端增设交流电抗器。</span></p><p><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&nbsp;&nbsp;&nbsp; </span><span style="font-size:13px">值得指出的是脉冲电压通过长的输电线时，由于长线上波的反射叠加使得在长线</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">(</span><span style="font-size:13px">即变频器输出导线</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">)</span><span style="font-size:13px">超过临界长度后，电压有可能达到直流母线</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">(</span><span style="font-size:13px">变频器内直流母线</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">)</span><span style="font-size:13px">电压的</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">2</span><span style="font-size:13px">倍。因此变频器输出线长度受到了限制，为解除这种限制，必须接入输出侧交流电抗器。接入后，送到电机等负载上的波形就接近正弦电压波形了。</span></p><p><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&nbsp;&nbsp;&nbsp; </span><span style="font-size:13px">但实际使用中，只要负载是电感性的，电抗器可采用</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">1%</span><span style="font-size:13px">阻抗或更低一些都是可行的，这是因为，</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">PWM</span><span style="font-size:13px">调制频率远高于基波频率，已经相当于</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&gt;(40-100)</span><span style="font-size:13px">次谐波的范围，因此，输出侧交流电抗器电感量：</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif"><br/>&nbsp; &nbsp;&nbsp;<img src="/upload/article/20231030/1698672742177035.png" title="1698672742177035.png" alt="image.png"/></span></p><p><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&nbsp;&nbsp;&nbsp; </span><span style="font-size:13px">例如：</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">380V</span><span style="font-size:13px">、</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">90kW</span><span style="font-size:13px">、</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">50Hz</span><span style="font-size:13px">、</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">170A</span><span style="font-size:13px">变频器的输出侧交流电抗器的选用：</span></p><p><span style="font-size:13px"><img src="/upload/article/20231030/1698672787787062.png" title="1698672787787062.png" alt="image.png"/></span></p><p><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">&nbsp;&nbsp;&nbsp; </span><span style="font-size:13px">取</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">:</span><span style="font-size: 13px">电感值在</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">0.041mH</span><span style="font-size:13px">左右</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">,</span><span style="font-size:13px">能长期能通</span><span style="font-size:13px;font-family:&#39;ˎ̥&#39;,serif">170A</span><span style="font-size:13px">电流的电抗器即可。</span></p>