emc趣闻3.htm

该资料时关于EMC的相关问题

    lang=EN-US style='font-size:9.0pt;font-family:Arial'>Milford Haven</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>的</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>Texaco</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>炼油厂发生了一起爆炸事件，其爆炸当量与四吨高能炸药相当，它引发了一场大火，一直花了两天多时间才完全扑灭。距出事地点</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>3</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>公里远的一个商店的窗户被吹进了房屋。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>26</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>人受了轻伤。幸亏爆炸发生在星期日午餐时间，现场人员很少，否则情况将严重得多。重建费用大约需要</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>800</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>万美圆。厂内产品也受到严重的损失（极大地影响了英国的炼油能力）。事故是由星期日早上</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>7</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>点</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>49</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分至</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>8</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>点</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>30</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分之间发生的一场电暴引起的，电暴导致炼油厂内的许多电子设备工作异常。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    <br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>短评：</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　剧事故调查的专家介绍，事故的原因是电暴引起的浪涌使一些动力泵电动机跳闸，而同时还有一部分电动机处于运行状态，这样就引发了大爆炸。由于在电暴期间，无数的小火载和设备异常的报警引起了极大的恐慌和混乱，人们忽略了一些本应清除的易燃物质残留在输油管道和储油桶中。五小时后这些物质被点燃，导致了激烈的爆炸。英国交流电配电网络中的浪涌发生频率是相当低的，这通常使人们忽略他们的产品、系统或设施抵抗电源浪涌的重要性。人们产生这种想法与一般的电磁兼容标准中不要求浪涌测试有关。上述的事故说明，对浪涌采取适当的防护策略是十分重要的。适合的基本测试标准有</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>IEC 61000-4-5</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>或</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>IEC 61000-4-12</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>（振铃波），两个标准都是模拟电源网络上电暴的间接效果的。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　工程技术人员总是尽力节省成本，预防措施的成本很容易估算出。然而，许多工程技术人员不习惯估算诸如雷暴之类的偶然发事件的风险，因此他们不能很好地与主管人员交换意见。就如有些人最近说过：医生的不慎导致一个人死亡，而工程师的不慎使一群人死亡。事业和个人的责任也在此显得得失攸关，因此，最好向管理部分提交一份书面的成本</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>/</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>风险报告。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    <br>
    17</span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>、近来一公司购买了一台</span><span
    style='font-size:9.0pt;font-family:Arial'> </span><span style='font-size:
    9.0pt;font-family:宋体;mso-ascii-font-family:Arial;mso-hansi-font-family:
    Arial;mso-bidi-font-family:Arial'>±</span><span lang=EN-US
    style='font-size:9.0pt;font-family:Arial'>8000</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>安培的特大功率直流驱动装置，安装在一个工厂里。订订购合同书上规定，并且厂商也宣称这台装置满足</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>EMC</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>指令要求。由于需要一间控制室（象大多数现代控制室一样，里面装满了计算机和</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>CRT</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>显示器），生产厂商声明，控制室可以位于该装置机柜的附近。当驱动装置运转起来时，视频显示器上的图像被挤成屏幕宽度的</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>50%</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>以下。从视频显示器屏幕的变化情况可以直接知道装置的运动方向和负载状态，但是根本无法读出上面的信息。这个装置产生的磁场强度在</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>235mT</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>量级，大多数基于</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>CRT</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>显示器的图象当周围的磁场强度超过</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>1mT</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>（</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>1mT</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>约为</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>0.8A/m</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>，也等于</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>10</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>毫高斯）时就开始抖动。厂商一再声明，尽管这台装置会干扰控制室内的视频显示器，但是它确实是满足</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>EMC</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>指令的。实际上，厂商的意思是该装置满足一般工业标准，但不包括任何低频磁场发射限制。但是如果你宣称满足了电磁兼容指令，就应该对任何干扰负责。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　这个问题最后通过采用</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>LCD</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>液晶显示屏获得了解决。虽然也考虑过采用磁屏蔽和有源场取消装置，但这会使控制室的投入使用延后几个月，这会对生产造成较大的影响。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    <br>
    18</span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>、我们在生活中遇到这样一种现象，如果我们半夜起床进卫生间，打开电灯时风扇的定时器就开始工作。风扇将连续运转</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>20</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分钟，当它停止运转时会产生干扰，点亮外面的安全灯（红外线触发</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>500W</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>的卤族气体电灯），这盏灯持续照明一段时间（</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>15</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分钟），灯光直射进卧室的窗户。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　下面这件事你就更难以相信了，在</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>500W</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>卤族气体电灯前面，我们有一盏带有电感镇流器的高压钠灯。当将它关闭时会产生干扰，有时会使附近的收音机打开。这出戏的剧情是这样的</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>......<br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　凌晨</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>2:00</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>起床，进入浴室点亮电灯，然后关掉电灯再回到卧室，</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>20</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分钟后，一束明亮的灯光将从窗户透射进来使你惊醒。如果你睡得很沉（或者是醒后又睡着了），</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>15</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>分钟后，当电灯熄灭时，收音机却突然打开，因此又将你再次吵醒。这件事情要说明的问题是什么呢？如果你家中电器的</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>EMC</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>抗扰性很差，一定在睡觉前去卫生间。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    <br>
    19</span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>、早在八十年代初，我上学的时候，带我的教授被一件可怕的事情缠在了新泽西。好象是一家医院产科病房区的婴儿死亡率相当高。深夜，监视婴儿的监视器上的警示灯总是无缘无故地熄灭。对此，护士们很恼火，于是她们将监视器关闭，来回逐一巡视。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　经过一番初步调查后，教授查明了这件事情的真相，原来附近一电视台的发射机得到美国通信委员会的许可，在大约午夜后可将其输出功率提高得相当高，但必须在早上六点前，或其它指定的时间，恢复到原来的水平。护士站与每个婴儿的监视器间的连接电缆在这些干扰频率处发生谐振，感应的电压而使监视器警示灯熄灭。医院在发现这个问题之前，已有差不多六名小孩死亡。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    <br>
    20</span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>、在落后国家中，电网电压过低或配置不当的现象是极其普遍的。我们知道，在西班牙，尽管官方专用供电网的电压在</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>230V</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>±</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>6%</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>左右，但是大部分地区白天大部分时间的电压都在</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>150V</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>左右，显然是由于电网负载配置不当引起的。在英国，人们从不会遇到类似的情况，除了在雷电彻底摧毁供电网的前一秒钟。我曾坚持认为，在我们的供电网条件下，上述情况不可能发生。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　一九九八年七月二十六日，星期日，晚上大约五点时，</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>Denshaw</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>村庄里的电压突然降到有效值为</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>140V</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>左右（低于额定值</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>40%</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>），虽然工程技术人员赶到现场解决了这一问题，但在这之前这种低电压一直持续了大约三个小时。在这期间，我们关掉了电冰箱和其他电机驱动的电器，因为它们会发出很奇怪的噪声。计算机虽然还在运转，但显示屏是黑的，这使我们担心数据会出什么问题，因此也同时将其统统关闭。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><br>
    </span><span style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
    Arial;mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>　　我知道，当电子控制设备工作在远离其额定交流电源的区间范围时，很可能会产生误动作，而且也明白低电压会损坏电机绕组和马达。显然，由于低电压，马达会减速，因此不会产生反电动势，这致使马达电流过大，绕组过热，烧坏绝缘层物质，使其过早地损坏（即使没有受到电击和火灾）。发展中国家相关电气产品的制造商及其安全测试实验室，通常不会在供电电压波动±</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>10%</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>的范围（有时是±</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'>15%</span><span
    style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:Arial;
    mso-hansi-font-family:Arial;mso-bidi-font-family:Arial'>）内进行测试。直到七月二十六日星期日这天，我才认识到这个问题的重要性。</span><span
    lang=EN-US style='font-size:9.0pt;font-family:Arial'><o:p></o:p></span></p>
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