船舶推进电机绝缘轴承

<p style="line-height: 1.75em; margin-top: 10px;"><span style="text-align: left; color: rgb(25, 25, 25); text-transform: none; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: float: none display: inline white-space: orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>近年来船舶电力推进系统需求日趋增多，交流变频调速应用日趋广泛。采用变频调速不但能实现电机无级调速，而且可以在不同应用场景和不同负载条件下使电动机始终运行在高效区，并确保优良的动态特性。随着推进电机容量的不断增大，轴电流导致电机损伤事故屡有发生，设计时应该重视由轴电流引起的危害。</span></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:><strong style="margin: 0px; padding: 0px; border: 0px currentColor; border-image: none; font-size: 16px; font-weight: 700;">轴电流产生机理和危害</strong></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>船舶交流电力推进系统一般包括推进变压器、推进变频器和推进电机，变频器一般采用电压型两电平交-直-交拓扑方案，变频器采用模块化设计，包括整流单元、制动单元、逆变单元等组成，力求达到较大的功率密度和高可靠性，主回路示意图如下图。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: center; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:><img title="船用.jpg" alt="船用.jpg" src="default/20210115/11d8cbbf231c5a6bae1dbfe015030c6a.jpg"></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>变频驱动系统运行时，转轴与轴承之间产生的电压叫做轴电压，若轴承绝缘不佳，则会通过轴承、轴承座或机座等构成回路，轴电流就产生了。轴电压是随着电机的旋转运行就存在的，一般普通工频电机轴电压产生主要是由电容电流、单极效应或磁路不对称等因素造成，最终还是由磁通脉动造成的，在正弦波供电的情况下，轴电压较小，危害不大"。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>但是对于船舶电力推进系统广泛应用的变频电机大都采用变频供电，这时电机的轴电压主要是由于电源三相输出电压不平衡的零序分量产生。变频调速驱动系统中谐波高频成份多，高次谐波分量在定子绕组、电缆和转轴中产生电磁感应，电机内分布电容的耦合作用形成共模回路，产生共模电压高频振荡，并与转子容性耦合，形成转轴对地电压，借助电机轴、轴承和机座等构成回路将产生轴电流。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>轴电压不高的时候，电机轴承润滑后形成的一层油膜可以起到绝缘作用，轴电流没有通路。但是当轴电压较高且润滑不充分时，轴电压过将使润滑油膜击穿放电产生轴电流，并导致发热产生高温烧灼，对轴承内圈外圈、或滚珠产生损伤，形成一些微小区域的凹槽损伤，对于高速旋转的电机来说，将引起异常噪声振动，不及时采取措施将在电机轴承的内外圈、滚珠上产生大面积损伤，导致轴承损坏，大大降低电机的使用寿命。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:><strong>轴电压轴电流限值规范</strong></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>电机运转时都会产生轴电压，变频驱动电机所允许的轴电压或轴电流的大小取决于现场运行环境、安装质量、电机运行状态、轴承状况、油膜厚度和回路阻抗等许多因素。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>实际应用中，对于滚动轴承电机，轴电压大于0.5V将产生有害轴电流，轴电压大于1 V时，电机轴承可能在运行后1年内就出现明显损伤;对于滑动轴承电机，润滑油膜绝缘效果稍好，轴电压大于1 V时会造成电机轴承明显损伤。某1500 kW、1000 r/min变频电机的空载轴电压和负载轴电压分别为0.65V和2.6 V，油膜电压分别为0.15 v和0.51 V，可以看出，变频电机轴电压还是比较大的，且负载时轴电压比空载时大，实际应用中必须采取措施，以减小或消除轴电流损伤。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:><strong>减小或消除变频电机轴电流损伤的措施</strong></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>轴电压对轴承等造成损害通常需要两个条件:一是轴电压较高;二是是轴承绝缘状态不佳，给轴电流提供了流通回路。轴电压无法避免，避免轴电流损害的重点应该是轴电流治理。对于采用滚动轴承的电机，轴承的润滑脂膜比较薄，并且在刚启动时润滑不充分，对轴电压的作用比较敏感，作为船舶推进变频驱动系统来说，必须采取措施预防轴电流。</p> <p style="margin: 0.63em 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>预防轴电流损害最有效的措施就是对变频驱动系统轴承进行绝缘设计。当轴电压高到一定程度时，电机设计时不仅要考虑轴承绝缘，电机辅助装置也要进行绝缘设计。轴承绝缘通常是采取非驱动端轴承绝缘，即采用绝缘轴承。绝缘轴承方案可彻底防止轴电流电蚀轴承，且安装维护方便。采用绝缘轴承在设计和安装时与普通轴承相同。</p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: center; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:><img title="ｖｘ.jpg" alt="ｖｘ.jpg" src="default/20210115/bbf391ad3bae51d3205d955e9cd181b8.jpg"></p> <p style="margin: 10px 0px 1.8em; padding: 0px; border: 0px currentColor; border-image: none; text-align: left; color: rgb(25, 25, 25); text-transform: none; line-height: 1.75em; text-indent: 0px; letter-spacing: normal; font-family: " pingfang sc arial simsun sans-serif font-size: font-style: normal font-weight: word-spacing: white-space: counter-reset: list-1 list-2 list-3 list-4 list-5 list-6 list-7 list-8 list-9 orphans: widows: background-color: rgb font-variant-ligatures: font-variant-caps: text-decoration-style: initial text-decoration-color:>而对于采用滑动轴承的电机，通常采用对滑动轴承的轴承座进行内部绝缘的设计方案，并在普通滑动轴承的基础上进行改进，设计出带绝缘结构的滑动轴承，成功解决变频电机滑动轴承的绝缘问题。</p>