ANSYS Emag“现代技术”新单元Plane233线性摄动分析有问题！

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17.2的线性摄动分析还是没有提高精度！

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plane53单元，输出的数据多很多，甚至包括了微分磁导率；而Plane233单元的输出项目要少很多。

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奇怪的是，Plane233单元计算的磁能，磁共能却是很精确的！

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永磁电机磁能，磁共能，视在磁能示意图

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从磁力线就可以看出来，3槽4极电机属于相间互感最大化的情形！

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线性摄动分析不精确，但是磁场能量计算却很精确！

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等 Ansys 18.0出来，看看摄动分析有没有改进和提高。

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今天发布了Ansys 18.0

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经实际算例，电磁摄动分析仍然是精度很低没有改变！

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Ansys 18.1出来了，试了一下线性摄动分析，还是老样子！

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与10楼的结果进行比较，可见16.2版本计算的，18.1版本计算的，两者看不出有什么区别！

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基本的计算理论不会有重大突破，因此程序算法也不可能明显改变，线性摄动分析大大加快了计算的速度，但是计算的精度却大大降低了。

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Inductance plays an important role in the characterization of magnetic devices, electrical machines,
sensors and actuators. The concept of a non-variant (time-independent), linear inductance of wire-like coils is discussed in every electrical engineering book. However, its extension to variant, nonlinear, distributed coil cases is far from obvious.

Time-variance is essential when the geometry of the device is changing: actuators and electrical machines, for example. In this case, the inductance depends on a stroke (in a 1-D motion case) which, in turn, depends on time.

Many magnetic devices apply iron for the conductance of magnetic flux. Most iron has a nonlinear BH
curve. Because of this nonlinear feature, two kinds of inductance must be considered: differential and
secant. The secant inductance is the ratio of the total flux over current. The differential inductance is
the ratio of flux change over a current excitation change.

The flux of a single wire coil can be defined as the surface integral of the flux density. However, when
the size of the wire is not negligible, it is not clear which contour spans the surface. The field within
the coil must be taken into account. Even larger difficulties occur when the current is not constant: for
example solid rotor or squirrel-caged induction machines.

The voltage induced in a variant coil can be decomposed into two major components: transformer
voltage and motion-induced voltage.

The transformer voltage is induced in coils by the rate change of exciting currents. It is present even if
the geometry of the system is constant, meaning the coils don't move or expand. To obtain the transformer voltage, the knowledge of flux change (i.e., that of differential flux) is necessary when the exciting currents are perturbed.

The motion-induced voltage (sometimes called back-EMF) is related to the geometry change of the
system. It is present even if the currents are kept constant. To obtain the motion-induced voltage, the
knowledge of absolute flux in the coils as a function of stroke is necessary.

Obtaining the proper differential and absolute flux values requires consistent calculations of magnetic
absolute and incremental energies and co-energies. For current-technology elements, the linear perturbation procedure can be used to calculate the differential inductance and the absolute flux using the incremental (IENE) and the co-energy (COEN) element records, respectively.

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这个功能难道没有人使用吗？

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Ansys的兼容性做得真是很不好，竟然自己的文件都会有问题！

我因项目需要重新调了以前5.6.1版本生成的db文件，能够打开，居然无法保存，一保存就崩溃退出，真是岂有此理！

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用简单的矢量磁位相减，也可以很方便地进行绝对磁链计算，APDL程序如下（以A相为例）。

CMSEL,s,A+,
Esla,s
ETABLE,A_Z,A,Z,
ETABLE,s,Volu
Smult,A_S,A_Z,S
Ssum
*Get,_Az,ssum,,item,A_S
*Get,Es,ssum,,item,S
*Set,Azh,_Az/Es
ALLSEL
Etable,eras

CMSEL,s,A-,
Esla,s
ETABLE,A_Z,A,Z,
ETABLE,s,Volu
Smult,A_S,A_Z,S
Ssum
*Get,_Az,ssum,,item,A_S
*Get,Es,ssum,,item,S
*Set,Af,_Az/Es
ALLSEL
Etable,eras

*Set,PSIA,(Azh-Af)*52*5*0.05

其中A+和A-是代表线圈的面积部件，施加线圈电流时是通过对该面积加电流密度实现的（用BFA命令）。

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选中面积后，再选中该面积的所有单元，每个单元的AZ矢量磁位（平均值）与该单元的面积相乘，所有乘积求和，再除以总面积，就是线圈边的矢量磁位，与另外一个线圈边的矢量磁位相减，就是单匝线圈的绝对磁链。

52是匝数，5是单元电机数，0.05是铁心长度

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Ansys 19.0发布了。

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还是用简单的矢量磁位相减，进行绝对磁链计算，再加上转矩计算结果，就可以完美刻画永磁电机的各种性能，其实电感的数值并不直接反映电机的性能，不加以计算也未尝不可！

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Ansys 19.1发布了