Rotating casing is helpful to improve effectively mud displacement efficiency and thus improve cementing quality.

旋转套管可以有效提高水泥浆顶替效率，从而提高固井质量。

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Think of it as a rotating transformer, with the primary windings residing in a stationary casing (stator) and the secondary conductors attached to an inner shaft (rotor).

你可以把这种电动机当作一个旋转变压器，其主要的线圈在固定套管(定子)内，二级导线附在一个内轴(转子)上。

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Tesla's invention is, in essence, a rotating transformer. Its primary windings reside in a stationary steel casing (the stator) and and secondary conductors are attached to an inner shaft (the rotor).

尼古拉·特斯拉发明的感应电动机本质上就是一台旋转变压器——首先在电动机的固定钢制外壳（定子）上安装上绕组，然后将导体安装入内轴（转子）。

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