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<p>was found to work well on frequencies around 50 to 60&nbsp;Hz, but the materials available in the 1890s would not work well at a frequency of, say, 133&nbsp;Hz. There is a fixed relationship between the number of magnetic poles in the induction motor field, the frequency of the alternating current, and the rotation speed; so, a given standard speed limits the choice of frequency (and the reverse). Once AC <a href="page.php?w=electric_motor">electric motor</a>s became common, it was important to standardize frequency for compatibility with the</p><p>
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