转 has two pronunciations: zhuǎn (to turn, to change) and zhuàn (to revolve, to spin). In 转动 it is zhuǎn when meaning 'to turn something' and zhuàn when meaning 'to spin or revolve'. Both are acceptable for this word.
usage
转动 emphasizes the physical rotating motion. Compare with 转变 (to transform / change) and 转移 (to transfer / shift).
