电机铁心一般由彼此绝缘的硅钢片叠成，其目的是（   ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69466' and id < 4499245 and id<>'4499245' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69466' and id > 4499245 and id<>'4499245' order by id asc limit 5