变压器带额定负载运行时，效率最高，称为经济运行。（    ）

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69208' and id < 4481125 and id<>'4481125' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69208' and id > 4481125 and id<>'4481125' order by id asc limit 5