.空载时变压器一、二次电压有效值之比可近似等于(    )。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69521' and id < 4504053 and id<>'4504053' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69521' and id > 4504053 and id<>'4504053' order by id asc limit 5