三相对称电路，当负载作星型连接时，此时中性线电流（     ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68466' and id < 4420858 and id<>'4420858' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68466' and id > 4420858 and id<>'4420858' order by id asc limit 5