data conversion error

Data conversion failed while converting column "NAME" (176) to column "Copy of NAME" (15).  The conversion returned status value 2 and status text "The value could not be converted because of a potential loss of data.".

Error: 0xC0209029 at

this has string(dt_str) 600 in flat file output column.

in my tabl eit is nvarchar(50).

what should i change