Windows server 2012 r2, only incremental backup

Hi,

I have a Windows server 2012 r2 and I´m using Windows backup Service for to make the backup of 10Tb, I make incremental backups but I have one problem, any random times windows decides to make a full backup, it needs 60 hours for to make a full backup for this  reason it is a serious problem for my.

I need to know how disable this random full backup.

Thanks.