By default if converting Excel (.xls or .xlsx) to CSV the result is comma delimited. This is because setting list separator in your control panel.
If we want to convert excel to csv with different delimitor, for example, semicolon delimited, the easy way is the changing list separator in control panel.
In Windows 7:
1. Control Panel
2. Region and Language
3. Additional settings
4. List separator, change from comma (,) to semicolon (;)
5. Ok, -Finish-