Er.990 fault in inovance IS650 servo drive indicates Power input phase loss warning. This means a loss of one or more phases in the input power supply. This can occur due to various reasons, including loose connections, faulty wiring, or power supply issues.

1. Check whether it is a three-phase servo drive allowed to run under single-phase power.
2. Check all power connections, including those to the power supply and the drive itself. Ensure they are tight and secure.
3. Repair or replace damaged cables and correct any wiring errors.