problem

It is important to consider the characteristics of the load as well. Is the motor compatible with the load characteristics at 60% speed? What current is it pulling at 60% speed, and does this figure exceed the current setting for the drive?

What is the fault code,High output current?output fault to ground? high DC buss voltage? there are a few reasons for an inverter to trip,Is it clean?getting hot at 60% load.There should be a fault code listed,and many have a fault history you can check.

I believe he was saying it is an "It" indication, meaning "I" as in Current and "t" as in thermal (in typical VFD parlance). That means it is likely a Motor Overload condition.

What you (Guest 1) may not realize is that when reducing the speed to 60%, you are reducing the absorbed power to 60%, which means the mechanical output power is also at 60%. Most loads look for constant torque, but IF your load is such hat you need constant power, you will overload the motor.