Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any ‘hiccups’ (be sure to completely shut down the air compressor!). Check the isolation of the motor winding.
[pdf] Uses a dedicated variable frequency drive (VFD) for permanent magnet synchronous motors, enabling stepless speed regulation, constant pressure air supply, and soft start. This eliminates idle power consumption and enables intelligent air supply.
[pdf] When pressing “Enter” the following interface will pop up and the password will be required (9999). NOTE: Customer Password can be modified in the CUSTOMER PARAMETER menu. Page 23 KRSD series ENTER PASSWORD ****. Page 24 UNLOAD P. *.**Mpa Unload pressure setting.
[pdf] 
