You do not. You can get killed. If an IGBT is bad, the drive will tell you that. If it does, there is no justification for working on it while the input is live.
When drive is not powered and motor disconnected, you can do diode test across outputs. AB, BC, CA. You will read diodes in both directions. If any of the IGBT's are shorted, they will read close to zero Ohms.
Hi,
You can use Siemens Drive test card. This card show you which phase IGBT is faulty. Even this will show you control main control board behavior.
This card will be placed in Place of CU2 or CUVC.