text: <s>[INST] Powerflex 40 faliure after power cycle We have 46 5 hp powerflex 40 drives in our plant and have had little trouble until the other day. We had a scheduled power outage with the power company they disconnected all phases at on time but repowered us one phase at a time. after that we noticed we had 7 drives that did not power back up and are fed from the same line as ones that did. we checked voltage at the drive line input and is fine. we are at a loss as what and why this has happened. [/INST] Hi Red, Perhaps those drives have failed due to a problem with the switchmode power supply. On some early PF4 and PF40 drives there were some components that were affected by heat a bit more than we expected and this problem showed up. We have since improved the design. There is a knowledgebase document that describes the issue. It is document number 34911. Only certain models of PF4 and PF40 drives had this issue, and only up to a certain date. Drives manuafactured after October 2005 have the improved design. Please contact your distributor for more information about this. Linkified for convenience - JHutch \\n </s>