text: <s>[INST] PowerFlex 525 Summary: PowerFlex 525 ,460, 3ph runs single phase without faulting out.I have a situation where a A/B PowerFlex 525 3ph,460vac ,15hp drive a motor with mechanical disc brake. The brake is fed separate from L1and L2 of PowerFlex , respective a contactor that turn on-off the brake, at some point fuse on L1 blown out , but the drive didn't fault but keep running with brake engaged (not released) My question is why the drive was still running single phase without any fault ? Was because feedback from L2 through brake coil to L1 to drive ? [/INST] Hi I do not have experience with PF 525 but do have it with PF 70-700, my recommendations for you are: Check if the phase lost detection is on or off, Read the Knowledgebase answer 578273 and Consider installing an external phase loss relay (this is what I have done) Bye \\n </s>