Safe Torque Off on a PowerFlex 755: How the 20-750-S Is Wired and What It Does Not Do

The safe torque off path through a PowerFlex 755: 24 V on SP and SE from the two contacts of a safety relay, the option module between them and the gate control driver, the driver feeding the IGBT bridge, and the AC line, DC bus and motor terminals marked as still live

A 20-750-S seated in port 4 of a PowerFlex 755, SP and SE landed on separate contacts of a 440R-D22R2, twenty-four volts measured on both pairs, and the drive faults the moment the contactor closes. The SAFETY enable jumper is still on the main control board, where it ships from the factory, and the manual … Read more

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