The Allen-Bradley PowerFlex 700S is the legacy high-performance AC drive: FORCE vector control with optional DriveLogix (the controller lives inside the drive), common-bus architecture, and SynchLink fiber linking multiple drives. It is the established choice for installed bases already running 700S, and the migration source for the large frames Rockwell discontinued.

700S or 755 — which high-performance drive?

The 700S is the legacy flagship: FORCE vector control with optional DriveLogix, common-bus and SynchLink fiber linking multiple drives. Choose it for installed bases already running 700S or where drive-embedded logic is the design. Choose PowerFlex 755 for new high-power builds — Rockwell discontinued the 700S frames at 200 Hp and above as of 2020-06-30, so any new large drive should be a 755. The alternative — staying on a discontinued 700S frame — leaves a future spares gap on the biggest, hardest-to-replace drives.

What does FORCE vector control plus PM control give you?

Beyond basic V/Hz, the 700S runs sensorless and closed-loop FORCE vector with permanent-magnet motor control, holding torque and speed on hoists, winders, and vertical axes without a feedback device in sensorless mode. On a crane or elevator that means controlled stopping under load. The alternative — a V/Hz-only drive — lets the load drift on a vertical axis the moment speed feedback is lost.

How is safety handled without external relays?

Safe Torque-Off is built in at PLd / SIL2 Cat 3, so the drive can drop motor torque on a safety trip without external contactors or a separate safety relay. That removes wiring and a failure point from the safety chain. The alternative — an external STO relay per drive — multiplies devices and commissioning across a multi-drive line. (Note: the 755 carries the higher SIL3 rating where that is required.)