Product Overview

The Emerson SP4403​ is a Frame 4 member of the Unidrive SP family, the universal AC-and-servo drive platform originally developed by Control Techniques and sold under the Emerson Industrial Automation brand before the business became part of Nidec. What the “SP” designation means in practice is that one heatsink, one DC bus and one set of power terminals support induction, permanent-magnet synchronous and servo motor control as selectable firmware modes rather than as three different hardware lines. The SP4403​ therefore occupies the upper-mid power band of the SP range: three-phase 380–480 V AC input, roughly 45 kW (60–75 HP) of motor rating depending on duty class, and a continuous output current in the 96–104 A band.The architecture is deliberately modular. The base Emerson SP4403​ ships without a keypad and without a fieldbus card, which is why the bare unit is so often described as a “drive only” part. Control comes from the onboard digital and analog I/O, from an RS-485 / Modbus RTU port, or from one of the SM-series option modules plugged into the drive’s expansion slot — a flexibility that is the whole point of the SP platform. A single SP4403​ on a winder can close a tension loop with an encoder on the mandrel, talk Profibus-DP to a Siemens PLC, and still accept a 0–10 V speed reference from a pot, all without adding a separate servo amplifier or a signal conditioner.Where the SP4403​ separates itself from a general-purpose VFD is in the control stack. Below 1 Hz the drive holds rated torque in closed-loop vector mode, and in servo mode it accepts a position or velocity command with the same current-loop bandwidth the platform uses for induction flux control. The built-in dynamic-brake transistor and DC-injection braking remove the usual external chopper and resistor from a straightforward hoist or fan stop, while the onboard EMC filter keeps conducted emissions inside the industrial envelope without a line filter in every cabinet. Add the embedded programmable logic (SyPTLite / CTSoft ladder), and the drive can own a small sequencing interlock — belt guard, lube pump, brake release — that would otherwise burn two inputs and a coil on the site PLC.For the maintenance organisation, the Emerson SP4403​ is valuable precisely because it is now a legacy, end-of-life part. The mechanical footprint, terminal pattern and heatsink mounting are fixed, so a failed unit comes out and an tested SP4403​ goes back in on the same din of busbar and motor cable. Parameter sets are portable through the SM-Keypad copy function or CTSoft, which turns a four-hour commissioning revisit into a 20-minute swap. That is the real product: not a brochure drive, but a known, tested shape that keeps a 15-year-old line running until the migration is actually funded.

Technical Specifications