Schneider ATV320U55N4B Retrofit-Ready VFD for Altivar 320

Schneider ATV320U55N4B Retrofit-Ready VFD for Altivar 320 Control Systems

The Schneider Electric ATV320U55N4B is a 5.5 kW, 400 V three-phase variable frequency drive from the Altivar 320 series, engineered for seamless integration into existing motor control architectures. Whether you are replacing an end-of-life ATV312HU55N4 or ATV31HU55N4, upgrading a legacy panel built around the older Altivar 31 platform, or modernizing a distributed control cabinet that relies on Modbus RTU or CANopen communication, the ATV320U55N4B delivers a verified drop-in upgrade path with minimal re-engineering.

Industrial facilities running continuous production lines — conveyors, pumps, compressors, fans, and packaging machinery — depend on uninterrupted motor control. When a legacy drive reaches end-of-life or spare parts become unavailable, the ATV320U55N4B provides a technically validated replacement that preserves existing wiring topology, retains compatible terminal assignments, and supports the same communication protocols already embedded in your SCADA or PLC program. This makes it the preferred choice for maintenance engineers who need to restore operation quickly without redesigning the control logic or retraining operators.

Upgrade Compatibility Table

Retrofit Planning for Existing Automation Systems

A successful retrofit of the ATV320U55N4B into an existing control cabinet begins well before the drive is physically installed. The first step is a thorough audit of the existing panel: confirm the incoming supply breaker rating, verify that the upstream GV2ME or GV3ME motor circuit breaker is sized for 13.7 A output, and check that the braking resistor — if fitted — is compatible with the ATV320 braking chopper specification. Many legacy panels also include a VW3A9801 line choke or EMC filter; these components are typically reusable and should be retained to maintain conducted emission compliance.

On the control wiring side, map every terminal from the old drive to its ATV320 equivalent before disconnecting any wire. The ATV320U55N4B uses a familiar Altivar logic terminal block, but subtle differences in analog input scaling (0–10 V vs. 4–20 mA selection) and relay output assignment may require parameter changes rather than rewiring. If the legacy system used a VW3A3608 PROFIBUS DP communication card, confirm that the card’s firmware is compatible with the ATV320 option slot before reusing it; in some cases a VW3A3607 DeviceNet card or a VW3A3616 EtherNet/IP card may be a more future-proof choice for the upgraded system.

For systems where the ATV320U55N4B replaces a drive connected to a Modicon M340 or Modicon M580 PLC via Modbus RTU, the slave address and baud rate stored in the old drive must be documented and re-entered into the new unit before the PLC program is restarted. If the control system uses a Magelis HMIGTO or HMISTO HMI panel, verify that the drive variable addresses referenced in the HMI screens match the ATV320 register map — minor offset differences between Altivar generations can cause incorrect speed readback or fault display if not corrected. Where I/O expansion is needed alongside the drive replacement, TM3 series I/O expansion modules connected to the PLC can absorb additional digital and analog signals without modifying the drive wiring.

Before closing the cabinet, perform a pre-energization checklist: confirm insulation resistance on the motor cable, verify that the DC bus capacitors have discharged from any previous drive, check that all control cable shields are grounded at one end only, and confirm that the programming cable — typically a VW3A8104 USB-RJ45 cable — is available for the SoMove commissioning session. Ship the unit with its factory parameter set intact; do not pre-load customer parameters until the drive is installed and the motor is confirmed connected.

Downtime Control During System Migration

Minimizing production downtime during a drive replacement requires a structured swap procedure. Begin by using SoMove software to export the full parameter file from the existing ATV312 or ATV31 drive while the machine is still running — this creates a baseline that can be imported into the ATV320U55N4B after adjusting for any parameter name or address differences between generations. Schedule the physical swap during a planned maintenance window; the mechanical installation of the ATV320U55N4B typically takes under 30 minutes given its identical mounting footprint.

Once the new drive is installed and wired, perform a no-load motor test at low speed (5–10 Hz) before restoring the process setpoint. This confirms that the direction of rotation, speed reference scaling, and relay output assignments are correct without risking a process upset. If the system uses a safety relay or STO (Safe Torque Off) circuit connected to terminals STO1 and STO2, verify the STO wiring continuity and test the safety function before returning the machine to automatic mode. Retain the removed ATV312 unit as a temporary spare until the ATV320U55N4B has completed at least one full production cycle without fault — this provides a rapid fallback option if an unexpected compatibility issue is discovered during initial operation.

For multi-drive panels where several units are being replaced in sequence, stagger the replacements across shifts to maintain partial production capacity. Document each drive’s node address, parameter file, and terminal wiring photograph before removal. This discipline reduces commissioning time for subsequent units and creates a permanent retrofit record that supports future maintenance and audit requirements.

Retrofit Support FAQ

Q1: Is the ATV320U55N4B a direct drop-in replacement for the ATV312HU55N4?
In most applications, yes. Both drives share the same power rating (5.5 kW), supply voltage (400 V, 3-phase), and output current (13.7 A), and both support Modbus RTU and CANopen natively. The terminal block layout is similar but not identical — a terminal-by-terminal comparison using the respective wiring diagrams is mandatory before energizing. Parameter names and menu structures differ between generations, so a full parameter re-entry via SoMove is required rather than a direct file import.

Q2: Can I reuse the existing motor cable and braking resistor?
The existing motor cable is reusable provided its cross-section and insulation rating are appropriate for 13.7 A at the installation’s ambient temperature. The braking resistor must be verified against the ATV320 braking chopper specification — minimum resistance value and continuous power rating. If the existing resistor was sized for the ATV312, it will typically be compatible, but confirm using the ATV320 programming manual before connecting.

Q3: What commissioning tests are required before returning the machine to production?
The minimum commissioning sequence includes: (1) insulation resistance test on the motor cable, (2) no-load rotation check at low speed, (3) verification of all digital input functions (run, stop, fault reset, speed reference selection), (4) confirmation of relay output assignments, (5) communication link test with the PLC or SCADA system, and (6) STO safety function test if applicable. Each step should be recorded in the retrofit documentation package.

Q4: What does the 12-month warranty cover?
Every ATV320U55N4B unit is covered by a 12-month warranty from the date of shipment. The warranty covers manufacturing defects, component failures under normal operating conditions, and dead-on-arrival (DOA) units. Each unit undergoes functional verification testing prior to dispatch. Warranty claims are processed via our sales team at [email protected]. The warranty does not cover damage resulting from incorrect installation, overvoltage events, or operation outside the drive’s rated environmental conditions.

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