Siemens 6SE7035-1EJ84-1BH0 Retrofit ABO Module Legacy VFD

Siemens 6SE7035-1EJ84-1BH0 Retrofit ABO Module: Legacy VFD System Compatibility & Smooth Upgrade

The Siemens 6SE7035-1EJ84-1BH0 is an Automatic Bypass Operation (ABO) module designed for the SIMOVERT MASTERDRIVES series — one of Siemens’ most widely deployed variable frequency drive platforms in heavy industrial environments. As the MASTERDRIVES line has reached end-of-production status, this ABO module has become a critical retrofit and spare part component for facilities operating legacy motor control systems in process automation, HVAC, water treatment, mining, and manufacturing applications.

The 6SE7035-1EJ84-1BH0 enables automatic bypass of the drive inverter section, allowing the connected motor to continue running at full-speed direct-on-line (DOL) operation in the event of a drive fault. This bypass capability is essential for maintaining process continuity in critical applications where unplanned downtime carries significant operational and financial consequences. When planning a retrofit or upgrade of an existing MASTERDRIVES installation, the ABO module must be evaluated alongside the drive’s power section, control board, and communication interface to ensure full system compatibility.

Upgrade Compatibility Table

Retrofit Planning for Existing Automation Systems

When integrating the 6SE7035-1EJ84-1BH0 into an existing MASTERDRIVES installation, a structured retrofit plan is essential to avoid commissioning delays and protect the integrity of the existing control logic. The ABO module interfaces directly with the drive’s internal backplane, and its bypass contactor sequencing is governed by the drive’s parameter set — particularly the P-group settings related to fault response and bypass activation thresholds.

Before installation, engineers should verify the current state of the SIMOVERT MASTERDRIVES control unit (CU), typically a 6SE7090-0XX84-0AB0 or equivalent, which manages the ABO module’s trigger logic. If the control unit firmware is outdated, a firmware compatibility check against the ABO module revision is recommended. In parallel, the power supply module (PSU) feeding the drive cabinet — often a 6SE7031 or 6SE7033 series unit — must be confirmed to have sufficient reserve capacity to support bypass contactor energization without voltage sag on the DC bus.

Terminal wiring for the bypass output contactors should be mapped against the existing cabinet wiring diagram. In many legacy installations, the bypass contactor wiring runs through the drive’s X9 or X101 terminal strips. Any deviation from the original wiring scheme must be documented and verified against the MASTERDRIVES hardware installation manual before energization. Where the original installation used a 6SE7090-0XX84-2FK0 technology board or a CBP2 PROFIBUS communication board, these boards must remain seated and functional during the ABO module swap to avoid loss of fieldbus communication with the PLC or DCS.

For facilities running SIMATIC S7-300 or S7-400 PLCs as the upstream controller, the drive’s PROFIBUS node address and GSD file configuration should be backed up before any hardware change. If the retrofit also involves migrating from PROFIBUS-DP to PROFINET — a common upgrade path when replacing legacy MASTERDRIVES with SINAMICS S120 or G120 drives — the ABO bypass logic may need to be re-implemented in the new drive’s safety or sequencing parameters. In such cases, the SINAMICS CU320-2 PN control unit and its associated Drive-CLiQ topology should be planned in advance.

I/O expansion during the retrofit should account for the ABO module’s digital output signals, which typically report bypass status back to the PLC via the drive’s terminal board (TB30 or equivalent). If additional I/O is required, an ET 200SP distributed I/O station or a SIMATIC ET 200M rack can be integrated into the control cabinet without disrupting the existing motor circuit. Signal isolators may be required where the bypass status signal crosses cabinet boundaries or interfaces with legacy 4–20 mA instrumentation loops.

HMI screens on existing SIMATIC OP/TP panels or WinCC SCADA systems that display drive status should be updated to reflect the ABO bypass state. In many installations, the bypass active signal is mapped to a dedicated HMI faceplate element — this mapping must be verified and updated if the module replacement changes the signal address or data block structure in the PLC program.

Downtime Control During System Migration

Minimizing downtime during an ABO module replacement requires careful pre-staging and a clear sequence of operations. The recommended approach is to perform all preparatory work — parameter backup, wiring documentation, spare contactor pre-wiring, and HMI update — during scheduled maintenance windows before the actual module swap.

The existing drive parameter set should be uploaded using STARTER or SCOUT commissioning software and saved to a PC or memory card (6SE7090-0XX84-0FF0 or equivalent) before the module is removed. This ensures that the full P-group configuration, including bypass timing, fault response, and motor data, can be restored immediately after the new 6SE7035-1EJ84-1BH0 is installed. If the drive has been running with a customized parameter set for years, this backup step is non-negotiable.

During the physical swap, the bypass contactor and its associated wiring should remain undisturbed. Only the ABO module itself is removed from the backplane slot. After seating the new module, a cold-start sequence should be performed with the motor decoupled from the load where possible, allowing the bypass contactor timing to be verified under no-load conditions before returning the system to production. The entire swap — from power-down to first production run — can typically be completed within a two- to four-hour maintenance window when all preparatory steps have been completed in advance.

For critical processes where even a two-hour window is difficult to schedule, a hot-standby drive cabinet with a pre-configured spare MASTERDRIVES unit can be pre-positioned adjacent to the existing cabinet. This approach allows the bypass module to be replaced in the standby unit while the primary drive continues to operate, with a controlled switchover performed at the next available opportunity. This strategy is particularly effective in continuous process industries such as chemical, pulp and paper, and water treatment, where motor availability is directly tied to production output.

Retrofit Support FAQ

Q1: Is the 6SE7035-1EJ84-1BH0 a direct drop-in replacement for other ABO modules in the MASTERDRIVES range?
The 6SE7035-1EJ84-1BH0 is designed for the high-power MASTERDRIVES frame range and is compatible with drives in the 6SE703x to 6SE705x power range sharing the same backplane architecture. Before ordering, confirm the frame size and backplane slot configuration of your existing drive. Minor wiring adjustments at the bypass contactor terminal strip may be required depending on the original installation.

Q2: What commissioning steps are required after installing this ABO module?
After physical installation, restore the backed-up parameter set using STARTER or SCOUT software. Verify bypass contactor timing parameters (P-group bypass settings), confirm digital output signal mapping to the PLC, and perform a functional bypass test with the motor running at reduced load. Check HMI bypass status indication before returning the drive to automatic operation.

Q3: Can this module be used during a migration from MASTERDRIVES to SINAMICS?
The 6SE7035-1EJ84-1BH0 is a MASTERDRIVES-native component and is not directly compatible with SINAMICS S120 or G120 platforms. However, it can serve as a bridge component — keeping the existing MASTERDRIVES system operational while the SINAMICS migration is planned and staged. This approach reduces migration risk by allowing the new drive platform to be commissioned and tested in parallel before the final cutover.

Q4: What warranty and pre-shipment testing is provided?
All units are covered by a 12-month warranty from the date of shipment. Each 6SE7035-1EJ84-1BH0 undergoes pre-shipment functional testing to verify bypass contactor control logic, backplane interface integrity, and output signal continuity. Test records are available upon request. In-stock units are available for immediate dispatch to minimize your system downtime.