Berger Lahr VRDM Series Servo Motors: VRDM 397/50 LNB

Technical Dossier

Product Details And Specifications

Berger Lahr VRDM Series: Comprehensive Module Range and Technical Overview

The Berger Lahr VRDM (Variable Reluctance Drive Motor) series represents one of the most widely deployed families of stepper and servo motors in global heavy industry. Installed across chemical processing plants, nuclear facility auxiliary systems, petroleum refining infrastructure, and continuous-process manufacturing lines, the VRDM series established a benchmark for precision motion control in environments demanding high torque density, thermal stability, and deterministic positioning. Manufactured in Germany under Berger Lahr's engineering standards — later absorbed into the Schneider Electric / IMS (Intelligent Motion Systems) portfolio — VRDM motors remain active in legacy DCS and PLC architectures worldwide, with installed bases that will require spare parts and maintenance support well into the 2030s.

The Evolution of VRDM Series Architecture

The VRDM series was introduced by Berger Lahr in the 1980s as a high-resolution stepper motor platform designed for integration with proprietary drive controllers (WDP, WDPM, and WDPD series). Early variants operated on 2-phase and 5-phase winding configurations, with frame sizes ranging from NEMA 17 equivalents up to large-frame 397 and 599 housings. The suffix nomenclature encodes critical configuration data: the numeric segment (e.g., 397) denotes the motor frame/torque class, the slash-number (e.g., /50) specifies the step resolution or winding variant, and the letter suffix (e.g., LNB, LNA, HNB) identifies the shaft configuration, encoder option, and connector type.

Through the 1990s, Berger Lahr expanded the VRDM range to include encoder-equipped variants (suffix E or with integrated resolvers) for closed-loop servo operation. The acquisition by Schneider Electric introduced compatibility bridges to Lexium and Modicon platforms, though the native VRDM interface remained tied to the RS-232/RS-485 WDP controller ecosystem. As of 2010, the VRDM series entered end-of-life status under Schneider Electric's product lifecycle policy, making third-party sourcing the primary supply channel for ongoing maintenance.

VRDM Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly sourced models within the Berger Lahr VRDM series, classified by frame size and configuration:

2-Phase / Small Frame Motors

VRDM 264/50 LNA: 2-phase, frame 264, standard shaft, no encoder, connector type A
VRDM 264/50 LNB: 2-phase, frame 264, standard shaft, no encoder, connector type B
VRDM 264/50 LHB: 2-phase, frame 264, high-resolution winding, connector type B
VRDM 264/50 LWB: 2-phase, frame 264, with integrated encoder feedback, connector B

5-Phase / Mid Frame Motors

VRDM 368/50 LNA: 5-phase, frame 368, standard shaft, no encoder, connector A
VRDM 368/50 LNB: 5-phase, frame 368, standard shaft, no encoder, connector B
VRDM 368/50 LHB: 5-phase, frame 368, high-torque winding variant, connector B
VRDM 368/50 LWB: 5-phase, frame 368, encoder-equipped closed-loop variant

Large Frame / High-Torque Motors (397 Series)

VRDM 397/50 LNA: 5-phase, frame 397, standard shaft, no encoder, connector A
VRDM 397/50 LNB: 5-phase, frame 397, standard shaft, no encoder, connector B — primary listing SKU
VRDM 397/50 LHB: 5-phase, frame 397, high-resolution winding, connector B
VRDM 397/50 LWB: 5-phase, frame 397, encoder-equipped, connector B

Extra-Large Frame Motors (599 Series)

VRDM 599/50 LNA: 5-phase, frame 599, high-torque, standard shaft, connector A
VRDM 599/50 LNB: 5-phase, frame 599, high-torque, standard shaft, connector B
VRDM 599/50 LHB: 5-phase, frame 599, high-resolution winding, connector B
VRDM 599/50 LWB: 5-phase, frame 599, encoder-equipped closed-loop, connector B

Sourcing Hard-to-Find & Obsolete VRDM Series Parts

The VRDM series reached official end-of-life under Schneider Electric's product management framework, meaning OEM new-stock availability is effectively zero through standard distribution channels. DriveKNMS maintains a dedicated inventory of tested, pull-out, and refurbished VRDM units sourced from decommissioned plant equipment, controlled factory shutdowns, and authorized surplus liquidations. Our procurement network spans industrial auctions, OEM warehouse clearances, and direct plant-to-plant transfers across Europe and Asia-Pacific.

For facilities operating legacy Berger Lahr WDP/WDPM controller systems paired with VRDM motors, DriveKNMS provides lifecycle extension support including: cross-reference verification between original Berger Lahr part numbers and Schneider Electric successor codes, functional equivalency assessment for substitute motor frames, and documentation of wiring pinout differences between LNA and LNB connector variants to prevent installation errors.

Quality Control for the VRDM Series Range

Each VRDM unit processed by DriveKNMS undergoes a structured inspection and functional test protocol specific to the motor's winding configuration and encoder status. Testing procedures include: winding resistance measurement across all phases (tolerance: ±5% of nameplate specification), insulation resistance test at 500VDC (minimum 100MΩ), back-EMF waveform verification under no-load rotation, shaft runout measurement (TIR ≤ 0.02mm), and encoder signal integrity check (for LWB variants) via oscilloscope capture at rated speed. Motors with integrated connectors are tested for contact resistance and mechanical retention force. Units failing any parameter are quarantined and documented; no borderline units are released to stock.

For sourcing inquiries, cross-reference requests, or bulk spare parts orders for the Berger Lahr VRDM series: