June 08, 2026

B843AT Industrial DC Motor Frame

The B843AT is a heavy-duty industrial DC motor frame standardized by Reliance Electric (now part of Rockwell Automation), designed for high-power, continuous-duty applications in harsh industrial environments. It serves as the mechanical and electrical foundation for a range of large DC motors, with power ratings typically from 400 HP up to 900 HP, and speeds from 400 RPM to 900 RPM.

Description

B843AT Industrial DC Motor Frame

Overview

The B843AT frame is built with robust cast-iron construction, engineered for maximum rigidity, vibration damping, and long-term reliability under heavy loads and cyclic operation. It accommodates various armature and field winding configurations, most commonly stabilized shunt wound (SPFV) or double-precision ventilated (DPFVBB) enclosures for enhanced cooling and protection against dust, moisture, and contaminants. This frame size is widely used in legacy industrial systems where high torque and precise speed control are required.

Key Specifications

Manufacturer: Reliance Electric (Rockwell Automation)
Frame Size: B843AT (standardized industrial frame)
Power Range: 400 HP to 900 HP
Speed Range: 400 RPM to 900 RPM
Armature Voltage (VA): 500 V or 600 V
Field Voltage (VF): 240 V DC or 300 V DC
Enclosure Types: DPFVBB (Double Precision Forced Ventilated), SPFV (Stabilized Precision Forced Ventilated), BB (Blower Ventilated)
Max Safe Speed: Up to 1935 RPM (model-dependent)
Winding Type: Stabilized Shunt Wound (standard)
Mounting: Horizontal base-mounted (heavy-duty steel base included)

Core Features

Heavy-Duty Cast-Iron Frame: Provides exceptional mechanical strength, reduces vibration, and ensures stable operation under full-load and shock-loading conditions.
High-Efficiency Ventilation: Forced ventilation designs (DPFVBB/SPFV) deliver consistent cooling to armature and field windings, enabling continuous 100% duty cycle operation without overheating.
Stabilized Shunt Winding: Delivers precise speed regulation, low speed droop, and stable performance across varying load conditions, ideal for process-critical applications.
Industrial-Grade Insulation: Class F or H insulation systems protect windings from high temperatures, moisture, and chemical exposure, extending service life in harsh environments.
Robust Bearing System: Equipped with heavy-duty anti-friction bearings (roller or sleeve type) rated for high radial and axial loads, minimizing maintenance and downtime.

Applications

The B843AT frame motors are deployed in high-power industrial applications requiring reliable DC drive performance, including:

Steel and metal rolling mills
Paper and pulp processing machinery
Mining conveyors and crushers
Cement plant kilns and mills
Heavy-duty cranes and hoists
Large industrial fans and blowers
Legacy process automation systems

Lifecycle and Availability

Original B843AT frame DC motors are obsolete and no longer in production by Reliance Electric. Current supply consists of new old stock (NOS), professionally refurbished units, and tested used motors from specialized industrial equipment dealers. Refurbished units typically include rewound windings, new bearings, updated insulation, and a 12-month warranty. These motors remain a critical replacement component for maintaining legacy industrial infrastructure, as direct modern AC drive replacements often require significant system redesign.

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