Description
B&R 8MSA4L.R0-31 – Synchronous Servo Motor
Product Introduction
The B&R 8MSA4L.R0-31 is a three-phase synchronous servo motor from B&R’s 8MSA series, designed for closed-loop motion applications requiring controlled speed, torque, and positioning. The documented rating is 6.4 Nm at 3,000 rpm, with approximately 2.01 kW rated output power and a 4.35 A rated current. Its electrical characteristics include a 3 Ω stator resistance, 19.2 mH stator inductance, and 94 V/1,000 rpm voltage constant. These parameters are important when matching the motor to the correct B&R ACOPOS drive and when checking whether an installed replacement has the same motor data set.
The B&R 8MSA4L.R0-31 belongs to the synchronous motor family used in B&R machine-automation systems. The “L” designation is associated with the longer version of the size-4 motor family, while the exact R0-31 suffix must be retained when sourcing a replacement. Available documentation identifies compatible ACOPOS servo-drive combinations including the 1045 and 1090 families, but the actual drive selection still depends on the machine’s DC bus, motor parameter set, load profile, acceleration requirements, and firmware configuration.
For maintenance procurement, the B&R 8MSA4L.R0-31 should be treated as an exact motor configuration rather than simply a generic 2 kW servo motor. Mechanical dimensions, shaft arrangement, feedback system, connector configuration, thermal behavior, and motor data stored in the controller all affect interchangeability. Secondary sources contain conflicting claims about feedback and protection ratings, so those details should be verified from the motor nameplate and original B&R documentation before substituting another 8MSA motor.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Model | 8MSA4L.R0-31 |
| Manufacturer | B&R Automation |
| Product Type | Three-phase synchronous servo motor |
| Product Series | 8MSA |
| Frame / Size | Size 4, L version |
| Rated Speed | 3,000 rpm |
| Rated Torque | 6.4 Nm |
| Rated Power | 2.01 kW |
| Rated Current | 4.35 A |
| Stall Torque | 7.5 Nm |
| Peak Current | 29.4 A |
| Stator Resistance | 3 Ω |
| Stator Inductance | 19.2 mH |
| Electrical Time Constant | 6.4 ms |
| Thermal Time Constant | 66 min |
| Voltage Constant | 94 V/1,000 rpm |
| Nominal Voltage | 330 V is reported on matching product documentation |
| Weight Without Brake | Approximately 7.7–8.0 kg |
| Brake | No brake for the documented standard configuration |
| Application | Industrial servo / machine motion |
| Lifecycle | Discontinued / cancelled |
The 6.4 Nm, 3,000 rpm, 2.01 kW, 4.35 A, 7.5 Nm, 29.4 A, resistance, inductance, and time-constant values are supported by matching technical listings.
8MSA4L.R0-31
Main Features and Engineering Considerations
Synchronous Servo Construction
The B&R 8MSA4L.R0-31 is intended for servo-controlled motion rather than fixed-speed motor operation. The servo drive regulates current and electrical angle to control the motor’s torque and speed. This makes the motor suitable for machine axes where acceleration, deceleration, positioning, and repeatable motion are part of the control requirement.
Motor-Drive Matching
The motor’s electrical parameters must be entered or selected correctly in the servo-drive configuration. The 6.4 Nm rated torque and 29.4 A peak-current figure should not be interpreted as a simple continuous-current requirement. The drive controls current dynamically according to the motor model and machine load.
A replacement motor with similar nominal power but different winding characteristics can produce incorrect current regulation, poor dynamic performance, or drive alarms. The safest replacement is an exact 8MSA4L.R0-31 configuration or a B&R-approved successor with confirmed parameter equivalence.
Mechanical Compatibility
The “4L” configuration is significant when replacing the motor. Even when the electrical rating is similar, a different motor length, shaft arrangement, mounting geometry, or connector orientation can create installation problems.
Before replacement, compare the complete motor nameplate and mechanical dimensions rather than relying on the family designation “8MSA4.”
Lifecycle Consideration
Current secondary lifecycle information identifies the 8MSA4L.R0-31 as discontinued/cancelled.
For an installed machine, this makes exact-stock procurement useful when the goal is to minimize engineering changes. For a redesign, a newer B&R motor should be selected through the complete motor-drive-machine combination rather than simply choosing a newer motor with the same nominal power.
Application Scenarios
- Packaging machinery
- Material-handling equipment
- CNC and machine-tool axes
- Printing and converting equipment
- Pick-and-place systems
- High-speed indexing mechanisms
- B&R ACOPOS motion-control systems
- Industrial machine-axis replacement
Engineer’s Guide: Field Pitfalls
1. Do not match only by kilowatts.
A 2 kW servo motor is not automatically interchangeable with the 8MSA4L.R0-31. Winding data, torque constant, feedback, mechanical dimensions, and drive parameters all matter.
2. Preserve the complete suffix.
The difference between 8MSA4L.R0-31 and another 8MSA4 motor can affect electrical and mechanical compatibility.
3. Check the actual nameplate.
Confirm rated speed, current, voltage, serial number, revision, and motor-specific identification before installing a replacement.
4. Verify the ACOPOS configuration.
The matching documentation associates this motor with ACOPOS 1045 and 1090 servo-drive families, but the installed machine configuration should be checked before selecting the drive.
5. Do not assume optional brake specifications apply.
Some secondary listings combine specifications for braked and non-braked versions. The exact R0-31 unit should be inspected physically and checked against its nameplate.
6. Check feedback compatibility before powering the motor.
The available secondary sources disagree about the exact feedback implementation. Do not rely on an online listing to determine the feedback device; verify the actual motor documentation and connector pinout.
Frequently Asked Questions
What is B&R 8MSA4L.R0-31?
It is a three-phase synchronous servo motor from B&R’s 8MSA series.
What is the rated torque?
The documented rated torque is 6.4 Nm at 3,000 rpm.
What is the rated power?
The matching technical data lists approximately 2.01 kW rated power.
What is the rated speed?
The rated speed is 3,000 rpm.
What is the peak current?
The listed peak current is 29.4 A. This should not be confused with the motor’s 4.35 A rated current.
Is the 8MSA4L.R0-31 discontinued?
Current secondary lifecycle listings identify it as discontinued or cancelled.
Procurement Note
For a replacement B&R 8MSA4L.R0-31, specify the complete part number rather than ordering simply by “8MSA4 servo motor.”
Before purchase, verify:
- Complete 8MSA4L.R0-31 designation
- Nameplate and serial information
- Rated speed and torque
- 330 V-class motor configuration
- Feedback type and connector
- Shaft and mounting dimensions
- Brake presence or absence
- Motor cable compatibility
- ACOPOS drive model
- Drive parameter/motor-data compatibility
- Electrical and insulation test results
- Bearing and shaft condition for used equipment
For a critical production axis, I would favor an exact part-number match and a documented motor test over a visually similar B&R motor with the same nominal power. The available public data contains conflicting secondary specifications, so feedback and mechanical details should be confirmed from the physical unit before committing to a substitute.
