Mitsubishi SJ-PF Series Servo Motors

Technical Dossier

Product Details And Specifications

Mitsubishi Electric SJ-PF Series: Comprehensive Module Range and Technical Overview

The Mitsubishi Electric SJ-PF series is a standardized line of general-purpose AC servo motors engineered for integration with Mitsubishi MR-J2S, MR-J3, and MR-J4 servo amplifier families. These motors are deployed across heavy industrial sectors including petrochemical processing plants, nuclear facility auxiliary systems, steel rolling mills, automotive assembly lines, and offshore platform equipment. The SJ-PF series is characterized by its flange-mount construction, IP65 ingress protection rating, and compatibility with incremental and absolute encoder feedback systems. Global installed base spans facilities in Japan, China, Southeast Asia, Europe, and the Americas, making long-term spare parts availability a critical operational concern for maintenance engineers worldwide.

The Evolution of SJ-PF Architecture

The SJ-PF series was introduced as a successor to Mitsubishi Electric's earlier HC-series and SC-series servo motors, consolidating frame sizes and encoder interfaces under a unified mechanical envelope. Early SJ-PF variants shipped with 17-bit incremental encoders and were paired exclusively with MR-J2S amplifiers operating on the SSCNET (Servo System Controller NETwork) protocol. As the MR-J3 platform emerged, Mitsubishi re-qualified the SJ-PF mechanical frames for use with 18-bit absolute encoders and SSCNET III fiber-optic communication. The MR-J4 generation further extended compatibility through SSCNET III/H, doubling communication bandwidth to 150 Mbps. Throughout these amplifier generations, the SJ-PF motor body remained mechanically backward-compatible, allowing facilities to upgrade drive electronics without replacing motor assemblies — a key factor in the series' longevity in brownfield installations. As of 2026, several lower-frame SJ-PF variants have entered the end-of-life phase, with Mitsubishi directing new designs toward the HG-series (HG-KR, HG-MR, HG-SR, HG-JR). Facilities running legacy SJ-PF installations must plan for extended maintenance support rather than direct OEM replacement.

SJ-PF Full Catalog & Functionalities (SKU List)

The following SKUs represent verified models within the Mitsubishi Electric SJ-PF series. Each entry includes rated output power and primary application classification:

SJ-PF0.5-01: 50W flange-mount servo motor, incremental encoder, MR-J2S compatible.
SJ-PF1-01: 100W servo motor, standard shaft, general-purpose positioning axis.
SJ-PF2-01: 200W servo motor, low-inertia rotor, high-cycle indexing applications.
SJ-PF4-01: 400W servo motor, IP65 rated, suitable for wash-down adjacent environments.
SJ-PF7.5-01: 750W servo motor, mid-range torque output, conveyor and feed axis use.
SJ-PF10-01: 1.0kW servo motor, balanced inertia ratio, multi-axis gantry systems.
SJ-PF15-01: 1.5kW servo motor, extended shaft option available, press and clamp axes.
SJ-PF20-01: 2.0kW servo motor, high-torque variant, heavy-load linear actuator drives.
SJ-PF25-01: 2.5kW servo motor, reinforced bearing, continuous-duty cycle rated.
SJ-PF35-01: 3.5kW servo motor, large flange frame, machine tool spindle assist.
SJ-PF50-01: 5.0kW servo motor, high-inertia load matching, rolling mill entry drives.
SJ-PF70-01: 7.0kW servo motor, heavy industrial frame, steel processing line use.
SJ-PF0.5-02: 50W variant with key-way shaft and electromagnetic brake pre-installed.
SJ-PF4-02: 400W brake-equipped model, vertical axis and gravity-load applications.
SJ-PF7.5-02: 750W brake-integrated servo motor, vertical feed and Z-axis positioning.
SJ-PF15-02: 1.5kW brake-integrated servo motor, vertical feed and Z-axis positioning.
SJ-PF20-02: 2.0kW brake variant, heavy vertical load holding, press and lift axes.
SJ-PF35-02: 3.5kW brake-equipped large-frame motor, crane auxiliary and hoist drives.

Sourcing Hard-to-Find & Obsolete SJ-PF Parts

Quality Control for the SJ-PF Range

SJ-PF series motors present specific inspection requirements due to their encoder interface complexity and bearing preload sensitivity. DriveKNMS applies the following test protocol to all SJ-PF units processed through its facility:

Encoder Signal Verification: Each unit is connected to a compatible MR-J2S or MR-J3 amplifier and subjected to full encoder signal integrity testing across A, B, Z incremental channels and serial absolute data frames. Signal amplitude, phase relationship, and noise floor are measured against Mitsubishi factory specification sheets.
Winding Resistance & Insulation Test: Three-phase winding resistance is measured per phase and compared against rated values. Insulation resistance is tested at 500VDC between windings and frame, with a minimum acceptance threshold of 100MΩ.
No-Load Run Test: Motors are run at rated speed under no-load conditions for a minimum of 30 minutes. Vibration velocity (mm/s RMS) and bearing temperature rise are logged and compared against ISO 10816 Class I limits.
Brake Function Test (where applicable): For SJ-PF-02 brake-equipped variants, static holding torque is verified at rated brake engagement voltage. Release response time is measured and confirmed within OEM specification.
Dimensional & Shaft Inspection: Shaft runout, flange flatness, and keyway dimensions are verified using calibrated gauges to confirm mechanical interchangeability with OEM specification.