Mitsubishi HC-SFS502 (HCSFS502) — 5kW AC Servo Motor, Straight Shaft, No Brake, MELSERVO-J2S Series

Product Identification

Part Number: HC-SFS502

Also Searched As: HCSFS502, HC-SFS-502

Series: Mitsubishi MELSERVO HC-SFS (J2-Super Generation)

Motor Type: AC Brushless Servo Motor — Straight Shaft, No Brake, 2000 rpm

Condition: New In Box, Factory Sealed

Overview

The Mitsubishi HC-SFS502 is a 5kW medium-inertia AC brushless servo motor from the MELSERVO-J2S platform — straight shaft, no brake, rated at 2,000 rpm with 23.9 Nm continuous torque and 71.6 Nm peak. It is the clean, unencumbered 5kW drive motor for horizontal axes and any application where the load is laterally supported, gravity plays no role in the direction of shaft rotation, and mechanical hold on servo-off is not a requirement.

Removing the brake and specifying a straight shaft does not reduce this motor in any meaningful performance sense. The output power is the same 5kW. The continuous and peak torque figures are the same. The 17-bit serial absolute encoder — 131,072 positions per revolution — is identical to every other motor in the HC-SFS family. What the HC-SFS502 offers over its BK or B sibling variants is exactly what many applications need: 5kW of well-controlled servo output on a straight shaft, without the wiring overhead, relay sequencing, and panel components that a brake system requires on axes that have no use for one.

This is the J2-Super generation at 5kW. The HC-SFS502 replaces the older HC-SF502 in the same flange envelope, with the same amplifier class now specifying MR-J2S-500 hardware, and brings the 17-bit encoder upgrade that the J2-Super platform introduced. For machines already running MR-J2S-500 amplifiers, or new builds specifying J2S hardware from the outset, the HC-SFS502 is the 5kW no-brake straight-shaft motor that the system design calls for.

Technical Specifications

What 5kW at 2000 rpm Means in Practice

The HC-SFS502 sits in a specific gap in the servo motor capacity range — demanding enough that mid-range motors cannot fill it, but not so large that it requires the infrastructure of a 7kW system. The 23.9 Nm continuous rating is the defining number: it is what the motor can sustain indefinitely under rated thermal conditions, axis after axis, shift after shift. When a machine's duty-cycle analysis shows that the worst-case sustained cutting torque or transfer torque on a given axis approaches or exceeds what a 3.5kW motor can handle continuously, 5kW is the capacity step that resolves the margin problem.

The 71.6 Nm peak — exactly three times the continuous figure — defines what the amplifier can demand during acceleration and deceleration transients. On a large CNC table moving a substantial workpiece and fixture from one position to the next in a rapid traverse, the torque demand during the acceleration ramp far exceeds what the sustained cutting load requires. The 71.6 Nm ceiling gives the axis authority to complete that rapid move quickly, with the motor returning to well within its continuous rating once the axis arrives at the target position and begins the machining operation.

The 7.5 kVA power facility capacity is the electrical supply footprint. At 25A rated current, panel wiring, circuit protection, and contactor selection must be sized appropriately. Regenerative energy — the energy returned to the DC bus when a large inertia load decelerates — is handled by the MR-J2S-500 amplifier, but regenerative resistor capacity should be confirmed for axes with frequent or high-energy deceleration events, such as heavy table axes cycling at high rapid traverse speeds.

Straight Shaft, No Brake: The Right Specification for Horizontal Drives

Every motor variant in the HC-SFS range exists because different applications have different requirements at the shaft and in the machine's safety architecture. The HC-SFS502 without brake and with a straight shaft is not a compromise — it is the optimised specification for a well-defined application category.

Why no brake? Position hold at rest on a horizontal axis comes from amplifier servo lock — the position loop remains closed, the encoder monitors shaft position continuously, and the amplifier supplies corrective current to maintain zero error. This is reliable, accurate, and draws no additional panel resources. A spring-applied brake on the same axis would add 24V DC wiring, a relay, a surge absorber, an MBR interlock circuit in the machine's safety logic, and ongoing maintenance of the brake disc and coil. None of that infrastructure provides any functional benefit on an axis where gravity does not act in the direction of shaft rotation and no unbalanced force threatens to move the axis when servo current is removed.

Across a machine with multiple 5kW axes — a large travelling-column machining centre, a gantry system, a multi-spindle transfer machine — eliminating brakes from the axes that do not need them produces a measurably simpler electrical design. Fewer relays, fewer wiring connections, less 24V current demand, and a commissioning process that does not require brake timing verification on those axes.

Why straight shaft? Friction-clamp couplings — disc couplings, bellows couplings, jaw couplings with split-clamp hubs — are the standard interface for high-performance servo axis ballscrew and direct-drive applications. They provide excellent torsional stiffness, zero backlash, and accommodate small angular and parallel misalignment without introducing compliance into the position loop. On a properly selected and installed friction-clamp coupling at 5kW, the clamping force is more than adequate to transmit 71.6 Nm peak without slip.

Where a keyed shaft and positive key connection are required — timing belt pulleys, gear hubs, sprocket drives — the correct motor is the HC-SFS502K (keyed shaft, no brake) or the HC-SFS502BK (keyed shaft with brake). The straight-shaft HC-SFS502 is for the coupling designs that do not need a keyway.

One installation note that matters at this frame size: use the shaft-end threaded hole and a drawbolt to seat the coupling hub axially onto the shaft rather than pressing or driving it on with impact force. At 5kW and the corresponding motor mass, shaft impact during hub installation transmits to the encoder assembly at the motor's rear. The resulting encoder damage tends to manifest not as an immediate fault but as intermittent position errors and encoder alarms that appear under vibration during production — difficult to trace, expensive to diagnose, entirely preventable.

17-Bit Encoder: J2-Super Performance at 5kW

The step from the HC-SF502 (J2 generation, 14-bit encoder, 16,384 ppr) to the HC-SFS502 (J2S generation, 17-bit encoder, 131,072 ppr) is an eight-fold increase in encoder resolution. At 5kW and 2,000 rpm, that resolution improvement pays off across the full operating speed range.

At rated speed, the velocity estimation quality improves directly. The MR-J2S amplifier computes axis velocity from consecutive encoder position samples. With 131,072 positions per revolution, each inter-sample angular step is eight times smaller than with 16,384 ppr. The speed loop sees a lower-noise velocity estimate, which allows higher proportional gain before mechanical resonances become a stability concern. Higher gain means faster disturbance rejection — cutting force disturbances, transmission compliance effects, and load changes are corrected more rapidly, keeping the axis on its commanded velocity profile during production.

At low feed rates — slow contouring moves, thread cutting, profile grinding — the 17-bit encoder provides the fine angular increments that smooth velocity control requires. Coarser encoder data at low speed produces velocity ripple that appears in the machined surface as a periodic pattern. The HC-SFS502's 131,072 ppr suppresses that ripple substantially compared to the older 14-bit device, a difference that is visible in surface finish quality on precision slow-feed operations.

The absolute function maintains its value regardless of speed rating. The A6BAT lithium battery in the MR-J2S amplifier keeps the multi-turn position counter alive through any power interruption. On the next power-up — whether after a planned shutdown, an alarm trip, or an unexpected power fault — the axis reads its absolute position and the machine resumes without a reference return cycle. For production operations where restart time directly affects throughput, eliminating mandatory homing cycles has genuine commercial value.

Compatible Amplifiers

The HC-SFS502 requires the MR-J2S-500 class amplifier from the MELSERVO-J2S platform. Three interface variants cover the main control architectures:

MR-J2S-500A accepts analog and pulse-train commands from CNC systems and PLCs. Position, speed, and torque control modes are all supported. Setup, diagnostics, and real-time monitoring through MR Configurator (MRZJW3-SETUP) via RS-232C interface. The standard choice for machines using CNC position command output or PLC pulse-train control.

MR-J2S-500B connects to Mitsubishi motion controllers via SSCNET fiber-optic serial bus — the coordinated multi-axis architecture used in A-series and Q-series motion controller systems. Position commands arrive over the network from the controller; the amplifier executes them locally using motor-shaft encoder feedback. Encoder cable runs between the amplifier and the CNC rack are replaced by the fiber-optic SSCNET cable.

MR-J2S-500CP incorporates a built-in point table for standalone positioning. Up to 31 target positions are stored in the amplifier and activated by I/O or CC-Link commands. This variant suits applications where a dedicated motion controller is not required and a simple indexed positioning function is sufficient.

All three variants fully support the HC-SFS502's 17-bit serial encoder and are rated for the motor's 25A continuous current. The HC-SFS502 is not compatible with original MR-J2-500 (first-generation, pre-J2S) amplifiers, which cannot read the 17-bit encoder format. For machines running first-generation MR-J2-500 hardware, the HC-SF502 (J2 generation, 14-bit encoder) is the correct motor to source — no amplifier upgrade required.

HC-SFS502 in the HC-SFS 2000 rpm Family

The HC-SFS502 sits between the 3.5kW and 7kW motors on the same 176 × 176 mm flange that all motors from 2kW upward share in this range. Within the 502 capacity point, the full suffix matrix covers every shaft-and-brake combination: straight shaft (HC-SFS502), straight shaft with brake (HC-SFS502B), keyed shaft (HC-SFS502K), and keyed shaft with brake (HC-SFS502BK). All four share the same flange, encoder, and MR-J2S-500 amplifier requirement. The shaft and brake suffix choices have no effect on amplifier selection.

HC-SFS502 vs HC-SF502: Which Motor Does Your Machine Need?

Output performance is identical. Mounting is identical. The encoder generation and amplifier requirement is the operative difference. Check the amplifier nameplate before sourcing: MR-J2-500 (without S) means the HC-SF502 is the correct motor. MR-J2S-500 means either motor is compatible, with the HC-SFS502 bringing higher encoder resolution.

Typical Applications

Large CNC machining centre X and Y table axes. Primary table feed axes on large-format vertical and horizontal machining centres move substantial workpiece masses at sustained cutting feedrates and high rapid traverse speeds. These are horizontal axes — no brake required — and the straight shaft suits the precision disc or bellows coupling interfaces used on high-performance ballscrew drives. The HC-SFS502's 23.9 Nm continuous provides the sustained torque authority these axes need without running near the thermal ceiling.

Travelling-column machining centre column drives. On travelling-column and bridge-type machining centres, the column or cross-rail drive axis moves a heavy structural casting along linear guideways. These are large-inertia, high-rapid-traverse axes where 5kW capacity is the correct specification for medium-to-large format machines. The 71.6 Nm peak handles the acceleration demand; the 23.9 Nm continuous covers the sustained traverse load between positioning events.

HMC table rotation (B-axis) drives. Horizontal machining centre B-axis rotary table drives that use direct coupling between the servo motor and the worm gear or table drive mechanism need sustained torque and high-resolution position feedback. The HC-SFS502's straight shaft suits the friction-clamp coupling designs used on precision B-axis drive units, and the 17-bit encoder provides the angular resolution required for accurate multi-face machining indexing.

Gantry and portal axis drives. Large-format gantry machining systems and portal-type coordinate measuring machines use servo drives on the gantry traversal axis to move the cross-beam assembly over long strokes at high speed. The combined inertia of the cross-beam and any tooling is substantial; 5kW provides the acceleration and sustained traverse capacity without oversizing the drive to the 7kW bracket.

Industrial robot joint drives. High-payload industrial robot primary joint axes — the waist rotation and shoulder joints on large 6-axis arms — use medium-inertia, medium-capacity servo drives in this power range. These are well-controlled balanced loads on properly counterweighted robot structures, making the no-brake straight-shaft configuration appropriate where the mechanical design provides adequate axis stability at rest.

New In Box, Factory Sealed

Factory sealed means original Mitsubishi packaging with nothing disturbed — outer carton, inner foam cradle, shaft-end protective cap, encoder connector cover, and power connector seal all intact and in as-manufactured condition. No prior installation. No thermal cycling from previous use. No bearing load history to account for.

For a machine stopped and waiting on this motor, in-stock new-in-box eliminates repair turnaround time entirely and delivers a unit in known condition with no variables from prior service. For planned spare parts inventories — particularly where this capacity and configuration appears on multiple axes in a machine fleet — factory-sealed stock provides consistent, ready-to-commission units.

Stored under appropriate conditions — stable, cool, dry environment away from vibration and direct light — factory-sealed HC-SFS502 stock maintains full specification over several years. Beyond five years in storage, a slow pre-commissioning shaft rotation helps redistribute bearing grease before the motor is placed in service.

Frequently Asked Questions

Q1: Which amplifiers are compatible with the HC-SFS502?

The HC-SFS502 requires a MR-J2S-500 class amplifier from the MELSERVO-J2S platform. The three standard variants are the MR-J2S-500A (general-purpose analog/pulse command), MR-J2S-500B (SSCNET fiber-optic bus for Mitsubishi motion controllers), and MR-J2S-500CP (built-in positioning with CC-Link). All support the 17-bit serial encoder and the motor's 25A rated current. The HC-SFS502 is not compatible with original MR-J2-500 amplifiers or with MR-J3 / MR-J4 amplifiers.

Q2: What is the difference between the HC-SFS502 and the HC-SF502?

Both motors deliver 23.9 Nm continuously and 71.6 Nm peak on a 176 × 176 mm flange with a straight shaft and no brake — mechanically interchangeable at the mounting face. The difference is the encoder generation: the HC-SF502 uses a 14-bit encoder (16,384 ppr) and is compatible with both MR-J2-500 and MR-J2S-500 amplifiers. The HC-SFS502 uses a 17-bit encoder (131,072 ppr) and requires MR-J2S-500 amplifiers only. Check the installed amplifier model before sourcing. If it shows MR-J2-500 (without S), source the HC-SF502.

Q3: Why is there no electromagnetic brake on the HC-SFS502?

The HC-SFS502 is designed for horizontal axes and drives where servo lock provides adequate position hold at all stop conditions. On these axes, adding a brake introduces wiring, relay hardware, MBR sequencing, and panel complexity that the application has no use for. For axes carrying a gravity load — vertical columns, inclined slides, unbalanced mechanisms — the correct motor is the HC-SFS502B (straight shaft with brake). The brake is a deliberate design choice for axis safety, not an optional accessory; specify it where the axis requires it.

Q4: How does the 17-bit encoder compare to the 14-bit encoder in the older HC-SF502?

The 17-bit encoder provides 131,072 positions per revolution versus 16,384 in the 14-bit device — an eight-fold resolution increase. In practical terms, the MR-J2S amplifier's speed loop receives a finer-grained velocity signal, which supports higher control bandwidth and better disturbance rejection. At low feed rates, the finer angular increments reduce velocity ripple that would otherwise appear as surface finish variation. The absolute function works identically in both; position is retained between power cycles via the A6BAT battery in the amplifier.

Q5: Does the absolute encoder battery need to be replaced periodically, and where is it?

Yes. The Mitsubishi A6BAT lithium battery that maintains the 17-bit absolute encoder's multi-turn position counter is housed inside the MR-J2S servo amplifier — not in the motor. Replace it when the amplifier displays its low-battery warning alarm. Do not wait for the battery to fully discharge: a depleted A6BAT causes the absolute position counter to reset, requiring a reference return cycle before the machine can resume production. Under normal operating conditions, the A6BAT typically lasts several years, but this varies with temperature and how frequently the machine is powered off.