One New Mitsubishi Servo Motor HC-SF502B HCSF502B HC-SF502B New In Box Factory Sealed

Mitsubishi HC-SF502B (HCSF502B) — 5kW AC Servo Motor with Electromagnetic Brake, MELSERVO J2 Series

Product Identification

Part Number: HC-SF502B

Also Searched As: HCSF502B, HC-SF502B

Series: Mitsubishi MELSERVO HC-SF Series (J2 Generation)

Motor Type: AC Brushless Servo Motor with Electromagnetic Brake

Condition: New In Box, Factory Sealed

What This Motor Is

The Mitsubishi HC-SF502B is a 5-kilowatt, medium-inertia AC servo motor from the MELSERVO HC-SF series — the motor family paired with Mitsubishi's MELSERVO-J2 generation servo amplifiers. At 5kW and a rated speed of 2,000 rpm, it sits at the top of the standard HC-SF 2000 rpm range, delivering 23.9 Nm of continuous rated torque with a 176 × 176mm flange that is standard across high-capacity Mitsubishi servo platforms.

The "B" in the part number identifies the spring-applied, 24V DC release electromagnetic brake built into this variant — the holding device required for any axis where gravity or process loads would cause uncontrolled movement on servo-off or emergency stop. Without the brake, this motor is the HC-SF502; mechanically and electrically identical in every other respect, but without the fail-safe hold. The HC-SF502B is the correct choice for vertical Z-axes, pallet columns, quill assemblies, and any horizontal axis with a significant friction deficit at standstill.

Technical Specifications

The HC-SF Series: Medium Inertia, Maximum Reliability

Mitsubishi organised its MELSERVO motor families around two key variables: capacity and inertia class. The HC-SF series occupies the medium-inertia, medium-to-large capacity band — motors designed for real machine tool axes rather than light assembly or packaging. Where the HC-MF and HC-UF series prioritise ultra-low rotor inertia for rapid point-to-point motion, the HC-SF accepts a somewhat heavier rotor in exchange for better thermal stability under sustained load, smoother torque delivery at low speed, and more forgiving response to real-world load variations that are typical of machining and forming work.

At 5kW, the HC-SF502B is the highest-power member of the standard 2000 rpm HC-SF family. Three-phase 200V class input is standard for this capacity range — single-phase supply is neither specified nor practical at this power level. The oil seal built into the motor body protects the shaft bearing from cutting fluid, lubricant mist, and wash-down water, keeping the motor compliant with IP65 across the entire shaft length including the seal interface.

Electromagnetic Brake — What It Does and Why It Matters

The spring-applied brake in the HC-SF502B is a holding device, not a deceleration brake. This distinction matters for both specification and maintenance.

Under normal operation, 24V DC current holds the brake open against the spring load — the shaft rotates freely and the amplifier controls all deceleration. When 24V DC is removed (e-stop, servo-off, power loss), the spring engages the brake and holds the shaft. The brake is designed to hold position, not to stop a moving load. Running a powered axis into the brake will prematurely wear the friction surfaces; the servo must decelerate the load to a stop before brake engagement is correct practice.

For vertical axes like Z-columns and quill heads on machining centres, the brake is mandatory. When the servo amplifier is de-energised — whether by normal end-of-program sequence, alarm trip, or power failure — the motor torque drops to zero in milliseconds. On a vertical axis with any significant unbalanced load, that means a free-fall event. The HC-SF502B's brake prevents that by physically locking the shaft whenever the hold voltage is absent.

The 24V DC supply to the brake coil should be wired through a dedicated surge absorber at the coil terminals. Brake coils are inductive loads; the voltage spike at brake release or engagement can damage relay contacts and amplifier I/O circuits if unsuppressed. This is standard practice in Mitsubishi's wiring guidance for brake-equipped motors and should not be skipped in field installations.

Brake circuit note for maintenance

The brake and motor power supply are independent. On emergency stop circuits, the brake must remain powered (i.e., open) until the axis has decelerated to a stop. Applying the brake while the motor is still driving into it creates a mechanical shock load on the brake disc and the motor shaft — repeated events like this will shorten brake service life significantly and may eventually result in shaft or coupling damage. The MELSERVO J2 amplifier brake interlock output (MBR signal) provides the correct timing for brake application; always use this signal to control the brake relay rather than wiring directly from the main e-stop circuit.

Compatible Amplifiers and System Context

The HC-SF502B is a MELSERVO-J2 generation motor and pairs with the MR-J2 series servo amplifiers in the 500A capacity class. The MR-J2S series (J2-Super) amplifiers are also compatible with HC-SF motors, as the J2S retained backward compatibility with the J2-era motor encoder protocol and connection scheme. This means that a machine originally built with MR-J2 amplifiers can be upgraded to MR-J2S drives while retaining existing HC-SF502B motors — a practical migration path that was common when the J2S generation was introduced.

The 14-bit (16,384 ppr) absolute encoder in the HC-SF series is an older-generation feedback device compared to the 17-bit (131,072 ppr) encoder found in the later HC-SFS motors. For the applications these motors serve — machine tool axis control at up to 2,000 rpm rated speed — the 14-bit absolute encoder provides sufficient resolution for accurate positioning. The absolute feature means that the machine does not require a homing cycle after power restoration if the amplifier battery has maintained the absolute position data.

Typical Applications in Machine Tools and Industrial Equipment

Vertical machining centre Z-axis. The quill column or Z-slide on a VMC is the canonical application for a brake-equipped servo motor. At rest between cuts, the Z-axis carries the weight of the spindle head and any attached tooling. The HC-SF502B holds that load through the electromagnetic brake whenever the servo is inactive, protecting both the machine and the workpiece from unintended movement.

Horizontal machining centre pallet and W-axis. HMC pallet drives and facing-head axes use similar logic: high capacity to move large pallets quickly, a brake to hold position during spindle engagement, and enough sustained torque to maintain feed rate through the cutting cycle.

Large CNC lathes — tailstock and turret axes. Turret index mechanisms on large turning centres benefit from the 5kW output for rapid, decisive indexing. Where the turret mounting geometry creates an offset load at certain index positions, the brake provides hold assurance while the turret clamp is engaged.

Positioning tables and transfer lines. Heavy pallet transfer systems, rotary transfer machines, and multi-station transfer lines often use servo-driven positioning with power-off hold requirements between stations — exactly the duty cycle the HC-SF502B is sized for.

Press and bending machine back-gauge axes. Back-gauges on press brakes and folding machines require the Z-stop to remain exactly in position while the press cycle occurs. Servo lock provides the hold while the brake is present as a fail-safe backup.

New-In-Box Stock: What "Factory Sealed" Means

New-in-box Mitsubishi servo motors retain the full original Mitsubishi packing — inner foam support, outer carton, protective shaft end cover, and connector caps. The motor has not been powered, stored on a shelf in operating orientation, or subjected to any installation torque on the shaft or brake terminals. For a machine builder building new equipment or a facilities team holding strategic spare stock, this is the correct starting condition.

Bearing grease on stored motors does not degrade meaningfully over several years when storage conditions are reasonable (cool, dry, vibration-free). For extended storage beyond five years, Mitsubishi's own guidance suggests manual shaft rotation periodically to redistribute bearing lubricant and inspection before first power-up. For motors going straight into a machine build or a short-term spare inventory, factory-sealed new stock is ready for installation without any pre-installation service.

HC-SF Family Overview — 2000 rpm Range

All models in this table share the 200V AC class input, 2,000 rpm rated speed, 14-bit absolute encoder, IP65 rating, and oil-sealed shaft. The flange size scales up at higher capacities — the 352 and 502 models use the larger 176 × 176mm flange frame shared with the HC-SFS series motors of equivalent capacity.

FAQ

Q1: What servo amplifiers are compatible with the HC-SF502B?

The HC-SF502B is compatible with Mitsubishi MR-J2 and MR-J2S series amplifiers at the 500A (5kW) capacity rating. The J2S amplifiers retain backward compatibility with the HC-SF motor's 14-bit encoder interface, so both generations can drive this motor. It is not compatible with MR-J3 or MR-J4 series amplifiers, which use a different communication protocol and encoder interface.

Q2: How does the electromagnetic brake need to be wired and controlled?

The brake requires a 24V DC supply held active during normal servo operation (brake open). Removing the 24V causes the spring to engage and hold the shaft. The brake coil should be wired through a surge absorber to protect adjacent circuits. For correct timing, use the amplifier's MBR (brake interlock) output to control the brake relay — this ensures the brake does not engage until the motor has decelerated to a stop, preventing unnecessary wear on the brake friction surfaces.

Q3: What is the difference between the HC-SF502 and HC-SF502B?

Electrically and mechanically they are identical except the HC-SF502B incorporates a spring-applied, fail-safe electromagnetic holding brake. The brake adds length to the motor body and requires a separate 24V DC supply. Use the brake variant on all vertical axes and any horizontal axis where an external hold force is required on servo-off or power failure.

Q4: Is the HC-SF502B interchangeable with the HC-SFS502 or newer Mitsubishi motors?

The HC-SF502B and HC-SFS502 share the same flange size and shaft dimensions, so mechanical fitment is compatible. However, the encoder interfaces differ — the HC-SF uses a 14-bit encoder protocol, while the HC-SFS uses a 17-bit serial encoder. Swapping between them requires a matching amplifier generation. The HC-SF502B is not a plug-in replacement for HC-SFS, HF-SP, or HG-SR series motors, which use different amplifier families entirely.

Q5: Does the absolute encoder require a battery, and how is absolute position maintained?

Yes. The HC-SF502B's 14-bit absolute encoder requires battery backup — typically an A6BAT cell held in the paired servo amplifier — to retain absolute position data during power-off periods. If the battery is depleted or the amplifier has been without power for an extended time, the absolute position data may be lost, requiring the machine to perform a re-homing (reference return) cycle before resuming normal operation. Check battery condition as part of any scheduled maintenance interval