New Original Mitsubishi Industrial Servo Motor HF-KN73JK HFKN73JK OEM

Mitsubishi HF-KN73JK | HF Series AC Servo Motor — 0.75 kW / 2.4 Nm / 3000 rpm / Keyed Shaft / Oil Seal / 17-Bit Absolute

0.75 kW with Keyed Shaft and Oil Seal — Two Configuration Details That Drive Compatibility

The HF-KN73JK is FANUC's MELSERVO HF series AC servo motor at 0.75 kW / 2.4 Nm continuous torque and 3000 rpm rated speed in the 80mm flange frame — configured with a keyed shaft and an oil seal at the shaft output end. These two suffix details (K = keyway, J = oil seal) define the mechanical interface and environmental sealing of this specific variant.

Keyed shaft: The keyway machined into the motor shaft allows a matching keyed coupling hub, pulley, or gear to transmit torque through a positive mechanical interlock. A correctly fitted coupling hub with a matching key transmits the 2.4 Nm continuous and 7.2 Nm peak torque without relying on friction clamping alone. For applications with frequent reversals, high peak torques, or vibration environments where friction-clamped hubs can develop micro-slip, the keyed shaft is the appropriate mechanical specification.

Oil seal: The oil seal fitted at the shaft exit point provides protection against oil, grease, and coolant ingress from the coupled machine mechanism into the motor bearing housing. On machines where the motor shaft connects into an oiled gearbox, lubricated ballscrew, or wet machining environment, the oil seal prevents lubricant from migrating along the shaft into the motor interior. The IP65 rating applies to the motor body; the oil seal adds specific shaft-entry protection beyond what the standard IP65 gasket provides.

Key Specifications

17-Bit Absolute Encoder — No Homing at Power-Up

The 17-bit absolute encoder provides 131,072 positions per revolution and retains shaft position through power-off cycles. At machine power-up, the servo controller knows the exact axis position immediately — no reference-return (homing) cycle is required. The backup battery for the multi-turn absolute counter is in the servo amplifier, not in the motor. Monitor the amplifier's battery alarm indicator and replace the battery before the alarm activates, to avoid absolute position data loss.

The HF-KN73JK is compatible with Mitsubishi MELSERVO amplifiers supporting the HF series encoder interface. Confirm amplifier compatibility before specifying as a replacement for a machine where the installed motor is from a later HG series — the HF and HG series use different amplifier generations.

FAQ

Q1: What is the difference between HF-KN73JK and HF-KN73J?

Both are HF series 0.75 kW motors with oil seal and 17-bit absolute encoder. The difference is the shaft: HF-KN73J has a straight smooth shaft (no keyway), while HF-KN73JK has a keyed shaft with a machined keyway. The coupling hub must match the shaft type — a smooth-bore hub for the straight shaft, a keyed hub for the keyed shaft. Verify which shaft type the machine's coupling hub accommodates before ordering.

Q2: Does the oil seal change the IP rating?

The motor body is rated IP65 both with and without the oil seal. The oil seal provides additional protection specifically at the shaft-to-housing interface against oil and grease penetration from the driven mechanism side. On machines without oiled shaft interfaces, the oil seal is not required but does not cause any harm. On machines with oiled gearboxes or lubricant-wetted couplings directly at the motor shaft, the J suffix oil seal is the correct specification.

Q3: What servo amplifiers are compatible with the HF-KN73JK?

Mitsubishi MELSERVO amplifiers from the series generation compatible with the HF motor family and its 17-bit absolute encoder interface. Confirm the specific amplifier model and its compatibility with the HF-KN73 motor class before pairing. The HF series is an older generation than the current HG series — the two series are not interchangeable on the same amplifier.

Q4: The motor shows an absolute position alarm at power-up. Is the encoder or the battery at fault?

The 17-bit absolute counter backup battery is in the servo amplifier, not in the motor. An absolute position alarm at power-up most commonly indicates a depleted amplifier battery that allowed the position counter to reset during a power-off period. Replace the amplifier battery and execute a reference position setup before resuming production. Only if the alarm persists with a confirmed healthy battery should the motor encoder be investigated.

Q5: What should be checked on a used HF-KN73JK before installation?

Check the keyed shaft surface for fretting marks or scoring from previous coupling installation. Inspect the oil seal for deformation or damage from prior installation. Measure three-phase winding resistance for balance and insulation resistance to earth (with encoder cable disconnected). Rotate the shaft by hand for smooth bearing movement. Verify the encoder cable connector for corrosion or pin damage. A controlled slow-speed test run with amplifier current monitoring before full production load is the preferred final check.