Motors-AC Servo Mitsubishi HC-SFs | Repairs Precision Zone

Mitsubishi HC-SF(s) AC Servo Motor Repair Specialists

Here at Precision Zone, we specialize in Mitsubishi product repairs, servicing a wide range of AC servo motors. One series that we work on quite often is the HC-SF(S) series AC servo motor.

The HC-SF(S) series AC servo motors from Mitsubishi come in quite a few different variations. These motors are primarily intended for 200V usage but the HC-SFS model is 400V compatible and both models are equipped with absolute position detectors as standard. Though both of these models are medium inertia, medium capacity, the high-precision available with the HC-SFS model shows the difference in positioning resolution. HC-SF has a resolution of 16,384 and the HC-SFS has a resolution well above that, at 131,072.

The rated capacity starts at 500 watts and can go up to a 7kW option. This series of motor has three shaft options – straight (standard, no keyway), with keyway, or splined (HC-SF model only). Along with these different shaft options, there is an option for an electromagnetic brake which would be necessary or unnecessary depending on the application. There are reduction gear options that will also be dependent on the application and these can be for general flange type industrial machining, general leg type industrial machining, or precision applications. The rated speeds are dependent on the rated output and are offered with the following combinations¹:

HC-SF(S)	0.5 kW	0.8 kW²	1.0 kW	1.2 kW²	1.5 kW	2.0 kW	3.0 kW²	3.5 kW	5.0 kW	7.0 kW
1000 rpm
2000 rpm
3000 rpm	Only HC-SFS

¹ Empty cell means capacity/rated speed combination is unavailable.
² Not available ratings for HC-SFS, 400V options.

When assessing the functionality of a motor, our engineering team typically conducts a six step check:

1. Visual Overview
2. Static Test
3. Back EMF
4. Feedback Check
5. Alarm Code Troubeshooting
6. Disassembly and Cleaning

This overview is Precision Zone’s basic troubleshooting process. Once our repair team starts on the job we use specialized, customized test fixtures, SKF Baker AVAIV-4, Huntron devices, signal generators, oscilloscopes, milli and mega ohm meters, and other necessary tools to assure quality repair.

Most importantly, every repair is fully tested in custom-built simulators under load to replicate real-life working conditions.

Repair Process for Mitsubishi HS-xF Series AC Servo Motors

Visual Overview

When conducting a visual check, the technician inspects the motor for any mechanical damage to the power connecter, junction box, rotor shaft, oil seals and encoder covers. During the visual inspection the technician notes excessive dirt, oil or grease on cooling fans and all other parts of the motor.

Static Check Basic

Precision Zone repair technicians use an SKF Baker Advanced Winding Analyzer to fully evaluate the stator winding. The SKF Baker performs a wide range of electrical tests, including surge, DC hi-pot, mega-ohm, and winding resistance tests. In the instance of winding resistance each phase is tested with each other; and the mega ohm readings should be no less than 200 mega ohms.

Winding Resistance Testing

Positive Lead	Negative Lead	Approximate Reading
U	V	0.2Ω - 10Ω³
V	W	0.2Ω - 10Ω³
W	U	0.2Ω - 10Ω³

³ Reading should be balanced across all three phases.

Mega Ohm Testing

Positive Lead	Negative Lead	Approximate Reading
U	Ground/Unpainted stator area	Well above 200 MΩ ⁴
V	Ground/Unpainted stator area	Well above 200 MΩ ⁴
W	Ground/Unpainted stator area	Well above 200 MΩ ⁴

⁴ Our recommended minimum is 200 MΩ. Anything close to that 200 MΩ reading can still cause issues as the motor heats up and that value begins to drop lower.

Back EMF Check

If a servo motor passes the static checks it will be back driven and have the back EMF checked. With our in house magnetizing service we can bring back to life servo motors with weak magnets.

Feedback Check

Repair technicians can test encoders in a number of different ways. Our Mitchell Electrics TI-5000EX system can be used to read, write and record encoder count and data information. We have Mitchell Electrics TI-5250 systems that can be used to see live encoder pulses on an oscilloscope. Connecting encoders directly to the manufacture’s drive is another way we can verify if an encoder is working correctly.

Disassembly and Cleaning

All motors are fully dissembled, washed, and baked. Rotors are checked for bent shafts and bearing journal common problems. The stator winding is rechecked after the baking process. Holding brakes are refurbished and the holding torque is checked. Both the drive end and opposite drive end housing bearing surfaces are checked. Once the evaluation is completed a computer report is generated with all the findings.

Common Failures and Troubleshooting with Mitsubishi AC Servo Motors

Failure Type	Common Cause	Troubleshooting
Overcurrent	Poor motor or cable insulation, phase to phase, short, phase to ground short	Perform mega ohm test, first through cables, then at motor terminals (if applicable) Perform winding resistance test contact Precision Zone for further troubleshooting
Encoder related alarms	Encoder failure, issue with feedback cabling, control board failure on drive side	Check encoder waveforms if oscilloscope and back-driving of motor is available Connect motor with a different drive if applicable, contact Precision Zone support for further information
Motor shaft is locked up	Demagnetization occurred, brake malfunction (where applicable), drive side fault	Disconnect motor from drive and attempt to spin by hand, if no brake is used If brake is used, verify that it is disengaging appropriately Contact Precision Zone support for further troubleshooting

This list of checks for certain alarms is primarily a good starting point and if any further troubleshooting or technical support is needed, feel free to contact us via phone or email to get in touch with our experienced tech support team.

Precision Zone offers free technical support on any component that you may be having issues with. We understand that when your machine goes down, your business stops. That is why our number one goal is to provide you with the best service possible so that you can get back up and running immediately. For any further product information or troubleshooting assistance is needed, please contact us via phone at 800-551-4420 or email us.

Precision Zone Repair Benefits for Mitsubishi HC-SF(s) AC Servo Motors

Free quotes and evaluations by our expert technicians include:
12-Month Warranty on Our Parts and Labor
Decades of Industry Experience
Exchange Options
Rush Service Options

Contact Us To Start Your Repair Today!

Recently Repaired Products

HC-SFS102 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SF102B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS702G1H is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Worn DE Housing, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 7.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: for general industrial machine (leg type)
Shaft type: Standard (straight shaft)

HC-SFS502G1H is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Encoder, Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 5.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: for general industrial machine (leg type)
Shaft type: Standard (straight shaft)

HC-SF81 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Incorrect Feed Back Alignment, Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad Encoder, Bad ODE Bearing, Broken Magnets on Rotor
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 0.8kW
Rated speed: 1000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SF102X is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Coil Insulation - Due to Coolant/Moisture Contamination, Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Incorrect Feed Back Alignment
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: Spline shaft

HC-SFS702B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Bad Power Connector, Worn Brake Needs Reconditioning, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 7.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS352B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Encoder, Bad Brake, Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing, Worn DE Housing, Worn ODE Housing, Worn Brake Needs Reconditioning
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 3.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS153BK is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad Encoder, Bad Encoder Bearings, Bad ODE Bearing, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.5kW
Rated speed: 3000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: With keyway

HC-SFS102K is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning, Bad Encoder
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: With keyway

HC-SFS52K is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning, Worn ODE Housing, Bad Encoder
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 0.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: With keyway

HC-SFS152BK is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad Encoder, Bad ODE Bearing, Bad Condition - Requires Reconditioning, Worn Brake Needs Reconditioning, Worn ODE Housing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: With keyway

HC-SFS103B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad ODE Bearing, Bad Condition - Requires Reconditioning, Worn Brake Needs Reconditioning, Worn ODE Housing, Bad DE Bearing, Bad Encoder, Bad Encoder Bearings
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.0kW
Rated speed: 3000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SF352B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Power Connector, Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 3.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS152B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Brake, Bad Condition - Requires Reconditioning
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SF102K is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad Encoder Bearings, Bad ODE Bearing, Bad Condition - Requires Reconditioning, Worn ODE Housing
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: With keyway

HC-SF102 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Power Connector, Bad DE Bearing, Bad Encoder Bearings, Bad ODE Bearing, Bad Condition - Requires Reconditioning, Worn ODE Housing
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS102BK is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Encoder Cover
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: With keyway

HC-SFS102B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 1.0kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS52B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 0.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SFS352 is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad Condition - Requires Reconditioning, Bad DE Bearing, Bad ODE Bearing
Servomotor Type: HC-SFS Series; Medium inertia,medium capacity,high resolution
Rated Output: 3.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: Standard (straight shaft)

HC-SF152K is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: none
Reduction Gear: Without
Shaft type: With keyway

HC-SF152B is an
Motors-AC Servo manufactured by Mitsubishi
Discovered issues: Bad DE Bearing, Bad ODE Bearing, Bad Condition - Requires Reconditioning
Servomotor Type: HC-SF Series; Medium inertia,medium capacity
Rated Output: 1.5kW
Rated speed: 2000 rpm
Voltage: 200V
Electromagnetic brake: with brake
Reduction Gear: Without
Shaft type: Standard (straight shaft)