17.02.2026 by Viktor Siebert

When Production Suddenly Stops.

Everything was running smoothly.
The machining process was stable, cutting conditions were normal, and nothing indicated an upcoming issue.

Then, without warning, the machine stopped.

The cause was quickly identified: a Mitsubishi MDS-D2-V2-8040 Servo Drive had shut down during operation. No gradual performance degradation. No clear early signal. Just an abrupt stop in the middle of production.

For the customer, this meant immediate downtime. For us, it meant one thing: systematic diagnosis.

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First Inspection No Visible Damage

When the unit arrived at our workshop, the housing showed no mechanical damage. No burn marks, no broken connectors, no obvious failure points.

But experience tells us that most failures inside servo drives are not visible from the outside.

After opening the unit, we noticed heavy contamination inside the cooling channels. Fine metallic dust and industrial debris had accumulated over time. The cooling fan showed noticeable bearing wear, and thermal stress discoloration was visible near the DC link capacitor section.

This was not a sudden catastrophic event.
It was the result of gradual aging.

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Diagnostic Bench Analysis

The drive was connected to our controlled test bench with simulated CNC enable signals and regulated DC bus supply.

Immediately after activating the power stage, the drive triggered a power module overcurrent condition. The protection system did exactly what it was designed to do: shut down instantly to prevent further damage.

Detailed measurements revealed:

• Elevated DC bus ripple voltage
• Increased ESR values of the DC link capacitors
• Leakage behavior in the IGBT power module
• Reduced cooling efficiency due to fan wear

These factors combined created a thermally unstable power stage. During machining load, the current demand exceeded what the weakened components could safely handle.

The overcurrent protection was not the problem. It was the symptom.

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Understanding the Root Cause

Servo drives like the MDS-D2-V2-8040 operate under continuous thermal stress. Over time:

Electrolytic capacitors lose capacitance and increase in ESR.
Cooling systems lose efficiency.
Power semiconductors experience cumulative thermal fatigue.

As ripple voltage increases, switching losses rise.
As switching losses rise, temperature increases.
As temperature increases, semiconductor stress accelerates.

Eventually, the protection system intervenes.

This is not a design flaw. It is the natural aging curve of power electronics.

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The Repair Process

To ensure long-term reliability, we followed a structured refurbishment procedure:

• Complete disassembly and deep cleaning of cooling channels
• Replacement of all DC link capacitors
• Replacement of the IGBT power module
• Installation of a new cooling fan
• Inspection of solder joints exposed to thermal cycling
• Renewal of thermal interface material
• Electrical insulation and safety testing

After component replacement, the drive was subjected to a endurance test under dynamic load conditions.

We simulated:

Acceleration cycles
Deceleration cycles
Continuous torque load
Elevated ambient temperature
Encoder communication monitoring
DC bus ripple analysis

Throughout the entire test period, current behavior remained stable.
DC bus voltage stayed within specification.
No further overcurrent events occurred.

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Why Preventive Maintenance Matters

This case highlights an important lesson:

Most servo drive failures are not random. They are predictable.

Capacitors typically show aging effects after 7 to 10 years depending on duty cycle.
Cooling fans often degrade after 3 to 5 years.
Dust accumulation significantly reduces heat dissipation efficiency.

Simple preventive actions can dramatically extend service life:

Annual internal cleaning
Scheduled fan replacement
Periodic DC bus capacitor ESR testing
Regular inspection of grounding and shielding

Preventive maintenance costs a fraction of unplanned downtime.

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The Customer Benefit

After refurbishment, the Mitsubishi MDS-D2-V2-8040 was returned fully operational and tested under load.

The customer avoided:

Extended machine downtime
Costly new drive replacement
Unnecessary system reconfiguration

Instead, they received a sustainable, component-level repair that restores operational safety while extending equipment lifetime.

In industrial environments, reliability is not just about technology.
It is about continuity.

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Conclusion

The failure of this Mitsubishi MDS-D2-V2-8040 Servo Drive was caused by gradual thermal aging combined with reduced cooling efficiency.

Protection systems worked correctly.
The electronics did what they were designed to do.

After professional refurbishment and extensive testing, the drive now operates within stable and safe parameters.

Electronic components age.
Cooling efficiency matters.
Preventive service prevents production stops.

And sometimes, what looks like a sudden breakdown is simply the end of a long and silent aging process.

To mentioned Mitsubishi Drive: Mitsubishi MDS-D2-V2-8040 Servo Drive Unit

More details about our Mitsubishi repair services can be found here:
Mitsubishi drive Repair by Industrypart

📞 Feel free to contact us with any questions about your Mitsubishi drive technology.
Our expert team is happy to help!

Technical Specifications

Device Type Mitsubishi Servo Drive Unit
Model MDS-D2-V2-8040
Manufacturer Mitsubishi Electric
Production Year 2015
Manual Reference Mitsubishi MDS-D/DH Series Instruction Manual

Parameter	Value
Voltage	DC 270 to 311 V bus, 3 phase 200 to 230 V AC
Current	Input approx 21 A DC, Output up to approx 14.6 A
Power	2.0 kW to 4.0 kW axis power depending on motor
Weight	approx 8 to 12 kg
Dimensions	approx 380 x 150 x 200 mm
Type	Digital servo drive with integrated power stage
Cooling	Forced air cooling
Control	Mitsubishi CNC servo interface
Manufacturer	Mitsubishi Electric Corporation
Production Year	2015
Manual Reference	MDS-D/DH Series Instruction Manual

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Application Environment and Compatible Equipment

The MDS-D2-V2-8040 is typically used in Mitsubishi CNC controlled machine tools such as:

Vertical machining centers
Turning machines
Grinding machines
Special multi axis machines

Compatible with:

Mitsubishi HF series servo motors
Absolute and incremental encoders
Mitsubishi CNC systems such as M700, M70

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Functional Description

The MDS-D2-V2-8040 is a digitally controlled servo drive with integrated power stage.

Main functions:

Conversion of DC bus voltage into three phase motor voltage
Precise torque and speed control
Position control via CNC feedback
Integrated safety monitoring

The LED display alternates axis number and alarm code during faults Alarme

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Alarm Messages and Troubleshooting

Based on Mitsubishi Manual Alarme

Code	Description	Cause	Solution
10	Insufficient voltage	Bus undervoltage	Check mains
17	A D converter error	Current feedback failure	Check drive
24	Grounding	Motor cable earth fault	Check insulation
30	Over regeneration	Brake resistor overload	Check resistor
31	Overspeed	Motor overspeed	Check parameters
32	Power module overcurrent	IGBT overcurrent	Inspect module
33	Overvoltage	DC bus overvoltage	Check supply
46	Motor overheat	Motor thermal triggered	Inspect motor
50	Overload 1	Continuous overload	Reduce load
72	Fan stop	Cooling fan failure	Replace fan

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Components

Assembly	Description	Function	Inspection
Power module	IGBT stage	Motor drive	Thermal check
DC link capacitors	Bus capacitors	Voltage stabilization	ESR test
Control PCB	Logic board	Signal processing	Visual inspection
Fan	Cooling fan	Heat dissipation	Bearing test
Current sensor	Feedback sensor	Current detection	Offset check
Encoder interface	Feedback board	Position feedback	Connector test

Components

Name	Designation on PCB	Quantity
Control Board	RM120B-22 XK or BC886A097G51A	1
Power Board	RM162C-V2 or BC886A010G52 C	1
Power Module	BKO-NC1207 H84 Axes A2-D2-V2-8040	1