18.10.2025 by Viktor Siebert
Repair of a Mitsubishi MDS-B-CV-110 Power Supply Unit
Repair Story: Express Repair due to Overheat Alarm
A customer reported an “n” display (Power Module Overheat). The MDS-B-CV-110 arrived via express service due to production downtime. Temperature readings showed that the IPM module was overheating although the fan was working.
Inspection revealed that the thermal compound between the power module and heatsink had hardened completely, preventing heat transfer. Capacitors showed bulging due to prolonged thermal stress.
Repair steps included:
- Complete disassembly and cleaning.
- Replacement of thermal compound and retightening of mounting screws.
- Replacement of critical components.
- Installation of new NMB 24 V cooling fan.
- Full-load testing on an original Mitsubishi system.
The repaired PSU ran for more than six hours without temperature warnings. Preventive thermal inspection is now part of our standard process to ensure reliability and long-term stability.
Preventive Tips
- Replace fans annually.
- Renew DC link capacitors every 5–7 years.
- Check phase balance and input cables.
- Always ensure proper thermal paste application.
- Inspect ventilation and cooling paths regularly.
Conclusion
The Mitsubishi MDS-B-CV-110 is durable but thermally sensitive. Failures often result from gradual heat degradation rather than electrical faults. Preventive replacement of capacitors and fans significantly extends service life. All repaired units are fully tested under load to guarantee machine readiness.
To mentioned Mitsubishi Drive: Mitsubishi MDS-B-CV-110 Power Supply Unit
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Technical Specifications
| Parameter | Value |
|---|
| Model | MDS-B-CV-110 |
| Type | Power Supply Unit for Servo and Spindle Drives |
| Rated Input Voltage | 3AC 200 / 200–230 V, 50/60 Hz, 35 A |
| Control Input Voltage | AC 200 / 200–230 V, 50/60 Hz, 0.2 A |
| Rated Output Voltage | DC 270–311 V, 41 A |
| Standard | DIN VDE 0160 |
| Manual No. | BNP-B3890 |
| Serial Number (S/N) | BND533W000A3 |
| Hardware Version | F |
| Production Date | 98/01 (January 1998) |
| Manufacturer | Mitsubishi Electric Corporation, Japan |
Operating Environment and Compatibility
This unit supplies DC power to Mitsubishi MDS-B Servo and Spindle amplifiers. It is used in machining centers such as Mazak, DMG MORI, and Mitsubishi Meldas systems.
Operating temperature range: 0 – +45 °C, clean industrial environments with constant airflow.
Typical test combination:
- Servo Drive: MDS-B-V1-70 or MDS-B-V2-6535
- Spindle Drive: MDS-B-SP-185
Function Description
The MDS-B-CV-110 converts three-phase AC into a stable DC link voltage. It monitors overcurrent, overheating, and phase loss and manages regeneration energy from drives. Communication between drives and PSU ensures coordinated operation and protection.
Common Alarms and Causes
| Code | LED | Description | Cause | Action |
|---|
| 61 | A | Power Module Error | Overcurrent in IPM detected | Check power module |
| 63 | 3 | Regeneration Error | Regeneration transistor ON too long | Check fan and load |
| 65 | 5 | Rush Relay Error | Inrush resistor not released | Check relay control |
| 67 | 7 | Open Phase | Missing input phase | Check AC input |
| 68 | 8 | Watch Dog | Software process timeout | Check control logic |
| 69 | 9 | Ground Fault | Ground fault in motor or link | Check insulation |
| 6A | A | Contactor Error | External contactor ON at wrong time | Verify wiring |
| 6C | C | Main Circuit Error | Main capacitor charge fault | Inspect capacitor board |
| 6F | F | AD Converter Error | Converter malfunction | Replace control PCB |
| 75 | L | Overvoltage | DC link exceeded 410 V | Verify mains voltage |
| 77 | n | Power Module Overheat | IPM overheated | Clean and check fan system |
Components
| Type | PCB Reference | Quantity |
|---|
| Control PCB | RK412A / BN634A770G51A C | 1 |
| Power PCB | RK427A-110 / BN634A781G51A G | 1 |
| Capacitor Board | RJ442A / BN634A614G51 | 1 |
| Power Section | IPM + Diodes + Regeneration Module | 1 |