23.12.2025 by Viktor Siebert

Initial Situation and Fault Description.

Both units, the Yaskawa CIMR-M5A20110-XXXB inverter and the Yaskawa CIMR-MR5N2011 converter, were delivered together from one machine. At the time of delivery, it was not clear to the machine operator which unit was responsible for the fault. Experience shows that converter and inverter faults often influence each other and should never be assessed separately.

On our test bench, a reproducible fault occurred under defined conditions. During braking at approximately 5300 rpm, the inverter generated alarm 11 main circuit overvoltage, while the converter simultaneously reported an output overvoltage alarm. This fault pattern is typical when braking energy can no longer be properly controlled or dissipated.

Initial Analysis and Recommendation

During the first inspection, it was already visible and measurable that several inverter components were in a critical condition. Thermal stress and aging effects were evident on power related components, which are known to cause unstable gate control behavior over time. Although the inverter was still operational at that moment, we clearly recommended overhauling both units together.

The customer decided to repair only the converter, as the inverter was still functioning in operation. This decision was documented, including a clear explanation of the potential risk of secondary damage.

Return After Two Months

Approximately two months later, both units returned to our facility. The customer reported a complaint, stating that the repaired system was showing an alarm again. However, the new inspection revealed a different fault scenario. This time, the inverter was clearly defective.

A power transistor module had completely failed. Root cause analysis showed that the failure was not initiated by the power module itself, but by a defective transistor driver stage. The driver delivered unstable control signals, which ultimately destroyed the transistor module. This risk had already been identified and communicated during the first repair.

Repair and Preventive Overhaul

During the second repair cycle, both units were fully restored. The inverter received not only a repair of the power stage but also a complete preventive overhaul of all relevant assemblies. The converter was rechecked and stabilized to ensure reliable interaction between both units.

After completion, inverter and converter were tested together under realistic load and braking conditions. The system remained stable, and no overvoltage alarms occurred even at high speeds and heavy braking cycles.

Practical Conclusion

This case clearly demonstrates the importance of treating inverter and converter systems as one functional unit. Even if a device still operates at the time of inspection, internal aging processes may already be at a critical stage. A timely preventive overhaul avoids unexpected downtime and prevents costly damage to power components.

Further information such as price and delivery time for:

Yaskawa CIMR-M5A20110-XXXB Inverter Unit

Yaskawa CIMR-MR5N2011 Converter Unit

More details about our Yaskawa repair expertise can be found here: Yaskawa Reparatur bei Industrypart

📞 Please feel free to contact us if you have any questions regarding your Omron drive technology. Our experienced team is always available to assist you.

Technical Specifications

Yaskawa CIMR-M5A20110-XXXB Inverter Unit

Parameter	Specification
Device type	Inverter Unit
Series	Varispeed 626M5
Manufacturer	Yaskawa Electric Corporation
Supply voltage	DC 270–325 V
Output voltage	AC 3-phase
Rated output current	25.8 A
Peak output current	approx. 39.3 A
Speed range	up to 5300 rpm
Control method	Vector control
Cooling method	Forced air cooling
Display	7-segment LED
Communication	CNC internal interface
Installation	Control cabinet mounting
Country of origin	Japan

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Technical Specifications

Yaskawa CIMR-MR5N2011 Converter Unit

Parameter	Specification
Device type	Converter Unit
Series	Varispeed 656MR5
Manufacturer	Yaskawa Electric Corporation
Input voltage	AC 3-phase 200–220 V
Input frequency	50 / 60 Hz
Output voltage	DC link
Rated output current	25.8 A
Regenerative function	Integrated
Cooling method	Forced air cooling
Display	7-segment LED
Installation	Control cabinet mounting
Country of origin	Japan

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Typical Application and System Integration

The combination of the MR5 converter unit and the M5 inverter unit is typically used in CNC machine tools, especially in applications with high dynamic requirements such as frequent acceleration and deceleration cycles.

Typical applications include:

• CNC lathes
• Machining centers
• Milling machines
• Rotary axes with high regenerative energy

The converter and inverter operate as a single functional system. The converter manages power supply and regenerative energy, while the inverter controls motor current, torque and speed.

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Functional Description of Converter and Inverter Interaction

The converter unit generates a stabilized DC link voltage from the three-phase AC supply. During deceleration, kinetic energy from the motor is fed back into the DC link. This energy must be processed and controlled by the converter.

The inverter unit converts the DC link voltage into a precisely controlled three-phase AC output for the motor. It continuously monitors current, voltage and temperature to ensure safe operation.

If the regenerative energy cannot be properly absorbed or controlled, the DC link voltage rises. This condition leads to overvoltage alarms on both the inverter and the converter.

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Inverter Alarm List

CIMR-M5 Series (Excerpt)

Code	Alarm description	Possible cause	Corrective action
AL-01	Overcurrent	Short circuit or overload	Check wiring and load
AL-04	Main circuit fuse blown	Power stage fault	Inspect power module
AL-05	Output overload	Continuous overload	Reduce load
AL-06	Motor overload	Excessive thermal load	Check mechanical system
AL-10	Converter fault	Converter error detected	Inspect converter
AL-11	Main circuit overvoltage	DC link overvoltage	Check regenerative behavior
AL-31	Overspeed	Speed exceeds limit	Verify parameters
AL-40	Heatsink overheat	Insufficient cooling	Check fan and airflow
AL-48	Cooling fan fault	Fan stopped or defective	Replace fan

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Converter Alarm List

CIMR-MR5 Series (Excerpt)

Code	Alarm description	Possible cause	Corrective action
01	Overcurrent	Excessive current	Check wiring and load
04	Main circuit fuse blown	Power stage damage	Inspect converter
05	Overload	Continuous overload	Reduce load
11	Output overvoltage	Excessive regenerative energy	Check braking conditions
12	Undervoltage	Low input voltage	Check power supply
15	Frequency fault	Supply frequency deviation	Check power source
16	Initial charging fault	DC link charging failure	Replace unit
43	Heatsink overheat	Cooling insufficient	Improve ventilation
45	Thermistor fault	Temperature sensor failure	Replace unit

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Main Components

CIMR-M5A20110-XXXB Inverter Unit

Assembly	Designation	Function
Control board	Control PCB	Control logic and monitoring
Drive board	Base drive PCB	Gate signal generation
Communication board	Interface PCB	CNC communication
Power module	Transistor module	Power conversion
Cooling system	Fan assembly	Heat dissipation

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Main Components

CIMR-MR5N2011 Converter Unit

Assembly	Designation	Function
Control board	Control PCB	Voltage regulation
Power board	Rectifier PCB	AC to DC conversion
Power stage	Power module	Energy processing
Cooling system	Fan assembly	Heat dissipation

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Preventive Maintenance Recommendations

• Always evaluate inverter and converter as a combined system
• Investigate overvoltage alarms during braking immediately
• Ensure proper cooling and clean airflow paths
• Perform preventive refurbishment before power stage damage occurs
• Verify braking and deceleration parameters regularly