First Understand What 30.1 Alarm Said
Simply put, when the motor decelerates or brakes, it will actually become a "generator", the excess energy back to the drive on the DC bus. This energy has to go somewhere, usually through a regenerative resistor or a regenerative transistor to consume it. If there is a problem in this area, the energy builds up, the voltage spikes instantly, and the system triggers alarm 30.1 for self-protection.
This alarm is common on quite a few series, such as the MDS-D and MDS-E spindle drives, the MR-J2, J3, and JE series of servo amplifiers, and the M70 through M800 series of CNCs.
A Few Common Culprits in the Field
From the statistics of our maintenance desk and customer feedback, the root cause of the 30.1 alarm basically runs out of the following categories:
- The most common is a bad brake resistor. The most common is a bad brake resistor. If the resistor burns out and becomes too large, there is no place for the regenerative energy to be released. Sometimes this is visible to the naked eye - the surface of the resistor is burnt and cracked, or blackened and deformed.
- Setting the wrong parameters is also a common problem. Such as Pr.70 to Pr.74 these parameters on the regenerative resistance settings, if clearly connected to an external resistor but set to "no external resistance", a power on the alarm immediately.
- Driver internal regeneration control IGBT module is also quite common. This module is responsible for controlling the release of energy, it is bad, energy can only be blocked in the road. This situation usually have to be disassembled and tested to determine.
- High supply voltage can also cause this problem. For example, if the input voltage of a 200V system reaches 240V, the DC bus voltage will naturally be high, which will easily trigger the protection.
- There are also small and seemingly insignificant problems - loose terminals, oxidized contacts, or P, C, DB terminals connected to the wrong. We have encountered a number of times, just because the wire loose lead to the current can not pass, the system reported 30.1.
Practical Troubleshooting Steps, Follow It on the Line
Don't panic when you encounter alarms in the field, follow this order to check, basically can find the problem:
1. First, disconnect and discharge to ensure safety. Then look at the appearance of the regenerative resistor has no cracks, burn marks or discoloration, to confirm the specifications with the original factory requirements are not consistent.
2. Use a multimeter to measure the resistance value of the two ends of the resistor. Normal is only a few ohms or so, open or short circuit is definitely not right. If the resistance deviation is too large, it is easy to alarm.
3. Check whether the wiring of P, DB or P, RB terminals is firm and oxidized. Sometimes loose screws or aging wires can cause false alarms.
4. Through the system or software to check Pr.70 to Pr.74 these parameters are set correctly. The parameters must match the actual wiring, otherwise the regeneration function will not work properly.
5. If the external are normal, then we must suspect the internal regenerative IGBT. We use a triple meter or transistor tester to measure the conduction between the P, N, DB, if measured short circuit, basically sure that this part of the circuit is bad, you need professional repair.
Under normal circumstances, the DC bus voltage of a 200V level driver should be between 280-310VDC. If it exceeds 400V or fluctuates abnormally, the regenerative control is not working properly.
Effective Solutions
These methods have been repeatedly verified by official manuals and our actual repairs:
- The burnt out regenerative resistor must be replaced, and the model, resistance value and power should match the original recommended value.
- If the parameters are set wrongly, adjust the parameters from Pr.70 to Pr.74, and restart after power off.
- Regeneration circuit or IGBT bad, need professional overhaul and replacement.
- If the equipment starts and stops especially frequently or the load inertia is very large, you can consider installing FR-RU or MR-RB such as external regeneration unit to enhance processing power.
- If the power supply is unstable, check the transformer taps to ensure that the voltage is within ±10%, and consider adding a reactor or voltage regulator to enhance stability.
Daily Maintenance Recommendations
To reduce the frequency of 30.1 alarms, it is recommended to do these daily maintenance:
- Keep the drive clean, dusty heat dissipation is certainly not good.
- Frequently check whether the cooling fan is spinning or not.
- Regularly measure the resistance value of the regenerative resistor to prevent aging.
- According to the actual demand to choose the appropriate resistance power, to avoid overheating.
- Pay attention to the braking frequency of the equipment, start and stop especially frequent models are recommended to install external regeneration unit.
Repair or Replace? How to Judge
According to our experience, it is more reliable to judge this way:
Recommended for repair: resistance or transistor is bad but the motherboard is intact; there is no obvious burn marks; stable test after repair.
Suggested replacement: IGBT burst, PCB board burned through; repair or repeated alarms; the main circuit is damaged at several points.
Why Choose Us Songwei
We Songwei specialize in industrial CNC automation parts sales and repair services, the main brands include Mitsubishi, FANUC, Siemens, OKUMA, HEIDENHAIN and so on. We have a perfect
Mitsubishi test bench, which can simulate regenerative circuits and braking processes, and conduct dynamic tests on each repair part. Whether you need to repair, test, or find a tested replacement drive, we can help you get back into production quickly.
Last Word
The Mitsubishi 30.1 alarm may seem troublesome, but the scope of the problem is actually quite clear. In most cases, simply checking the regenerative resistor, transistor, or parameter settings will pinpoint the problem.
If you still can't find the cause after on-site troubleshooting, feel free to contact us at
Songwei, we provide Mitsubishi drive repair, testing and replacement services to help you get your equipment back up and running as soon as possible.
