Technical knowledge | Electric rope saw machine frequency converter 6: LU undervoltage protection triggering logic and on-site disposal
Aug 10,2026
In construction cutting operations, if the electric wire saw machine frequently reports fault code 6: LU, most of the time it points to the same problem - the input voltage of the frequency converter is too low, causing undervoltage protection of the frequency converter. This is not because the equipment is "sick", but rather its self-protection mechanism is reminding that the input power is "not enough to feed" the machine!
First check the voltage, then check the hardware. This is the efficient troubleshooting sequence summarized by front-line after-sales service
1. Actual measured incoming voltage
Measure the three-phase voltage at the terminal of the equipment using a multimeter. If it is lower than the rated value (such as 380V system lower than 340V), or if the voltage drop is severe during operation, the on-site transformer capacity and cable diameter need to be checked. When providing long-distance power, it is recommended to use cables that are one level thicker.
2. Eliminate potential hazards of line contact
Loose wiring terminals and aging air switch contacts can cause additional voltage drop during heavy loads. This type of problem is often accompanied by terminal heating. During inspection, feel it with the back of your hand (operate after power off) to make a preliminary judgment.
3. Distinguish between instantaneous undervoltage and sustained undervoltage
Instantaneous flicker (such as simultaneous startup of large equipment): You can try adjusting the undervoltage recovery time parameter of the frequency converter to allow it to temporarily ride through low voltage.
Continuously low: It is necessary to connect an external voltage regulator or replace the power supply point, otherwise frequent protection will damage the rectifier module.
When encountering a 6: LU alarm, do not blindly reset and forcefully start. First, confirm that the power supply has sufficient confidence, and the machine will naturally obey. In daily maintenance, including power quality inspection in the pre startup checklist can effectively reduce false alarms and shutdowns.
The reference picture of the electric rope saw machine is as follows:
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