LG (LS) inverter common faults and countermeasures - Solutions - Huaqiang Electronic Network

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LG inverters have been rebranded as (LS) models. As the saying goes, "changing the soup doesn’t change the medicine," so fault analysis and maintenance remain largely similar. LG inverters are still widely used in China, which means that faults are common and inevitable. Let’s take a closer look at some of the typical issues and how to address them:

1. OC Fault – Overcurrent Alarm The OC fault is one of the most common issues found in LG inverters, just like in other brands. After ruling out parameter settings such as acceleration/deceleration time, the main causes usually lie in hardware. For example, damage to high-power modules can trigger an OC alarm. The low-power economical inverters typically use TYCO PIM modules, while general-purpose medium-power inverters may use Fujitsu or Mitsubishi IGBT modules. High-power models often use Siemens IGBT modules. Common reasons for power module failure include:

• (1) Short circuit or phase loss in the output load.
• (2) Excessive load causing continuous high current.
• (3) Large fluctuations in the load leading to surge currents, which can damage the power module and trigger an OC alarm.

2. HW Fault – This issue is unique to the LG-IG5 series inverters. Possible causes include:

• (1) Damage to the cooling fan, possibly due to excessive bearing friction caused by environmental factors.
• (2) Faults in the temperature detection circuit within the power module.
• (3) Issues with the motherboard could also lead to HW faults.

3. Ground Fault – This is a common problem encountered during maintenance. While motor grounding issues can be a cause, the most likely culprit is often the Hall sensor. Environmental factors like temperature and humidity can affect the sensor's performance, causing its operating point to drift and triggering a GF alarm.

4. No Display Fault – This usually occurs when the switching power supply is damaged. Unlike traditional self-excited or other-excited power supplies, LG inverters use a controllable voltage regulator called TL431 to adjust the duty cycle of the switching transistor and maintain stable output voltage. In cases of a short circuit, the power supply may shut down, resulting in no display on the panel.

Like other inverters, LG models can also face issues like LV, OV, or drive circuit failures. These problems require ongoing practice and experience to diagnose and resolve effectively.

5. FU Fault – The LG-IS5 and IH series inverters are equipped with fast fuse detection. The fast fuse has a breaking capacity of about 5 ms, allowing it to protect the high-power modules when large currents occur. However, if the fast fuse is damaged, it can lead to a FU fault. In such cases, replacing the fuse is the recommended solution.