Hello, a solar inverter hisel brand has a strange issue, it has 6 MOSFETs on DC side in two pairs one pair is severely heating up while the other heats up but not much without any load connected. I have checked the gate voltages which are ok. Gate resistors are also good. What can be the issue. @Coulomb

On 2025/07/16 at 9:35 AM, tanveerhabib said:

it has 6 MOSFETs on DC side

Do you mean two sets of three MOSFETs each are heating up? And the other 6 are normal?

On 2025/07/16 at 9:35 AM, tanveerhabib said:

one pair is severely heating up while the other heats up but not much without any load connected.

Have you replaced these MOSFETs? Ut sounds like they have excessive leakage or are slow to turn on or off.

On 2025/07/16 at 9:35 AM, tanveerhabib said:

Gate resistors are also good. What can be the issue.

It could be other gate driver parts, or the SG3525 is running too fast. Since only one set gets very hot, it doesn't seem like the dead time is too short

When you say that the gate voltages are OK, do you mean the voltages are adequate, or have you checked the waveform with an oscilloscope?

On 2025/07/20 at 5:01 AM, Coulomb said:

Do you mean two sets of three MOSFETs each are heating up? And the other 6 are normal?

Have you replaced these MOSFETs? Ut sounds like they have excessive leakage or are slow to turn on or off.

It could be other gate driver parts, or the SG3525 is running too fast. Since only one set gets very hot, it doesn't seem like the dead time is too short

When you say that the gate voltages are OK, do you mean the voltages are adequate, or have you checked the waveform with an oscilloscope

Here is the chopper DC side legs picture, can that be the reason for heating of the mosfets