Fuse Blown

What does FU mean?

This fault indicates that an internal fuse in the inverter has blown, likely due to an overcurrent condition, a short circuit, or an internal component failure. A blown fuse often signifies a significant protective event and requires careful investigation before replacement. Operating with blown fuses can lead to further damage to the inverter's internal circuitry.

• Short circuit in the motor windings or motor cable (U, V, W terminals) causing excessive output current.
• Ground fault condition on the inverter output or motor, leading to high fault currents.
• Inverter internal component failure (e.g., IGBT short, rectifier bridge failure) causing an internal overcurrent.
• Transient overvoltage on the input power supply exceeding the inverter's surge protection capabilities.
• Sustained motor overload condition drawing current above the fuse rating for an extended period.

Click steps to track your progress.

1. 1

   Disconnect input power to the inverter and discharge DC bus capacitors (wait 5-10 minutes).

2. 2

   Use an ohmmeter to check for shorts between output terminals (U-V, V-W, W-U) and between each output terminal and ground.

3. 3

   Measure the insulation resistance of the motor windings (phase-to-phase, phase-to-ground) using a megohmmeter (e.g., 1000V DC).

4. 4

   Visually inspect internal fuses for signs of rupture; identify the specific fuse (e.g., input rectifier fuse, DC bus fuse).

5. 5

   If internal fuses are accessible and replaceable, replace ONLY with fuses of identical type and rating (e.g., 600V, 10A fast-acting fuse).

6. 6

   If fuses are integrated or non-replaceable, the inverter typically requires service or replacement.