DC Bus Fuse Open

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The Drive detects that the DC bus fuse has opened. This is typically caused by shorted output transistor(s) or output terminals, indicating a severe internal fault in the power circuit. The fuse opens to protect upstream components but requires addressing the underlying short.

• Short circuit in one or more IGBTs (Insulated Gate Bipolar Transistors) in the drive's output power stage, causing excessive current and blowing the DC bus fuse.
• Short circuit on the drive's output terminals (U/T1, V/T2, W/T3) to ground or between phases, usually due to motor cable insulation breakdown or motor winding fault.
• Severe overcurrent condition caused by an extreme mechanical overload on the motor, leading to instantaneous current draw that exceeds the fuse rating.
• Internal DC bus capacitor failure or short, though less common than IGBT failure, which can create a direct path for high current.
• Incorrect fuse rating installed, or fuse degradation causing it to open prematurely under normal operating conditions.

Klicken Sie auf Schritte, um Ihren Fortschritt zu verfolgen.

1. 1

   1. **Safety First**: Disconnect all AC input power to the drive. Wait for the DC bus voltage (measure at DC+/DC- terminals) to discharge below 50VDC before proceeding.

2. 2

   2. Disconnect the motor cables from the drive output terminals (U/T1, V/T2, W/T3).

3. 3

   3. With the motor disconnected, perform a static check (diode test with a multimeter) on the drive's output IGBTs (between DC+ and U, V, W; and DC- and U, V, W) as per the drive service manual to identify shorted power devices.

4. 4

   4. Visually inspect the DC bus fuse (typically located near the rectifier or DC link) for signs of opening. If an external fuse, check its continuity with a multimeter.

5. 5

   5. If IGBTs are confirmed faulty, the power module or the entire drive likely needs replacement. Replacing the fuse without addressing the underlying short circuit will result in immediate re-fault.

6. 6

   6. Before re-applying power after replacing any components, ensure motor insulation resistance (megger test) is good and motor cable integrity is verified.