During initial testing of the 24V blower fan, a smoothing capacitor was added across the supply in an attempt to reduce noise and stabilize operation.

However, this capacitor failed during operation.

Further investigation suggested that placing a bulk capacitor directly across the BLDC fan supply was not appropriate for this type of load.

Unlike simple DC motors, BLDC fans typically include internal driver electronics that expect a certain supply behavior. Adding large capacitance externally can interfere with the internal switching characteristics and lead to undesirable current surges.

In this case, the capacitor likely experienced high ripple currents and stress conditions beyond its intended operating limits, leading to failure.

After removing the capacitor:

• Fan operation remained stable
• No adverse effects were observed
• System reliability improved

This highlighted an important point:

Not all loads benefit from additional bulk capacitance, especially when internal control electronics are involved.

Understanding the nature of the load is essential before applying standard filtering approaches.

This experience reinforced the importance of validating assumptions when working with integrated electromechanical components.

Based on these observations, the power stage was further refined with additional filtering and protection elements, which will be discussed in a subsequent log.”

Would be interested to know if others have observed similar behavior with BLDC fans and external filtering.