Consequences Of Short-circuiting The Dc Bus Of A Frequency Converter

When the frequency converter 50hz to 400hz DC bus is short-circuited, the DC links within the system will experience abnormal current surges. The 60hz to 400hz frequency converter DC bus, composed of a rectifier bridge, filter capacitors, and inverter bridge, is used to maintain a stable DC voltage during normal operation. Once the positive and negative buses are short-circuited, these capacitors will instantly release their stored energy, potentially generating noticeable sparks or high heat, and may even experience internal breakdown.

In the initial stage of the short circuit, the transient current on the DC bus will rise rapidly. Without sufficient protection, this current may cause protective components in the main circuit, such as fuses, to blow, or damage power devices such as IGBTs. A convert 480v 60hz to 400v 50hz internal capacitor short circuit typically manifests as the capacitor breaking down and the internal plates directly connecting, making it impossible to maintain voltage, which may damage the rectifier bridge and inverter module.

The 480v 60hz to 380v 50hz converter control circuit will typically detect abnormal DC bus voltage and trigger protection actions. The control system will attempt to suppress the output, sometimes directly cutting off the drive signals of switching elements, causing the inverter bridge to stop working. A short circuit will prevent normal voltage build-up, causing the inverter to fail to start or immediately stop outputting.