A customer selected a 471KD14 MOV for their power module design, which theoretically met the requirement for a 2KV common-mode surge test.
However, during actual testing, the power module repeatedly failed after only 5–10 surge pulses, indicating that the MOV was not providing effective protection under repeated surge conditions.
JEC Analysis
After detailed inspection, the failure was traced to the insufficient creep-age distance and clearance on the PCB layout.
The metal fuse holder was placed too close to adjacent components, allowing high-voltage surge energy to create arc discharge paths and bypass the MOV protection route.
As a result, the surge voltage directly reached the downstream circuit, causing damage to the power module.
JEC Solution
JEC engineers analyzed the surge protection path and recommended optimizing the PCB layout design according to safety standards.
Key improvements included:
Increasing the creep-age distance and electrical clearance between high-voltage components
Eliminating potential arc discharge paths around the MOV protection circuit
Ensuring the surge current flows through the intended MOV protection path
After the PCB redesign, the power module successfully passed both 2KV and 4KV common-mode surge tests.
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Post time: Aug-06-2026