EVERY PART, EVERY TIME

The routine tests

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Capacitance and DF On an LCR meter, against the tolerance

Insulation resistance A DC voltage and a tiny leakage current

Hipot Terminal to terminal, and terminal to case

Partial discharge On high-voltage parts, to prove impregnation worked

Leak check For oil-filled cans: heat soak, then look for oil

Routine tests screen every part; life tests prove the design on samples.

HIPOT

Proving the insulation

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What it is A voltage above rating, often 110–150% DC, held for seconds

Terminal to terminal Stresses the dielectric to flush out weak spots

Terminal to case Proves the insulation between the stack and the can

Balance Strong enough to catch weak parts, not so strong it damages good ones

Hipot is a deliberate overstress: a part that survives it should survive its working voltage.

PARTIAL DISCHARGE

Listening for tiny sparks

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What it measures Small discharges inside voids, counted in picocoulombs (pC)

Inception voltage Where discharges start as voltage rises

Extinction voltage Where they stop as voltage falls

What it tells you High PD usually means poor drying or impregnation, or trapped contamination

Partial discharge is the early warning of the failure that would happen in the field.

RING-DOWN

Short it and watch it ring

Charge the capacitor, discharge it into a short, and record the ringing. The frequency gives the inductance, and how fast it dies gives the resistance.

One discharge waveform measures ESL, ESR, peak current and reversal together.

LIFE TESTING

Proving the design

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Charge-discharge cycling Sample parts fire at rated voltage, current and reversal

High-temperature DC life Parts held at voltage in an oven

Shot life Defibrillator-style parts are fired thousands of times

Drift Metallized parts are tracked for capacitance loss over life

Life tests are slow and destructive, so they run on samples to qualify a design or a process change.

UNIT 10 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen the routine tests every part passes, and the ring-down and life tests that characterize a design.