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Electrical & Controls

Capacitor discharge time calculator

Time for a capacitor to bleed down to a safe voltage, and stored energy.

µF
V
V
kΩ

Calculating…

How it's calculated

t = R × C × ln(V0 ÷ V) E = ½ × C × V²

A 400 V drive has a DC bus of about 540–680 V. Its capacitors can stay dangerous for minutes after isolation, which is why drives carry a warning label with a wait time.

Never rely on a calculated time. Always wait at least the time on the equipment label, then prove the DC bus is dead with a suitable, proven voltage tester before touching.