Electrical · Free Calculator
Capacitor Energy and Charge Calculator
Find how much energy and charge a capacitor stores at a given voltage, useful for DC bus, hold up and safety discharge calculations.
E = ½CV²Q = CVDC bus energyJoules
V
More than 10 J can cause a dangerous shock. Verify discharge with a meter before touching.
Stored energy345 J
Charge1.232 C
Energy0.09582 Wh
How this result was calculated
- E = ½ × C × V² = 0.5 × 0.0022 × 560² = 345 J
- Q = C × V = 1.232 C
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Capacitor Energy Formulas
E = ½ × C × V²
Q = C × V
Q = C × V
Worked example
A VFD DC bus of 2,200 µF at 560 V stores 0.5 × 0.0022 × 560² = 345 J, enough to be lethal.
Key insight: stored energy rises with the square of voltage. Always wait the time stated on the drive label and measure the DC bus before working inside.
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Frequently Asked Questions
How much energy does a capacitor store?
E = ½CV². Doubling the voltage stores four times the energy.
How long should I wait before opening a VFD?
Follow the warning label, typically 5 to 15 minutes, and confirm with a meter that the DC bus is below 50 V.
Can capacitors replace batteries?
Supercapacitors can provide short hold up, but their energy density is far lower than batteries.
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