Calculator
Example Data Table
| Capacitor | Value | Voltage rating | Applied string voltage | Ideal voltage share |
|---|---|---|---|---|
| C1 | 10 µF | 25 V | 12 V | 7.20 V |
| C2 | 22 µF | 25 V | 12 V | 3.27 V |
| C3 | 47 µF | 16 V | 12 V | 1.53 V |
| Equivalent | 6.00 µF | 66 V total | 12 V | 0.000432 J stored |
Formula Used
For capacitors in series, reciprocal capacitance values are added.
1 / Ceq = 1 / C1 + 1 / C2 + 1 / C3 + ... + 1 / Cn
Q = Ceq × V
Vi = Q / Ci
E = 0.5 × Ceq × V²
Derated limit = total voltage rating × derating percent
How to Use This Calculator
- Enter at least two capacitor values.
- Select the correct unit for each capacitor.
- Add voltage ratings when you need margin checks.
- Enter applied voltage for charge and energy results.
- Set tolerance to estimate the possible capacitance range.
- Add a derating percent for safer voltage planning.
- Use the balancer field for resistor-chain estimates.
- Click Calculate, or export CSV and PDF reports.
Electrical Design Notes
Understanding Series Capacitors
Series capacitors are used when one part cannot meet a voltage goal. The connection also reduces total capacitance. That tradeoff matters in filters, timing networks, energy storage, pulse circuits, and repair work. A careful calculation helps you see both sides before parts are ordered.
What the Result Means
In a series string, the same charge passes through every capacitor. The equivalent capacitance is found from reciprocal values. A smaller capacitor has more influence on the final value. One very small part can pull the total down sharply. The calculator converts each entered value to farads first. It then returns results in useful units.
Voltage and Charge
Applied voltage is shared across the string. Ideal sharing follows capacitance. Lower capacitance usually receives higher voltage. Real parts also have leakage current, tolerance, temperature drift, and aging. These effects can cause uneven stress. Designers often add balancing resistors across high voltage capacitors. The calculator gives an ideal estimate, so safety margins still matter.
Tolerance and Derating
Capacitor tolerance changes the useful range. A ten percent part may be above or below its marked value. This tool estimates minimum and maximum equivalent capacitance from a shared tolerance entry. Voltage derating also protects reliability. Many designs avoid running capacitors at their full rating. A conservative margin reduces heat, leakage, and failure risk.
Practical Use
Use this calculator during early design checks. Enter capacitance values, choose units, and add voltage ratings. Add applied voltage when you want charge, energy, and voltage split results. Keep notes about dielectric type, ripple current, and package limits. Export the results for design files or workshop records.
Why Balance Matters
Matched parts behave better during tests. Mixed values can overload one device quickly. Balancing resistors waste small power, yet they improve steady voltage sharing under load. For pulsed use, also check surge current and dielectric heating carefully first.
Final Advice
The math is simple, but the application can be serious. High voltage capacitor banks can store dangerous energy after power is removed. Always discharge parts with a suitable resistor. Verify with a meter before touching conductors. Use rated components, proper insulation, and safe spacing. Treat the calculator as a planning guide, not a substitute for tested engineering judgment.
FAQs
What is a capacitor in series?
It is a connection where capacitors are placed end to end. The same charge flows through each part. The total capacitance becomes smaller than the smallest individual capacitor.
Why does series capacitance decrease?
Each capacitor adds dielectric separation to the string. The reciprocal formula reflects that added separation. More parts in series usually means lower equivalent capacitance.
Can I add voltage ratings in series?
In ideal conditions, voltage ratings can be summed. Real voltage sharing may not be equal. Use matched capacitors, derating, and balancing resistors for safer designs.
What is voltage sharing?
Voltage sharing is how the applied voltage divides across capacitors. In ideal series circuits, lower capacitance takes higher voltage. Leakage and tolerance can change that split.
What does tolerance do here?
Tolerance estimates the possible low and high capacitance range. It helps you see how manufacturing variation can affect the final equivalent value.
Why use balancing resistors?
Balancing resistors help equalize steady voltage across series capacitors. They are common in high voltage strings. They also create a discharge path after shutdown.
Does this calculator handle AC circuits?
It calculates capacitance, charge, voltage split, and stored energy. For AC work, also check reactance, ripple current, frequency, dielectric loss, and heating.
Is the stored energy dangerous?
Yes, stored capacitor energy can be hazardous. High voltage strings can remain charged after power is removed. Always discharge safely and verify with a meter.