Advanced Energy Stored Calculator
Default time is -0.12 ms. Use waveform mode for sampled AC or transient studies. Use direct mode when voltage and current at the instant are already known.
Formula Used
The calculator uses the standard field energy equations for capacitors and inductors. For a capacitor, stored energy is:
For an inductor, stored energy is:
Total stored energy is Etotal = EC + EL. In waveform mode, the instantaneous signal is found with V(t) = Voffset + Vamp cos(2πft + φ) e-αt. The same form is used for current.
How to Use This Calculator
- Enter the time point. The default value is -0.12 ms.
- Select waveform mode or direct measured mode.
- Enter capacitance, inductance, signal size, frequency, phase, and damping.
- Press the calculate button to see energy above the form.
- Use CSV or print output when you need a saved report.
Example Data Table
| Case | Time | C | L | Voltage | Current | Total Energy |
|---|---|---|---|---|---|---|
| Direct sample | -0.12 ms | 10 µF | 2.2 mH | 12 V | 1.8 A | 0.004284 J |
| Small capacitor | -0.12 ms | 470 nF | 0 mH | 24 V | 0 A | 0.000135 J |
| Inductor pulse | -0.12 ms | 0 µF | 5 mH | 0 V | 3 A | 0.0225 J |
Understanding Stored Energy at a Time Sample
Why the Time Point Matters
Energy storage in a circuit is not fixed during motion. It changes as voltage and current change. A value such as -0.12 ms usually means a sample before the chosen trigger time. This is common in oscilloscopes, simulations, and transient captures. The time sign does not make energy negative. Energy remains positive because voltage and current are squared.
Capacitor Energy
A capacitor stores energy in its electric field. The amount depends on capacitance and instantaneous voltage. Doubling voltage makes stored energy four times larger. This square relation is important. It makes high voltage designs sensitive. A small measurement error can produce a larger energy error. The calculator lets you enter the voltage directly, or it can find voltage from a sinusoidal waveform.
Inductor Energy
An inductor stores energy in its magnetic field. Its energy depends on inductance and instantaneous current. Current is squared in the formula. A pulse with high current can store large energy even when voltage is low. This is useful in coils, converters, motors, filters, and ignition circuits. The result also reports flux linkage, which helps describe magnetic storage.
Waveform Phase and Damping
Advanced time based work often needs phase. Voltage and current may not peak together. In a reactive circuit, they can be shifted by many degrees. The form uses a cosine wave with frequency, phase, and optional damping. Damping represents loss or decay. With signed time, negative time can increase the factor. With absolute time, distance from zero controls decay.
Choosing the Right Mode
Use direct mode when you already know voltage and current at the exact sample. This is the cleanest option for measured data. Use waveform mode when you know amplitude, frequency, phase, and damping. It is better for planning and simulation checks. You can set either capacitance or inductance to zero when only one storage element matters.
Reading the Result
The total energy is shown in joules, millijoules, and microjoules. The split between capacitor and inductor energy is also shown. This helps compare electric field storage with magnetic field storage. For design safety, use peak likely values, not only average values. Stored energy can discharge quickly. Always compare the result with component ratings and safe handling rules.
Practical Accuracy Tips
Good input data gives better energy estimates. Use actual component values when possible, because real capacitance and inductance can shift with tolerance, temperature, bias, and frequency. Check whether amplitude means peak value or RMS value. The waveform equation expects peak amplitude. Convert RMS to peak before entering it for sinusoidal work. Also confirm phase convention. A positive phase moves the cosine argument forward. A negative phase delays it. For damped transients, choose the damping rule that matches your model. Signed time is useful for mathematical waveforms. Absolute time is useful for distance from the reference sample. Document every assumption so later reviews remain simple and traceable.
FAQs
1. Can energy stored at -0.12 ms be negative?
No. The time value may be negative, but stored energy is not negative. The equations square voltage and current, so the result is zero or positive.
2. What does -0.12 ms mean?
It means the sample is 0.12 milliseconds before the chosen zero reference. It is often used for pre-trigger readings in waveform captures.
3. Which formula is used for capacitor energy?
The calculator uses E = ½CV². C is capacitance in farads. V is the instantaneous voltage at the selected time.
4. Which formula is used for inductor energy?
The calculator uses E = ½LI². L is inductance in henries. I is the instantaneous current at the selected time.
5. When should I use direct mode?
Use direct mode when your meter, scope, or simulation already gives voltage and current at the exact time sample.
6. When should I use waveform mode?
Use waveform mode when voltage and current must be calculated from amplitude, frequency, phase angle, and damping before energy is found.
7. What does damping coefficient mean?
It describes exponential decay of the waveform. A larger value reduces amplitude faster when the selected damping rule treats time as decay time.
8. Why is phase included?
Phase shifts the waveform in time. It lets the calculator estimate voltage and current when they do not peak at the same instant.
9. Can I calculate only capacitor energy?
Yes. Enter the capacitance and voltage data. Set inductance or current to zero if magnetic energy is not part of your problem.
10. Can I calculate only inductor energy?
Yes. Enter the inductance and current data. Set capacitance or voltage to zero if electric field energy is not needed.
11. Is this calculator suitable for circuit safety?
It helps estimate stored energy, but safety design needs margins. Always check component ratings, discharge paths, and local electrical safety practices.