Calculation
W = ½·L·I²
Stored energy grows with the square of current, similar to a capacitor's stored energy growing with the square of voltage.
Busch 2006, Abschnitt 2.7.1, Gl. (2.64) Energieinhalt des Magnetfeldes
Energy stored in an inductor's magnetic field
Stored energy grows with the square of current, similar to a capacitor's stored energy growing with the square of voltage.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Magnetic energy W — Energy stored in the magnetic field at steady current I.
- Inductance L — Coil inductance with no saturation over the considered current range.
- Coil current I — Steady current through the coil at which energy is evaluated.
Example
L=100 mH and I=1 A give W=½·0.1·1²=0.05 J.
Assumptions and limits
Constant, saturation-free inductance; winding resistance and its resistive losses are not included.
Understand Energy stored in an inductor's magnetic field
This calculator determines the energy stored in a current-carrying inductor's magnetic field, the magnetic counterpart to the existing electrical energy of a charged capacitor.
What does this quantity describe?
Building up current in a coil stores energy in its magnetic field: W=½·L·I². This energy is released again at switch-off, e.g. as an induced voltage spike.
Formula and variables
W = ½·L·I²
W = ½·L·I²
| Symbol / input | Meaning |
|---|---|
| Magnetic energy W | Energy stored in the magnetic field at steady current I. |
| Inductance L | Coil inductance with no saturation over the considered current range. |
| Coil current I | Steady current through the coil at which energy is evaluated. |
Choose the inputs correctly
L is the coil's inductance, I the steady current at which energy is evaluated.
How to use the calculator
Take L from a datasheet or measurement and use the actual operating current I.
Worked example
L=100 mH and I=1 A give W=½·0.1·1²=0.05 J.
Understand the result and units
Energy grows with the square of current; doubling current quadruples stored energy.
L is an inductance, I a current. W is output as an energy.
Typical applications
Estimating energy released at switch-off in relay, contactor and solenoid-valve coils, and a basis for sizing freewheeling paths.
Assumptions, limits and common mistakes
Constant, saturation-free inductance; winding resistance and its resistive losses are not included.
Common mistake: Do not confuse a switch-on transient peak current with the steady current at which energy is actually to be evaluated.
Frequently asked questions
What is “Energy stored in an inductor's magnetic field” used for?
Estimating energy released at switch-off in relay, contactor and solenoid-valve coils, and a basis for sizing freewheeling paths.
Where do the input values come from?
L is the coil's inductance, I the steady current at which energy is evaluated.
What does the result not cover?
Constant, saturation-free inductance; winding resistance and its resistive losses are not included.