Part of Power and energy calculators
Inductor Energy Calculator
Calculate stored magnetic energy from inductance and current.
Inputs
Select which inductor value to solve, then enter the other two values and their tolerances.
Results
Stored energy uses current squared, so changes in current strongly affect the stored energy result.
Use inductor energy checks for peak-current, clamp, and saturation awareness
Inductors store energy in a magnetic field. That energy is useful in converters and filters, but it also matters for switch stress, clamp design, snubbers, saturation margin, and fault behaviour when current is interrupted.
Switching converters
Estimate energy at peak inductor current before checking saturation and switch stress.
Clamp and snubber paths
Quantify energy that must be safely transferred or dissipated when current is interrupted.
Fault cases
Check how peak current and inductance combine during short circuits, load dumps, or disconnects.
Equations and model
The calculator uses the ideal inductor energy relationship and applies tolerance ranges to the selected values. Use effective inductance at the relevant operating current.
Stored magnetic energy
Energy stored in an ideal inductor at current I.
Solve inductance
Estimate inductance from target stored energy and current.
Solve current
Estimate current required for a target energy at a known inductance.
E - Stored energy
Unit: joules (J)
Magnetic energy stored in the inductor field before losses and clamp behaviour are considered.
L - Inductance
Unit: henries (H)
Effective inductance at the operating current, frequency, temperature, and bias condition.
I - Current
Unit: amps (A)
Usually the peak or instantaneous current through the inductor for the energy case being checked.
I² - Current-squared term
Unit: A²
Energy is proportional to current squared, so peak current errors strongly affect the result.
Worked example
This example is covered by the stored-energy test suite.
Design question: A 100 µH inductor reaches 2 A peak current. How much magnetic energy is stored?
Inputs: L = 100 µH, I = 2 A.
Energy: E = 1/2 × 100 µH × 2² = 200 µJ.
Current sensitivity: if peak current increases to 3 A, energy rises to 450 µJ because current is squared.
Next check: confirm the inductor has not saturated at 2 A and that any switch-off event has a defined energy path.
Saturation and interrupted-current checks
The ideal equation is useful, but inductor behaviour becomes less ideal near current, thermal, and switching limits.
Saturation margin
- Inductance can fall as current approaches saturation.
- Peak current, not just average current, usually sets saturation risk.
- Temperature can reduce saturation-current and RMS-current capability.
Energy path
- Interrupted current creates voltage until current can continue flowing.
- Clamp, diode, snubber, switch avalanche, or capacitor path must be intentional.
- The receiving part must survive the transferred energy and heat.
Assumptions and limitations
Ideal inductance
The calculation assumes inductance remains constant at the specified current. Real inductors vary with current, frequency, and temperature.
Losses not modelled
Winding resistance, core loss, skin effect, proximity effect, and thermal rise are not included in the stored-energy result.
Clamp design is separate
Clamp voltage, switch stress, avalanche rating, snubber sizing, and thermal dissipation need their own design checks.
Related calculators and next checks
Follow the next check based on whether the energy is transferred to a capacitor, dissipated as heat, or simply needs unit conversion.
Capacitor energy calculator
Compare stored magnetic energy with stored electric-field energy in capacitors.
Engineering conversion calculator
Convert µH, mH, amps, joules, millijoules, and SI-prefixed values.
Resistor power calculator
Check dissipation in clamp, bleed, sense, or damping resistors when energy is dissipated as heat.
Power and energy hub
Follow related stored-energy and power-design workflows.
RC time constant calculator
Use for capacitor charge/discharge timing when an inductor energy path charges a capacitor or snubber.
FAQ
Should I use RMS current or peak current?
Use the current relevant to the stored-energy event. For switching converters, clamps, and fault cases, that is often peak current rather than RMS current.
Does the labelled inductance always apply at high current?
No. Inductance can fall as the core approaches saturation. Check the inductance versus current curve and saturation-current rating, not just the nominal inductance value.
Why does interrupted inductor current need a clamp path?
Inductor current cannot stop instantly. If the switching path opens, the stored energy must go somewhere, such as a diode, TVS, snubber, clamp capacitor, or controlled switch path.
Engineering reference
Equations, assumptions, and design guidance
Solves inductor stored energy, inductance, or current and reports tolerance-derived minimum and maximum values.
Equations and variables
E = 0.5 * L * I^2- E
- Stored energy (J)
- L
- Inductance (H)
- I
- Inductor current (A)
Assumptions and limitations
Assumptions
- Inductance is constant at the entered current.
- Current is non-negative and DC or peak current for the stored-energy check.
Limitations
- Saturation, winding resistance, core loss, temperature rise, and switching clamp behaviour are not modelled.
Worked example and design use
100 uH at 2 A
Inputs: L = 100 uH, I = 2 A
Outputs: E = 200 uJ
Design guidance
- Check saturation current at temperature before relying on nominal inductance.
- Switching circuits need a defined path for stored energy when current is interrupted.