How To Select an Inrush Current Limiter

Choosing the correct inrush current limiter for your inrush current limiting needs can be vital for any project. Ametherm’s NTC inrush current limiters are designed to protect your components from damaging levels of inrush current at startup.

Below you will find information about measurements you will need to select the right inrush current limiter for your projects, calculators to help determine these values, and information about our NTC inrush current limiter lines and other useful content.

Download Ametherm’s Inrush Current Limiter Infographic


Inrush Current Limiters CSA approvalUL rated

UL-recognized MegaSurge inrush current limiter are certified for single and three-phase input voltages up to 480 VAC. Target Applications: Power Supplies, Motor Controllers, Audio Amplifiers, Battery Chargers, Frequency Generators, Plasma Cutting Tools, MRI Machines, and Toroidal Transformers.

UL-recognized bigAMP inrush current limiter are specially designed to withstand up to 36 amperes of continuous current and 260 joules of input energy. Target Applications: Switching Power Supplies, AC Motors, Uninterruptible Power Supplies and, Frequency Generators.

UL-recognized miniAMP inrush current limiter are rated for 250 mA to 3 Amperes continuous current and up to 20 joules of input energy. Target Applications: Packaged bulk, they are available on Tape and Reel and designed for applications where board space is limited and cool operation is desired.

Industrial-strength high power inrush current limiter with continuous current ratings from 50A to 80A at 680V RMS and energy to 1,200 joules.
Target Applications: Single and Three Phase Applications Including – AC Motors, Transformers, Power Supplies, and Inverters.

Large variety of the sizes and electrical specifications of our most common inrush current limiters.

Inrush Current Application Notes

Inrush Current FAQ
Frequently Asked Questions about inrush current limiting thermistors.
Inrush Current in Transformers

Case example where a transformer has to be protected from inrush current.

Capacitor Inrush Current

Calculating the amount of current flowing to the capacitor, then protect your load from this initial flow of current is important for any electronic device.

Calculate Inrush Current in Three Steps

Inrush Current Limiters are designed with different characteristics such as resistance versus temperature curve to accommodate numerous applications. Because of this, it is necessary to make some calculations based on your system requirements to select the best Inrush Current Limiter for your needs.

Lithium Ion Pre-charge Circuit Inrush

Thermistor Protection for a Pre-charge Circuit on Lithium Ion Batteries.

Special Thermistors Limit Inrush Current

Power Electronics Technology article discusses applications and uses of inrush current limiting thermistors.

Ametherm Imax Derating Curve
Ametherm Derating Curve – indicates how much a device will dissipate without getting damaged at any given case temperature.
Ametherm Zero Power Resistance Curve
Ametherm Zero Power Resistance Curve