What Is an Inrush Current Limiter? Types, Uses, & Benefits

When the initial power is turned on, the initial current drawn by electrical devices is the inrush current, which can be many times higher than the normal running operating current. Failure to manage the initial current spike can damage equipment and its components or cause blown fuses and tripped circuit breakers. Current spikes can also reduce equipment reliability and durability, and stress power supplies, sometimes making the equipment inoperable.

Inrush current limiters are devices that prevent these spikes by limiting the amount of current at start-up and subsequently allowing normal current flow so that the system starts and operates as designed.

Inrush current limiters minimize inrush current spikes. Inrush current limiters are often thermistors or thermally sensitive resistors whose resistance changes significantly due to the inrush current flow through the device. While there are several types of inrush current limiters, their core function is to minimize the current spike that occurs at turn-on from passing through and damaging the system’s sensitive components.

Their resistance drops significantly after initially limiting the current flow, and the reduced resistance allows the normal running current to flow freely, so the system starts and operates properly.

Inrush current limiters provide a single device solution value by safeguarding systems, offering enhanced functionality, and providing design and cost advantages over alternatives.

Safeguard Systems and Components. Inrush current limiters limit the initial current surges that can damage sensitive components like capacitors, rectifiers, and power switches during turn-on. They also improve system reliability by preventing blown fuses and tripped circuit breakers that keep systems from operating or operating correctly. Excessive Inrush current also increases the wear on many components, so inrush current limiters extend the operational life of those components.

Design and Cost. Most inrush current limiters are small, so they easily fit on electronic circuits and in other applications where size matters. Thermistors are also an inexpensive single component solution compared to the complex active circuits that can be used as alternatives.