Inrush Current Limiters

Several different components, including negative temperature co-efficient (NTC) thermistors and fixed resistors, can be used as inrush current limiters. These components are generally used to limit inrush current with the aim of reducing gradual damage to other components and preventing fuses blowing or circuit breakers tripping. Specific types of inrush current limiters will be used depending on the size and function of a specific electronic device.

How do inrush current limiters work?

Inrush current limiters measure and limit the inrush current flowing into an electrical device in the fractions of a second immediately after it is switched on. Inrush current limiters are typically high resistance components, preventing huge electrical currents from flowing immediately after switching on, while ensuring enough electric flows for devices to operate as required.

How do I choose an inrush current limiter?

If choosing an inrush current limiter for an electrical device, you will need to consider three things: the rated resistance of the component you’re going to use, the maximum permissible continuous current allowed by the limiter under rated operating conditions, and maximum capacitance that will be switched.

How can I reduce my inrush current?

There are several ways to reduce inrush current when switching on a device; you can do this by increasing voltage rise time during load capacitance, while simultaneously slowing down the rate at which capacitors charge. Voltage regulators, the use of discreet components, the use of integrated load switches can all be involved in the reduction of inrush current.

How long does inrush current last?

Inrush current only lasts for around a thousandth of a second. However, in that time, the flow of electrical current can be as high as 20 times the eventual steady state current. In that time frame, up to 40 cycles of inrush current will occur before a current stablises.