How can I select NTC for inrush current limiter?

1. Use Equations (1) and (4) to determine the energy of the inrush current: 73.18 J needs to be safely absorbed by the NTC thermistor.
2. Use Equation (2) to determine the minimum resistance required by the NTC thermistor: RMIN = 171.1 V / 30 A. 5.70 Ω is required from the NTC thermistor at 25 ºC.
3. Steady-state current: 10 A.

How do I limit inrush current?

Inrush current can be reduced by increasing the voltage rise time on the load capacitance and slowing down the rate at which the capacitors charge. Three different solutions to reduce inrush current are shown below: voltage regulators, discrete components, and integrated load switches.

How does inrush current limiter work?

The nature of the inrush current limiter to self-heat as an increasing amount of current is applied, which generates heat, causes resistance to drop, allowing the current to flow freely. This self-heating effect is the underlying reason that allows the inrush current limiter to work effectively.

Where is inrush current limiter used?

A typical application of inrush current limiters is in the input stage of non-power factor corrected switching supplies, to reduce the initial surge of current from the line input to the reservoir capacitor. The most popular application is the inrush protection of the AC current in switching power supplies (SPS).

How long does inrush current last?

The inrush may be as much as 14 times the steady-state current and may persist for a few milliseconds for smaller lamps up to several seconds for lamps of 500 watts or more.

Why is inrush current harmful?

Inrush current increases the risk of ground faults and installation circuit breaker failure, which can cause entire electrical installations to fail. Large inrush currents can also lead to voltage dips, which in turn may also result in equipment failure.

How is led inrush current calculated?

For our calculation, Inrush Current for an LED Driver is 100 times the Steady State Current rating of the single LED Driver.

Why does inrush current occur?

Inrush current is the instantaneous high input current drawn by a power supply or electrical equipment at turn-on. This arises due to the high initial currents required to charge the capacitors and inductors or transformers. These currents can be as high as 20 times the steady state currents.

Why is inrush current bad?

The ratio of inrush current to normal full-load current can range from 5 to 100 times greater. This current surge can cause component damage and/or failure within the equipment itself, blown fuses, tripped circuit breakers, and may severely limit the number of devices connected to a common power source.

How does NTC thermistor work?

With an NTC thermistor, when the temperature increases, resistance decreases. Conversely, when temperature decreases, resistance increases. When temperature increases, the resistance increases, and when temperature decreases, resistance decreases. This type of thermistor is generally used as a fuse.

What are NTC thermistors made of?

Many NTC thermistors are made from a pressed disc, rod, plate, bead or cast chip of semiconducting material such as sintered metal oxides. They work because raising the temperature of a semiconductor increases the number of active charge carriers it promotes them into the conduction band.

How does NTC-based limiting work in inrush current?

This creates multiple instances of inrush current. NTC-based limiting operates on the nature of the NTC thermistor to self-heat and lower its resistance. However, when a system is quickly turned off and then on again, the NTC thermistor may not have completely cooled.

How does the NTC thermistor affect the inrush current?

Placing an NTC thermistor between the power supply and system limits inrush current (see Figure 1). At first, the initial temperature of the NTC thermistor is low, providing high resistance. When the system is powered on, it energizes the NTC thermistor, causing the temperature to rise, and thus lowering resistance.

Can a fixed resistance be used to limit inrush currents?

A fixed resistance or an NTC thermistor can be used to limit inrush currents. However, a fixed resistor always causes a power loss and a decrease in performance.

Is there a way to reduce the inrush current?

A safe and cost effective way to reduce inrush current is to use an inrush current limiter (surge limiter), which is a special type of negative temperature coefficient (NTC) thermistor. Inrush current occurs at the moment the power switch is thrown.