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Every time an industrial power supply or motor-driven system starts up, it experiences a momentary surge of current — known as inrush current. This surge can be several times higher than the normal operating current and can cause stress, damage, or even failure of components such as fuses, rectifiers, capacitors, or transformers.

That’s where NTC inrush current limiters come in. These power thermistors are simple, passive components that offer highly effective protection with minimal cost or circuit complexity.

What is inrush current and why is it a problem? When power is first applied, uncharged capacitors act like short circuits and transformers draw magnetizing current. This can result in inrush currents up to 10–20 times the rated current, leading to:

• Premature aging of components.
• Fuse blowing during startup.
• Voltage dips affecting other equipment.
• Reduced system reliability.

How NTC thermistors limit inrush current? NTC (Negative Temperature Coefficient) thermistors offer high resistance when cold and drop to low resistance as they heat up. At startup:

• High cold resistance limits the initial surge.
• Self-heating causes resistance to fall during operation.
• Low hot resistance allows efficient steady-state current flow.

This passive behavior makes them ideal for protecting circuits without adding complexity or control logic.

Selection tips for engineers when choosing an inrush current limiter, consider:

• Rated current and cold resistance (R25).
• Thermal time constant and dissipation factor.
• Maximum energy handling capacity (Joule rating).
• Mounting style: radial, axial, or disk-shaped.

 NTC thermistors must be selected based on the peak inrush current, ambient temperature, and frequency of on-off cycles.

Why choose power thermistors at Shiheng Electronics, we offer a full line of power NTC thermistors specifically designed for inrush current limiting:

• Stable performance and long life.
• RoHS and REACH compliant.
• Custom specifications available.
• Fast sampling and reliable production capacity.

Inrush current is one of the most overlooked stress factors in industrial power design. Integrating an NTC thermistor is a simple and proven way to prevent damage, reduce service calls, and extend the lifespan of your equipment.

Need help selecting the right inrush limiter? Contact our team at Shiheng Electronics for expert guidance and fast-turn samples.