NTC 5D-11 Thermistor

🔹 NTC 5D-11 Thermistor (5 Ohm 11mm Disc)

A high-power Negative Temperature Coefficient (NTC) thermistor designed for inrush current limiting in AC/DC power supplies and electrical equipment. Its resistance decreases as temperature increases, making it ideal for protecting circuits from high startup currents.

✅ Specifications:

• Type: NTC Thermistor (Disc Type)

• Resistance (R25): 5 Ohms ±20% (at 25°C / 77°F)

• Diameter: 11mm

• Max Steady-State Current: ~2A (dependent on heat dissipation)

• Max Allowable Inrush Current: ~20A (typical)

• Thermal Dissipation Constant (δ): ~8 mW/°C (in free air)

• Time Constant (τ): ~60 seconds (in free air)

• Operating Temperature Range: -40°C to +105°C

• Lead Type: Tinned copper wire leads

⚙️ Features:

• Inrush Current Suppression: Effectively limits high startup surge currents in power supplies, motors, and transformers.

• High Power Handling: Robust disc construction designed for repeated high-energy pulse absorption.

• Reliable & Durable: Stable performance over extended operational life.

• Simple Integration: Easy to install in series with the AC mains or DC power input line.

📦 Applications:

• Power Supply Protection: Switching power supplies, AC-DC adapters, and UPS systems.

• Appliance & Motor Starters: Refrigerators, air conditioners, and compressor startup circuits.

• Industrial Electronics: Inverter drives, industrial power controllers, and lighting ballasts.

• DIY & Repair: Perfect for upgrading or repairing power circuits requiring inrush current protection.

• Energy Management: Soft-start circuits to reduce stress on capacitors, fuses, and switches.

🔧 Typical Wiring Configuration:

• Series Connection: Connect one lead of the NTC thermistor in series with the main AC or DC power line (often on the live/hot side before the rectifier or transformer).

• Purpose: At cold startup, its high resistance (~5Ω) limits current. As it self-heats from current flow, its resistance drops dramatically, allowing full operating current with minimal voltage drop.

• Note: It needs a cooldown period (typically 30-60 seconds) between power cycles to reset its resistance for the next inrush event.

⚠️ Important Considerations:

• This is an inrush current limiter, not a fuse or overcurrent protector.

• Ensure proper heat dissipation and do not exceed rated steady-state current to avoid overheating.

• For safety-critical designs, always derate specifications and verify in the actual circuit.