Unlike linear sensors, the PTC130 behaves like a thermal switch.

The simplified modeling of resistance as a function of temperature can be expressed as follows:

R(T) = ​{ R₀ × [1 + α(T - 25)] for T < T_N 

​ ​{ R_N × e^{β(T - T_N)} for T ≥ T_N

with: 

• R₀ = 150 Ω: resistance at 25°C

• α ≈ 3 × 10⁻³ K⁻¹ 

• R_N = 1650 Ω: nominal threshold resistance at 130°C 

• β ≈ 0.25 K⁻¹: exponential growth coefficient

🔹 Example 1: operation under normal conditions (80 °C)

R(80) = 150 × [1 + 3×10⁻³ × (80 - 25)] = 150 × 1.165 = 174.8 Ω

✅ Resistance ≈ 175 Ω → sensor "closed," no alarm.

🔹 Example 2: overheating operation (140 °C)

R(140) = 1650 × e^(0.25 × (140 - 130)) = 1650 × e^2.5 ≈ 1650 × 12.18 = 20100 Ω

✅ Resistance ≈ 20 kΩ → threshold exceeded, the protection system may trigger.

🔹 Practical notes

The PTC130 does not provide a "continuous" temperature value, but a threshold signal.

The change in resistance is often interpreted through a detection module or a PTC relay.

A series of multiple PTCs can be connected in series to monitor several windings at once.

The PTC130 is often used in a motor protection circuit associated with a PTC detection relay (compliant with DIN 44081/82).

When the sensor resistance exceeds approximately 1.5 kΩ, the relay cuts off the control circuit.

🔹 Typical components

        +24 V
          │
        [PTC Relay]
          │
     ├────┴────┐
     │         │
 [PTC130]   [PTC130]
 (in series, 1 per winding)
     │         │
     └────┬────┘
          │
         GND

🔹 Operating Principle

1️⃣ Each PTC is placed in the motor winding.

2️⃣ As long as T < Tₙ, the resistances are low → the relay remains closed.

3️⃣ As soon as a PTC reaches Tₙ ≈ 130 °C → its resistance skyrockets → the relay opens the circuit.

🔹 Best Practices

• 🧩 Measure the resistance at 25 °C before installation for verification.
• ⚡ Limit the test current < 2.5 mA to avoid self-heating.
• 🔄 Replace PTCs in pairs or in series to maintain uniformity.
• 💧 Avoid immersion in oil or resin that is not electrically compatible.
• 🧠 Use a certified DIN detection module (ABB, Siemens, Schneider…).