Trip Coil – Turning a Standard Breaker into a Smart Relay

💡 The Concept

In a conventional thermal-magnetic circuit breaker, the trip occurs only as a result of overcurrent or short circuit.
When a Trip Coil is added, the breaker gains an electrical control capability — it doesn’t just protect, it also becomes remotely controllable.
A small control-voltage pulse from a PLC or control system energizes the coil, triggering the internal mechanism to trip the breaker.
This turns a simple circuit breaker into a smart relay-breaker — combining protection, mechanical reliability, and remote operation.

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⚙️ Types of Trip Coils

Shunt Trip – Activated by an external voltage pulse (typically 12 VDC / 24 VDC).
Used for remote shutdowns, E-STOP functions, or intentional disconnection by a control system.

Undervoltage Release (UVR) – Keeps the breaker latched as long as a “permission” voltage is present.
When the voltage drops, the breaker automatically opens — an ideal solution for Enable / Interlock / Fail-Safe logic.

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🧠 Engineering Advantage

Adding a Trip Coil to a thermal-magnetic breaker creates a hybrid smart device:

• A control relay with true mechanical disconnection

• Built-in overcurrent and overload protection

• Auxiliary contacts for monitoring and smart control

Instead of combining separate modules — relay, breaker, and control interface — you get one compact, precise, and durable unit.

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⚙️ What Is a Trip Coil in Practice

The Trip Coil is an electromagnetic module integrated into the breaker housing and powered by an external control voltage (12 VDC, 24 VDC, 48 VDC, or 115/230 VAC).
When a short pulse is applied, the coil mechanically activates the trip mechanism and opens the breaker — just like an intelligent relay, but with the added benefit of built-in thermal-magnetic protection.

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💡 Typical Applications

• Smart power protection systems

• Military power units – remote disconnect or enable logic from a controller

• Industrial machinery and PLC control panels

• Emergency stop and E-STOP circuits

• Energy management and maintenance control systems

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⚡ Amironic Ltd. – Official Representative of Sensata / Airpax in Israel

Amironic Ltd. is the authorized representative of Sensata Technologies / Airpax in Israel, providing:

• Full technical support for breakers with Trip Coil and Undervoltage Release options

• Assistance in defining voltage, current, timing, and environmental requirements

• Custom integration in advanced control and protection systems

• Available stock and engineering samples for evaluation and testing

The Sensata Airpax Trip Coil enables any thermal-magnetic breaker to become a smart protection solution – a relay, protector, and breaker in one compact device.

Trip Coil – Operating Principle

The graph illustrates the operation of a Trip Coil inside a thermal-magnetic breaker during an overcurrent event or a deliberate command from the operator.
During Normal Operation, the nominal current flows through the load.
When the current exceeds the threshold — or when a trip command is received from the control system — the Trip Coil is energized by a short 250 VAC Or DC pulse.
The pulse triggers the internal trip mechanism, opening the circuit immediately.
After the trip, the system enters a protected state (Circuit Breaker Open – Load Protected) with zero current and safe disconnection of the load.

Trip Coil Operation Sequence

This engineering graph shows the system’s response during an overload and trip sequence.

• Top Graph – Load Current (A): The load current gradually increases until reaching the 10 A threshold, where the overload condition begins.

• Middle Graph – Trip Coil Voltage (V): Upon detecting the overload (or receiving a remote command), a short 250 VAC pulse is sent to the Trip Coil.

• Bottom Graph – Breaker State: Immediately after the coil is energized, the trip mechanism activates, opening the circuit and switching the breaker from ON to OFF.

The red vertical line marks the Trip Event — the exact moment when the coil is energized and the system transitions from normal operation to protection mode.
Afterward, the current drops to 0 A, and the load is safely isolated.