Why Your Circuit Breaker Works in the Lab – But Trips in the Field

And How AIRPAX Solves the Problem That Brings Down Entire Systems

In the laboratory, everything is perfect.
A stable power supply.
Constant temperature.
No vibration.
No shock.
No electrical noise.

Then the system is deployed into the real world – into a military vehicle, a UAV, a communications shelter, or a weapon platform – and suddenly:

The circuit breaker trips for no apparent reason.
There is no short circuit.
There is no overload.
Yet the system shuts down.

Every engineer has seen this.
The circuit breaker that passed all laboratory tests fails exactly when it is not allowed to fail.

And this is not a bug.
It is the result of choosing the wrong circuit breaker technology.

This graph shows the inrush current of a motor or DC-DC converter plotted against the trip curve of an AIRPAX hydraulic-magnetic circuit breaker.

Inrush currents create high but short-duration current peaks.
AIRPAX circuit breakers are designed to allow these peaks to pass without tripping, and to trip only when high current persists long enough to represent a real fault.

This is the difference between a normal startup and a true overload.

The Real Problem: The Lab Is Lying to You

Most laboratory testing is performed under sterile conditions:

• 25°C

• Clean DC power

• No vibration

• Stable load

But in the real world:

Most circuit breakers behave very differently when any of these parameters changes.

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Why Conventional Circuit Breakers “Imagine” a Fault

Most industrial and automotive circuit breakers are based on:

• Thermal (bimetal)

• Or thermal-magnetic mechanisms

This means they are sensitive to:

• Temperature

• Short current peaks

• Self-heating

• Electrical noise

In military vehicles, UAVs, and field-deployed systems, this is a recipe for failure.

Typical real-world triggers:

• A DC motor or DC-DC converter generates high inrush current

• Ripple on a 28V bus creates current spikes

• High ambient temperature lowers the trip threshold

• Vibration moves the mechanical trip mechanism

The result:

The circuit breaker “thinks” there is a fault and trips, even though the system is perfectly healthy.

This is called a nuisance trip.
In a mission-critical system, it is a disaster.

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This Is Where AIRPAX Comes In

AIRPAX circuit breakers (Sensata) are not thermal.

They are based on a:

Hydraulic-magnetic trip mechanism

And that is why they behave completely differently.

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What Does That Mean in Practice?

The AIRPAX mechanism uses:

• Magnetic force

• Hydraulic damping (internal silicone fluid)

Which means:

The system responds to real overloads over time – not to short electrical transients.

This graph compares a conventional thermal circuit breaker with an AIRPAX hydraulic-magnetic circuit breaker.

A thermal breaker trips much faster due to self-heating, ambient temperature, and inrush currents.
AIRPAX maintains a stable trip curve that is not affected by temperature or vibration.

That is why thermal breakers fail in the field – while AIRPAX keeps operating.

Why AIRPAX Does Not Panic in the Field

The secret lies in the real trip curve.

AIRPAX circuit breakers are designed so that:

• Short inrush currents do not cause a trip

• True sustained overloads do cause a trip

• Ambient temperature does not shift the trip point

This is exactly what military, UAV, communications, and vehicle power systems require.

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The Difference Between a System That Works and One That Fails

Most field failures are not caused by:

• A short circuit

• Or a real overload

They are caused by:
Using the wrong circuit breaker for the environment

The system itself is fine.
The circuit breaker is not.

And when you replace it with AIRPAX:

• The mysterious trips disappear

• System availability increases

• The “ghost faults” are gone

The inrush current of a motor easily exceeds the trip threshold of a thermal circuit breaker, causing a nuisance trip.

In contrast, the AIRPAX trip threshold is higher for short-duration peaks, allowing the system to start up without a false shutdown.

The Bottom Line

If your system:

• Passed all laboratory tests

• But fails in the field

There is a very high chance that:
The circuit breaker was not designed for the real environment.

AIRPAX circuit breakers were not designed for the lab bench.
They were designed for combat vehicles, aircraft, UAVs, and field-deployed systems.

And that is the difference.

The trip curve shows the time required to disconnect as a function of current.

Very high currents cause a fast trip,
but high currents for a short duration (inrush) are absorbed and do not cause a trip.

This is how AIRPAX distinguishes between a real fault and a normal system behavior.