- MIL-PRF-39019 Circuit Breakers: Selection, Trip Curves, and Aerospace Power Protection
- Why M39019 Is Not Just a Standard – It’s an Identity
- Understanding Trip Curves in Hydraulic-Magnetic Circuit Breakers
- Power Protection in Military Ground Platforms: Electrical Stability Under Vibration, Shock, and 28V Vehicle Systems
- The Airpax AP Series: The Engineering Logic Behind a Hydraulic-Magnetic Circuit Breaker That Became a Military Standard
- Hydraulic-Magnetic vs Thermal Circuit Breakers
- Airpax IULN and IUGN Circuit Breakers: Sealed Hydraulic-Magnetic Protection for Rugged Electronic Systems
- How Engineers Choose Between Airpax AP, IUL, IUG, and Commercial Circuit Breakers
- SNAPAK Circuit Protectors: When Circuit Protection Becomes a User Interface
- DIN Rail Circuit Breakers – Why Industrial Systems Demand More Than a Standard MCB
- Why MIL-PRF-39019 Circuit Breakers Still Appear in New Defense Programs
- Why a 10A Circuit Breaker Is Not Always Suitable for a 10A Load
Modern data centers are expected to do one thing above all else: stay online.
Whether supporting cloud services, enterprise applications, telecommunications infrastructure, financial transactions, or industrial operations, today’s facilities are measured by uptime. Even a brief power interruption can affect thousands of users, disrupt critical services, and result in significant financial losses.
As power demands continue to increase, much of the industry discussion focuses on UPS systems, battery energy storage, cooling technologies, backup generators, and power distribution architectures. These are all essential elements of a modern data center.
However, there is another component that rarely receives attention despite being present throughout the entire power chain:
Circuit protection.
From utility entrance equipment to power distribution units (PDUs), battery systems, cooling infrastructure, control electronics, and auxiliary power circuits, reliable circuit protection plays a critical role in maintaining system availability and preventing costly failures.
The Growing Challenge of Data Center Power
The power requirements of modern data centers are changing rapidly.
A decade ago, a rack consuming 5 kW was considered substantial. Today, AI servers and high-performance computing systems can push rack densities beyond 50 kW, with some installations targeting even higher values.
As power density increases, so do the demands placed on electrical infrastructure:
- Higher continuous currents
- Larger battery backup systems
- More distributed power architectures
- Increased use of DC power distribution
- More sophisticated monitoring and control systems
- Greater pressure to avoid unplanned downtime
The result is a more complex electrical environment where every protection device becomes part of the overall reliability strategy.
The Hidden Risk: Small Electrical Faults
Most catastrophic outages do not begin as catastrophic events.
They often start with something much smaller:
- A wiring fault
- A short circuit
- An overloaded branch circuit
- A failed fan
- A malfunctioning power supply
- A damaged cable
- A maintenance mistake
If these faults are not isolated quickly and accurately, the impact can spread through larger portions of the system.
The purpose of circuit protection is simple:
Disconnect the fault while keeping the rest of the system operational.
When properly selected, circuit breakers limit damage, reduce repair costs, and help maintain service continuity.
Why Traditional Thermal Protection Is Not Always Enough
Many conventional protection devices rely on thermal operation.
In these devices, current creates heat, and the accumulated heat determines when the device trips.
While effective in many applications, thermal devices can be influenced by ambient temperature.
In a cool environment, a device may carry current longer before tripping.
In a hot environment, the same device may trip sooner.
Data centers are not uniform temperature environments. Electrical panels, power shelves, battery rooms, and equipment racks can experience significantly different operating temperatures.
For mission-critical infrastructure, predictable performance becomes increasingly important.
The Advantage of Hydraulic-Magnetic Circuit Breakers
Hydraulic-magnetic circuit breakers operate differently.
Instead of relying primarily on heat, they respond directly to current levels using a magnetic sensing mechanism. Because of this design, their trip characteristics remain largely independent of ambient temperature. This allows more consistent protection across a wide operating range.
This technology has been used for decades in demanding applications including:
- Data processing equipment
- Telecommunications systems
- Medical equipment
- Transportation infrastructure
- Aerospace and defense platforms
- Industrial control systems
The same characteristics that make hydraulic-magnetic protection attractive in these environments also align well with modern data center requirements.
Key advantages include:
Consistent Performance
Trip characteristics remain stable across changing ambient temperatures, helping maintain predictable protection behavior.
Reduced Nuisance Tripping
Protection can be tailored to accommodate normal inrush conditions while still responding appropriately to fault currents.
Long Service Life
Hydraulic-magnetic breakers are designed for repeated operation and long-term reliability in critical systems.
AC and DC Capability
Many modern data center architectures include both AC and DC subsystems. Hydraulic-magnetic technologies are available for both environments.
Where Circuit Protection Matters Inside a Data Center
Circuit breakers are not limited to a single location.
They can be found throughout the facility:
Power Distribution Panels
Protecting branch circuits and isolating faults before they affect larger portions of the electrical system.
Battery Backup Systems
Providing protection for battery strings, monitoring systems, and auxiliary circuits.
UPS and Power Conversion Equipment
Helping protect critical electronics and support systems.
Cooling Infrastructure
Protecting fans, pumps, control electronics, and supporting equipment essential for thermal management.
Monitoring and Control Systems
Ensuring that management, communications, and supervisory equipment remain protected and operational.
Network and Telecommunications Equipment
Supporting continuous operation of the systems that connect data center infrastructure to users and operators.
Selecting the Right Protection Strategy
When evaluating circuit protection for data center applications, engineers should consider more than just current rating.
Important factors include:
- Operating environment
- Ambient temperature range
- AC or DC operation
- Inrush current characteristics
- Required certifications
- Available panel space
- Maintenance requirements
- Long-term reliability expectations
A properly selected circuit breaker becomes part of the facility’s uptime strategy rather than simply another electrical component.
Airpax Hydraulic-Magnetic Solutions
Sensata’s Airpax™ portfolio includes a wide range of hydraulic-magnetic circuit breakers and circuit protectors used across industrial, telecom, transportation, and data center applications. Available product families include compact protection solutions such as IEG, IUG and IAG, as well as higher-current platforms including IEL, IUL and related configurations. These products are designed to provide reliable overcurrent protection while maintaining the performance advantages associated with hydraulic-magnetic technology.
Conclusion
As data centers continue to grow in scale and power density, reliability remains the industry’s most important metric.
Backup generators, UPS systems, batteries, cooling infrastructure, and monitoring platforms all play visible roles in maintaining uptime.
Circuit protection is less visible.
Yet every power path depends on it.
The ability to isolate faults quickly, operate consistently across varying conditions, and maintain reliable protection over years of service makes circuit breakers an essential part of modern data center design.
Because in the end, keeping a data center running is not only about delivering power.
It is also about protecting it.
Choosing the Right Airpax Circuit Protector for Data Center Applications
Not all circuits inside a data center have the same protection requirements.
A battery string carrying tens of amperes requires a different protection strategy than a monitoring controller, network switch or environmental control system.
For this reason, Airpax offers several hydraulic-magnetic product families, each optimized for specific applications.
Airpax Product Family Comparison
| Series | Typical Current Range | Typical Use | Key Advantage |
|---|---|---|---|
| IEG / IUG | Up to 50A | Control circuits, monitoring, telecom equipment | Compact size, international approvals |
| IPA | Low to medium current | PCB-mounted equipment and embedded systems | Direct equipment integration |
| IAR / IER | Up to 50A | Rack-mounted equipment | Designed for 1U / 1RU installations |
| IEL / LEL | High current | Power distribution and battery systems | Heavy-duty power protection |
| Snapak | Low to medium current | Operator interfaces and front panels | Switch + fuse holder + protection in one device |
IEG Series – The Workhorse of Electronic Infrastructure
The IEG family is one of the most widely used Airpax hydraulic-magnetic protectors.
It combines:
- UL1077 approvals
- IEC spacing compliance
- Multi-pole configurations
- Auxiliary switch options
- AC and DC operation
- Temperature-independent performance
The series was specifically designed for applications such as data processing equipment, business machines, instrumentation and other precision systems.
Typical Data Center Applications
- DC control circuits
- Environmental monitoring systems
- BMS controllers
- Power shelf control electronics
- Telecom equipment
- Network infrastructure
IEL Series – Protecting the Power Path
While the IEG family protects the control layer, the IEL family protects the power layer.
The IEL series offers:
- IEC spacing compliance
- UL1077 recognition
- CSA certification
- Multi-pole versions
- High-current capability
- AC and DC operation
The CEL variant extends capability up to 125A in a single pole and up to 400A in parallel four-pole configurations.
Typical Data Center Applications
- Battery backup systems
- Rectifier cabinets
- DC distribution panels
- Power shelves
- Auxiliary power distribution
- Edge data center power systems
For higher-current applications, IEL is often the preferred choice.
IAR / IER – Designed for Rack Equipment
One interesting family for data center designers is the IAR/IER series.
Unlike traditional panel breakers, these units were specifically designed for:
1U / 1RU rack installations.
Key characteristics include:
- Compact rack-friendly dimensions
- Up to 5,000 AIC at 80VDC
- Auxiliary alarm contacts
- Single and dual-pole versions
- Operation from -40°C to +85°C
Typical Data Center Applications
- Telecom racks
- Network appliances
- Power shelves
- Edge computing cabinets
- Industrial servers
IPA Series – Protection Inside the Equipment
Not every protection device sits on a distribution panel.
Many OEMs integrate protection directly into equipment.
The IPA series was designed specifically for this role.
Features include:
- Compact footprint
- PCB mounting options
- Multi-pole versions
- IEC and UL approvals
- Precision hydraulic-magnetic operation
The series is recommended for data processing equipment, instrumentation and applications where precise operation is required.
Typical Data Center Applications
- Embedded controllers
- Monitoring modules
- Custom power electronics
- Communication boards
Snapak – Combining Protection and Switching
The Snapak family combines three functions into one device:
- Power switch
- Circuit protection
- Fuse-holder replacement
According to Airpax, this allows OEMs to reduce assembly complexity and increase panel density.
Typical Applications
- Service panels
- Operator control panels
- Maintenance interfaces
- Auxiliary systems
Data Center Application Guide
| Application | Recommended Series |
|---|---|
| Battery String Protection | IEL |
| DC Distribution Panel | IEL |
| Rectifier Cabinet | IEL |
| Power Shelf | IEL / IAR |
| Rack Equipment | IAR / IER |
| Network Infrastructure | IEG |
| BMS Controllers | IEG |
| Environmental Monitoring | IEG |
| Embedded Power Electronics | IPA |
| Operator Service Panels | Snapak |
Case Study: Designing a 48VDC Power Distribution Cabinet
Consider a modern edge data center using:
- 48VDC battery backup
- Rectifier modules
- Network switches
- Environmental monitoring
- Remote management electronics
A typical architecture could use:
IEL
For:
- Main battery branches
- DC power distribution
- Rectifier outputs
IEG
For:
- Monitoring systems
- Alarm circuits
- Controller power feeds
- Communications equipment
IPA
For:
- Embedded protection inside custom electronic assemblies
This layered approach helps isolate faults at the correct level while maintaining uptime for the rest of the system.
Why Amironic?
As Sensata Airpax’s representative in Israel, Amironic supports customers from concept through production.
Whether designing:
- A telecom cabinet
- An edge data center
- A battery energy storage system
- A DC distribution panel
- A rack-mounted appliance
our engineering team can help select the appropriate Airpax hydraulic-magnetic protection solution based on current, voltage, certifications, fault levels and installation requirements.
Frequently Asked Questions (FAQ)
What is a hydraulic-magnetic circuit breaker?
A hydraulic-magnetic circuit breaker uses a magnetic sensing mechanism rather than heat to detect overcurrent conditions. This allows the breaker to maintain consistent trip characteristics across a wide temperature range, making it suitable for mission-critical applications such as data centers, telecommunications systems and industrial equipment.
Why are hydraulic-magnetic breakers used in data centers?
Data centers require reliable and predictable circuit protection. Unlike traditional thermal breakers, hydraulic-magnetic breakers are largely unaffected by ambient temperature, helping reduce unexpected trips and ensuring consistent protection performance.
What is the difference between a thermal and a hydraulic-magnetic circuit breaker?
Thermal breakers rely on heat generated by current flow and can be influenced by surrounding temperature.
Hydraulic-magnetic breakers respond directly to current levels, providing more consistent protection across varying environmental conditions.
Are hydraulic-magnetic breakers suitable for DC applications?
Yes.
Hydraulic-magnetic technology is widely used in both AC and DC systems and is particularly well suited for modern 24VDC, 48VDC and battery-backed power architectures commonly found in data centers and telecommunications equipment.
Where are circuit breakers typically used inside a data center?
Circuit protection can be found throughout the facility, including:
- Power distribution panels
- Battery backup systems
- UPS equipment
- Rectifier systems
- Power shelves
- Cooling systems
- Monitoring and control equipment
- Telecommunications infrastructure
What are nuisance trips?
A nuisance trip occurs when a circuit breaker opens even though no actual fault condition exists.
Common causes include inrush currents, incorrect breaker selection or environmental influences. Minimizing nuisance trips is important because unnecessary outages can affect system availability.
What is a trip-free circuit breaker?
A trip-free circuit breaker will disconnect the circuit during an overload condition even if the handle is physically held in the ON position. This feature is available on many Airpax hydraulic-magnetic circuit protectors.
Which Airpax series is commonly used for rack-mounted equipment?
The Airpax IAR / IER family was specifically developed for rack-mounted applications and is designed to fit within 1U and 1RU installations.
Which Airpax series is suitable for compact equipment and control circuits?
The IAG, IUG and IEG families are widely used in electronic equipment, instrumentation, control systems and data processing applications where precise circuit protection is required.
Which Airpax series is suitable for embedded equipment protection?
The IPA family is often selected for embedded electronic equipment, instrumentation and applications requiring compact protection solutions and precise operation.
Can Airpax circuit protectors be used in battery-backed power systems?
Yes.
Airpax hydraulic-magnetic circuit protectors are available in AC and DC versions and are commonly used in applications involving power conversion, telecommunications, battery systems and critical infrastructure.
Why choose Airpax hydraulic-magnetic circuit protection?
Key advantages include:
- Consistent performance across temperature variations
- Accurate and repeatable trip characteristics
- AC and DC capability
- Long service life
- Multiple mounting and configuration options
- Proven use in telecom, industrial, military and critical infrastructure applications