DIN Rail Smart Protection: RACPRO1 E-Fuse Modules
2025/02/12
The RACPRO1 e-Fuse series offers advanced DC protection with intelligent load current limiting, overload and fault detection, and simplified installation. Unlike traditional fuses, the modules integrate advanced logic for reliable fault handling in industrial automation systems.
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Abstract
The RACPRO1 e-Fuse series represents a breakthrough in DC power protection, offering intelligent load current limiting and prioritization, enhanced overload and fault detection, and simplified installation and wiring. Unlike traditional fuses or circuit breakers, RACPRO1-4SP modules integrate advanced logic for seamless fault handling, enabling reliable and efficient system assembly and operation in industrial automation applications. This paper discusses the key features, advantages, and technical specifications of RACPRO1-4SP e-Fuses, highlighting their role in advanced automation power supply systems.
Introduction
Electrical systems rely on dependable protection mechanisms to ensure operational continuity and safeguard components against electrical faults. Conventional fuses and circuit breakers have served this purpose but come with inherent limitations such as the need for manual replacement, slow fault response, or changing performance with age, load and temperature.
The RACPRO1-4SP series are 4-channel electronic fuse (e-Fuse) load switches with independent overcurrent limit control and real-time output current indication. Each channel is separately protected so that overload or fault conditions on an individual load do not affect overall system reliability or function. The useful LED indicators show the output current and change from green to yellow (current within limit) to orange (current at limit) to red (overcurrent or short-circuit). A volt-free DC-OK output can be used to monitor system function. Each channel can also be switched ON or OFF to ease fault diagnostics or for maintenance.
The RECOM e-Fuses RACPRO1-4SP/24V/5A are available with 5A maximum channel current and 150% power boost for 5s but can handle >150% overload for up to 100ms to avoid nuisance tripping. The channels power up in sequence to reduce the input inrush current with a pre-settable delay time. Under system overload conditions, the channels will disconnect the loads in reverse sequence, keeping essential functions running to the last. Output overload hiccup or tripping mode is adjustable by a switch and the 5A modules can also be set to limit the available power to below 100W per channel for LPS installations. The e-Fuses have a high lifetime expectancy >80,000h/40°C and easy wiring with tool-less push-in and lever-release terminals. The input and output terminals are also paired to allow easy daisy-chaining between modules.
There are currently two 4-Channel 24V modules available, the RACPRO1-4SP/24V/10A with four outputs of up to 10A each and the RACPRO1-4SP/24V/5A with four outputs of up to 5A (or 3.75A in LPS mode). More variations will be developed in due course.
Why e-Fuses? Compared to traditional fuses or circuit breakers:
The RACPRO1-4SP series are 4-channel electronic fuse (e-Fuse) load switches with independent overcurrent limit control and real-time output current indication. Each channel is separately protected so that overload or fault conditions on an individual load do not affect overall system reliability or function. The useful LED indicators show the output current and change from green to yellow (current within limit) to orange (current at limit) to red (overcurrent or short-circuit). A volt-free DC-OK output can be used to monitor system function. Each channel can also be switched ON or OFF to ease fault diagnostics or for maintenance.
The RECOM e-Fuses RACPRO1-4SP/24V/5A are available with 5A maximum channel current and 150% power boost for 5s but can handle >150% overload for up to 100ms to avoid nuisance tripping. The channels power up in sequence to reduce the input inrush current with a pre-settable delay time. Under system overload conditions, the channels will disconnect the loads in reverse sequence, keeping essential functions running to the last. Output overload hiccup or tripping mode is adjustable by a switch and the 5A modules can also be set to limit the available power to below 100W per channel for LPS installations. The e-Fuses have a high lifetime expectancy >80,000h/40°C and easy wiring with tool-less push-in and lever-release terminals. The input and output terminals are also paired to allow easy daisy-chaining between modules.
There are currently two 4-Channel 24V modules available, the RACPRO1-4SP/24V/10A with four outputs of up to 10A each and the RACPRO1-4SP/24V/5A with four outputs of up to 5A (or 3.75A in LPS mode). More variations will be developed in due course.
Why e-Fuses? Compared to traditional fuses or circuit breakers:
- E-Fuses offer fast fault detection and either latching or automatic reset. Each channel’s current limit is independently adjustable with up to 150%/5s power boost.
- They handle overcurrent, undervoltage, and short circuit conditions in a controlled and repeatable way under all operating conditions.
- E-Fuses allow for load prioritization and sequential startup and shutdown to reduce inrush currents, making them ideal for complex electrical systems.
Key Benefits and Features
Fast and Intelligent Fault Reaction
Traditional protection devices like fuses react quickly to overcurrent events but lack reset functionality, while electromechanical circuit breakers (RCD) or polymer PTCs are resettable but are slow to respond.
RACPRO1 e-Fuses integrate the best of both worlds:
RACPRO1 e-Fuses integrate the best of both worlds:
- Quick load disconnection during severe overload or short circuit conditions with automatic recovery after fault resolution.
- Overcurrent tolerance of up to 150% for 5 seconds to eliminate false triggering.
- Programmable fault response modes (e.g., latching with remote reset or automatic restart).
Priority Load Management
- Sequential start-up minimizes inrush currents. Each channel is switched on in sequence at power up, spreading the inrush current over time to protect the main power supply (Fig.1).
- On power-down, the sequence is reversed, ensuring that the channel with the highest priority (Ch.1 – typically the system controller power supply) always starts up first and shuts down last.
- Under system overload conditions, the modules also offer sequential load shedding.
- This ensures that critical loads are maintained while non-essential devices are temporarily disconnected under overload conditions.
Fig. 1: Sequential start-up
Overload and Short-Circuit Protection
- Temporarily accommodates overloads without immediate disconnection.
- Automatically isolates severe faults to protect power supplies and connected loads, while ensuring that the remaining loads remain powered up (Fig.2).
Fig. 2: Short circuit (e.g. on Channel 2) does not affect the operation of the other outputs
Under Voltage Lockout Protection
The input voltage is constantly monitored. If the DC supply voltage starts to dip because the main power supply is overloaded or the AC line suffers a Brown Out, then the e-Fuse starts sequentially shedding loads to ensure that the priority load always stays powered up (Fig.3).
Fig. 3: Load shedding with priority during a supply under voltage condition
If the input voltage falls below the under voltage lockout limit (UVLO), then the e-Fuse disconnects all the load channels. This function avoids operational problems caused by insufficient supply voltage during start-up and operational dips/brown-out conditions such as:
A hysteresis ensures clean UVLO function to increase overall system stability (Fig 4).
Fig. 4: UVLO Function
Fig. 3: Load shedding with priority during a supply under voltage condition
If the input voltage falls below the under voltage lockout limit (UVLO), then the e-Fuse disconnects all the load channels. This function avoids operational problems caused by insufficient supply voltage during start-up and operational dips/brown-out conditions such as:
- Signal corruption
- Weak transistor gate drive
- Latch-up
A hysteresis ensures clean UVLO function to increase overall system stability (Fig 4).
Fig. 4: UVLO Function
Intelligent Hiccup Protection (When in Hiccup Mode)
- In the event of a sustained short circuit or overload, the hiccup function will check if the condition still exists in ever increasing time intervals (100ms, 200ms, 400ms, 800ms, etc.) up to 6.4s (Fig.5). The DC-OK contact opens to indicate a fault condition.
- This unique intelligent hiccup function significantly reduces the hiccup stress on the power supply, system components and wiring and makes fault diagnosis easier by reducing the interference due to repetitive hiccup spikes, yet still offers an acceptable automatic reset time once the fault has been cleared.
- After the fault has been cleared, the channel is automatically enabled and the DC-OK contact closed to indicate normal operation.
Fig. 5: Intelligent Hiccup Interval Control
Intelligent Latch Protection (When in Latching mode)
- In the event of a sustained short circuit or overload lasting more than 100ms, the latching mode will disable the affected output and open the DC-OK contact to indicate a fault condition.
- After the fault has been cleared, the latched output can be reset remotely using the remote reset input or by manually turning off and on the affected channel or by powering down the module.
- The DC-OK contact is then closed to indicate normal operation.