DIN Rail Smart Protection: RACPRO1 E-Fuse Modules
Feb 12, 2025
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 marks a significant advancement in DC power protection, providing intelligent load current limiting, prioritization, enhanced overload and fault detection, and simplified installation and wiring. Unlike traditional fuses or circuit breakers, RACPRO1-4SP modules incorporate advanced logic for seamless fault management, ensuring reliable and efficient system assembly and operation in industrial automation environments. This paper outlines the key features, benefits, and technical specifications of the RACPRO1-4SP e-Fuses, emphasizing their critical role in modern automation power supply systems.
Introduction
Electrical systems require dependable protection mechanisms to maintain operational continuity and safeguard components from electrical faults. While conventional fuses and circuit breakers have long served this role, they present inherent limitations – such as the need for manual replacement, slow response to faults, and performance degradation over time due to age, load variations, and temperature.
The RACPRO1-4SP series consists of 4-channel electronic fuse (e-Fuse) load switches with independent overcurrent limit control and real-time output current monitoring. Each channel is individually protected, ensuring that an overload or fault on one load does not compromise the overall system's reliability or functionality. Multicolor LED indicators clearly display the output current status – green (within limit), yellow (approaching limit), orange (at limit), and red (overcurrent or short-circuit). A volt-free DC-OK output provides system health monitoring. Each channel can be independently switched ON or OFF to facilitate maintenance or fault diagnostics. The RACPRO1-4SP/24V/5A model supports a maximum of 5A per channel and offers a 150% power boost for 5 seconds, with the ability to tolerate overloads exceeding 150% for up to 100ms to prevent nuisance tripping.
Channels start up in a sequential manner to reduce input inrush current, with a configurable delay time. During system-wide overload conditions, channels disconnect in reverse order – ensuring that priority functions remain powered as long as possible. Output overload behavior is selectable between hiccup and tripping modes. For LPS (Limited Power Source) applications, the 5A modules can be configured to limit output power to below 100W per channel. With a high operational life expectancy of over 80,000 hours at 40°C, the modules also feature tool-less push-in and lever-release terminals for simplified wiring. Paired input and output terminals support straightforward daisy-chaining across multiple modules.
Currently, two 4-channel 24V modules are available: the RACPRO1-4SP/24V/10A, which provides four outputs rated up to 10A each, and the RACPRO1-4SP/24V/5A, offering four outputs of up to 5A (or 3.75A per channel when configured for LPS mode). Additional variants are planned for future release.
Why choose e-Fuses? Compared to conventional solutions, e-Fuses:
The RACPRO1-4SP series consists of 4-channel electronic fuse (e-Fuse) load switches with independent overcurrent limit control and real-time output current monitoring. Each channel is individually protected, ensuring that an overload or fault on one load does not compromise the overall system's reliability or functionality. Multicolor LED indicators clearly display the output current status – green (within limit), yellow (approaching limit), orange (at limit), and red (overcurrent or short-circuit). A volt-free DC-OK output provides system health monitoring. Each channel can be independently switched ON or OFF to facilitate maintenance or fault diagnostics. The RACPRO1-4SP/24V/5A model supports a maximum of 5A per channel and offers a 150% power boost for 5 seconds, with the ability to tolerate overloads exceeding 150% for up to 100ms to prevent nuisance tripping.
Channels start up in a sequential manner to reduce input inrush current, with a configurable delay time. During system-wide overload conditions, channels disconnect in reverse order – ensuring that priority functions remain powered as long as possible. Output overload behavior is selectable between hiccup and tripping modes. For LPS (Limited Power Source) applications, the 5A modules can be configured to limit output power to below 100W per channel. With a high operational life expectancy of over 80,000 hours at 40°C, the modules also feature tool-less push-in and lever-release terminals for simplified wiring. Paired input and output terminals support straightforward daisy-chaining across multiple modules.
Currently, two 4-channel 24V modules are available: the RACPRO1-4SP/24V/10A, which provides four outputs rated up to 10A each, and the RACPRO1-4SP/24V/5A, offering four outputs of up to 5A (or 3.75A per channel when configured for LPS mode). Additional variants are planned for future release.
Why choose e-Fuses? Compared to conventional solutions, e-Fuses:
- 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 of RACPRO1 E-Fuse Modules
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 continuously monitored. If the DC supply begins to drop – due to an overloaded main power source or an AC line brownout – the e-Fuse initiates sequential load shedding to ensure the highest-priority load remains powered (Fig. 3).
Fig. 3: Load shedding with priority during a supply under voltage condition
If the input voltage drops below the under voltage lockout (UVLO) threshold, the e-Fuse disconnects all load channels. This function prevents operational issues caused by inadequate supply voltage during startup or brownout conditions, including:
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 drops below the under voltage lockout (UVLO) threshold, the e-Fuse disconnects all load channels. This function prevents operational issues caused by inadequate supply voltage during startup or brownout conditions, including:
- 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 checks whether the fault condition persists at progressively longer intervals (100ms, 200ms, 400ms, 800ms, etc.), up to a maximum of 6.4 seconds (Fig. 5). During this time, the DC-OK contact opens to signal a fault condition.
- This intelligent hiccup mechanism significantly reduces electrical and thermal stress on the power supply, system components, and wiring. It also simplifies fault diagnosis by minimizing interference from repetitive hiccup spikes, while still providing a reasonable automatic reset time once the fault is resolved.
- After the fault has cleared, the affected channel automatically re-enables, and the DC-OK contact closes to indicate normal operation.
Fig. 5: Intelligent Hiccup Interval Control
Intelligent Latch Protection (When in Latching mode)
- If a sustained short circuit or overload lasts longer than 100ms, the latching mode disables the affected output and opens the DC-OK contact to signal a fault condition.
- Once the fault is resolved, ...
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