Intelligent Fault Strategy for DIN Rail Power Supplies

Jul 31, 2026
RECOM RACPRO electronic fuse modules for industrial power systems
Switch Mode Channel Protection: 24V DIN rail control cabinets contain critical power supply and electronic fuse (e-Fuse) protection equipment for a wide range of industrial applications. Quality and reliability of power delivery are essential system attributes. However, it is not only individual source failures that require protection. Equally important is preventing a fault in one piece of equipment from affecting the rest of the cabinet. Faults within the system must not compromise the stability of the overall control cabinet.

Table of Contents

If a single piece of equipment supplied by a module within the cabinet experiences a serious fault, a properly designed system maintains system stability and contains the failure within the affected supply. RACPRO1 DIN rail power supplies are typically designed with an overhead capability of 120% power at 45°C and a 150% power boost for up to 5s. They feature fast fuse tripping for rapid fault response and improved protection of both the power supply and the load.

DIN Rail Power Supply: Head-to-Head Comparison

RECOM compared its RACPRO1 DIN rail power supplies and e-fuses with those of two other leading manufacturers (referred to as Manufacturer A and Manufacturer B). The tests covered short circuit, overload, and capacitive startup conditions.

Short Circuit Protection Performance

Without proper protection, short circuit failures can lead to cascading effects and system-wide faults throughout the control cabinet.
Oscilloscope ripple on power supply outputs
Figure 1: Manufacturer A's equipment exhibited ripple on all outputs
In head-to-head tests, RECOM found that a short circuit in a cabinet stocked with equipment from Manufacturer A resulted in voltage spikes and ripple on all outputs. RECOMs e-Fuse isolates the effected channel without influencing the behavior of the other channels.
Oscilloscope showing voltage collapse
Figure 2: Manufacturer B’s equipment exhibited complete voltage collapse
The same test with equipment from Manufacturer B led to a complete voltage collapse, with all channels shut down. After repeated events, one channel sustained permanent damage.
Oscilloscope showing isolated channel fault
Figure 3: With RECOM’s RACPRO1, only the impacted channel was affected
RECOM RACPRO1 equipment isolated the failure. Only the affected channel shut down; no other channels experienced a voltage drop or ripple.

Overload Protection Performance

This series of tests simulated an overload fault on a 20A supply by subjecting four outputs each to an 8A load, for a total of 32A. The RACPRO1 units can be configured to prioritize outputs, and, in this scenario, the overload condition only affects the lowest-priority output. The RACPRO1 actively manages power instead of reacting unpredictably, reducing downtime and preventing erratic machine behavior.

Neither Manufacturer A nor Manufacturer B allows for channel prioritization. Under this test condition, both delivered the same result: an unpredictable failure with random channels shutting down.

Capacitive Startup and Inrush Current

Capacitive loads can draw large inrush current at startup. Without protection from high inrush loading, supplies can deliver poorly regulated power, fault to overload, or trip the circuit breaker. The RACPRO1 operates in true constant-current mode. Constant current regulates the startup load. RACPRO1 handles up to 4mF per ampere with adaptive startup extension up to 100ms.

The capacitive load test involved 40mF capacitance with an additional 10A load. The RACPRO1-4SP e-Fuse delivered a smooth ramp-up without impacting other channels under this test condition.
Smooth voltage ramp-up without disturbance
Figure 4: RACPRO1’s smooth ramp-up did not disturb other channels
The RACPRO1 delivers a linear voltage ramp-up without exceeding the power supply’s current limits.
Power supply failure with heavy ripple
Figure 5: Manufacturer A's equipment exhibited failure or heavy ripple
Equipment from Manufacturer A exhibited heavy ripple throughout the inrush load period. Manufacturer B’s equipment failed even with small capacitive loads.

RECOM Intelligent Fault Protection Strategy

Hiccup protection timing with increasing retry intervals up to 6.4s
Figure 6: Simple Daisy-Chaining und Load Wiring
RECOM’s built-in fault strategy for the RACPRO1 minimizes thermal stress, prevents faults from cascading across channels, and ultimately extends system lifetime and mean time between failure (MTBF).

The three pillars are:

  • Instant isolation of short circuits
  • Priority-based shutdown during overload conditions
  • Adaptive restart with hiccup mode up to 6.2s
Further, the true constant-current design keeps operational conditions such as high capacitive inrush loads from becoming a fault. The modules can be daisy‑chained or configured for sequential startup, making the RACPRO1 a foundational building block for stable, scalable cabinet architectures.
DIN rail power distribution comparison showing simplified daisy-chaining and reduced wiring complexity
Figure 7: Simple Daisy-Chaining und Load Wiring

Summary: System Stability in Control Cabinets

The RACPRO1 series performs a role far beyond that of a simple e-fuse and functions as an intelligent power distribution unit engineered for predictable and resilient system behavior. With constant-current startup, channel prioritization, guaranteed selectivity, and true channel-to-channel fault isolation, the RACPRO1 ensures that every load behaves as expected.
Intelligent e-Fuse solution in combination with a RACPRO AC/DC power supply
Applications
  Series
1 RECOM | RACPRO1-4SP Series | AC/DC, DIN-Rail, 4 Channels Output
Focus
  • Push-in connectors for tool-less wiring
  • Start-Up delay adjustable by switch
  • NEC Class 2 limit switchable (for 5A module)
  • Adjustable power limit & load indication by LED