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Module Overview
This circuit breaker module protects field wiring and connected devices from overloads. You can install Siemens 6ES5490-8MB21 directly into any SIMATIC S5 rack slot. The unit provides individual circuit protection for up to four external load circuits. it trips automatically when detecting overcurrent conditions on any channel.
Technical Specifications
| Parameter | Value |
|---|---|
| Dimensions (W x H x D) | 250 mm x 25 mm x 130 mm |
| Weight | 0.41 kg |
| Number of protected circuits | 4 independent channels |
| Rated voltage | 230V AC or 24V DC |
| Current rating per channel | 2 A (continuous) |
| Trip current threshold | 2.5 A ±10% |
| Trip time | < 100 ms at 2.5x rated current |
| Trip type | Thermal-magnetic (bimetallic + solenoid) |
| Reset method | Manual push-button per channel |
| Status indicators | 1 red flag per channel (tripped position) |
| Interface to backplane | S5 backplane connector (monitoring only) |
| Field wiring | Screw terminal block (input + output per channel) |
| Total onboard components | 68 discrete parts |
| Energy storage type | No capacitors (passive protection only) |
| Operating temperature | -10°C to +60°C |
Board Layout and Components
The PCB mounts four thermal-magnetic circuit breakers in a single row. Each breaker includes a bimetallic strip and a magnetic trip coil. Moreover, 68 discrete components include auxiliary contacts and status indication LEDs. The passive design contains no electrolytic capacitors or energy storage devices. Consequently, the module introduces no additional failure points to the control system.
Installation Process
You can mount Siemens 6ES5490-8MB21 into any standard SIMATIC S5 rack slot. The backplane connector provides optional status monitoring for the CPU. Furthermore, the front panel screw terminals accept incoming power and outgoing load wiring. Red trip indicators show clearly which channel has experienced an overcurrent fault.
Performance Advantages
This module trips within 100 milliseconds during severe overload conditions. The manual reset buttons require deliberate operator action after fault clearance. Therefore, equipment does not restart automatically after electrical faults. The four independent channels also protect multiple circuits within a single rack slot.
Safety and Compliance
Siemens 6ES5490-8MB21 meets CE, UL 508A, and RoHS standards. The unit stores no electrical energy that could create shock hazards. Hence, technicians can handle the module safely without any discharge delays.