Why Choose the ABB CM-SRS.21S Current Monitoring Relay?
The ABB CM-SRS.21S (1SVR730840R0400) is a compact and reliable single-phase current monitoring relay designed to detect overcurrent and undercurrent conditions in industrial electrical systems. As part of the ABB CM-SRS measuring and monitoring relay series, it provides accurate current supervision for electrical equipment, machinery and automation applications requiring dependable monitoring and control.
This monitoring relay features RMS current measurement for AC and DC currents, with three selectable measuring ranges and adjustable switching thresholds. Its configurable overcurrent and undercurrent monitoring functions, adjustable hysteresis and time delay allow engineers to adapt the relay to different operating requirements. Two changeover output contacts provide flexible signalling and integration with industrial control circuits.
With a wide 24–240 V AC/DC control supply and selectable current measuring ranges of 3–30 mA, 10–100 mA and 0.1–1 A, the CM-SRS.21S is suitable for monitoring electrical loads, control circuits and industrial equipment. Its compact 22.5 mm housing and DIN rail mounting design enable straightforward installation inside electrical control panels and automation cabinets.
Key Advantages
- Reliable single-phase current monitoring relay for industrial electrical systems.
- Wide 24–240 V AC/DC control supply for flexible installation.
- Three selectable measuring ranges covering 3 mA to 1 A.
- Configurable overcurrent and undercurrent monitoring functions.
- True RMS measurement for accurate AC and DC current supervision.
- Two changeover (SPDT) output contacts rated at 250 V / 4 A.
- Adjustable hysteresis and tripping delay help prevent unnecessary switching.
- Compact DIN rail mounting design simplifies installation in control cabinets.
- Screw terminals provide secure electrical connections.
Key Features
- ABB CM-SRS current monitoring relay series.
- Manufacturer part number: 1SVR730840R0400.
- 24–240 V AC/DC rated control supply voltage.
- Three selectable current measuring ranges: 3–30 mA, 10–100 mA and 0.1–1 A.
- RMS measuring principle for AC and DC current monitoring.
- Selectable overcurrent or undercurrent monitoring.
- Adjustable hysteresis: 3–30% of the threshold value.
- Adjustable tripping delay: instantaneous or 0.1–30 s.
- Two changeover output contacts with 250 V / 4 A contact rating.
- Open-circuit operating principle.
- Double-chamber cage connection terminals with screw connections.
- Compact 22.5 mm width for space-efficient panel installation.
- Optional sealable transparent cover for protection against unauthorised adjustments.
Technical Specifications
- Manufacturer: ABB
- Series: CM-SRS Current Monitoring Relays
- Model: CM-SRS.21S
- ABB order code: 1SVR730840R0400
- ABB product group: 310921-Measuring & Monitoring Relays
- Product type: Single-phase current monitoring relay
- Rated control supply voltage: 24–240 V AC/DC
- Monitoring function: Overcurrent or undercurrent
- Measuring principle: RMS measurement for AC and DC currents
- Measuring range 1: 3–30 mA
- Measuring range 2: 10–100 mA
- Measuring range 3: 0.1–1 A
- Hysteresis: Adjustable, 3–30% of threshold value
- Tripping delay: 0 s or adjustable 0.1–30 s
- Output contacts: 2 changeover (SPDT) contacts
- Contact rating: 250 V / 4 A
- Operating principle: Open-circuit principle
- Terminal type: Screw terminals with double-chamber cage connections
- Mounting type: DIN rail mounting
- Operating ambient temperature: −20 to +60 °C
- Storage temperature: −40 to +85 °C
- Dimensions (H × W × D): 85.6 × 22.5 × 103.7 mm
- Net weight: 0.152 kg
- EAN: 4016779852241
Reliable Current Monitoring for Industrial Electrical Systems
Current monitoring relays such as the ABB CM-SRS.21S continuously supervise electrical current and respond when the measured value crosses a configured threshold. By monitoring overcurrent or undercurrent conditions, the relay helps identify abnormal operating states such as excessive electrical loading, unexpected reductions in current or changes in equipment operation.
The CM-SRS.21S uses RMS measurement to monitor AC and DC currents across three selectable ranges. Engineers can configure the switching threshold, hysteresis and tripping delay to suit the application. When the configured switching conditions are met, the relay changes the state of its output contacts, allowing connected control systems to activate alarms, initiate shutdown sequences or perform other protective actions.
Its two changeover contacts allow integration with PLC inputs, contactor control circuits and industrial alarm systems. The wide control supply voltage range reduces the need for different relay variants across installations, while the compact DIN rail housing makes the device suitable for modern electrical distribution and automation panels.
Typical Applications
- Industrial electrical current monitoring and supervision.
- Overcurrent and undercurrent detection in control circuits.
- Electrical load monitoring in machinery and automation equipment.
- Motor and equipment operating condition monitoring.
- Current supervision in pumps, fans and processing machinery.
- PLC-based monitoring and alarm signalling systems.
- Industrial control panels and electrical distribution cabinets.
- Manufacturing and production equipment monitoring.
- OEM machinery and automated control systems.
- Electrical maintenance and condition monitoring applications.
