Why Choose the ABB CM-SRS.21S Current Monitoring Relay?
The ABB CM-SRS.21S is a compact single-phase current monitoring relay designed for reliable overcurrent or undercurrent supervision in industrial control and automation systems. With ABB order code 1SVR730841R1400, this CM-SRS series relay operates from a 220–240 V AC control supply and monitors both AC and DC currents using an RMS measuring principle.
The CM-SRS.21S provides three selectable measuring ranges of 3–30 mA, 10–100 mA and 0.1–1 A. It can be configured for either overcurrent or undercurrent monitoring, with adjustable hysteresis from 3–30% of the selected threshold value to provide stable switching behaviour for a wide range of current-supervision applications.
Two changeover (SPDT) output contacts rated at 250 V / 4 A provide flexible interfacing with PLC inputs, contactors, alarms and interlocking circuits. An adjustable ON-delay tripping time of 0 or 0.1–30 s, screw connection technology and a compact 22.5 mm housing make the CM-SRS.21S well suited to DIN-rail control-panel installations.
Key Advantages
- Reliable overcurrent or undercurrent monitoring for industrial electrical systems.
- 220–240 V AC control supply for compatible industrial control circuits.
- Three selectable measuring ranges covering 3 mA to 1 A.
- RMS measuring principle supports AC and DC current monitoring.
- Adjustable 3–30% hysteresis for stable threshold switching.
- Adjustable 0 or 0.1–30 s tripping delay helps accommodate transient current conditions.
- Two changeover output contacts provide flexible control and signalling options.
- Compact 22.5 mm-wide housing conserves DIN-rail space.
Key Features
- ABB CM-SRS single-phase current monitoring relay series.
- 220–240 V AC rated control supply voltage.
- Configurable overcurrent or undercurrent monitoring.
- Selectable measuring ranges of 3–30 mA, 10–100 mA and 0.1–1 A.
- RMS measuring principle for AC and DC currents.
- 3–30% adjustable hysteresis.
- 0 or 0.1–30 s adjustable ON-delay tripping time.
- 2 c/o (SPDT) relay outputs.
- Output contacts rated at 250 V / 4 A.
- Open-circuit operating principle.
- Screw connection technology with double-chamber cage terminals.
- Compact DIN-rail mounting format.
Reliable Current Monitoring for Industrial Systems
Current monitoring relays enable industrial control systems to identify electrical loads operating above or below defined current limits. The ABB CM-SRS.21S can be configured for overcurrent or undercurrent supervision, making it suitable for detecting overload, underload, loss of load and other current-dependent operating conditions.
Its three selectable RMS measuring ranges enable supervision from 3 mA up to 1 A. Adjustable hysteresis provides stable switching around the selected threshold, while the adjustable tripping delay can help prevent brief current variations from causing unnecessary alarm, control or shutdown actions.
Typical Applications
- Industrial control and automation panels.
- AC and DC current supervision.
- Machine load and operating-state monitoring.
- Motor and actuator control circuits.
- Pump and fan monitoring systems.
- Heating element and electrical load supervision.
- Alarm, signalling and interlocking circuits.
- OEM machinery and production equipment.
