Why Choose the ABB CM-SRS.21S Current Monitoring Relay?
The ABB CM-SRS.21S is a compact and reliable single-phase current monitoring relay designed for overcurrent or undercurrent supervision in industrial control and automation systems. With ABB order code 1SVR730841R0400, this CM-SRS series relay operates from a 110–130 V AC control supply and provides RMS measurement of both AC and DC currents.
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, while adjustable hysteresis from 3–30% of the selected threshold value enables stable switching behaviour matched to the requirements of the application.
The relay provides two changeover (SPDT) output contacts rated at 250 V / 4 A and 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 particularly suitable for DIN-rail installation in industrial control panels.
Key Advantages
- Reliable overcurrent or undercurrent monitoring for industrial electrical systems.
- 110–130 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 (SPDT) output contacts provide flexible control and signalling.
- Compact 22.5 mm-wide housing conserves DIN-rail space.
Key Features
- ABB CM-SRS single-phase current monitoring relay series.
- 110–130 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.
- 250 V / 4 A contact rating.
- 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 allow industrial control systems to detect 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 excessive load, 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 control or alarm 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.
