Why Choose the ABB CM-SFS.21S Current Monitoring Relay?
The ABB CM-SFS.21S 1SVR730760R0400 is a versatile single-phase current monitoring relay designed for overcurrent and undercurrent supervision in AC and DC electrical systems. Part of ABB's CM single-phase monitoring range, it combines RMS current measurement with configurable thresholds, timing functions and relay outputs for dependable industrial current monitoring.
The CM-SFS.21S provides three selectable measuring ranges of 3–30 mA, 10–100 mA and 0.1–1 A. It supports window monitoring for both overcurrent and undercurrent conditions and uses a fixed hysteresis of 5% of the selected threshold value, allowing abnormal load or process-current conditions to be detected reliably.
A wide 24–240 V AC/DC control supply simplifies integration into different control systems. The relay provides two changeover (SPDT) contacts rated at 250 V / 4 A, configurable for separate minimum and maximum signals or a common signal, while adjustable start-up and tripping delays, selectable ON/OFF delay, latching and operating-principle functions provide additional flexibility.
Key Advantages
- Monitors both AC and DC current using an RMS measuring principle.
- Three selectable ranges: 3–30 mA, 10–100 mA and 0.1–1 A.
- Supports combined overcurrent and undercurrent window monitoring.
- Wide 24–240 V AC/DC control supply simplifies system integration.
- Configurable 2 × 1 c/o or 1 × 2 c/o output arrangement.
- Adjustable start-up and tripping delays help prevent unwanted switching.
- Selectable ON- or OFF-delay operation.
- Selectable open- or closed-circuit operating principle.
- Selectable latching function for retaining detected fault conditions.
- Compact 22.5 mm wide DIN-rail housing.
Key Features
- ABB CM-SFS.21S current monitoring relay.
- RMS measuring principle for AC and DC currents.
- 24–240 V AC/DC rated control supply.
- Overcurrent and undercurrent monitoring.
- 3–30 mA measuring range.
- 10–100 mA measuring range.
- 0.1–1 A measuring range.
- Fixed hysteresis of 5% of the threshold value.
- Start-up delay selectable between instantaneous and 0.1–30 s.
- Tripping delay selectable between instantaneous and 0.1–30 s.
- Selectable ON- or OFF-delay function.
- Selectable latching function.
- 2 changeover (SPDT) output contacts.
- Screw connection technology.
Flexible AC/DC Overcurrent and Undercurrent Monitoring
The ABB CM-SFS.21S uses an RMS measuring principle to monitor AC and DC currents across three selectable ranges from 3 mA to 1 A. Adjustable minimum and maximum thresholds enable window monitoring so that the relay can identify both undercurrent and overcurrent conditions and initiate the required alarm or control response.
The two changeover outputs can provide separate minimum and maximum threshold signals or operate together as a common signal. Adjustable start-up and tripping delays, selectable ON/OFF delay, open- or closed-circuit operation and latching provide further flexibility for monitoring motors, heaters, loads and industrial process currents.
Typical Applications
- AC and DC load current monitoring.
- Overcurrent and undercurrent supervision.
- Motor and machine load monitoring.
- Heater and heating-element supervision.
- Industrial process current monitoring.
- Detection of load loss or abnormal operating current.
- Automation and process control systems.
- Electrical control and distribution panels.
