Why Choose the ABB CM-PSS.31S Three-Phase Monitoring Relay?
The ABB CM-PSS.31S (1SVR730784R2300) is an industrial three-phase monitoring relay designed to supervise phase failure, phase sequence, overvoltage and undervoltage conditions in three-phase electrical systems. Part of ABB's CM-PSS monitoring relay range, it provides a practical solution for monitoring the quality and availability of electrical supplies serving motors, machinery and industrial automation equipment.
Designed for a nominal three-phase voltage of 380 V AC, the CM-PSS.31S monitors line-to-line voltages against fixed overvoltage and undervoltage thresholds of ±10%. This corresponds to a monitored voltage band of 342–418 V AC. The relay also detects phase failure and offers selectable phase sequence monitoring, helping identify supply conditions that could disrupt the operation of connected three-phase equipment.
The ABB CM-PSS.31S uses a True RMS measuring principle and provides two change-over relay contacts for signalling to motor starters, contactors, alarms and automation controllers. A selectable ON-delay or OFF-delay, adjustable from 0.1 to 30 s or set to zero, allows the monitoring response to be adapted to the installation.
Powered directly by the monitored three-phase circuit, the relay requires no separate auxiliary power supply. Its compact 22.5 mm DIN rail-mounted housing, screw-terminal connections and three LED status indicators make it suitable for industrial control panels and motor control centres.
Key Advantages
- Comprehensive three-phase supply monitoring for industrial electrical installations.
- Detects overvoltage, undervoltage and phase failure.
- Selectable phase sequence monitoring helps identify incorrect phase rotation.
- Designed for 380 V AC nominal three-phase systems.
- Fixed ±10% voltage thresholds provide defined monitoring limits.
- 342–418 V AC monitoring band supports supervision of the specified supply voltage.
- True RMS measurement provides dependable voltage evaluation.
- Selectable ON-delayed or OFF-delayed tripping behaviour.
- Adjustable 0.1–30 s tripping delay, with a separate zero-delay setting.
- Two change-over contacts support control and alarm signalling.
- 250 V AC / 4 A output contact rating for compatible control circuits.
- Self-powered operation eliminates the need for a separate auxiliary supply.
- Three LED indicators provide convenient operating status information.
- Front-mounted controls simplify commissioning and configuration.
- Compact 22.5 mm housing width saves control cabinet space.
- Double-chamber cage screw terminals support secure electrical connections.
- Optional sealable transparent cover helps prevent unintended changes to the settings.
- Suitable for motor protection control circuits, industrial automation and electrical distribution monitoring.
Key Features
- ABB CM-PSS three-phase monitoring relay series.
- CM-PSS.31S model with screw-terminal connections.
- 380 V AC nominal line-to-line measuring voltage.
- 342–418 V AC monitored voltage band.
- 50/60 Hz rated supply frequency.
- Overvoltage monitoring with a fixed upper threshold.
- Undervoltage monitoring with a fixed lower threshold.
- Phase failure detection.
- Selectable phase sequence monitoring.
- Fixed ±10% overvoltage and undervoltage thresholds.
- True RMS measuring principle.
- Two change-over (SPDT) output contacts.
- 250 V AC / 4 A contact rating.
- Selectable ON-delay or OFF-delay.
- 0 s or 0.1–30 s adjustable tripping delay.
- 200 ms start-up delay.
- Powered directly by the monitored three-phase supply.
- Three LED status indicators.
- Front-mounted operating controls for delay and monitoring settings.
- Double-chamber cage screw-terminal technology.
- DIN rail mounting for industrial control cabinets.
- IP50 housing protection and IP20 terminal protection.
- Compatible with the optional ABB COV.11 sealable transparent cover.
Technical Specifications
- Manufacturer: ABB
- Series: CM-PSS Three-Phase Monitoring Relays
- Model: CM-PSS.31S
- ABB order code: 1SVR730784R2300
- ABB product group: 310921-Measuring & Monitoring Relays
- Product type: Three-phase monitoring relay
- Monitoring functions: Phase failure, phase sequence, overvoltage and undervoltage
- Rated control supply voltage: 3 × 380 V AC
- Nominal measuring voltage: 380 V AC line-to-line
- Overvoltage threshold: 418 V AC (+10%)
- Undervoltage threshold: 342 V AC (-10%)
- Monitored voltage band: 342–418 V AC line-to-line
- Voltage threshold adjustment: Fixed
- Phase sequence monitoring: Selectable
- Supply frequency: 50/60 Hz
- Supply type: AC
- Monitored conductors: L1, L2 and L3
- Neutral connection: Not required
- Measuring principle: True RMS (TRMS)
- Tripping delay: 0 s or adjustable from 0.1 to 30 s
- Tripping delay mode: ON-delay or OFF-delay, selectable
- Start-up delay: 200 ms
- Auxiliary supply: Not required; powered by measuring circuit
- Output contacts: 2 change-over contacts
- Contact configuration: 2 c/o (2 × SPDT)
- Contact rating: 250 V AC / 4 A
- Rated operational current AC-12: 4 A at 230 V AC
- Rated operational current AC-15: 3 A at 230 V AC
- Rated operational current DC-12: 4 A at 24 V DC
- Rated operational current DC-13: 2 A at 24 V DC
- Status indication: 3 LEDs
- Operating ambient temperature: -25 to +60 °C
- Storage temperature: -40 to +85 °C
- Housing protection rating: IP50
- Terminal protection rating: IP20
- Terminal type: Screw terminals
- Connection technology: Double-chamber cage screw terminals
- Mounting type: DIN rail mounting
- Product height: 85.6 mm
- Product width: 22.5 mm
- Product depth: 103.7 mm
- Dimensions (H × W × D): 85.6 × 22.5 × 103.7 mm
- Net weight: 0.132 kg
- EAN: 4016779851817
- Minimum order quantity: 1 piece
- Customs tariff number: 85364900
- RoHS compliance: Following EU Directive 2011/65/EU
Reliable Three-Phase Voltage Monitoring for Industrial Motor Protection
Industrial motors and automated machinery depend on stable three-phase electrical supplies. Excessive voltage, insufficient voltage, missing phases or incorrect phase rotation can lead to reduced motor performance, overheating, unexpected stoppages and damage to connected equipment. The ABB CM-PSS.31S three-phase monitoring relay helps detect these abnormal supply conditions and provides switching signals for appropriately designed protective control circuits.
The CM-PSS.31S continuously monitors the voltages between L1, L2 and L3 using its True RMS measuring principle. It is specifically designed for 380 V AC nominal three-phase supplies, with fixed undervoltage and overvoltage thresholds at 342 V AC and 418 V AC respectively. These thresholds correspond to ±10% of nominal voltage and are not user-adjustable.
When a monitored voltage moves outside the permitted band, the relay responds according to the selected delay mode. This enables the CM-PSS.31S to provide a signal that can be used to activate an alarm, stop a motor through an external contactor or inform a programmable logic controller that the three-phase supply is outside its specified limits.
The relay also includes phase failure detection, helping identify the loss of a phase in the monitored supply. Its selectable phase sequence monitoring can be enabled when correct phase rotation is important, such as in pump, compressor, conveyor and fan installations. This function is particularly useful during commissioning or after electrical maintenance, when supply conductors may have been reconnected.
The adjustable tripping delay offers additional flexibility. Users can select immediate operation or a delay from 0.1 to 30 s, with a choice of ON-delayed or OFF-delayed behaviour. This allows the response to be coordinated with the monitored process and helps avoid unnecessary reactions to certain brief supply disturbances, where the application permits delayed operation.
The two change-over output contacts can be connected to compatible control and alarm circuits. These contacts are intended for signalling and control purposes; the relay is not a circuit breaker, motor overload relay or direct motor power switching device. Any required disconnection of the main supply must be performed by appropriately rated external protective and switching equipment.
The self-powered design simplifies wiring because no separate auxiliary voltage source is required. The compact DIN rail housing, screw terminals, LED status indicators and front-mounted controls support efficient installation, commissioning and maintenance in industrial control cabinets.
Typical Applications
- Three-phase voltage monitoring in industrial electrical systems.
- Overvoltage and undervoltage detection for 380 V AC networks.
- Phase failure detection in motor starter circuits.
- Incorrect phase sequence detection during commissioning.
- Industrial motor control centres.
- Three-phase pump and pumping installations.
- Compressors and refrigeration equipment.
- Industrial fans, blowers and ventilation systems.
- Conveyor systems and material handling machinery.
- Automated production and packaging equipment.
- Industrial electrical distribution panels.
- Process control and industrial automation systems.
- OEM machinery requiring three-phase supply supervision.
- Alarm circuits for abnormal three-phase voltage conditions.
