ABB CM Measuring & Monitoring Relays

CM products serve different monitoring tasks in machinery, motor-control panels, power-distribution controls and process equipment. A voltage relay, a temperature relay and a liquid-level relay use different measuring inputs and cannot be selected by the CM prefix alone. Their output contacts form part of the control or alarm circuit; the connected switching and protective equipment must also be selected for the application.

Monitoring Functions in the Existing Model List

• Voltage and current: listed CM-ESS/CM-EFS voltage references and CM-SRS/CM-SFS current references support monitoring of electrical signals. Over/under or window monitoring, AC/DC input suitability and adjustable ranges depend on the device.
• Three-phase supplies: the table includes CM-MPS, CM-MPN, CM-PFS, CM-PVS, CM-PAS and CM-PSS references. Available functions include phase sequence, phase loss, voltage limits or phase unbalance, depending on the model. Confirm whether neutral is required and which faults the selected device detects.
• Motor thermistor protection: CM-MSS references monitor motor-winding temperature through PTC sensors. Check sensor-circuit requirements, fault detection and reset behavior in the exact product instructions. This is different from measuring motor load current with an overload relay.
• Temperature monitoring: CM-TCS and CM-TCN references evaluate temperature sensors. Confirm the supported sensor, number of inputs, measurement range, thresholds and output assignment. Display, communications and configuration features are version-specific.
• Liquid level: CM-ENS and CM-ENE references are for conductive liquids, with functions such as filling, draining or level alarms depending on the version. Check liquid conductivity, electrode arrangement and sensitivity; this is not a universal measurement method for every fluid.
• Insulation monitoring: CM-IWS and CM-IWN references monitor insulation resistance in unearthed IT systems. Match the device to the network’s AC/DC characteristics and permitted voltage/capacitance conditions. These devices are not interchangeable with residual-current circuit breakers.

CM-IVN.S and CM-IVN.P are coupling units: ABB lists them as related insulation-monitoring devices, rather than independent monitoring-relay bodies. They remain in the existing table; confirm the required monitoring relay and coupling arrangement together. Earlier CM references also remain available for identification, with their exact specifications checked individually.

Inputs, Supply & Output Contacts

Distinguish the monitored circuit or sensor input from the control supply. Some versions are powered by the monitored circuit; others require a separate supply. Confirm voltage, AC/DC suitability, frequency and terminal wiring from the selected device’s diagram. For current inputs, check the permitted measuring input and any required transformer arrangement in the exact instructions.

Confirm the required threshold or window, hysteresis and response/start-up delay where adjustable. Check fault memory, automatic/manual reset and open- or closed-circuit operating principle where applicable. Available settings and diagnostic functions vary between product families and versions.

Choose the required normally open/closed or changeover contacts and check their rating for the actual load and utilization category. A resistive-load rating does not establish suitability for every inductive coil. Match the output to the alarm, contactor or controller interface and check the required fault-state behavior.

Confirming a CM Selection & Requesting a Quote

Send the full product model, ABB order code or article number, quantity and destination country. For a new selection, include the monitoring task, system and control-supply voltage, AC/DC and frequency, wiring including neutral where relevant, sensor/electrode details, thresholds, delays, reset behavior and required output contacts. Confirm terminal type, installation space, ambient conditions and applicable regional approvals using the exact product data.

For an existing installation, add a readable nameplate photo and wiring or equipment details. Do not select an older reference or a proposed replacement solely by matching a headline voltage or the CM family name.

Related pages: Relays & Monitoring; CT Time Relays for timing functions; and Contact for quotation.

ABB references: Monitoring and control overview; temperature monitoring; liquid-level monitoring; insulation monitoring.