1SVR550805R9300 ABB CM-MSE 24VAC Thermistor Motor Protection Relay

Why Choose the ABB CM-MSE 24VAC Thermistor Relay?

The ABB CM-MSE 24VAC (1SVR550805R9300) is a compact and reliable motor thermistor protection relay designed to monitor motor winding temperatures and help protect industrial electric motors against overheating. As part of the ABB CM-MSE thermistor relay series, it works with compatible PTC thermistor sensors embedded in motor windings to detect excessive temperatures and initiate a protective switching response.

This thermistor motor protection relay provides temperature-dependent monitoring rather than relying solely on motor current measurements. By evaluating the resistance of connected PTC sensors, the CM-MSE can detect overheating caused by motor overload, inadequate cooling, frequent starting or other abnormal operating conditions. Its integrated output relay enables straightforward connection to motor control and contactor circuits.

Designed for a 24 V AC control supply, the ABB CM-MSE offers a practical motor protection solution for industrial machinery, pumps, fans, compressors and automation systems. Its compact DIN rail-mounted housing makes it suitable for installation inside electrical control panels and motor control cabinets.

Key Advantages

• Reliable thermistor motor protection relay for industrial electric motors.
• 24 V AC rated control supply for compatible industrial control systems.
• Monitors motor winding temperatures using PTC thermistor sensors.
• Provides protection against excessive motor temperatures caused by overload or insufficient cooling.
• Temperature-based monitoring responds to actual motor thermal conditions rather than relying exclusively on current measurement.
• Integrated relay output supports motor contactor and control circuit integration.
• Automatic monitoring of the connected thermistor circuit during motor operation.
• Compact DIN rail-mounted construction saves space inside industrial control cabinets.
• Suitable for integration with motor starters, contactors and automation systems.
• Helps reduce unexpected motor failures, maintenance costs and production downtime.

Key Features

• ABB CM-MSE thermistor relay series.
• 24 V AC rated supply voltage.
• Designed for PTC thermistor motor temperature monitoring.
• Resistance-based monitoring of connected motor winding temperature sensors.
• Protective switching response when the thermistor resistance reaches the relay's operating threshold.
• Integrated output relay contact for motor protection signalling and control.
• Supports protection against motor overheating caused by abnormal operating conditions.
• Suitable for monitoring motors with embedded PTC thermistor sensors.
• Compact modular housing for industrial electrical control panels.
• DIN rail mounting for straightforward installation.
• Connection terminals for the control supply, thermistor sensor circuit and relay output.
• Designed for integration with industrial motor starters and control circuits.

Technical Specifications

• Manufacturer: ABB
• Series: CM-MSE Thermistor Relays
• Model: CM-MSE 24VAC
• ABB order code: 1SVR550805R9300
• ABB product group: 310921-Measuring & Monitoring Relays
• Product type: Thermistor motor protection relay
• Protection function: Motor winding overtemperature monitoring
• Rated control supply voltage: 24 V AC
• Supply type: Alternating current (AC)
• Sensor type: PTC thermistor
• Measurement principle: Temperature-dependent thermistor resistance monitoring
• Monitored equipment: Electric motors with embedded PTC temperature sensors
• Output type: Electromechanical relay
• Protective action: Output relay switching on detected overtemperature
• Mounting type: DIN rail mounting
• Installation location: Electrical control panels and motor control cabinets
• Connection type: Terminal connections
• Application category: Industrial motor temperature protection

Reliable Thermistor Motor Protection for Industrial Automation

Industrial electric motors can experience excessive temperatures as a result of overload, blocked ventilation, frequent starting, mechanical problems or unsuitable operating conditions. Conventional current-dependent motor protection devices may not detect every condition that causes excessive winding temperatures. The ABB CM-MSE thermistor relay provides additional thermal protection by monitoring temperature-sensitive PTC sensors installed directly within the motor.

During normal operation, the resistance of the connected PTC thermistors remains within the relay's permitted monitoring range. When the motor winding temperature reaches the sensors' rated response temperature, their resistance rises sharply. The CM-MSE detects this resistance change and switches its output relay, allowing the associated motor control circuit to disconnect the motor supply or initiate an appropriate protective response.

The 24 V AC supply configuration makes this version suitable for control systems using low-voltage AC control power. Its compact DIN rail-mounted design enables convenient installation alongside motor contactors, overload protection devices and industrial automation components.

For effective protection, the relay must be connected to compatible PTC thermistor sensors and correctly integrated into the motor control circuit. The CM-MSE monitors motor temperature through its sensor circuit and does not directly interrupt the motor's main power supply. An appropriately rated contactor or other suitable switching device is required to disconnect the motor when necessary.

Typical Applications

• Industrial three-phase motor winding temperature protection.
• Electric motors equipped with embedded PTC thermistor sensors.
• Pumps and industrial pumping systems.
• Fans, blowers and ventilation equipment.
• Industrial compressors and refrigeration machinery.
• Conveyor systems and material handling equipment.
• Packaging and manufacturing machinery.
• Industrial motor starters and contactor control panels.
• Processing machinery and automated production systems.
• OEM machine building and industrial automation installations.