Thermistor overload relay ABB CM-MSS

Description

Features of ABB CM-MSS

1 measuring circuit
Automatic reset
Overvoltage-protected power supply and measurement inputs
Increased immunity to interference according to EN 62061 with evaluation criterion "Fail-Safe"
Enclosure material with max. fire protection class UL 94 V-0
Tool-free mounting and dismounting on DIN rail
Screw connection
Width 22.5mm (0.89 inch)
For rail width 35mm
UL 508, CAN/CSA C22.2 No.14, IEC/EN 60947-5-1, IEC/EN 60947-8

Functionality and application possibilities

Thermistor Motor Protection Relay - Benefits and Advantages, Applications

The CM-MSx series thermistor motor protection relays protect motors with PTC temperature sensors against high temperatures. The temperature sensors are integrated into the motor windings, allowing them to directly measure motor heating.

Direct Temperature Measurement

In general, motor damage caused by overload or overheating can be prevented in various ways. Compared to indirect temperature measurement, which monitors the current flowing in the motor, the temperature inside the motor can be measured through direct temperature measurement. This allows for the direct control and evaluation of the following operating conditions:

Therefore, the effects of overheating, such as wear and electrical failures, can be avoided.

The direct measurement principle involves a combination of the thermistor motor protection relay and 3 PTC sensors that are directly installed by the manufacturer in the motor. These 3 PTC sensors are placed directly at the thermally hot spots, the motor windings.

Motor Monitoring

The thermistor motor protection relay measures the resistance of the PTC sensors, which indicates the internal motor temperature at any time. If the temperature in the motor winding rises excessively and

the rated response temperature (NAT) is reached, the thermistor motor protection relay detects this condition, and the output relay switches off.

This triggers the motor protector and disconnects the motor.

Application / Monitoring Function

The thermistor motor protection relay CM-MSS monitors the winding temperature and thus protects the motor against overheating, overload, and inadequate cooling according to the product standard IEC 60947-8, control units for built-in thermal protection (PTC) for rotating electrical machines.

Operation

The thermistor motor protection relays CM-MSS.12 and CM-MSS.13 are used to monitor the temperature of motors or generators equipped with PTC thermistor sensors (PTC temperature sensors) type A. The sensors are installed in the motor windings and measure the heating of the motor. As the temperature in the motor increases, the resistance in the PTC sensor also rises. If the motor overheats (>2.7 kO), the output relay drops out, and the corresponding LED signals overtemperature. A reset is only possible after the motor has cooled down (<1.2 kO).