Page 758 - Motor protection and control Manual motor starters, contactors and overload relays

7/2 ABB MOTOR PROTECTION AND CONTROL

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Thermistor motor protection relays
Benefits and advantages, Applications

The thermistor motor protection relays of the CM-MSx range protect motors with
PTC sensors against high temperature. These sensors are incorporated in the motor
windings thus measuring the motor heat directly.

Direct temperature measuring Monitoring the motor
Generally, motor damages caused by overload or overheat- The thermistor motor protection relay measures the resis-
ing situations can be prevented in different ways. Compared tance of the PTC sensors which reflects the internal motor
to the indirect temperature measuring which monitors the temperature permanently.
motor current, the temperature inside the motor can be If the temperature in the motor windings rises excessively
measured by direct temperature measuring. and reaches the nominal response temperature (NRT), the
This enables direct control and evaluation of the following thermistor motor protection relay detects this situation and
operating conditions like: the output relay switches off.
• Heavy duty starting By doing so the motor contactor gets triggered and
• Increased switching frequency switches off the motor.
• Single phase operation
• Phase unbalance CM-MSS functionality video
• High ambient temperature
• Insufficient cooling
• Breaking operation
07
Therefore the consequences from overheating like abrasion
as well as electrical failures can be prevented.
The direct measuring principle is carried out by a combina-
tion of the thermistor motor protection relay and 3 PTC sen-
sors which are installed directly in the motor by the manu-
facturer. Those 3 PTC sensors are placed directly at the
thermal hotspots, the motor windings.

Characteristics CM-MSS(1) Features (1)

• Different types of contacts available • Additional functions:
- 1 x 2 c/o (SPDT) contacts - Dynamic interrupted wire detection
- 2 x 1 c/o (SPDT) contact - Short-circuit monitoring of the sensor circuit
- 1 n/o and 1 n/c contact - Non-volatile fault storage
• 1 or 2 measuring circuits - Single or sum evaluation
• Different types of reset functions • Easy configuration via DIP switches
- Automatic • LEDs to distinguish between different failure causes
- Manual • Screw connection technology or Easy Connect Technology
- Remote available
• Rated control supply voltages • Test/Reset button available
- 24 V AC/DC (1) Depending on device the characteristics vary, for detailed overview see "Selection
- 24-240 V AC/DC table CM-MSx range" on page 4.
- 110-130 V AC, 220-240 V AC
• Approvals / Marks

A C R K E I(1) / a b
Characteristics CM-MSE
• Auto reset
• Connection of several sensors (max. 6 sensors connected
in series)
• Monitoring of bimetals
• 1 n/o contact
• Excellent cost / performance ratio