Thermistor Trip Protection Relays


DIN rail mounting protection relays for use in single and three phase systems. Available in 55mm x 112mm or 100 x 112mm DIN rail cases.


For over protection, under protection and combined under & over protection available in AC current AC voltage & frequency versions. Millivolt trip, DC voltage trip, Reverse Power, Phase sequence & Phase balance relays also available in our extensive range of protection relays.

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Selection Guide

M200-TTAAutomatic reset
M200-TTMManual reset

Typical Applications

The M200 thermistor trip accepts positive temperature coefficient inputs. Typically used to monitor temperature in motor windings. When the thermistor is below its predetermined temperature the resistance is low and the M200-TTA/TTM relay is energised. A green LED indicates the safe condition. When the temperature exceeds the predetermined temperature the resistance of the thermistor rapidly increases, this increase in temperature is detected by M200-TTA/TTM and the relay is de-energised. The M200-TTM is manually set, once the relay has de-energised it will stay de-energised regardless of the temperature being monitored. The relay can only be reset via the reset push button on the front of the unit. The M200-TTA automatically resets once the temperature has dropped below the trip point. A yellow LED is provided to indicate the condition of the power supply.

Technical Specifications

Positive temperature coefficient thermistors:Sensors can be connected in series but 1500Ohms must not be exceeded
Trip Point2500-3500 Ohm
Reset Point1500-2300 Ohm
Total resistance of sensor loop1500 Ohms max at nominal temperature
DifferentialFixed 5%
RepeatabilityBetter than 5%
M200-TTMManual via push switch on front of product
A.C. Voltage115/230/400V±25%/45-65Hz/2VA
D.C. Voltage24 volt(±20% / non-isolated)< 3 watt
WEIGHT&CASEApprox 0.3kg. 55mm case

Ordering Information

Product CodeAuxFreqOption


1A.C. auxiliary in range 57.7 to 480 volts
2Calibration at temperature other than 23ºC

Connection Diagrams

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