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Motor thermistor relay MTR02

MTR02 relay controls motor winding temperature. It is based on the measurement of PTC thermistor which is built in electrical motor. Device also controls short-circuit or probe disconnection. The relay has galvanically separated measuring inputs and one output double-throw contact 8 A.

  • motor winding temperature monitoring
  • short circuit monitoring and sensor disconnection
  • galvanic insulated measuring inputs
  • output relay contact 8 A
  • univerzal power supply 89 ... 264 VAC
  • one DIN rail module size
  • optical status LED signalization


If the motor temperature is under maximum limit (PTC = 3.3 kΩ), green LED is ON and contact 15-16 is closed. As soon as the motor winding is overheated (PTC > 3.3 kΩ), red LED turns ON and contact 15-18 switches ON. Switch OFF operation will occur after the motor winding temperature drops down (PTC 1.8 kΩ) and button RESET has been pressed. This feature protects motor against spontaneous start and it is possible to be disabled by cross connection of terminals T1, R1 (AUTORESET). There is also possibility to use terminals T1, R1 for external reset. If the PTC input is short-circuited, alarm appears and terminal 15-18 will switch ON.

Technical features

Parameter Value
supply voltage 89 ... 264 VAC
self consumption max. 1.5 VA
galvanic insulation of measuring terminals ANO
thermistor resistance PTC operating state 200 Ω ... 3.3 kΩ
thermistor resistance PTC alarm state > 3.3 kΩ
condition of alarm status canceling PTC < 1.8 kΩ + RESET
number and type of output contacts 1 x changeover
nominal current 8 A
switching power max. AC 2000 VA
trigger current 30 A
nominal/max switching voltage 250 VAC / 440 VAC
mechanical lifetime 3 x 107
electrical lifetime 1 x 105 250 VAC, 8 A
ambient temperature -20 ... +55 °C
working position any
mounting IEC 60715 (DIN 35)
protection degree IP 20
electrical strength 4 kV
maximum input wire diameter max. 2 x 1.5 mm2; 1 x 2.5 mm2
weight 75 g
dimensions 90 x 18 x 65 mm
related norms IEC 60255-1


BMR trading - Hasal s.r.o.
Horní lán 1200/17
779 00 Olomouc
Czech Republic

+420 778 066 566