Thermistor Protection - Eaton EMT62 Manual

1.3.2 Thermistor protection

1 EMT6 Thermistor Overload Relays for Machine Protection
For the protection against overtemperature, up to six PTC resistor
temperature sensors to DIN 44081 PTC thermistors, or up to two
temperature sensors to DIN 44082 Triple PTC thermistors with a PTC
resistance of R ≦ 250 Ω , or nine sensors with a PTC resistance of
K
R ≦ 100 Ω can be connected to the EMT6 terminals T1-T2 (￫ Figure 6,
K
page 49).
12000
4000
3600
IEC-
Tripping range
1650 1600
Resetting
range
750
60
NAT
NAT NAT NAT
–20° –5° +5°
Figure 2: Characteristic for temperature monitoring with thermistor
The EMT6 overload relay switches off at R = 3600 Ω ±10 % and switches on
again R = 1600 Ω ±10 %. The contacts 13-14 and 21-22 change over in the
event of a shutdown caused by a signal at the thermistor input (￫ Figure 3,
page 46).
￫
With temperature monitoring with thermistors, no dangerous
condition can occur should a sensor fail as the device would
directly switch off.
DANGER

Response of the thermistor monitoring unit must also result in a
direct shutdown when the motor is controlled by means of an
inverter. This must be ensured by circuit design.
DANGER

A separate overload protection system must be installed for the
electrical equipment.
EMT6 10/16 MN03407006Z-DE/EN www.eaton.com
Tripping
Reset
Tolerance limits
Temperature [°C]
NAT
+15°
1.3 Description of device
39