12.Temperature Protection Using Thermistors - ABB REM 610 Technical Reference Manual

REM 610 Motor Protection Relay 1MRS 755537
Technical Reference Manual
Note!
RTD6 can be used to measure the ambient temperature for the thermal protection
element. In this case, RTD6A and RTD6T will not be in use. This state will be
indicated by dashes on the LCD and by "-999" when the set alarm/trip value is read
via the SPA bus.
Note!
For as long as the emergency start is activated, RTD1...6T will be increased by 10
per cent.
Temperature protection using thermistors
REM610 supports PTC thermistors.
When input RTD1/RTD4 is used with thermistors, a trip value, PTC1/PTC2, is set
for the respective input.
When the resistance of the thermistor exceeds the set trip value, PTC1/PTC2,
/
element 49/38-1 49/38-2 will generate a trip signal on expiration of the 2 s' fixed
operate time.
/
The trip signal from 49/38-1 49/38-2 will be reset in 800 ms after the resistance has
fallen below set trip value PTC1/PTC2>.
RTD sensor/thermistor connection
When connecting the RTD sensors and the thermistors to the RTD inputs, a
double-shielded cable is to be used. The cable shield is to be connected to the chassis
ground screw on the rear panel of the relay.
The RTD sensors and thermistors are to be connected to the RTD inputs according
to the three-wire connection principle. Consequently, the wire resistance will be
automatically compensated. The RTD sensor/thermistor is connected across the plus
and the minus terminal, and the negative side of the RTD sensor/thermistor to the
common terminal. The leads connected to the plus and the common terminal must
be of the same type and length.
36