ABB REM 610 Technical Reference Manual page 54

REM 610
54
Motor Protection Relay
Technical Reference Manual
Under normal operating conditions, the applied external voltage is divided between
the relay's internal circuit and the external trip circuit so that at least 20 V remains
over the relay's internal circuit. If the external trip circuit's resistance is too high or
the internal circuit's too low, due to welded relay contacts, for instance, the voltage
over the relay's internal circuit will fall below 20 V (15...20 V), which will activate
the trip-circuit supervision.
The operation condition is:
(
U – R + R + R
c ext int s
where
• U = operating voltage over the supervised trip circuit
c
• I = current flowing through the trip circuit, ~1.5 mA
c
• R = external shunt resistor
ext
• R = internal shunt resistor, 1k
int
• R = trip coil resistance
s
The external shunt resistor is used to enable trip-circuit supervision also when the
circuit breaker is open.
The resistance of the external shunt resistor is to be calculated so that it does not
cause malfunction of the trip-circuit supervision or affect the operation of the trip
coil. Too high a resistance will cause too high a voltage drop, which in turn will
result in the operation conditions not being fulfilled, whereas too low a resistance
may cause faulty operation of the trip coil.
The following values are recommended for the external resistor, R
Table 4.1.5-1 Recommended values for R
Operating voltage, U
48 V dc
60 V dc
110 V dc
220 V dc
The circuit breaker is to be provided with two external contacts, one opening and one
closing contact. The closing contact is to be connected in parallel with the external
shunt resistor (R ), which will enable trip-circuit supervision when the circuit
ext
breaker is closed. The opening contact is to be connected in series with the external
shunt resistor (R ), which will enable trip-circuit supervision when the circuit
ext
breaker is open; see Fig. 4.1.5.-1.
Trip-circuit supervision can be selected either via the HMI or with parameter V113.
) I × ≥ ⁄
20Vac dc
c
Ω
ext
Shunt resistor R
c
,
1.2 kΩ 5 W
,
5.6 kΩ 5 W
,
22 kΩ 5 W
,
33 kΩ 5 W
1MRS 752263-MUM
:
ext
ext