Siemens SIRIUS 3RT Series System Manual page 131

Technical background information
The operating range of the coil for coupling relays covers a voltage range of 0.7 to 1.25 x U
(U = rated control supply voltage). This wide operating range has been used as a basis in
s
order to ensure that the supply voltage of the electronic controls stays within the required
voltage tolerances. According to DIN 19240, the supply voltage of electronic controls with
24 V DC covers a range of 20.4 V to 28.8 V. If you take an additional voltage drop of up to
3 V within the output stages into account, the contactor drive must function without errors at
voltages of between 17.4 V and 28.8 V. The 3RT20 and 3RH21 coupling relays for electronic
controls work reliably from 17 V to 30 V, which corresponds to a voltage range of
0.7 x U
contactor relays according to IEC 60947, DIN EN 60947 (VDE 0660), this is a significantly
expanded operating range.
The illustration below shows the voltage ranges for electronic controls and mechanisms of
contactors and contactor relays with a rated control supply voltage U
1
2
3
4
Figure 2-7
SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
to 1.25 x U . Compared to the operating range of 0.85 to 1.1 x U
s s
Supply voltage range for electronic controls according to DIN 19340
Operating range for contactors according to (VDE 0660 Part 102)
Voltage range for electronic outputs at ≤ 3 V internal voltage drop
Operating range of contactors for electronic controls
Coupling relays, voltage ranges
SIRIUS 3RT2 contactors/contactor assemblies
s
2.4 Configuration
s
for contactors and
s
= 24 V DC:
131