Off-Delay Device; Description; Configuration; Mounting - Siemens SIRIUS 3RT Series System Manual

2.7.5

OFF-delay device

2.7.5.1

Description

The OFF-delay device prevents a contactor from dropping out unintentionally when there is a
short-time voltage dip or voltage failure. The OFF-delay device supplies a downstream, DC-
operated contactor with the necessary energy during a voltage dip, ensuring that the
contactor does not drop out. The 3RT2916-. OFF-delay devices have been specially adapted
to the 3RT contactors (sizes S00 and S0) and the 3RH21 contactor relays (size S00), and
are available in the versions shown below.
Table 2- 35
Design of the OFF-delay device (operating
mechanism system)
24 V DC
110 V UC
220/230 V UC
2.7.5.2

Configuration

The OFF-delay device operates without external voltage on a capacitive basis and can be
energized with either AC or DC (24 V version for DC operation only). Voltage matching is
only required for AC operation and is performed using a rectifier bridge.
A contactor opens after a delay when the capacitors integrated in the OFF-delay device are
switched in parallel to the contactor's magnet coil. In the event of voltage failures, the
capacitors discharge via the magnet coil, thus delaying opening of the contactor.
If the command devices are located upstream of the OFF-delay device in the circuit, the
device will be activated with every opening operation. If the activation takes place
downstream of the OFF-delay device, an OFF-delay only applies if the line voltage fails. The
mean OFF-delay value is around 1.5 times the specified minimum time.
2.7.5.3

Mounting

The 3RT2916-. OFF-delay devices are available with the following mounting types:
● Screwing onto a mounting plate
● Snapping onto a 35 mm DIN rail according to DIN EN 60715.
SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
Versions of the OFF-delay device
SIRIUS 3RT2 contactors/contactor assemblies
Order number
3RT2916-2BE01
3RT2916-2BK01
3RT2916-2BL01
2.7 Accessories
183