Snubber Use For Relay - Presys DMY-2011 Technical Manual

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Instruments
Figure 23 - Jumpers not used for 0 to 10V input placed in the board conector

4.3 - Snubber use for relay

Relay modules are provided with circuits for eliminating electrical arch (RC
snubber). The snubbers are put in parallel with the relay contacts, by placing the
jumpers J1 and J2 localized on the back of the relay board. When the jumpers are
not placed, the relay contacts are kept without snubbers. The relay module is sent
from factory with the jumpers placed.
Note the position of the jumpers in the following figure. Depending on the relay
board version, the jumpers may be on the front or rear side.
Fig. 24 - Jumpers for selection of snubbers on the relay board
Alarm and control relays are extremely critical in control and safety of
industrial processes. In order to ensure the expected relay behaviour, consider the
following two loading conditions.
• High currents circulating through the relay contacts (from 20mA to 3A). When the
relay switches high currents there is the occurence of elecrical arch which damage
quickly the relay contacts. Besides, electrical noise is generated. In these conditions,
it is recommended to use the RC snubbers which come with the relay module
(placed jumpers).
• Low currents circulating through the relay contacts (less than 20mA). The relays
could not function properly when the jumpers are placed. In this case, the snubbers
mantain a 4.5mAac/9.0mAac current when connected to a 120VAC/220VAC circuit.
This current is enough, in certain casses, to power a horn or alarm lamps, preventing
their deactivation. In this situation, there is no need to use the snubbers and the
jumpers must be removed.
DMY-2011, DMY-2035 and DMY-2036
Jumpers 1 e 2
Maintenance
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