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PRESYS
Instruments
4.2 - Using snubber with relays
Relay modules are provided with circuits for eliminating electrical arch (RC
snubber). The snubbers can be 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 not placed.
Note the position of the jumpers in the following figure. The jumpers may be
localized on the front or the back side of the board, depending on its version.
Fig. 22 - 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 behavior, consider the following two
loading conditions.
High currents circulating through the relay contacts (from 20 mA to 3 A). When the
relay switches high currents there is the occurrence of electrical 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 20 mA). The relays
could not function properly when the jumpers are placed. In this case, the snubbers
maintain a 4.5 mAac/9.0 mAac current when connected to a 120 Vac/220 Vac circuit.
This current is enough, in certain cases, 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.
Note: If your relay module board does not have the mentioned jumpers, is
because it belongs to an older version. Apply it for the same reasons explained
above regarding the use of RC snubber. However, in this case, to remove the
snubber, it should remove the two capacitors of 0.1 x 250 V F located above the
relay.
Maintenance
Page 30
DMY-2030-Light-5S-Energy
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