A timing relay is a component which is designed to time events in industrial automation systems by closing or opening contacts before, during or after a set timing period. There are three main families of timing relays: b DIN rail mounted relays ( RE7 , RE8 , RE9 , RE17 , RE22 , REXL ) designed for mounting on DIN rails in an enclosure. b Miniature plug-in relays ( REXL ) designed to be plugged into sockets. b Panel mounted/plug-in relays RE48A designed for mounting on the panel front to five users easy access to the settings. These relays have one, two or four outputs. Sometimes the second output can be either timed or instantaneous. If the power is switched off during the timing period, the relay reverts to its initial position. Application examples: b opening of automatic doors b alarm b lighting in toilets b car park barriers, etc
The following definitions explain the operation of the relays: b Relay output: This is the most common type of output. When the relay is energized, the moving armature is attracted by the coil and so actuates the contacts, which change state. When the relay is de-energized, both the armature and the contacts revert to their initial position. This type of output allows complete isolation between the supply and the output. There are three types of output contacts: C/O : changeover contact, i.e. when the relay is de-energized, the circuit between the common point C and N/C is closed and when the relay is operating (coil energized), it closes the circuit between the common point C and N/O.
C NC NO
N/C : a contact that is closed without being actuated is called a Normally Closed (N/C) contact.
N/O : a contact that closes when actuated is called a Normally Open (N/O) contact.
b Solid state output: This output is entirely electronic and involve no moving parts; service life is therefore increased. b Breaking capacity: The current value that a contact is capable of breaking in specified conditions. b Mechanical durability: The number of mechanical operating cycles of the contact or contacts. b Minimum switching capacity (or minimum breaking capacity): This is the minimum required current which can flow through the contacts of a relay. b G (Gate) input: Gate input allows timing in progress to be interrupted without it being reset.
Zelio Timer Relays
DIN rail mounted timer relays Miniature plug-in timer relays with sockets Panel-mounted/plug-in timer relays
RE48A RE22 RE17 REXL