Electromagnetic relay is a relay that drives the movable part of the magnetic circuit by the electromagnetic attraction generated by the control current passing through the coil, and realizes the function of opening, closing or switching the contacts. Common electromagnetic relays include DC electromagnetic relay and AC electromagnetic relay.
Several factors to be considered in selecting relay;
(1) The rated working voltage refers to the voltage required by the coil when the relay works normally. Depending on the model of relay, it can be AC voltage or DC voltage.
(2) DC resistance refers to the DC resistance of the coil in the relay, which can be measured by a multimeter.
(3) The pull-in current refers to the small current that the relay can generate pull-in action. In normal use, the given current must be slightly larger than the pull-in current, so that the relay can work stably.
(4) Generally, the working voltage applied to the coil should not exceed 1.5 times of the rated working voltage, otherwise, a large current will be generated and the coil will be burned.
(5) The release current refers to the large current generated by the relay to release the action. When the current in the pull-in state of the relay decreases to a certain extent, the relay will return to the non-energized release state. At this time, the current is far less than the pull-in current.
(6) Contact switching voltage and current refer to the voltage and current that the relay is allowed to load. It determines that the relay can control the voltage and current, and it cannot exceed this value when it is used, otherwise it will easily damage the contacts of the relay.