Voltage Sensing Relay

Written by Charles Peacock
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Voltage sensing relays have a lot of advantages over regular relays. They can be of particular use to electricians whose needs go beyond simple voltage metering and regulation. Let's take a look at some of the features of the better voltage sensing relays that you'll be able to find from electronics suppliers.

Features of Voltage Sensing Relays

A good voltage sensing relay will feature a 240VAC supply voltage with 45-60hz. It will typically have relay contacts for 16A 250VAC, 20A 120VAC and 20A 24VDC with a contact isolation of five kilovolts. These units have high temperature thresholds, and can be operated in conditions from -20 degrees centigrade to 50 degrees centigrade.

Voltage sensing relays can be used in both control and monitoring applications. They should have an eleven pin plug-in relay base, which is considered the industry standard. They should also feature indicators that display both power and the operating state.

When the input level coming into the unit passes a certain level (which can be set on the front control panel of the unit) the voltage and current relays will both energize. The relay will then stay energized until the voltage or current drops below the predetermined threshold (usually 10 per cent less than the trigger level). The other way to de-energize the unit is to simply disconnect the power supply.

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