David asked in Science & MathematicsEngineering · 8 years ago

# need help understanding dpdt relays?

This is my first time building a circuit which includes a power dpdt relay. Could someone please explain what do coil voltage, turn on voltage (max), and turn off voltage (min) mean? For example, this one particular dpdt relay that I saw online has coil voltage, turn on voltage, and turn off voltage ratings at 24VDC, 18VDC, 2.4VDC, respectively.

Relevance
• 8 years ago

The coil is rated to handle continuous 24V. on its coil (read 24/7), without overheating.

Because of the distance from the coil core, the voltage has to be approaching 18V. (this is the maximum voltage at which changeover occurs) on the coil to attract the armature. But having now closed the gap between armature and coil core, it stays there until the voltage on the coil reduces to not less than 2.4V. Then the armature releases.

This all relates to ANY relay, not just DPDT. However pull in and drop out voltages can change, you only have the data for 1 particular relay make and configuration.

In the end, you use 24V. on the coil. In most circuits there will be no voltage when the armature releases, but in some electronically switched voltages, some voltage can remain on the coil, which is why in this case it must not exceed 2.5V., or the relay armature will not release. The relay remains ON when it should have moved to OFF.

• 3 years ago

Relay Turn On Voltage

• Anonymous
8 years ago

The relay is rated to operate reliably at 24 volts DC. 18 volts is the minimum voltage that will cause the relay to operate the contacts. The relay will stay operated until the voltage drops below 2.4 volts. This is because the current required to attract the armature is more than the current required to hold it once attracted.

• Gale
Lv 4
4 years ago

For the best answers, search on this site https://shorturl.im/axe5l

Some of the terms you used to label your photobucket picture are confusing. This is what you need: Blu N/C = from generator NTRL Yel Comm = output, connect to APC Backup Battery NTRL120 vac input. Org N/O = from Mains/ service power breaker NTRL Gry N/C = from generator HOT Prp Comm = output, connect to APC Backup Battery HOT120 vac input. Brn N/O = from Mains/ service power breaker HOT The N/C and N/O relay connections are inputs. The Comm relay connections are outputs. The N/C connection is normally closed when the relay coil is de-energized. It opens when the relay coil is energixed. The N/O connection is normally open when the relay coil is de-energized. It closes when the relay coil is energized. These terms can be confusing to a person not accustomed to working with relays. The (relay in a box) coil connections = two wires that are Wht/ Blk should be connected to the Mains breaker. If mains power is on, the (relay in a box) coil will be energized. The Yel Comm = output, connect to server NTRL input and Org N/O = from Mains breaker NTRL will be connected. The Prp Comm = output, connect to server HOT input and Brn N/O = from Mains breaker HOT will be connected. You are operating on mains power. If mains power fails, the (relay in a box) coil will be de-energized. The Blu N/C = from generator NTRL and Yel Comm = output, connect to server NTRL input will be connected. The Gry N/C = from generator HOT and Prp Comm = output, connect to server HOT input.will be connected. You are operating on generator power. If the server requires less than 20 amps to operate, the (relay in a box) which is rated at 20 amps should be okay. If you do not understand my explanation, I will do a drawing and post it for you to look at. If you need it, click on my Avatar picture, go to my Activity Page and email me. Ben

• Irv S
Lv 7
8 years ago

Sounds like an elelctrically held relay with a coil rated for 24V. (Max.), holding,

that will operate to 'close' at 18V. and 'drop-out', (or 'open'). at 2.4V.