Relay: DPCO..?

Discussion in 'The Projects Forum' started by crankler, Dec 16, 2010.

  1. crankler

    Thread Starter New Member

    Dec 14, 2010
    I wanted to ask how DPCO (double pole change over) relay is operated. From what I've read, it's also called DPTT (Double Pole Triple Throw). It's amazing that with a very small size and coil voltage rating of only 5Vdc, it can switch loads of up to 250Vac and 150watts according to the datasheets. It just seem impossible to me knowing that most SPDT and DPDT relays of the same coil rating can't do it.

    So i wanna ask if with those given ratings, it can be used to simultaneously switch 2 electric fans, 220V 60watts each?

    Another question: How is it operated/used? There are 3 contacts for 1 pole. With 1 contact normally closed, how can i switch the wiper to the 2nd contact? to the 3rd contact?

  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    Can you link to a reference? I think you're confused by the terminology. From a Google search for: DPCO relay

    DPCO is a DPDT relay.

  3. crankler

    Thread Starter New Member

    Dec 14, 2010
    Looks like you're right. I just got confused with the terms.


    Senior Member

    Jul 1, 2008
    The current that relay contacts can handle are more related to coil current than coil voltage. Imagine these two scenarios. Two relays with a coil rating of 5V. One of these relays is the size of a sugar cube and the other is the size of a brick. The sugar cube relay contacts can handle 5A max and the coil draws current in the mA region. The brick relay, on the other hand, has contacts rated at 500 Amps. The massiveness of this relay would dictate that the coil would have to be powerful. This in turn would dictate that the coil would draw far more current than the sugar cube relay, probably in excess of 5 Amps. As an example, a starter motor solenoid coil, which is actually a relay, pulls quite a bit of current. It has massive contacts and a very heavy spring,