Max Relay Output Conversion

Discussion in 'General Electronics Chat' started by ERobishaw, Jul 28, 2008.

  1. ERobishaw

    Thread Starter New Member

    Jul 21, 2008
    3
    0
    Given a DPDT relay rated at .5A @ 120VAC,
    Using 24VAC instead of 120V,
    Does it compute that the relay will handle 2.5A @ 24VAC ?

    (i.e., 120/24 * .5A = 2.5A)

    Or is that bad math?

    Here's the full specs, if it matters:
    http://www.altronics.com.au/download/ndb/brochures/s/S4150.PDF

    Meisei m4-24h
    1A 24V DC / .5A 120V AC
    Max ratings
    Power 60W DC / 120VA AC
    Switching Current 2A DC/AC
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    It already tells you in your datasheet.

    Contacts
    Arrangement.......................................................................... 2 Form C
    Type ......................................................................Bifurcated Crossbar
    Material
    Movable Contact ................................Gold clad Silver-Palladium Alloy
    Stationary Contact..............................Gold clad Silver-Palladium Alloy
    Ratings (Resistive Load) ..........................1A 24V DC / 0.5A 120V AC
    Max. Ratings (Resistive Load)
    Max. Switching Power..........................................60W DC / 125VA AC
    Max. Switching Voltage ........................................220V DC / 250V AC
    Max. Switching Current ......................................................2A DC / AC
    Min. Switching Load ..................0.01mA 10mV DC (Reference Value)
    Expected Life (Min. Operations)
    Mechanical............................................................................100 million
    Electrical (Resistive Load) ............................0.5 million at 1A 24V DC
    0.2 million at 0.5A 120V AC
    Contact Resistance ..............................................50mΩ Max. at initial

    Greetings,
    Bertus
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    The answer was given by bertus but i want to add that the current rating of a relay is not calculated like the way you did it. The voltage rating for a relay is not given to calculate the power rating but not to apply a voltage greater than this voltage because you will create sparks on the contacts. Of course the voltage plays a little role on how much current the contacts can carry but because they have very low resistance the power dissipated by them is almost the same even with low and high voltages.
     
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