Electromechanical latching relay pull-in voltage_Technical issue under different environments

Discussion in 'General Electronics Chat' started by vinodquilon, Nov 2, 2014.

  1. vinodquilon

    Thread Starter Member

    Dec 24, 2009
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    We are using MIL standard Latching Electro-mechanical relays having dual ON/OFF coils. During screening process the relays are being subjected to pull-in voltage

    measurements for both ON & OFF coils in SRC (25 degree Celsius),COLD (8 degree Celsius) & HOT (80 degree Celsius) conditions. For pull-in measurement, the coil voltage

    starts at 0V and gradually increasing to 28V in continuous manner. Pull-in will occur in 6-16V range. Status monitoring (Open/Close) is done at relay poles.

    The anomaly is that the pull-in voltage measured at Hot is showing values lesser than Cold and Cold value is higher than SRC. This observation is against the normal

    intuition of pull-in voltage HOT>SRC>COLD.
    For example, The pull-in of RL-1 ON coil shows 11.496V (ISRC), 15.042V (Cold), 17.719V (Hot). That is SRC reading is 3.5V lesser than Cold.Also the difference voltage

    (3.5V) shows inconsistency under repeated tests of the same part.The curreny limit of 30V source is set at maximum coil current of relay as per data sheet.
    The relay specifications are 450 Ohm coil, 15A/28V DC contact, 30V DC coil/500mA.

    The deviation is observed only for 0.2% of total relays screened per batch.All others are operating well.

    I hope for feedback.
     
    Last edited: Nov 2, 2014
  2. ScottWang

    Moderator

    Aug 23, 2012
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    I_Relay=30Vdc/450Ω = 66.7mA, where did the 500mA came from?
     
  3. vinodquilon

    Thread Starter Member

    Dec 24, 2009
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    it is the max current limit set
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    Do you have the link of spec about the relay?
     
  5. vinodquilon

    Thread Starter Member

    Dec 24, 2009
    234
    0
  6. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
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