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.

 

I_Relay=30Vdc/450Ω = 66.7mA, where did the 500mA came from?

 

I_Relay=30Vdc/450Ω = 66.7mA, where did the 500mA came from?

it is the max current limit set

 

it is the max current limit set

Do you have the link of spec about the relay?

 

Do you have the link of spec about the relay?

http://www.leachintl2.com/english/english2/vol0/properties/00095.html

 

http://www.leachintl2.com/english/english2/vol0/properties/00095.html

I still can't find where is the 500mA, but I think it's ok, because the relay will draw current by itself according to the resistance, but the resistance will affected by the temperature.