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NO CONTACT CURRENT AND NC CONTACT CURRENT OF RELAY

forever074

Mar 14, 2014
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Mar 14, 2014
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I see datasheet of some C form relay, it show that NO contact current is greater than NC contact current.
Can you explain?
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AnalogKid

Jun 10, 2015
2,927
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Jun 10, 2015
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Yes. One of the things that determines contact rating is the force or pressure applied, pressing the contacts together. The higher the force, the higher the contact rating.

For the NC contact, the contact pressure is provided by the return spring only. This sprint strength is a compromise, because a strong spring places more force on the contacts, for higher contact rating, but the higher force spring requires a large relay coil to overcome when it operates. The NO contact pressure comes from the relay coil, and usually is much higher than the return spring force.

ak
 
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