230V 40A relay contact material

[hemnath]

I want to allow 230V, 40A Through a element, Which material will withstand. Please suggest.

 

[smijesh]

Copper with palladium coating is best ,
Current withstanding capacity depend on material property and material cross sectional area.

 

[hemnath]

Silver Tin Oxide AgSnO2 : Material is more resistant to welding at high making current peaks due to the tin oxide. Has a very high burn out resistance when switching high loads. Low degree of material migration under DC loads. Useful where very high inrush currents occur. Silver Tin Oxide is frequently chosen as the replacement relay contact material for Silver Cadmium Oxide which is more harmful.

Silver Tin Indium AgSnOinO : Similar to Silver Tin Oxide but more resistant to inrush.


How about Silver Tin Indium AgSnOinO or Silver Tin oxide AgSnO2?

Also It should be economical.

Can you help me to calculate the material cross sectional area.

 

[FvM]

What's the actual problem? Starting a relays fabrication? Or choosing a suitable relays from market?

The specification is rather incomplete, you surely know if you already reviewed manufacturer datasheets. Besides voltage and current capability, you'll also specify switched power and load type (resistive or inductive) together with a lifetime.

 

[hemnath]

I'm not finding the suitable relay from market. Not starting a relay fabrication.

Actually One of my friend has a relay with this contacts carry 415V, 9A. He asked me what to do if that contacts wants to carry 230V, 40A inductive load. I found that from many relay manufacturers datasheet, their contact material is AgSnOinO for 40A contact rating.

 

[FvM]

There are relays like Finder series 67 https://www.finder-relais.net/en/finder-relays-series-67.pdf, but they are not capable of disconnecting 40A 230V inductive load (AC-3 or AC-15). "Slightly" inductive load (AC-7a) is however feasible.

That's why I'm asking for an exact load specification. Problem with massive inductive load is the required volume for arc extinguishing. Only larger contactors have it.

 

[KlausST]

Hi,

Yes, resistive load is the most uncritical
Capacitive load causes very high inrush current but no problem when switching OFF
Inductive load causes low currents at switch ON (maybe just for the first microseconds), but high voltage when switching OFF --> arcing
Transformers may cause high inrush current for the first couple of halfwaves caused by core saturation.
Motors may cause high inrush current caused by the inertia of moving mass.

Klaus

 

[hemnath]

Thank you all for the valuable information.

Should I have to refer UL 508 for the contactor design and test requirements. Please clarify