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HV Relays - Power Capacity

ElecDesigner

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Hi,

I'm looking to switch High Voltage DC (a few KV) and am looking at relays such as these.....


My question is related to the switching power capability (stated here as 50W).
My understanding is that say if there is 1kV across the contacts just before they close I must have a current of 50mA or less directly after the contacts close (I assume that part is right using ohms law).
When the relay opens though, no matter what current is flowing, the volt drop across the contacts is going to be almost zero. Does this mean that switching power only comes into to the relay "make". I'm confused as I thought DC particularly causes a problem with "breaking" but here is seems that the limitation is very much the making I.V.
 

cupoftea

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make and break are the same pretty well...due to the bouncing that happens in each case.......they both involve multiple make and breaks.
Use an RC damper across the relay, it will reduce the sparking on the contacts at make/break.
 

ElecDesigner

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I was thinking there would be some inherent difference as (for DC) there will be close to 0V across the contacts on break but will likely be say 1KV across on make.
 

FvM

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Your considerations apply to a capacitive load that tends to maintain the voltage across the contact. That's not the case with resistive or even inductive load.
 

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