leitmotif
Member
I thought I had posted this question here previously and tried looking it up - to no avail. If someone else can find it well thank you.
BACKGROUND belong to this electrical vehicle website and got into argument regarding using two swithces to switch 250 VDC.
Some people who I believe (generally) know what they are talking about say it can be done AND make the implication it can be done safely.
ASSUME a contactor two pole single throw rated at 125 VDC.
Both contacts are NO and rated for 20 or 25 amp. Not a fancy unit say cost about $25 so no blowout coils arc chutes or stuff you would find on larger units.
ADDED AFTER Chistoff 84 responded cause I forgot -- and assume contactor made by reputable outfit ie P & B Square D Allen Bradley etc - sorry Chris
QUESTION Can you safely use two contacts on a double pole relay that are each individually rated at 125 VDC
AND connect them in series to switch 250 VDC?
I have never seen this done (just dont recall it?) but that does not necessarily mean it can or cannot be done.
Seems to me that the logic I was told here before went
"both contacts will NOT open simulaneously therefore on is going to open the full voltage ie 250 which is double the rating of the contact"
I know that a lot of motor starter relays use a bar with contacts at each end which in theory supports the argument BUT these are designed from ground up to operate as designed.
Seems to me the answer is simple --
buy a contactor whose contacts are designed to switch the designed voltage and current.
Just checking to see if there is something I forgot or is there an exception to the rule??
Dan Bentler
BACKGROUND belong to this electrical vehicle website and got into argument regarding using two swithces to switch 250 VDC.
Some people who I believe (generally) know what they are talking about say it can be done AND make the implication it can be done safely.
ASSUME a contactor two pole single throw rated at 125 VDC.
Both contacts are NO and rated for 20 or 25 amp. Not a fancy unit say cost about $25 so no blowout coils arc chutes or stuff you would find on larger units.
ADDED AFTER Chistoff 84 responded cause I forgot -- and assume contactor made by reputable outfit ie P & B Square D Allen Bradley etc - sorry Chris
QUESTION Can you safely use two contacts on a double pole relay that are each individually rated at 125 VDC
AND connect them in series to switch 250 VDC?
I have never seen this done (just dont recall it?) but that does not necessarily mean it can or cannot be done.
Seems to me that the logic I was told here before went
"both contacts will NOT open simulaneously therefore on is going to open the full voltage ie 250 which is double the rating of the contact"
I know that a lot of motor starter relays use a bar with contacts at each end which in theory supports the argument BUT these are designed from ground up to operate as designed.
Seems to me the answer is simple --
buy a contactor whose contacts are designed to switch the designed voltage and current.
Just checking to see if there is something I forgot or is there an exception to the rule??
Dan Bentler
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