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Re: Contactor question

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

David -

No, you can't use the (4) 30A contacts in parallel to switch a 120A load.

The reason is that the contacts are not mechanically "synchronized",  so
that they all do not make or break at exactly the same instant.

In the end, there will be one contact that carries the entire initial load,
even though the other contacts will close a few microseconds later. With
paralleled contacts switching an inductive load it will be the contact that
opens last that burns and erodes faster that the rest of the contacts.

Possibly the greatest danger in using a setup like this to switch the
primary circuit on a large Tesla coil is that because of excessive current
the first contact to close can weld closed, and maintain power to the system
even though power to the contactor coil is interrupted. In any large Tesla
coil system, there should be a backup manual power interrupt switch rated to
handle the full load current.

Regards,
Scott Hanson



Regards,
Scott Hanson
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, August 14, 2005 3:46 PM
Subject: Contactor question


> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Hi all,
>
> Just a quick question about relay contactors. Let's say that I have
> a 4-pole, 30 FLA inductive per pole rated contactor. Does this mean
> that I will have up 120 amp inductive rating of the contact points if I
> use all 4 of the poles in a parallel or series parallel fashion in a
single
> circuit to switch my pole pig transformer under a load?
>
> Thanks,
> David Rieben
>
>