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Re: Contactor question

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi David,

Yes, I know well what your are thinking here. But, the contactors do not all make or break at the same time. Thus, the last in line to open will see the "full" load for that brief moment. (Inductive loads are nasty on contacts of any size). Likely, this particular contact will always be the "slow one" and it will eventually weld closed if opened and closed during a load, which is the key to it's use.

I use a 50A contactor. It is controlled by the PLC and will open if the VFD has an error or for a few other reasons (dead man switch open, key off, PLC glitch, etc.). This is "error" mode and is the only time the contactor would actually open during a load. During normal operation, I always have the contactor on before putting V and I into the tranny. The contactor I use has had no problems so far. IMO, 30A is a bit small for these swinging pig loads. Even 50A ratings I would consider risky.

Take care,
Bart

Tesla list wrote:

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