Keith Marshall wrote:

"Jon Elson" wrote in message
...

No, this is totally normal for control transformers
on a 3-phase supply.


Thanks!! That's really what I was asking about. It's just not a
situation I've needed to work on before.

But, where does your 3 phase power come from?
Is this an industrial location with utility 3-phase, or are you using
a "phase converter" in your garage?


It's an industrial situation, a welding & fabrication business with real
3-phase power.

You can measure the DC resistance of the contactor coil, but that
does not
indicate the AC load. Due to inductance,


I understand that, but often a resistance value is good enough to
determine whether the contactor's coil might be shorted. If I knew the
expected resistance I could at least have a starting point for
troubleshooting since resistance is much easier to test.

Since the thing still works, connect a meter in the secondary circuit
and
read the current with the contactor turned on. Then, get a
transformer to
suit.


The secondary is fused at 1-amp and this is supposed to be a 4-amp
transformer so Im not too concerned about that part of it.

I'm more concerned with the primary current because the primary of the
original (bad) transformer is open. I didn't check that before and was
expecting the secondary to be open instead. The problem with the new
transformer seems to be on the primary since it's happening even without
a load connected to the secondary. At this point I'm pretty much
convinced the new transformer was faulty.

I wish I'd measured the current draw on the primary but at this point
I'm figuring it's too late. Since it's smoking it's probably already
somewhat shorted and drawing far more current that it normally would.
At any rate, my next move is to contact mpja.com and see if they'll
replace it. If not I'll get one from a local appliance parts dealer
which I probably should have done in the first place. They show a 35VA
transformer for $18.95 and a 40VA version for $25.50. Either way I'll
be sure to check several things before I pull the trigger next time.

I may still try and check the secondary current first though.


something smells funny here. If You disconnected the load on the
secondary side and you are still getting heat on the secondary side?
Something is not correct.

Going by memory, you stated you had 2 primaries that allows you to
wire for 120 or 240 on the input, that being the case you should have an
order of H1 H2 H3 H4 in your case, L1 = H1, H2+H3, L2/L3 = H4; in other
words, you use both primary windings but in series. If that was a 120
volt source it would be L1 = H1+H3, L2/L3= H2+H4

Also, it may sound stupid however, make sure you do have the ground
as the ground on the plug coming in and no legs are grounded in the shop.

If you knew how many times this kind of stupid error happen with
extension cords and equipment cords being missed wired like this, hot
attached to ground etc., you'd be shocked.


Jamie