3 Phases to 2 phases.

[itsmoked]

I've assembled a 3 phase motor starter for a 1/2hp pump that was, "going to be 3 phase", but is now "going to be single phase".

It's a small contactor with electronic overloads. I don't really want to rip these out (it's all 2x) since next week it will probably relapse to, "it's going to be 3 phase", again.

The contactors are more than adequate for the current change.

Does anyone see a problem with just running the second phase back thru the third phase so the electronic overloads remain happy and the system remains three phaseable?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

That's usually the fix. All it will care about is that current is flowing through all 3 elements, it's not going to be comparing phase angles or anything. What brand of SSOLs?

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[waross]

I agree with Jeff.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[DTR2011]

Thats how its tested (1 phase) in the field. Loop a single phase current through all three phases.

 

[itsmoked]

The make is Metasol.


Bottom of first page:

http://factorymation.info/catalog/fmcat_LScont_ol.pdf

Thanks for the confirmation everyone.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[panelman]

those look like standard thermal rather than electronic.

You'll be lucky if one selected for three phase current will turn up enough to cover the equivalent single phase current

 

[electricpete]

I'm not familiar with electronic overloads.

What happens if you left a phase with no current... unbalance trip? (and the unbalance based on magnitude, not considering phase angle?)

=====================================
(2B)+(2B)' ?

 

[itsmoked]

Hmmm.. It states protection is:
Differential
Phase loss
and
Overcurrent.

It doesn't really say "electronic" does it..

I don't expect it to cover the entire range with just one model.

Funny thing.. Today they said, "Ah, I think we're going to stick with three phase."

This was after they'd decided 120V single phase on Thursday.


EP that's what the discussion on running one phase back thru the third set was about.

What exactly do they mean about Differential?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[panelman]

Differential means it will trip if the current through each pole isn’t the same, they are pretty low tech, each pole has a resistance in it which heats up with current flow and mechanical linkages trip it if either all three poles are passing too much current or one pole is different to the others.

As others have mentioned, on single phase motors the trick is to loop a current path back and put it through the overload again so you end up with each pole carrying the same current.

 

[LionelHutz]

It is just a fairly basic bimetallic overload so you just pass current through each pole by looping if necessary.

The story would be different if you had used an electronic LS overload. They monitor for phase order and phase loss and they look for more than simply having current in each phase.