changing single phase to three phase

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Stevenfyeager

Senior Member
Location
United States, Indiana
Occupation
electrical contractor
A customer has single phase in a store and is asking me if I can change single phase to three phase for a couple of new machines. (a compactor and a baler)
I do mostly residential, I am not familiar with this. What transformer and approximate cost would that take? Thank you.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The only way without involving the POCO is a rotary converter or a solid-state equivalent.

Otherwise, this is why the high-leg delta came into being; modification of an existing service.

Is 3-phase power available from the existing utility, where you could add a 3-phase panel?
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Depending on HP, small VFDs can be a very cost efficient method for changing 1 PH
to 3 PH.

Adding them to a new piece of equipment that already comes setup might be a bit of an undertaking the first time. Plus all the liabilities you assume. Guessing they are already on location.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Is 3-phase power available from the existing utility, where you could add a 3-phase panel?
First best idea.
Depending on HP, small VFDs can be a very cost efficient method for changing 1 PH
to 3 PH. ...
Third best idea.

The second best idea is to see if changing the motor to a single phase is possible, it often is and changing a motor is not that hard most of the time. The manufacturer or a motor shop can help with this.
 

jumper

Senior Member

Besoeker

Senior Member
Location
UK
The second best idea is to see if changing the motor to a single phase is possible, it often is and changing a motor is not that hard most of the time. The manufacturer or a motor shop can help with this.
That's probably the most sensible option. Especially if the kit has not yet been procured.

That ignores the obvious question of why consider purchasing 3-phase plant when the site has just single phase?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
180214-0842 EST

In the post by Larry Fine at
http://forums.mikeholt.com/showthread.php?t=86869&page=3&p=691475#post691475

A primary (pardon the pun) advantage of the open Delta system over a closed Delta is that a third primary conductor is not required. In fact, only an open Delta system can be derived without three primary conductors.

Not only that, the primaries must be connected single-ended, meaning each uses the system neutral as one of its conductors. That's the only way to get the phase timing differences from two hot wires.

To clarify.

An open delta on its primary side must have 3 wires, one can be the neutral of a wye source, or the 3 wires can be from a delta source, or the 3 wires can be from the hot lines of a wye which can be viewed at the destination as a non-floating delta source..

The phasing of the input wires must be correct to get an open delta output. Further the choice of input wires will determine phase rotation.

.
 
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kwired

Electron manager
Location
NE Nebraska
That's probably the most sensible option. Especially if the kit has not yet been procured.

That ignores the obvious question of why consider purchasing 3-phase plant when the site has just single phase?
Unless it is over 15-20 hp where they just don't ordinarily make single phase motors that large, next most common reason I have run into is getting a "steal" on used equipment. Then they find out they don't have the correct supply to run them. If purchasing new equipment, usually is no problem to order the correct phase/voltage so long as it isn't something with a large motor to begin with.
 

Ingenieur

Senior Member
Location
Earth
10 HP
230 vac x 50 A = 11500 va
P = 10 x 746 = 7460 w
pf x eff = 7460/11500 = 0.65
if eff = 90%, pf = 0.72
convert to 480/100 hp base = 230/480 x 100/10 x 50
= 240 A (vs rated 163)

100 HP
480 x 163 = 78.24 kva
P = 100 x 746 = 74.6 kw
pf x eff = 74.6/78.24 = 0.954
if eff = 0.955 (as claimed), pf = 0.998

hmmmmm
 
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