10 hp inverter

darekelec

Senior Member
Location
nyc
Hi, guys.
I have a piece of machinery from Europe that contains 2 motors (3hp and 4hp) 3 phase and some other electronics. It was working well in a shop that had 3 phases available. On a new shop there is only 2 phases available.
what is your recommendation on an inverter?
 

darekelec

Senior Member
Location
nyc
Recommendations on make, model, place to buy or ask.
I can see this technology developed a lot within the last 10 years.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
... On a new shop there is only 2 phases available.
So you have L1, L2, N available but not L3? If you feed those into the wye side of a delta-wye transformer (with the delta side not connected to anything), then the 3rd phase will be present at the L3 wye terminal. The taps on the delta could be adjusted to tweak the L3 voltage if desired.
 

darekelec

Senior Member
Location
nyc
Do you mean that you only have two hots and a neutral, as in a single phase service?
Currently I have 2 hot legs and a neutral of 4 wire wye system. This is what local utility provides. In the old shop I had 3 hot legs and a neutral of 3 phase wye system. 208v nominal, 220 actual reading voltage.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Hi, guys.
I have a piece of machinery from Europe that contains 2 motors (3hp and 4hp) 3 phase and some other electronics. It was working well in a shop that had 3 phases available. On a new shop there is only 2 phases available.
what is your recommendation on an inverter?
For the 3HP motor you can buy a VFD that will accept single phase input and run a 3 phase motor, they are common and inexpensive. 4HP is not a valid HP size so it is likely an IEC motor rated in kW that comes out to 4HP when given 60Hz. Depending on the actual motor nameplate FLA you MIGHT find a single phase input VFD that would work, but you can always buy a 3 phase input VFD that is rated for at least 2X the motor FLA and will not trip on Phase Loss, it will do the same thing. The thing I will caution you against though is that there are numerous “no-name” or obscure VFDs on e-commerce sites like Amazon, eBay and others that are absolute junk coming from China and sold at impossibly low prices. Steer clear of those, stick to name brands that you recognize.

When you do this, it generally means changing the controls of your machine, because you have the drive REPLACE the motor starters, not go down stream of them, otherwise it damages the drives. It’s not too difficult to do though.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
Currently I have 2 hot legs and a neutral of 4 wire wye system. This is what local utility provides. In the old shop I had 3 hot legs and a neutral of 3 phase wye system. 208v nominal, 220 actual reading voltage.
That is really strange that the poco only provides two of the three phases when they have the third right there if it is truly a wye bank?
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Yes, you can use two 120V/120V single phase transformers like gar mentioned in post #6 to synthesize the third phase. I showed a connection of such transformers in posts 8 and 10 of this thread:
https://forums.mikeholt.com/threads/1-ph-to-3-ph-converter.2546600/#post-2546705

Like I said above you can also use a delta-wye. The voltage rating of the delta side is not important because it would not be externally connected.
In the drawing below windings 1, 2, and 3 of the wye are each coupled magnetically to windings 1, 2, and 3 of the delta, respectively.
You would connect your L1, L2, N to terminals A, B, and N of of the wye shown below. Windings 1 and 2 of the wye will therefore provide power to windings 1 and 2 of the delta (equivalently forming an "open delta" which then provides power to winding 3 of the delta). Delta winding 3 then powers winding 3 of the wye to produce the desired third phase C.

delta-wye_third_phase_from_L1-L2-N .jpg

Taps on the delta could be selected to achieve fine adjustments of the voltage on phase C.
 

kwired

Electron manager
Location
NE Nebraska
The fact I need 3 phases

It’s more of a residential and small commercial area. ‘Everybody gets 2 of 3 phases’
One other option can be to just have a full three phase service installed, it is already nearby and available unlike some isolated place miles away from the main distribution that only has a single phase line run to the location.

What it will take from POCO might factor in, but you can probably install a 100 or 200 amp three phase loadcenter and meter socket for around same price you will spend on conversion equipment, and will have three phase available should you ever need it for other equipment down the road.
 

darekelec

Senior Member
Location
nyc
Yes, you can use two 120V/120V single phase transformers like gar mentioned in post #6 to synthesize the third phase. I showed a connection of such transformers in posts 8 and 10 of this thread:
https://forums.mikeholt.com/threads/1-ph-to-3-ph-converter.2546600/#post-2546705

Like I said above you can also use a delta-wye. The voltage rating of the delta side is not important because it would not be externally connected.
In the drawing below windings 1, 2, and 3 of the wye are each coupled magnetically to windings 1, 2, and 3 of the delta, respectively.
You would connect your L1, L2, N to terminals A, B, and N of of the wye shown below. Windings 1 and 2 of the wye will therefore provide power to windings 1 and 2 of the delta (equivalently forming an "open delta" which then provides power to winding 3 of the delta). Delta winding 3 then powers winding 3 of the wye to produce the desired third phase C.

View attachment 2557786

Taps on the delta could be selected to achieve fine adjustments of the voltage on phase C.
71AF70FC-FC9C-4072-BE17-7197ECE5787F.jpeg Are you telling me I can wire a transformer like this to give me 3rd phase?
Delta - wye are easily available here , especially slightly used.
that would be the awesome

I don’t know where I would get 2 transformers that are 120/120 V
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
View attachment 2557790 Are you telling me I can wire a transformer like this to give me 3rd phase?
Delta - wye are easily available here , especially slightly used.
that would be the awesome

I don’t know where I would get 2 transformers that are 120/120 V

Yes, a delta-wye such as that one could be used if it has a sufficient kVA rating for your loads. A given load current on the 3rd phase coming from the transformer (say X3) will cause the same amount of current to be drawn by each of the other two windings of the wye (e.g., X1, X2) as that drawn from X3. And so a 15 kVA transformer could supply 5 kVA/120V ≈ 41.7A on the 3rd phase.

The X0 should not be bonded to the transformer housing or EGC.
One possible issue I see is whether the transformer will have sufficient margin below saturation with the 220V/208V ≈1.058 or 5.8% above nominal voltage that you mentioned. The taps on the delta side would have no effect on the volts-per-turn applied by the line inputs to X1 and X2, and so they would not be useful for compensating the input voltage level. Perhaps others could comment on whether this is a valid concern.
 
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darekelec

Senior Member
Location
nyc
Wow! This is interestin
My motors like higher voltages because they are from Europe. 230V is fine.
I oversized the transformer already.
Should I go this way?
 
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