Does anyone have some information on what rating an individual transformer would need to be when configured into a Auto-Wye connection from 208 to 230 in order to feed a 400 amp panelboard. Some of the conductor sizing on the engineers submitted diagram doesn't seem quite right. I read some information regarding this connection and they say it can handle much more than the rated kva. Haven't ran into this one before, any information would be helpful.
3 phase boost set-up for tanning beds
- Thread starter phil
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Re: 3 phase boost set-up for tanning beds
Based on the assumption that you a applying a 4w system wye-wye and the reference that I have you will need (3) 5kva 1ph B-B transformers with 120x240 pri -12/24 sec wired correctly as boost transformers. The transformer manufacturer should have a the correct transformer ordering information and wiring diagram available for you.
Based on the assumption that you a applying a 4w system wye-wye and the reference that I have you will need (3) 5kva 1ph B-B transformers with 120x240 pri -12/24 sec wired correctly as boost transformers. The transformer manufacturer should have a the correct transformer ordering information and wiring diagram available for you.
hurk27
Senior Member
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- Portage, Indiana NEC: 2008
Re: 3 phase boost set-up for tanning beds
Phil
Buck boost transformers are only boosting a few KVA to raise the voltage so they will be many times lower then the rated load. Square D has allot of info on them at :
Square D buck/boost
Click on the calculator to figure what size you need.
Phil
Buck boost transformers are only boosting a few KVA to raise the voltage so they will be many times lower then the rated load. Square D has allot of info on them at :
Square D buck/boost
Click on the calculator to figure what size you need.
Re: 3 phase boost set-up for tanning beds
I will try to explain what he meant.
Lets say the tan bed is 30 amps. at 230 volts that equals 30 x 230=6900 or 6.9 Kw.
But in this case of a boosting transformer we are only boosting the voltage 24 volts.
That same 6.9 Kw transformer is good for 288 amps. at 24 volts.So you size the Kw accoring to your boosting voltage which is 24 volts.
24x30=720 watts or .720 kw.
I will try to explain what he meant.
Lets say the tan bed is 30 amps. at 230 volts that equals 30 x 230=6900 or 6.9 Kw.
But in this case of a boosting transformer we are only boosting the voltage 24 volts.
That same 6.9 Kw transformer is good for 288 amps. at 24 volts.So you size the Kw accoring to your boosting voltage which is 24 volts.
24x30=720 watts or .720 kw.
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Re: 3 phase boost set-up for tanning beds
Please be aware that if you are boosting a wye system that the neutral will also get boosted. Your 208Y/120 will become 230Y/133.
Please be aware that if you are boosting a wye system that the neutral will also get boosted. Your 208Y/120 will become 230Y/133.
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Re: 3 phase boost set-up for tanning beds
Vln = Vll/1.732
Vln = Vll/1.732
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Re: 3 phase boost set-up for tanning beds
No, I meant neutral. Actually the voltage N-G may be different as well as the voltage L-N.
On a wye system the neutral point of a buck-boost transfomer may not be the same point as the original wye location. In these cases you can not bond the new neutral to ground.
If the transformer is derived by buck-boosting the original line-neutral voltage then the resulting neutral will be the same as the original. If the transformer is based on line-line voltages then the new neutral will be electrically different than the original. This is a major concern when supplying single phase loads buck-boosted from three phase wye systems.
Whish I knew how to post drawings.
For simplicity, assume a 280Y/120 transformer with normal X1, X2, X3, and X0 terminals and a boost transformer from 208 to 228.8V which will be a series connection of windings E, F, G, H, and K. X2 connects to F, X3 connects to H the load is connected to E and K. This leaves G as the center point (or neutral). What we now have is a right triangle XO to X2(F) is the hypotenuse at 120V, X2(F) to G is the vertical leg at 104V, and X0 to G is the horizontal leg at 60V.
No, I meant neutral. Actually the voltage N-G may be different as well as the voltage L-N.
On a wye system the neutral point of a buck-boost transfomer may not be the same point as the original wye location. In these cases you can not bond the new neutral to ground.
If the transformer is derived by buck-boosting the original line-neutral voltage then the resulting neutral will be the same as the original. If the transformer is based on line-line voltages then the new neutral will be electrically different than the original. This is a major concern when supplying single phase loads buck-boosted from three phase wye systems.
Whish I knew how to post drawings.
For simplicity, assume a 280Y/120 transformer with normal X1, X2, X3, and X0 terminals and a boost transformer from 208 to 228.8V which will be a series connection of windings E, F, G, H, and K. X2 connects to F, X3 connects to H the load is connected to E and K. This leaves G as the center point (or neutral). What we now have is a right triangle XO to X2(F) is the hypotenuse at 120V, X2(F) to G is the vertical leg at 104V, and X0 to G is the horizontal leg at 60V.
Re: 3 phase boost set-up for tanning beds
With a 12 volt boosting voltage with Wye I came up with 228 volts Lines 1,2 and 3 and 132 neutral.
120 + 12=132 volts neutral
Phase voltages line to line 132x1.73=228 volts
Heres the one I had in mind
This diagram did not give the voltages my guess would be H=120 and x=12
[ July 22, 2005, 06:04 PM: Message edited by: ronaldrc ]
With a 12 volt boosting voltage with Wye I came up with 228 volts Lines 1,2 and 3 and 132 neutral.
120 + 12=132 volts neutral
Phase voltages line to line 132x1.73=228 volts
Heres the one I had in mind
This diagram did not give the voltages my guess would be H=120 and x=12
[ July 22, 2005, 06:04 PM: Message edited by: ronaldrc ]
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: 3 phase boost set-up for tanning beds
Yes, that is a connection, but note how they do not bond the new neutral.
Yes, that is a connection, but note how they do not bond the new neutral.
Re: 3 phase boost set-up for tanning beds
Jim I don't understand what you mean,if you take that center tap to your Tan bed panel neutral bar and not ground to equipment you would have a neutral. But it would be a higher voltage.Or am I missing something here?
Ronald
Jim I don't understand what you mean,if you take that center tap to your Tan bed panel neutral bar and not ground to equipment you would have a neutral. But it would be a higher voltage.Or am I missing something here?
Ronald
Re: 3 phase boost set-up for tanning beds
Ronald, I think Jim is configuring a buck-boost xfrmr (2 cores)as an auto-xfrmr. The windings are connected as follows:
LV, HV, HV, LV
208V is applied to the HV windings, and the LV windings provide the boost to 230V.
There are two neutrals--a 3-phase neutral which is unchanged, and a single phase neutral which is 60V away from the 3-phase neutral (ground). This second neutral cannot be grounded. Two more buck-boosts could be connected in the same way, and the original 120/208 wye is still available.
Right Jim?
Rattus
Ronald, I think Jim is configuring a buck-boost xfrmr (2 cores)as an auto-xfrmr. The windings are connected as follows:
LV, HV, HV, LV
208V is applied to the HV windings, and the LV windings provide the boost to 230V.
There are two neutrals--a 3-phase neutral which is unchanged, and a single phase neutral which is 60V away from the 3-phase neutral (ground). This second neutral cannot be grounded. Two more buck-boosts could be connected in the same way, and the original 120/208 wye is still available.
Right Jim?
Rattus
Re: 3 phase boost set-up for tanning beds
Rattus do you think this is what Jim had in mind
[ July 22, 2005, 07:07 PM: Message edited by: ronaldrc ]
Rattus do you think this is what Jim had in mind
[ July 22, 2005, 07:07 PM: Message edited by: ronaldrc ]
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