I need to install a buck boost transformer on a natural gas filling station (no prior experience with these transformers). The supply voltage of the equipment is listed 208/240 volts 1 phase. The unit draws about 8 amps at full load. It has an electronic control board and a compressor. The supply voltage dips to 197 volts under load and shows 207 volts with no load. The transformer I have ordered will boost the voltage by 10%. This will put the voltage without load at +/-228 volts. If it wasn't for the dual voltage ratings on the nameplate I would have been leary due to being so far over 208 volts without load and what it might due to the electronic board. By the way this equipment is about 400 feet from the source with #12 wire. Obviously the wire size should have been larger from new (I didn't install it). I am only using this transformer as a short term solution and will look at the bigger picture because I can see more problems arising in the future in this corner of the building. Anything else I should be concerned about.
Buck boost transformers
- Thread starter jinglis
- Start date
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brian john
Senior Member
- Location
- Leesburg, VA
The best way to learn anything beyond a fast post here would be to read this.
http://www.sola-hevi-duty.com/support/index.htm
http://www.sola-hevi-duty.com/support/index.htm
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Jing, I do have one recommendation: place the BB at the source end of the run, rather than at the load end. The reason is that you want the long run to be at the highest voltage, and thus lowest current, possible.
Probably the most difficult thing for installers to understand is how to wire a buck-boost transformer. I is common for a singe B-B transformer of set of 2-3 B-B transformers to be provided with a number of wiring diagram configurations. It's trying to figure out which diagram to use and then wiring the tranforemr(s). When you don't do that many of have done none at all that can be difficult.
The wiring diagram on the transformer itself alone isn't going to make it happen.
The wiring diagram on the transformer itself alone isn't going to make it happen.
brian john
Senior Member
- Location
- Leesburg, VA
Actually for me the drawings are the answer. Pre-Internet I had to wire buck boost XMFR's I got the Hevi-Duty catalog read the info on buck boost study the drawings looked at the available conductors and their tags. Not that complicated IF YOU DO NOT LET IT BAFFLE YOU.
mdshunk
Senior Member
- Location
- Right here.
I remember the first buck boost transformers I ever wired, and I was so ticked off. "They sent me the wrong transformers", I declared. "These are only 24 volt transformers". :grin:
Life's road is funny.
Life's road is funny.
jameselectric
Senior Member
I would like to know exactly a 'buck boost' transformer' is or does?? is it just a low voltage power supply?? like taking 120 v ac and stepping it down to 12v or 24v ac for low voltage wireing.??
e57
Senior Member
- Location
- San Francisco, CA
+/or used as an autotransformer - depending on how it is connected - a certain voltage above or below 120. Commonly used also to go from 208 to 240. (or there bouts...)jameselectric said:
- Location
- Massachusetts
jameselectric said:
No.
Typically you use a BB Trans to move the voltage up or down just a small percentage.
For me this often mean boosting 208 to 230, some 230 volt equipment can not run on 208.
The advantage is the BB transformer will be very small, inexpensive and easier to install compared to a standard transformer.
They are typically name plated as 120/240 to 12/24 transformers and can be used that way when wired 'normally'
But when connected as an "autotransformer," they can handle loads up to 20 times the nameplate rating.
Check out this site
Here is one way to wire a buck boost, notice that the primaries (H) and the secondaries (X) are wired together and that one circuit conductor more or less just passes straight through.
Compare that to conventional transformer connections where primaries and secondaries are only magnetically connected.
Last edited:
I have looked at the wiring diagram that goes with the transformer that I have ordered. It is a simple four wire diagram with two primary leads and two secondary leads, the same as the diagrams in the recent post. The transfomer I ordered will give me a fixed 10% boost which puts my voltage in an acceptable range for the equipment in question. Why did I pick this transformer over an autotransformer with multiple taps? Power of suggestion from the service tech that noticed the problem? Are there any advantages of a buck/boost compared to an autotransformer?
e57
Senior Member
- Location
- San Francisco, CA
jinglis said:
Used in that context they are one in the same. Do you have a multi-tapped isolation transformer? Got a link?
No, I don't have a multitap isolation transformer. The reason for the buck/boost was cost (under $100) and 2 day delivery. This is only a short term solution to get the equipment up and running properly in a short period of time. The long term solution is probably $10,000 to install another service at this end of the building. Roughly 450 feet and probably a 600 volt feed, transformer and panel due to the fact I anticipate other problems in this area over the years.
I must point out that B-B transformers have 2 separate windings. As iwire pointed out primaries are commonly 120/240 with secondaries of 12/24, 16/32.
If you looked at the NP of a transformer that is intended for B-B application you wouldn't have a clue as to how in the world to wire it unless you had a separate wiring diagram to do so.
The wiring diagrams will show that a given Transformer will have a multiple of wiring configurations for various B-B voltage requirements.
The neat thing about this application is that it allows you to purchase an affordable transformer to make an incremental voltage adjustment. That is only enough transformer kva is require for that adjustment not that the transformer must carry the entire load as a common "isolation transformer" where a separate source is established. The most common use is to buck (lower) or boost (raise) the supply voltage a small amount, usually 5 to 27%.
Remember that A B-B transformer or 3ph-transformer bank does not provide isolation. It is extremely important that the overload protection be applied according to art. 450 of the NEC. Should OCP be applied incorrectly the load can be exposed to an extremely high voltage should a fuse blow in an unacceptable location in the B-B circuit.
Unlike a B-B and an autotransformer a transformer with only one winding.
This single coil has one or more extra taps or electrical connections in various positions along the winding. Each tap corresponds to a different voltage so that effectively a portion of the same inductor acts as part of both the primary and secondary winding. Depending on the application, that portion of the winding used solely in the higher-voltage (lower current) portion may be wound with wire of a smaller gauge, though the entire winding is directly connected.
Autotransformers are usually economical only with turns ratios no higher than about 4:1. For a given power rating, they can be made smaller and more compact than transformers with two windings.
As with a B-B transformer the autotransformer does not provide isolation and, therefore, doesn't derive a separate source.
If you looked at the NP of a transformer that is intended for B-B application you wouldn't have a clue as to how in the world to wire it unless you had a separate wiring diagram to do so.
The wiring diagrams will show that a given Transformer will have a multiple of wiring configurations for various B-B voltage requirements.
The neat thing about this application is that it allows you to purchase an affordable transformer to make an incremental voltage adjustment. That is only enough transformer kva is require for that adjustment not that the transformer must carry the entire load as a common "isolation transformer" where a separate source is established. The most common use is to buck (lower) or boost (raise) the supply voltage a small amount, usually 5 to 27%.
Remember that A B-B transformer or 3ph-transformer bank does not provide isolation. It is extremely important that the overload protection be applied according to art. 450 of the NEC. Should OCP be applied incorrectly the load can be exposed to an extremely high voltage should a fuse blow in an unacceptable location in the B-B circuit.
Unlike a B-B and an autotransformer a transformer with only one winding.
This single coil has one or more extra taps or electrical connections in various positions along the winding. Each tap corresponds to a different voltage so that effectively a portion of the same inductor acts as part of both the primary and secondary winding. Depending on the application, that portion of the winding used solely in the higher-voltage (lower current) portion may be wound with wire of a smaller gauge, though the entire winding is directly connected.
Autotransformers are usually economical only with turns ratios no higher than about 4:1. For a given power rating, they can be made smaller and more compact than transformers with two windings.
As with a B-B transformer the autotransformer does not provide isolation and, therefore, doesn't derive a separate source.
jameselectric
Senior Member
iwire said:No.
Typically you use a BB Trans to move the voltage up or down just a small percentage.
For me this often mean boosting 208 to 230, some 230 volt equipment can not run on 208.
The advantage is the BB transformer will be very small, inexpensive and easier to install compared to a standard transformer.
They are typically name plated as 120/240 to 12/24 transformers and can be used that way when wired 'normally'
But when connected as an "autotransformer," they can handle loads up to 20 times the nameplate rating.
Check out this site
Here is one way to wire a buck boost, notice that the primaries (H) and the secondaries (X) are wired together and that one circuit conductor more or less just passes straight through.
Compare that to conventional transformer connections where primaries and secondaries are only magnetically connected.
thanks for the link, however i do see on that website that it can be used for the 12v 24v etc.. low voltage for lighting too.
- Location
- Massachusetts
jameselectric said:
Yes, the same transformer that can take 120 or 240 volt primary and create a 12 or 24 secondary can be used as a buck boost.
The difference is in how you make the field connections.
There are at least 3 or 4 ways to make the connections as a buck boost depending on the voltages and if you are boosting or bucking.
e57
Senior Member
- Location
- San Francisco, CA
FYI - many "less expensive" (CHEAPO) "Listed" low voltage lighting transformers are actually modified Buck and Boosts with a new "Manufacturer" sticker, and some OCP installed. (Some painted black too...) A guy I know apparently got a few (factory) wired incorrectly for ~130v output - a real shocker! A good idea to check the connections before you fire them up.
I am a student in the faculty of engineering , and in my project i need to use buck boost transformer , and i can't find it in my country so i have no way except manufacture it manually with my group , and i haven't more information about it . so if u don't mind to help me in this , plz provide me with the information i need to make this , i hope not to annoyed u but am very sorry as indeed i need it very much . thnx at all .
plz , help me
plz , help me
plz , can i ask u , how can i manufacture the buck boost transformer manually , as i need it so much and i can't find it in my country . so if u dun mind tell me all information i can need , * i made google search * and i can't reach to what i need , it told me what is the buck boost and it's wiring and volt , amp , kva .... i know that they are important things but i don't have the transformer itself . i want to design it from zero step . plz i need it so much as my project based on it . thnx at all .
plz , help me
plz , can i ask u , how can i manufacture the buck boost transformer manually , as i need it so much and i can't find it in my country . so if u dun mind tell me all information i can need , * i made google search * and i can't reach to what i need , it told me what is the buck boost and it's wiring and volt , amp , kva .... i know that they are important things but i don't have the transformer itself . i want to design it from zero step . plz i need it so much as my project based on it . thnx at all .
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
You've just asked a question that would require a book to answer; a library is a far better resource than a discussion board to answer 'How do I design and build a transformer?'
With that said, perhaps we can point you in a more specific direction if you describe in more detail what you need. Perhaps we can point you to a piece of hardware that could be used as a buck-boost transformer.
Do you need to adjust a power supply voltage?
What input voltage?
What output voltage?
What frequency?
What power and current?
Etc.
Best Regards,
Jonathan Edelson
With that said, perhaps we can point you in a more specific direction if you describe in more detail what you need. Perhaps we can point you to a piece of hardware that could be used as a buck-boost transformer.
Do you need to adjust a power supply voltage?
What input voltage?
What output voltage?
What frequency?
What power and current?
Etc.
Best Regards,
Jonathan Edelson
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080528-2020 EST
jinglis:
You indicated that your voltage dropped was about 5% (10 V) from no load to full load, and that you have about 400 ft of #12. The loop resistance is about 1.6*800/1000 = 1.28 ohms. At 8 A this is a voltage drop of 10.2 V. A good correlation with your measured drop. Probably no reason to go to a larger wire. It is well within the current capability of the wire and the percentage voltage change is not excessive. This assumes there is no starting current problem.
You need to determine from the manufacturer how much above the 240 V rating the system is capable of working at without damage. My guess would be maybe 5% to 10%. If this is the case, then I would choose a boost voltage from 208 to 240 or 32 V. A 240 V to 36 V transformer supplied with 208 at the input would provide 31 V. The VA rating would need to be about 31*10 = 310 VA or larger.
If you still had the 10 V line drop, then the motor control would receive about 230 V under load. But the current might drop because of the higher input voltage.
If you study how transformers work and how sine waves of different phase angles add, then you can can answer most of the questions on how to wire this on your own.
With the transformer you have already purchased you indicated it has only two primary wires and only two secondary wires. This makes wiring easy. Also you indicated a 10% boost which means about 20 V. Thus, the transformer needs to be at least 20*10 = 200 VA in round numbers.
Connect the two primary wires to the same 208 phase from which you are powering the motor.
Connect one of the two secondary wires to one end of the 208 supply. Now measure from the other side of the 208 supply to the free end of the secondary. If this voltage is 208 + the secondary voltage or about 230, then your phasing is as required for boost. If the voltage is about 208 - 20 or about 190, then reverse the two secondary wires.
When you have the approximately 230 V then move the motor wire from the junction of the 208 and the boost secondary to the free end of the boost secondary.
As was mentioned by LarryFine put the boost transformer at the input end of your 400 ft line.
.
jinglis:
You indicated that your voltage dropped was about 5% (10 V) from no load to full load, and that you have about 400 ft of #12. The loop resistance is about 1.6*800/1000 = 1.28 ohms. At 8 A this is a voltage drop of 10.2 V. A good correlation with your measured drop. Probably no reason to go to a larger wire. It is well within the current capability of the wire and the percentage voltage change is not excessive. This assumes there is no starting current problem.
You need to determine from the manufacturer how much above the 240 V rating the system is capable of working at without damage. My guess would be maybe 5% to 10%. If this is the case, then I would choose a boost voltage from 208 to 240 or 32 V. A 240 V to 36 V transformer supplied with 208 at the input would provide 31 V. The VA rating would need to be about 31*10 = 310 VA or larger.
If you still had the 10 V line drop, then the motor control would receive about 230 V under load. But the current might drop because of the higher input voltage.
If you study how transformers work and how sine waves of different phase angles add, then you can can answer most of the questions on how to wire this on your own.
With the transformer you have already purchased you indicated it has only two primary wires and only two secondary wires. This makes wiring easy. Also you indicated a 10% boost which means about 20 V. Thus, the transformer needs to be at least 20*10 = 200 VA in round numbers.
Connect the two primary wires to the same 208 phase from which you are powering the motor.
Connect one of the two secondary wires to one end of the 208 supply. Now measure from the other side of the 208 supply to the free end of the secondary. If this voltage is 208 + the secondary voltage or about 230, then your phasing is as required for boost. If the voltage is about 208 - 20 or about 190, then reverse the two secondary wires.
When you have the approximately 230 V then move the motor wire from the junction of the 208 and the boost secondary to the free end of the boost secondary.
As was mentioned by LarryFine put the boost transformer at the input end of your 400 ft line.
.
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