I have a situation where it has been suggested a buck/boost transformer be used to boost the voltage at the end of a long feeder run. Here is what I know. 1500' run in 3" PVC to 100 amp sub panel, the voltage is 3 phase 120/208. The idea is to pull 2/0 and then correct for voltage drop over the distance. This will then feed about 20 small 3 phase heaters and single phase fans. I don't know the FLA of each unit, I can find out if needed. I was thinking of step up/step down tranformers but that would be more expensive. I've only seen boost transformers used for single pieces of equipment so I wasn't quite sure how well this would work.
will a buck/boost work?
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jimwalker
Senior Member
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- TAMPA FLORIDA
Re: will a buck/boost work?
Thats because you need a set load.Varying loads will not work
Thats because you need a set load.Varying loads will not work
jimwalker
Senior Member
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- TAMPA FLORIDA
Re: will a buck/boost work?
I think yes but will that always be true.Should some get turned off then the voltage raises to maybe an unsafe number.Use the step up step down method
I think yes but will that always be true.Should some get turned off then the voltage raises to maybe an unsafe number.Use the step up step down method
jtester
Senior Member
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- Las Cruces N.M.
Re: will a buck/boost work?
sdider 2
Don't use a buck boost transformer, it won't work. When there is no load there is no voltage drop,and the transformer is still boosting. If you buy one for each fan and heater it still won't work for the same reason.
A buck boost transformer works when you need to raise the voltage by a specific amount all of the time. For example you have a 208 volt system and need a litle bit of 240 for one piece of equipment.
It is not a cure for voltage drop as you described.
sdider 2
Don't use a buck boost transformer, it won't work. When there is no load there is no voltage drop,and the transformer is still boosting. If you buy one for each fan and heater it still won't work for the same reason.
A buck boost transformer works when you need to raise the voltage by a specific amount all of the time. For example you have a 208 volt system and need a litle bit of 240 for one piece of equipment.
It is not a cure for voltage drop as you described.
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Re: will a buck/boost work?
Does your budget (and the available space) allow you to use a step-up transformer (i.e., to 480 volts) at the beginning of the run, and a step-down (i.e., back to 120/208) at the end of the run?
Does your budget (and the available space) allow you to use a step-up transformer (i.e., to 480 volts) at the beginning of the run, and a step-down (i.e., back to 120/208) at the end of the run?
steveve1
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- Tucson, AZ
Re: will a buck/boost work?
Here's what I suggest. Determine full load amps with all heaters/fans on. Calculate voltage loss based on that load at the end of the feeder. Select the proper buck/boost transformer configuration from tables available on line from ACME or Jefferson. Buck/boost will work for your application but another method, ie. larger feeder conductor size or higher distribution voltage as suggested by Charlie may be more cost efficient.
Here's what I suggest. Determine full load amps with all heaters/fans on. Calculate voltage loss based on that load at the end of the feeder. Select the proper buck/boost transformer configuration from tables available on line from ACME or Jefferson. Buck/boost will work for your application but another method, ie. larger feeder conductor size or higher distribution voltage as suggested by Charlie may be more cost efficient.
steveve1
Member
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- Tucson, AZ
Re: will a buck/boost work?
Your 3 phase voltage drop calculator will work regardless of applied voltage. The % voltage loss is based on conductor size, length of circuit, and the load applied.
Your 3 phase voltage drop calculator will work regardless of applied voltage. The % voltage loss is based on conductor size, length of circuit, and the load applied.
jtester
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Re: will a buck/boost work?
quote from steveve1
Here's what I'd suggest. Determine the...
Steve your idea will likely cause serious problems. For example lets say the voltage drop at full load is 40 volts. If I raise the voltage 40 volts when the load is on we will have 208 volts when the load is on. What do you think the voltage will be when the load is not on? It will be 208 + 40 or 240 volts, much too high.
In almost all instances a buck boost won't work here,
quote from steveve1
Here's what I'd suggest. Determine the...
Steve your idea will likely cause serious problems. For example lets say the voltage drop at full load is 40 volts. If I raise the voltage 40 volts when the load is on we will have 208 volts when the load is on. What do you think the voltage will be when the load is not on? It will be 208 + 40 or 240 volts, much too high.
In almost all instances a buck boost won't work here,
Re: will a buck/boost work?
Formula for voltage drop:
Amp load on cicuit X Length of circuit X 2 X Constant for wire size (12.9 should be close for copper conductors) X .866 (if three phase circuit - omit if single phase) divide this by the circle mils of your conductor and you will have your voltage drop.
You need to determine exactly what the maximum load will be on this feeder. I doubt that your 100 amp panel will be loaded 100%. Then you will need to determine how many amps this load will be at 600 volts. There are no shortcuts. You must get all of the information and do all of the calculations. For example if you have 50 amps of single phase load at 208 volts that would equal 10.4 KW. If you supply this at 600 volts 3-phase and then transform it down to 208 volt at the panel you would only have 10 amps load on the feeder. If the load is 208 volt 3-phase at 50 amps the wattage would be 18,000. The amperage on the 600-volt feeder would be 17.32 amps. This would reduce your voltage drop dramatically. If you have a mixture of 3-phase and single phase loads in your panel you will have to determine the load on each phase and use the phase with the greatest load to determine your amperage load. I don't believe you have gathered all of the information that you need to make your calculation yet.
Formula for voltage drop:
Amp load on cicuit X Length of circuit X 2 X Constant for wire size (12.9 should be close for copper conductors) X .866 (if three phase circuit - omit if single phase) divide this by the circle mils of your conductor and you will have your voltage drop.
You need to determine exactly what the maximum load will be on this feeder. I doubt that your 100 amp panel will be loaded 100%. Then you will need to determine how many amps this load will be at 600 volts. There are no shortcuts. You must get all of the information and do all of the calculations. For example if you have 50 amps of single phase load at 208 volts that would equal 10.4 KW. If you supply this at 600 volts 3-phase and then transform it down to 208 volt at the panel you would only have 10 amps load on the feeder. If the load is 208 volt 3-phase at 50 amps the wattage would be 18,000. The amperage on the 600-volt feeder would be 17.32 amps. This would reduce your voltage drop dramatically. If you have a mixture of 3-phase and single phase loads in your panel you will have to determine the load on each phase and use the phase with the greatest load to determine your amperage load. I don't believe you have gathered all of the information that you need to make your calculation yet.
Re: will a buck/boost work?
Did a similar job 10 years ago that is still working. We ran 208 single phase for 2600' YES 1/2 mile. At the load end we installed a constant voltage transformer. Output is 120V. The original voltage drop was about 80, I think. I don't have all the engineering data easily available. Anyways the transformer was made by SOLA. Hope this helps.
Did a similar job 10 years ago that is still working. We ran 208 single phase for 2600' YES 1/2 mile. At the load end we installed a constant voltage transformer. Output is 120V. The original voltage drop was about 80, I think. I don't have all the engineering data easily available. Anyways the transformer was made by SOLA. Hope this helps.
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