In theory will this work?

[Ponchik]

Lets assume we have a piece of equipment that operates between 120-130V single phase and draws 10 Amps and requires hot and neutral.

The power source is 208V single phase and is 4000' away. By using 10awg copper the voltage drop will be 84V in 100 degree F environment at which we will have 124source voltage by the equipment.

My question:
will the piece of equipment that is designed for 120-130V work in the above condition?

 

[GoldDigger]

Lets assume we have a piece of equipment that operates between 120-130V single phase and draws 10 Amps and requires hot and neutral.

The power source is 208V single phase and is 4000' away. By using 10awg copper the voltage drop will be 84V in 100 degree F environment at which we will have 124source voltage by the equipment.

My question:
will the piece of equipment that is designed for 120-130V work in the above condition?

Probably not.
It depends on what the equipment is and how constant that 10 amp draw is.
If, for example, it is a motor, the voltage drop with twice or more the current during the starting surge will keep the motor from starting up at all.
If the load amperage goes up and down (controlled heater, intermittent operation of motor, etc.) the voltage will be the full 208 on it much of the time. That may be very bad.
If it is a bank of grow lights (??) then when one burns out, the voltage will go up, burning out the rest in rapid sequence like string of xmas tree lights.

Instead, use a transformer to raise the 208 to 480 at one end, run larger wire (aluminum of larger gauge if you are cost conscious) and use another transformer to get down to 120 at the other end.

 

[nizak]

I am curious though. What type of application would require a 4000' run???

 

[PetrosA]

I am curious though. What type of application would require a 4000' run???

The perfect man-cave?

 

[Ponchik]

I am curious though. What type of application would require a 4000' run???

This is more of a hypothetical / curiosity question not a real time question. So some of us can learn from the expertise and the knowledge that is on this forum.

 

[nizak]

Didn't mean to sound arrogant. Just found that type of application odd.

 

[tortuga]

I used to work with an old railroad electrician whom also did allot of work in mines. He described some extremely long runs of 300W incandescent lamps i think. I think they were 240V though and some railway lighting that was powered by a transformer that raised and lowered the primary away from the secondary? Constant current or something?
Cheers

 

[GoldDigger]

I used to work with an old railroad electrician whom also did allot of work in mines. He described some extremely long runs of 300W incandescent lamps i think. I think they were 240V though and some railway lighting that was powered by a transformer that raised and lowered the primary away from the secondary? Constant current or something?
Cheers

Another thread described how old series string street lights had a constant current transformer at each lamp that made the lamp current roughly independent of the overall series string current. Each lamp (or small group of lamps) got the same current and voltage as all the others, but if one lamp burned out the series string still carried current and the current at the other lamps did not increase either. I never actually saw one, but I found an old manual online here.

 

[fmtjfw]

Old Series Streetlights

Old Series Streetlights

An early method was to use a single CONSTANT CURRENT output transformer that fed all the lights which were wired in series. If you had 40 120V 120W light you would have 1 amp 4800 volts (ignoring line resistance). In parallel with each light was a pair of springs separated by a thin sheet of mica (which is an insulator). When the bulb burned out the full voltage of the series circuit was impressed across the mica (~4800), which would break down the mica, shorting out the burned out bulb. Now you have 39 bulbs in series and the voltage would drop to 4680 volts to maintain the 1 amp current.

 

[kwired]

I am curious though. What type of application would require a 4000' run???

It is kind of odd to most of us, but think of street lighting, airport lighting, and other similar things, but of course those are not typically a long run to a single load, but rather long run with loads connected along the run. And then you have all kinds of possibilities in the industrial world.

 

[BAHTAH]

In theory will this work?

I am curious though. What type of application would require a 4000' run???

I remember doing several installations for microwave facilities located on mountains with line-of-site all across Nevada. Service was 200amp 120/240 Single-Phase from a meter pedestal at the bottom of the mountains. We would back-Feed an Oil Filled transformer stepping up to 5KV and then make a 5KV splice every mile for five miles terminating in
another oil filled transformer at the microwave building, stepping back down to 200amp 120/240 1ph3w for service to the building.

Did several similar installations for large ranches where the owners did not want the utility company having facilities on their land.

 

[hurk27]

Lets assume we have a piece of equipment that operates between 120-130V single phase and draws 10 Amps and requires hot and neutral.

The power source is 208V single phase and is 4000' away. By using 10awg copper the voltage drop will be 84V in 100 degree F environment at which we will have 124source voltage by the equipment.

My question:
will the piece of equipment that is designed for 120-130V work in the above condition?

The problem of stepping up a voltage to overcome the voltage loss because of the resistance in a long run is and has always been a very bad idea, even if the load was a single 120 volt light bulb, when the switch is first turned on the filament will be hit with the full voltage until the voltage drops, with a cold lamp you could probably get away with it but if the lamp was on for a while and if the power was to shut off and turn right back on, it would most likely shorten the life of the lamp, like was said if the load current was not kept very constant then you could end up over voltage the load which is not very desirable, this is why I always tell people on here not to use buck/boost transformers to raise the voltage from a voltage drop problem, buck/boost transformers are more designed to reduce or bring up the supply voltage of a service where it is too high or low for the load, such as boosting a 208 voltage service to 236 volts which is about as close as you can get with BB's for a 240 volt load that won't work on the 208.

The best method is of course resizing of the circuit conductors or using step up then step down transformers at the load end, for 10 amps your only talking 1.2kva or 1200 watts so a small 1.5kva transformer that is 120/600 then 600/120 would give you around a 16 volt drop at 1200 watts so if the equipment will be happy on 103.2 volts then your good to go, but if not then you will have to up size the conductors till you lower the VD to the amount needed, 600 volt transformers are a 5:1 ratio and the highest voltage without getting into the requirements of over 600 volts wiring and is the max limit of most of the conductors we use.

 

[hurk27]

It is kind of odd to most of us, but think of street lighting, airport lighting, and other similar things, but of course those are not typically a long run to a single load, but rather long run with loads connected along the run. And then you have all kinds of possibilities in the industrial world.

The main thing with series lighting was that because of Kirchoff's law and the CCT, all the lights in the circuit would have the same brightness, the common currents was 6.5 and 7.5 amps so many lights could be fed from the 1200 volts or more and I read of even 7200 volt systems, also many of the older systems were 25hz systems Tesla's selected the frequency for his two phase Polly system based upon a balance between efficiency and lamp flicker, the lights back then were the 100 volt Edison lamps.

 

[Bang]

This is more of a hypothetical / curiosity question not a real time question. So some of us can learn from the expertise and the knowledge that is on this forum.

I know I have much benefit from this over the time I've been on the forum! Keep it coming!

 

[Bang]

An early method was to use a single CONSTANT CURRENT output transformer that fed all the lights which were wired in series. If you had 40 120V 120W light you would have 1 amp 4800 volts (ignoring line resistance). In parallel with each light was a pair of springs separated by a thin sheet of mica (which is an insulator). When the bulb burned out the full voltage of the series circuit was impressed across the mica (~4800), which would break down the mica, shorting out the burned out bulb. Now you have 39 bulbs in series and the voltage would drop to 4680 volts to maintain the 1 amp current.

This constant current regulator is still utilized on airfield lighting applications (don't know about commercial but definitely used for military runways)

 

[kwired]

The main thing with series lighting was that because of Kirchoff's law and the CCT, all the lights in the circuit would have the same brightness, the common currents was 6.5 and 7.5 amps so many lights could be fed from the 1200 volts or more and I read of even 7200 volt systems, also many of the older systems were 25hz systems Tesla's selected the frequency for his two phase Polly system based upon a balance between efficiency and lamp flicker, the lights back then were the 100 volt Edison lamps.

I wasn't trying to say street or airport lighting is run in series, but rather indicating this as one example where such long conductor runs is common.