Need Electric Engineers help.

[BriaBeck]

[QUOTE=cavie;2045300]

Originally Posted by Scottmarm

I’ve worked as an industrial electrician for over 40 years in a pulp mill and I’ve worked with autotransformers many times.
After reading all the responses you got, I can’t help but wonder why you would be looking into increasing the voltage in your RV? Yes you are right in applying the math to P=IxV but as an electrician, you know that any increase in voltage to a 120 volt appliance is dangerous to that appliance… so I am wondering if this is the information you really need?

Scottmarm, you need to stop reading between the lines and stick to the printed words. Cost has absolutely Nothing to do with the question at hand. It just happens to be an unexcepted enjoyable by product. My site has very low voltage. A/C will NOT start on it own on a busy weekend. I installed a hard start the very 1st year. I'm not trying to save $$ on my electric. I am protecting my equipment and allowing it to operate correctly. The 132 volts is not there once the A/C starts up. The example of $15 dollars was proof to me that KWH was down do to the much needed boost from the Transformer that I installed thru experience and not from asking questions. My cost went down in spite of the trans being on 24/7. Which brought me to the question that started all this. If the transformer uses the parks Electric why did my usage go down in caparison with the previous yeas 4 months of summer last year with no transformer at the same $.24 KWH rate? The trans is working at Idle when nothing is being used buy anything obviously not causing a draw on park power or it would by recorded in my site electric meter which is 4' from my trailer.

As a 35 year licensed Master Electrician I know exactly what a autotransformer is used for and A surge protector in reverse is not it!

As for why I wish to raise the voltage. If you read the print only you would see it is to get my voltage up to AT LEAST 120 VOLTS TO SAFELY USE MY EQUIPMENT.

Cavie,

Did you take into account the heating degree days / cooling degree days for this year compared to last year? You may not have ran your heat or AC as much this year...

Just something to consider if you're trying to figure out how you used less electrons.

[Flybob]

Originally Posted by ejohnson1144

A watt is a watt

Depends on what watt .

[TitanMike]

Originally Posted by ejohnson1144

A watt is a watt

True but when input voltage is low it takes more current to provide the same "watts"out.
More current means more heat in the wires feeding the power.

H=I^2Rt

H= heat
I = Amperage
R= Resistance (squared)
t= time

As stated earlier, as the load starts to reach the upper limits of a circuit an AF will cause input current to rise as load(s) cause input voltage to drop. Wiring will heat as well as connections and circuit breakers, depending on resistance.

This is only a problem with overloaded or marginal systems.

[babock]

Originally Posted by TitanMike

True but when input voltage is low it takes more current to provide the same "watts"out.

And as was already stated numerous times, lowering the voltage doesn't always translate to more current. An electric heater is a prime example.

As an electrical circuit design engineer we see this all the time in our designs. Lower the supply voltage and lower the current typically.

[TitanMike]

Originally Posted by babock

And as was already stated numerous times, lowering the voltage doesn't always translate to more current. An electric heater is a prime example.

As an electrical circuit design engineer we see this all the time in our designs. Lower the supply voltage and lower the current typically.

Restive loads like heating and incandescent lighting will reduce current as voltage goes down. Inductive loads like motors are the reverse. In the RV world the largest loads are the A/C and Microwave. Also the most likely reason people buy AutoFormers. Especially if they have two 15,000 btu A/C units.

Anything in the RV with an internally regulated power supply like a 120v TV, Laptop, 120v sound system is usually not affected because their regulators are "overdriven" with much higher voltages than are sent out to the system. In some cases close to 100% more than the regulated output is fed to the regulator. Depends of course on the device but look at the input voltage specs and you'll often see TV's and computer power supplies rated for 100-240 volts. Makes it easy to run them in foreign countries without having to lug a transformer around (as I had to when in Germany back in the 60's.

[babock]

Originally Posted by TitanMike

Restive loads like heating and incandescent lighting will reduce current as voltage goes down. Inductive loads like motors are the reverse. In the RV world the largest loads are the A/C and Microwave. Also the most likely reason people buy AutoFormers. Especially if they have two 15,000 btu A/C units.

Yep...as was stated numerous times.

Doesn't really matter if you have two ACs or one. They will each run on their own leg of the 240V input.

[cavie]

Originally Posted by Scrapper

I don't understand this statement,

"This from Hughes autotrans web site:
The Autoformer DOES NOT take power from the park."

So if this is the case then why does it need to be plugged into the pedestal? I guess my measly brain can't comprehend that statement as there is no such thing as 100% efficiency.

It means the autotransformer itself is not consuming any park electricity. There is some loss but it is minimal.

[cavie]

[QUOTE=BriaBeck;2045842]

Originally Posted by cavie

Cavie,

Did you take into account the heating degree days / cooling degree days for this year compared to last year? You may not have ran your heat or AC as much this year...

Just something to consider if you're trying to figure out how you used less electrons.

Just for the record. The temps last summer were the highest on record in the Bershires. Much A/C. Heat is propane and not part of this equation.

For the umpteenth time. I wish people on this forum would learn how to read!!
This tread was never stated by me as looking to save $$ or Electrons or any this else. It is a thread to rebuke the naysayers that the statement on Hughes web site is not correct. In my experience the autotrans does not draw any measurable power from the park! So I have to agree with the Website statement. I'm done with this. Thank you.

[rk06382]

Originally Posted by cavie

I wish to get the skinny on Autotransformers. I'm just a dumb retired electrician of 50 years or so. 35 as a Master. I have been told over the years that an autotransformer DOES NOT use park electricity.

My simple brain says: Raise the voltage, lower the amperage and in turn lower the KWH. Am I wrong in my thinking?

There seems to be a lot of naysayers on this site that say YES.

I don't need answers from DIY guys. For the first time in my electric career I'm looking for an engineers advice

I have enjoyed this thread. But the original question was unanswered.

My answer is if you raise the voltage 10%, you lower the amperage 10%. Wattage or Power stays the same as it is a product of voltage times amperage.
Meaning that from the park 50 amp circuit breaker will max out at 10% less or 45 amps. Also the "An Autoformer running at full output (50 amps) will use 1 amp." Meaning: MAX 50 amp input it will have a MAX output of about 44 amps. (98% efficientincy)

I would buy a Hughes Autoformers if I needed one. If they come out with a bluetooth version, it would be even better.



Cavie, Please let us know how the Hughes Autoformer works for you.




From Hughes Autoformers website: How Does It Work?

At first we are tempted to say very ‘well’. But this may not be the answer you are looking for!

Autoformers are used in industries to stabilize voltage and lower the operating cost of equipment. The Autoformer has 5 windings: 2 primary and 3 secondary. All models have surge and spike protection. When the unit is in Automatic and the park or input voltage is 116 volts or below, the output is 10% over the input. When the input is over 118 volts, the output is 2% over the input.

The Autoformer DOES NOT take power from the park.

It does not affect the park or input voltage, or make electricity.

What it is doing is changing the voltage – amperage relationship, lowering the amperage and raising the voltage. Since appliances run better on higher voltage, lower amperage, less overall power is used from the park, and better service is enjoyed from your RV

An Autoformer running at full output (50amps) will use 1 amp, but will cause appliances to cycle more often and run cooler. This will use less total power from the park.

Enjoy Your Autoformer Knowing You Are Doing Your Part For The Environment.

[Old Forester]

I tried to tell you.. Go back and read my post.

[babock]

Originally Posted by rk06382

My answer is if you raise the voltage 10%, you lower the amperage 10%. Wattage or Power stays the same as it is a product of voltage times amperage.

And that answer is incorrect. As has been stated numerous times by knowledgeable people, resistive loads will draw less current at lower voltages. Inductive loads MAY draw more current at lower voltages and nothing is linear.

[ependydad]

Too long, didn't read- where does this land?

Am I a demon that is making the power situation worse by using my AutoFormer when power is bad at a campground?

[babock]

Originally Posted by ependydad

Too long, didn't read- where does this land?

Am I a demon that is making the power situation worse by using my AutoFormer when power is bad at a campground?

If you are using your AC, you likely just made it better. If you are using your electric heater, you are making it worse.

[srcpaid]

I have used autotransformers for decades. They provide stable voltage to protect sensitive equipment (like computers) by adjusting the incoming voltage to a preset voltage output. Does so by changing amperage, but power (watts) does not change. Light bulbs don't care if voltage sags, tronics do. Most a-ts I use are big hunks of iron, which makes them great surge protectors too. Good ones are heavy.

Better call them voltage regulators, they raise low voltage input (ie. 95 volts) or clip over voltage (ie. 140 volts) and provide clean 115 (+/-) volt output.

My BSME includes computer/electronics career of 40+ years. Cancel the title, some of the answers posted are not so good..'

[babock]

Originally Posted by srcpaid

I have used autotransformers for decades. They provide stable voltage to protect sensitive equipment (like computers) by adjusting the incoming voltage to a preset voltage output. Does so by changing amperage, but power (watts) does not change. Light bulbs don't care if voltage sags, tronics do. Most a-ts I use are big hunks of iron, which makes them great surge protectors too. Good ones are heavy.

Better call them voltage regulators, they raise low voltage input (ie. 95 volts) or clip over voltage (ie. 140 volts) and provide clean 115 (+/-) volt output.

My BSME includes computer/electronics career of 40+ years. Cancel the title, some of the answers posted are not so good..'

Incorrect. It's a multi tap transformer. It just selects the appropriate tap to boost voltage. Doesn't know anything about current.

It also doesn't regulate. It just boosts by the ratio of the primary and secondary winding selected.

[cavie]

Originally Posted by babock

Incorrect. It's a multi tap transformer. It just selects the appropriate tap to boost voltage. Doesn't know anything about current.

[tucson]

remember ohms law, amps times volts equals watts. The same power is used, they are just a voltage stabilizer

[bohacek]

Having been an electrical engineer for many years at Xerox Corp. I see a lot of confusion if the answers that were given. First an auto-transformer is nothing more than a transformer with only one winding that is tapped so that the output voltage can be slightly higher or lower than the input voltage. Works on the very same principal as a transformer. So one mentioned that.


Second: to say it does not "take" power from the park is "essentially" true. no auto-transformer is 100% efficient the same as no transformer is 100% efficient. So there is a little loss which results if consuming some power from the park. Not enough to be concerned about by a long shot.


Three: The auto-transformer is usually used in the situation that you described to increase the voltage to your camper. This does not necessarily reduce the power drawn by the device. In fact heating elements will actually dram more current when the voltage is increased. However, motors will run more efficiently and thus will either draw less current and run better and therefore reduce the on time of the service cycle, with the next result being less total power.
Forth: Please do not use the term "AMPERAGE". While we all know what you are talking about, the correct term is CURRENT. Maybe I am just an old fuddy duffy on this last one.
I hope I have been able to clean up some of the confusion. Feel free to contact me if you with.
Tom

[srcpaid]

Mostly right, but all transformers trade volts for amps or vice-versa. I prefer sliding core to multi-tap, but they don't travel easy.

[bohacek]

I did not talk about trading voltage for current. The total power on both sides of the transformer are about the same, with a little bit of power consumed by the transformer for the loss in the transformer itself. So if the output voltage is doubled from the input voltage, the output current will be half of the input current. This assumes a different load on the output however.