AUTOTRANSFORMERS Manufactured by Hughes, Frank’s and Power Master.
- At 105 volts we get 30 amps of power, or 3150 watts of energy.
- At 130 volts we get 30 amps of power, or 3900 watts of energy.
- We get 8% increase in usable energy. Or 750 watts of power.
- 750 watts can run some coffee pots, a blender, vacuum cleaner, and some toasters
- Most space heaters draw 15 amps.
- The circuit breakers in most rigs are 20amps. But not hair dryers, microwave ovens, or larger appliance.
- Most campgrounds have 6-8 sites on a 200-amp breaker.
- 200 divided by 6 is 33 amps, but line losses can subtract another 5 amps.
- HEAT is a major loss on energy from any electrical device.
- We lose less heat (energy) the lower the amperage we can obtain.
- The higher the voltage (up to 130volts) the less power we use while operating any electrical device.
- A 600-watt electrical appliance will use 5.45 amps at 110 volts.
- This 600-watt device will draw 4.6 amps at 130 volts.
- We save almost one amp using the higher voltage.
- Your converter/battery charger will use 3-4 amps off the top.
- These autotransformers act as a superior Surge-spike protector.
- The autotransformer will draw ½ to one amp of power on it’s own.
Do we steal power-when we use an autotransformer?
The following scenario is offered by Dave & Helen Dmouth, www.damouth.com:
You and one neighbor in a remote part of the RV Park share a long power
feed from the park’s distant feed. I’ll assume that the main feed is always at
120vac, but that the long power wires shared by these remote sites have a
resistance of 0.25 ohms (not unlikely – that’s only 200 feet of #8 cable).
You and one neighbor in a remote part of the RV Park share a long power
feed from the park’s distant feed. I’ll assume that the main feed is always at
120vac, but that the long power wires shared by these two remote sites have a
resistance of 0.25 ohms (not unlikely – that’s only 200 feet of #8 cable).
Further assume that both of you are using exactly the same appliances which
would add up to each of you drawing 25 amps, if the voltage remained at 120
volts.
But the voltage won’t remain at 120 volts (because of the resistance in the
long power feed). Under these conditions, the voltage at each site will b
e108.68 volts and each site will be drawing 22.64 amps.
Now suppose you, but not your neighbor installs an autotransformer. The
(older) Autoformer increases the voltage by a fixed 10% in a low-voltage
situation, so inside you Rv, you now have 118.88vac. This raises your current
draw inside the RV up to 24.66 amps. (This additional load causes more
voltage drop in the shared line, dropping the voltage coming into each RV to
1-7.62 volts, so your inside voltage increased a bit less than the expected
10%).
Your use of the Autoformer has reduced your neighbor’s voltage from 108.68
to 107.62 volts. Reduced his current from 22.64 to 22.42 amps, and reduced
his power usage from 2.46 kilowatt to 2.41 kilowatts. You voltage inside the
RV increased from 108.88 to 118.88, your inside current increased from
22.64 amps to 24.66, and you power from 2.46 to 2.92 kw. Your neighbor has
a 2% power reduction while you see a 19% increase in you own power usage.
This analysis assumes that the loads in your RV are resistive. (Fred’s
comment = no motors)
This seems like a pretty good tradeoff, unless your neighbor has a power
management system that shuts off her power when the voltage drops below a
certain level. In some situations your ability to use additional power by using
the Autoformer could result in enough additional incoming voltage reduction
so that your neighbor loses power completely. If you want to be a nice guy,
you can turn off a bit more of your own power usage, returning her voltage
and power to where it was before you used your Autoformer while still
retaining the advantage of having normal voltage in your own rig.
Note that even though you may have a 30-amp power pedestal, you cannot
increase your internal current all the way up to 30 amps in a low-voltage
situation. This is because when the Autoformer increases the inside voltage
by 10%, (which is 20% increase in power), it also must increase the current
drawn from the power pedestal by a bit over 20%. So if you turned on 30
amps of load inside the RV, you would be drawing considerably more than
the 30 amps from the pedestal, tripping the 30 amp circuit breaker.
Happy Camping,
Fred b. 101BYFRED.COM
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Phil Iati
The Hugh’s AutoTransformer flat out doesn’t work. What a waste of money…it doesn’t even protect you against power spikes! Hopefully I can find a bigger fool to sell it to…
Warren
And it’s not that splash lube is bad. It is that pressurized lubrication is much better. But then it does cost more initially.
Warren
Low oil pressure shut down is essential on engines that spend a lot of time running unattended, such as irrigation pumps, generators, etc.
This self preservation feature is not possible with splash lube.
Rich D.
Dave Taylor, THANKS for bringing to light the many misleading statements in the original article. More research should have been done before that original article was published.
Tommy
Hey,
Autoformers, Surge Guards, etc., all serve a purpose. If park power were great, they’d have no customers and be run out of business. But, as we all know very well, park power is typically unpredictable – especially if you travel to new locations a great deal.
I’ve seen 30A breakers that trip at 20A, voltages ranging from below 105 to over 133 at the pedestal, reversed polarity, no neutral or ground (or both!), and had a pedestal burn up the hot blade on my cord!
When RV park power becomes reliable, I will get rid of the extra weight/power taken by the equipment I use to protect our home on wheels. Until then, my electronics (3 computers), digital TVs, Air Conditioners, satellite gear, etc…, will be protected from the threats emanating from the typical park power pedestal.
tom
Dave Taylor
Splash lubrication….hmmmm
I’ve once observed a V8 running with a see-through oil pan–there certainly was lots of oil sloshing around. So, if I remove the oil pump on my F-150, I guess I will save some horsepower and get much better gas mileage!
Wonder why Ford didn’t think of that?
Darthvagrant
**sigh***
Yeah Thomas, my “lawnmower” does make use of splash lubrication. The lawnmower is a $500. device with an easily replaced engine.. An Onan Microquiet / Microlite 4K generator is $2K plus. I don’t know why I’m even taking time to make this reply, as the advantages of pressure lubrication to bearings (particularly conncting rod) and a full flow oil filter (with the resultant oil cooling) are inarguable, Doubly so in a device of moderate importance.
.
Let me recall the automotive, truck, heavy equipment engines that are singularly splash lubricated…..Uhhh….gee! I can’t remember any. I won’t argue that splash lubrication is expected in a throwaway inexpensive device.
Thomas Becher
Why are splash oiled generators bad? Your lawnmower engine has one and they are used a whole lot more than a generator I bet unless you are a full timer. My lawn mower is 19 years old and used more than 50 hours a year. Change the oil once a year. BIG DEAL
Don Hopper(RV.net hoppers4)
The nominal voltage for an 1875W hair dryer is 125VAC (125 X 15 = 1875). The impedance of the hair dryer doesn’t change. At 110VAC the current draw will be less than 15A since impedance doesn’t change. Even if the current stayed at 15A, the power it used would only be 1650W. Therefore your 600W device listed above would simply draw less current and use less power at a lower voltage.
Dave Taylor
Just a few thoughts people might want to consider…
If I used the following statements, I never would have been hired as an electrical engineer:
* At 105 volts we get 30 amps of power, or 3150 watts of energy.
* At 130 volts we get 30 amps of power, or 3900 watts of energy.
As was previously posted, this not true for a resistive load and any loads that are mostly resistive (high power factor loads).
* We get 8% increase in usable energy. Or 750 watts of power.
* 750 watts can run some coffee pots, a blender, vacuum cleaner, and some toasters
There is no “free” power. Period.
* 200 divided by 6 is 33 amps, but line losses can subtract another 5 amps.
Line losses do not “subtract amps.” Line losses in feeders create a resistive voltage drop, which in some cases reduces the available power, and in other cases may cause a powered device to draw too much amperage, overheat, and then fail.
* The higher the voltage (up to 130volts) the less power we use while operating any electrical device.
No necessarily true. With a primarily resistive load (high power factor load), increased voltage will result in MORE power being used.
* A 600-watt electrical appliance will use 5.45 amps at 110 volts.
* This 600-watt device will draw 4.6 amps at 130 volts.
Not necessarily true. The actual amperage used will depend upon the power factor of the appliance at each voltage, the ambient temperature, the ability of the appliance to dissipate heat, and how much “work” the appliance does at each voltage.
* We save almost one amp using the higher voltage.
What we are really interested in is saving power. If you “save amps” at a certain voltage, you end up doing less work (because less power is expended).
* These autotransformers act as a superior Surge-spike protector.
An inductor in the circuit certainly will reduce the amplitude of short duration voltage spikes (in the microsecond to millisecond range); however, long term transients will be AMPLIFIED by the auto-transformer, and might even impose voltages on the load which exceed its ratings.
* The autotransformer will draw ½ to one amp of power on it’s own.
If an RV park has 200 sites and each one is using an auto-transformer, this will add an additional 10 Kw of system load–which probably is not a good idea.
Unfortunately, there is no perpetual motion machine. Auto-transformers and other voltage-adjusting (raising) transformers have their place. But such devices will not create free power: they only steal it from something (or someone) else.
drod67
Yep, I’d say the calculations are questionable. They just don’t “wring right.” However, I’m not an expert.
Wish the calculations were in kva rather than the form submitted.
See ya on the highway!
Darthvagrant
Yeah…and at 105 volts or less, your air conditioner compressor might fail to start properly and in a”locked rotor” state might go up in smoke. I carry around an inexpensive “Killawatt” (sp?) to check on shore station voltage and my generator cycles. The inefficient (can I say ‘crappy’) Onan Microquiet and Microlite and the like must maintain a 3600 RPM speed to maintain 60 cycles.
.
Yeah-Sadly I have an Onan Microquiet , (Nononouisy) no oil pump-no oil filter-splash lubricated generator. ‘Ya gotta’ love the new invertor type generators! Granted; they’re also splash lubricated but don’t beat themselved to death at 3600RPM.
Jon Vermilye
“The higher the voltage (up to 130volts) the less power we use while operating any electrical device.
A 600-watt electrical appliance will use 5.45 amps at 110 volts.
This 600-watt device will draw 4.6 amps at 130 volts.
We save almost one amp using the higher voltage.”
The above statements are only true for a reactive load, and questionable even then. A heater or other resistive load will draw more power as the voltage increases. The resistance of a heater, lamp or other resistive load is built in – it doesn’t change with voltage.
A 600 watt heater, hair dryer, etc designed to operate at 120v will have a built in resistance of 24 ohms. (R = E squared / W). At 110V it will draw 4.58 amps (I = E/R) & produce 503.8 watts (W = IXE), At 130v it will draw 5.42 amps & produce 704.6 watts.
A motor load such as your air conditioner may react more like the above quote, but it is worth checking with Wayne Dohnal’s http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/20628157/gotomsg/20640913.cfm#20640913 post for real measurements using an AC.
Overall, whether or not a autoformer will help or hurt others at a park is still up in the air. Until a large scale test is done with multiple RVs under real conditions, who knows?
Dan Rambow
The headline of this article, by using the word ‘steal’ suggests that you are doing something wrong by using an autotransformer.
Of course, when you use a particular piece of electrical equipment, it is going to use power that is shared with the neighbors. Use enough, and their power is going to decrease. If you are just posting an article to show electrical calculations, that is great, I can’t fault your work as I don’t do electrical calculations.
Is it wrong to use a device that uses extra power to boost your own? What about if you have a 30a hook-up, and I use 50a. If I use all my appliances, it will draw more power than your draw, is that wrong?
If you are posing a moral question here, to use or not use an autotransformer, my answer is obvious. Yes, use whatever equipment you need to enjoy your rv experience. The autotransformer looks like a good way to make the best of low voltage in some parks. If you want to use as little external power as possible, then use your generator or load up on solar cells and batteries, an equally good answer for those that lean in that direction.
You are still using far less power than you ever could living in a normal house, so even with the autotransformers, RVers are much more efficent than the housebound population at large.