Jayco RV Owners Forum
 


Reply
 
Thread Tools Display Modes
 
Old 09-06-2011, 11:33 AM   #1
Senior Member
 
David472's Avatar
 
Join Date: Feb 2011
Location: SW Ontario
Posts: 1,393
What is an Autotransformer?

At the risk of posting something which can be found elsewhere......
A couple people here on the JOF have mentioned Autotransformers for their shore power. For this device name, Auto does not mean automatic, but rather a single winding in a transformer. They can be made to function in an automatic manner though. Some RVer's use them to boost a low pedistal voltage up to a more useable level. Typically, for the products sold to RVer's, a fixed boost of 10% is either switched into play or out of play (bypass). Here is a link which describes Autotransformers in general;

http://en.wikipedia.org/wiki/Autotransformer

And here is a link which shows one made by Surge Guard for RVer's;

http://tweetys.com/surge-guard-30-am...r-booster.aspx

At some campgrounds, there seems to be mis-understanding about what impact an Autotransformer would have on the CG electrical supply system. As with all transformers, the electrical power (watts) into it will equal the electrical power out of it. There will be a small amout of Eddie Current loss in the transformer, but that is minor in this context. With a low pedistal voltage of say 100 volts, the pedistal circuit breaker will still have a 30A limit (or maybe 50A), so, the power formula being current times voltage, 100x30 is 3,000 watts. If the pedistal delivered a healthy 120v at 30A, then you would in theory have 3,600 watts available. So you see, a low pedistal voltage being fed into an Autotransformer, does not increase the electrical power drawn from the pedistal. In fact, there is less power available before the circuit breaker trips. I hope you found this post informative and helpful.
__________________

__________________
Jayco Eagle 31.5RLDS
GMC Sierra 2500 HD
David472 is offline   Reply With Quote
Old 09-06-2011, 01:35 PM   #2
Senior Member
 
Terry's Avatar
 
Join Date: Feb 2011
Location: Germantown, TN
Posts: 4,923
Thanks David - good explanation.
__________________

__________________
Terry
2009 Jayco 26BH
2004 Chevy Silverado 1500
2009 JayFlight Manual Library

Want to add a signature to your posts? --> Click Here
Terry is offline   Reply With Quote
Old 09-07-2011, 03:37 AM   #3
Senior Member
 
Join Date: May 2011
Location: Aldergrove British Columbia
Posts: 815
David, what would you recommend for protecting a trailer with a 30 amp service? Would a person be better off buying a EMS devise that seems to be popular here or would going with a line conditioner be a better choice?
__________________
Richard
2011 Jay Feather Select 28U
2007 Silverado Crewcab LT 6.0L
Happily married and father of
two university students.
Cancer survivor
Murphie is offline   Reply With Quote
Old 09-07-2011, 09:39 AM   #4
Senior Member
 
Join Date: Apr 2011
Location: AZ, USA, Earth
Posts: 1,342
I'm not David but I would strongly recommend an EMS unit (not just a surge protector). All an autoformer does is boost low voltage, up to a point. If the voltage drops low enough, it will revert to bypass mode. The newer Hughes Autoformers do have surge protection but can't be user serviced if the MOVs are damaged by a really large surge por spike. The autoformer has no excessvely low or high voltage protection whereas an EMS unit will shut off the power if it goes too low or too high.

One would think using an EMS after an autoformer would give better protection than just the EMS or autoformer alone but reports I've read on other forums say that, in practice, the better EMS units (such as the Progressives) will shut down before the autoformers can react to a low voltage situation. My choice would be to use the EMS unit to ensure my electronics and other electric appliance don't fry and if chronic low voltage becomes a problem, move.
__________________
Jeannie
Lady Fitzgerald is offline   Reply With Quote
Old 09-07-2011, 12:52 PM   #5
Senior Member
 
David472's Avatar
 
Join Date: Feb 2011
Location: SW Ontario
Posts: 1,393
Murphie,
My preference is to have an EMS unit, for much the same reasons stated by Lady Fitzgerald. The wife and I travel when we camp, and so don't stay more than several days at any one CG. Typically, I measure the line voltage, and the lowest I have seen under load so far is 110 volts, which is just adequate and not a worry. For us, an autotransformer would not be of much benefit, but an EMS type device would provide protection for those sudden events which may come along. There is no way a person could react as fast as an EMS. A few weeks ago, at a CG in Mich, during the evening our interior lights suddenly went bright for 5 or 6 minutes. I measured the voltage, and it was about 7% higher than normal. Not likely enough to trigger any EMS (although there could have been a small spike first), but it demonstrates how suddenly and unexpectedly something can happen. At present, we have only a surge protection device, and my manual voltage monitoring. In the future we may be looking at getting an EMS device, for the hi-low voltage protection they offer over what we currently have.

P.S. - You asked if a line conditioner would be a good choice. Please know that an Autotransformer is not a line voltage conditioner. Those are typically made for industrial applications, are quite complex and expensive, like $3,000 range and up.
__________________
Jayco Eagle 31.5RLDS
GMC Sierra 2500 HD
David472 is offline   Reply With Quote
Old 09-07-2011, 05:35 PM   #6
Senior Member
 
Join Date: May 2011
Location: Aldergrove British Columbia
Posts: 815
David, thanks for your input, I will budget for an EMS next year.

Lady, your info has not gone unnoticed and is appreciated.
__________________
Richard
2011 Jay Feather Select 28U
2007 Silverado Crewcab LT 6.0L
Happily married and father of
two university students.
Cancer survivor
Murphie is offline   Reply With Quote
Old 09-08-2011, 08:18 AM   #7
Senior Member
 
Seann45's Avatar
 
Join Date: Jun 2010
Location: Saskatoon Sask Canada
Posts: 9,701
Measuring the voltage at the post is next to useless... what happens 10 min after you measure it? When 30 people flip on their A/C units? That is why I have the surge guard. It constantly measures line voltage and polarity. If anything happens to the voltage (over or under) it cuts off power to the RV. I Cannot say enough good things about this device.
Seann
__________________
Seann
2004 Chev Silverado Duramax optioned past the max. 2009 Jayco Eagle 308 RLS 765 watts of solar, 6-6 volt batteries (696 amp hour), 2000 watt (4000 surge) whole house inverter.
175 days boondocking in 2017
215/2016, 211/2015, 196/14, 247/13, 193/12

Seann45 is offline   Reply With Quote
Old 09-08-2011, 08:54 AM   #8
Senior Member
 
Terry's Avatar
 
Join Date: Feb 2011
Location: Germantown, TN
Posts: 4,923
Quote:
Originally Posted by Seann45 View Post
Measuring the voltage at the post is next to useless... what happens 10 min after you measure it? When 30 people flip on their A/C units? That is why I have the surge guard. It constantly measures line voltage and polarity. If anything happens to the voltage (over or under) it cuts off power to the RV. I Cannot say enough good things about this device.
Seann
Well not only the 30 people - but when the pedestal is static and no current is being pulled by you, it will probably register just fine. Have a bad connection inside and as soon as you crank up the AC or the Micro - bam - sparks fly. Ask me how I know? lol....after that experience I researched and purchased one.
__________________
Terry
2009 Jayco 26BH
2004 Chevy Silverado 1500
2009 JayFlight Manual Library

Want to add a signature to your posts? --> Click Here
Terry is offline   Reply With Quote
Old 09-08-2011, 09:49 AM   #9
Senior Member
 
David472's Avatar
 
Join Date: Feb 2011
Location: SW Ontario
Posts: 1,393
Quote:
Originally Posted by tafische View Post
Well not only the 30 people - but when the pedestal is static and no current is being pulled by you, it will probably register just fine. Have a bad connection inside and as soon as you crank up the AC or the Micro - bam - sparks fly. Ask me how I know? lol....after that experience I researched and purchased one.
Notice, I said UNDER LOAD.
__________________
Jayco Eagle 31.5RLDS
GMC Sierra 2500 HD
David472 is offline   Reply With Quote
Old 09-08-2011, 10:20 AM   #10
Senior Member
 
Seann45's Avatar
 
Join Date: Jun 2010
Location: Saskatoon Sask Canada
Posts: 9,701
Since you are on a common line other RV's effect your voltage.

Since we are talking about this and I am a HUGE believer in them .. I noticed that camping world has Surge Guards on sale right now...
http://www.campingworld.com/browse/p...=61711&rewrote
__________________

__________________
Seann
2004 Chev Silverado Duramax optioned past the max. 2009 Jayco Eagle 308 RLS 765 watts of solar, 6-6 volt batteries (696 amp hour), 2000 watt (4000 surge) whole house inverter.
175 days boondocking in 2017
215/2016, 211/2015, 196/14, 247/13, 193/12

Seann45 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Virginia State Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -6. The time now is 09:43 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 2002-2016 Social Knowledge, LLC All Rights Reserved.