Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-11-2016, 05:14   #1
Registered User

Join Date: Jun 2010
Location: Sailing the Caribbean
Boat: Switch 51
Posts: 1,488
Unbalanced Generator Loads

I know running unbalanced loads on the legs of a 240v generator is not a good idea. But why not and how much is too much (considering that it is difficult to have an exact balance)?
__________________

__________________
SVNeko is offline   Reply With Quote
Old 29-11-2016, 05:38   #2
Registered User
 
CaptainChip's Avatar

Join Date: Nov 2016
Location: St Thomas, USVI
Posts: 5
Re: Unbalanced Generator Loads

Without getting into physics.. basically if you have things on leg 1 pulling a total of 40 amps and leg 2 is only pulling 5 you have an unbalanced load. The probem, and damage, occurs because of something called negative sequence magnetic flux. Both leg 1 and 2 share a neutral wire. And because of physics and heat, you can damage your generator. No generator will have a perfectly balanced load between phases, but getting it close is important for extending the life of the electronics in your generator.
This is some complex sh*t, people get doctorates just to figure it out.
__________________

__________________
CaptainChip is offline   Reply With Quote
Old 29-11-2016, 05:41   #3
Registered User
 
CaptainChip's Avatar

Join Date: Nov 2016
Location: St Thomas, USVI
Posts: 5
Re: Unbalanced Generator Loads

This may leave you just as confused:
https://electricalsimplified.blogspo...rrent.html?m=1
__________________
CaptainChip is offline   Reply With Quote
Old 29-11-2016, 06:39   #4
Registered User

Join Date: Jun 2010
Location: Sailing the Caribbean
Boat: Switch 51
Posts: 1,488
Re: Unbalanced Generator Loads

OK, but what about guidelines for how far out of balance and for how long? I am asking because I usually run 2 230V chargers. One is out, so I am supplementing charging with a 100a 120v inverter charger. So, with other loads, I have about 10A on one leg and 10A on the other on an 8kw genset while charging for an hour or two. This will continue until I get the bad charger repaired.
__________________
SVNeko is offline   Reply With Quote
Old 29-11-2016, 07:06   #5
Registered User
 
CaptainChip's Avatar

Join Date: Nov 2016
Location: St Thomas, USVI
Posts: 5
Re: Unbalanced Generator Loads

If you have 10 amps on each leg then it's balanced and there is no issue... was that a typo?
__________________
CaptainChip is offline   Reply With Quote
Old 29-11-2016, 07:09   #6
Marine Service Provider
 
Scott Berg's Avatar

Join Date: Jul 2011
Location: Aboard
Boat: Seaton 60' Ketch
Posts: 942
Re: Unbalanced Generator Loads

After considering this on my boat we chose to wire it so as to have both shore power AND the genset run through our isolation transformer and picking up the 'neutral' for 120v service off of the transformer. Treating it as a 240v only genset isn't a perfect solution, but makes many things easier...
__________________
Scott Berg
WAĜLSS
SV CHARDONNAY
Scott Berg is online now   Reply With Quote
Old 29-11-2016, 08:36   #7
Registered User

Join Date: May 2016
Location: Gunkholing along the Chesapeake Bay
Boat: 81 Hunter Cherubini 27
Posts: 292
Re: Unbalanced Generator Loads

Quote:
Originally Posted by SVNeko View Post
OK, but what about guidelines for how far out of balance and for how long? I am asking because I usually run 2 230V chargers. One is out, so I am supplementing charging with a 100a 120v inverter charger. So, with other loads, I have about 10A on one leg and 10A on the other on an 8kw genset while charging for an hour or two. This will continue until I get the bad charger repaired.
SVNeko, Captain Chip is correct , no Gen-Set will have a perfect balance. I try to balance within 15% or less on larger generators, 10% or less on a generator such as yours. And yes, this is a kind of rocket science trying to determine how to balance between inductive loads (electric motors and compressors), resistive loads (electric stove tops, lighting), and those that fall into both categories (dryers, jacuzzis). There's more involved than just volts and amps when it comes to load balancing. Don't even ask about phase balancing or Lead/Lag coefficients!

If I have read and understood your last post correctly, and depending on what equipment you are operating on the non-inverter leg, then you are probably at a good place with load balancing until you get your bad charger repaired.
__________________
Teknishn (Technician): One who fixes stuff you can't, based on dubious information provided by those with questionable knowledge and/or experience.
Teknishn is offline   Reply With Quote
Old 29-11-2016, 11:23   #8
Registered User

Join Date: Jun 2010
Location: Sailing the Caribbean
Boat: Switch 51
Posts: 1,488
Re: Unbalanced Generator Loads

Quote:
Originally Posted by CaptainChip View Post
If you have 10 amps on each leg then it's balanced and there is no issue... was that a typo?
Yes, sorry, should be 20a on the other one.
__________________
SVNeko is offline   Reply With Quote
Old 29-11-2016, 12:04   #9
Registered User

Join Date: May 2016
Location: Gunkholing along the Chesapeake Bay
Boat: 81 Hunter Cherubini 27
Posts: 292
Re: Unbalanced Generator Loads

SVNeko, what electrical loads are you running on the 20A leg? A bit more information would help in determining if you need to temporarily shift electrical loads from one leg to the other.
__________________
Teknishn (Technician): One who fixes stuff you can't, based on dubious information provided by those with questionable knowledge and/or experience.
Teknishn is offline   Reply With Quote
Old 29-11-2016, 13:21   #10
Registered User

Join Date: Jun 2010
Location: Sailing the Caribbean
Boat: Switch 51
Posts: 1,488
Re: Unbalanced Generator Loads

A 100a charger. Along with minor loads on the 110v outlets - iPad charging and such. There is a 80a charger and water heater loads that are on 240.
__________________
SVNeko is offline   Reply With Quote
Old 29-11-2016, 13:56   #11
Elvish meaning 'Far-Wanderer'
 
Palarran's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: Me - Michigan / Boat - Greece
Boat: 56' Fountaine Pajot Marquises
Posts: 2,580
Re: Unbalanced Generator Loads

I don't think it really matters much. The generator has a breaker in it that will trip if one line of the 230v is overloaded. In my case, I can have up to 50 amps of 115v power coming off one leg and 0 off the other. It would be worse, IMO, to run the generator at 50 amps 230v total as the heat is what kills the generator.

Would it be better to have 25 amps off each, sure. But the generator windings are designed to put out the maximum on each leg.
__________________
Not all who wander are lost

http://www.sailblogs.com/member/palarran/
Palarran is offline   Reply With Quote
Old 28-01-2017, 21:35   #12
Registered User

Join Date: Mar 2013
Location: Andaman
Posts: 159
Re: Unbalanced Generator Loads

Would running off 230v from generator to a step down transformer 230v/115v to provide a balanced 115v output instead of trying balance the 2 legs of 115v?
__________________
ericoh88 is offline   Reply With Quote
Old 28-01-2017, 22:24   #13
Registered User

Join Date: Feb 2015
Posts: 249
Images: 1
Re: Unbalanced Generator Loads

Quote:
Originally Posted by ericoh88 View Post
Would running off 230v from generator to a step down transformer 230v/115v to provide a balanced 115v output instead of trying balance the 2 legs of 115v?
Yes, you could do that. That's how my 120V service works - via a 240V to 120V transformer.
__________________
www.MVTanglewood.com
tanglewood is offline   Reply With Quote
Old 29-01-2017, 06:34   #14
Registered User
 
CaptTom's Avatar

Join Date: Apr 2004
Location: Southern Maine
Boat: Prairie 36 Coastal Cruiser
Posts: 841
Re: Unbalanced Generator Loads

Quote:
Originally Posted by CaptainChip View Post
... something called negative sequence magnetic flux...
Another new thing I learned today from CF!

I can't wait to find a way to work this phrase into a conversation.

I always wondered about this too. Thanks! Not sure I still understand 100%, but I got enough out of the link above to get the gist of it.
__________________
CaptTom is offline   Reply With Quote
Old 29-01-2017, 20:50   #15
Registered User

Join Date: Oct 2009
Location: Redondo Beach, CA
Boat: 1990 Oyster 55
Posts: 282
Re: Unbalanced Generator Loads

You could install an "autotransformer" this allows a load imbalance of up to the allowed value of the transformer and present a balanced load to the generator.

Sent from my SM-G935V using Cruisers Sailing Forum mobile app
__________________

__________________
botanybay is offline   Reply With Quote
Reply

Tags
generator, loa

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Unbalanced diesel? Cheechako Engines and Propulsion Systems 15 17-03-2013 10:34
Pool Navy Anchor - Balanced vs Unbalanced Singleprop Anchoring & Mooring 4 20-05-2011 20:34
Anchor Loads Ocean Girl Anchoring & Mooring 25 01-05-2010 17:17
Isolate Shore Power Loads from Inverter Loads RoyHB Electrical: Batteries, Generators & Solar 4 19-04-2010 05:02
Vessel Substructure to Support Rigging Loads beiland Multihull Sailboats 6 01-07-2008 04:45


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:53.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.