Isolation Transformer: Victron vs Mastervolt vs Charles

[s/v Jedi]

Originally Posted by Palarran

Nick,
That is a lot of information. Great installation. I'm not clear what "floating" voltage is.

We have quite a few 240v mechanicals, 2 water heaters, 1 80 amp charger, Sea Frost refrigeration, 3 A/C's and laundry set-up. But I'm rather easy and only really need to run one or two at the same time. So if I can run my a/c and the charger, I can make ice and enjoy it in a cool cabin .

My situation is that we won't be at docks much and the ones we are at most likely won't have power. You know how Greece is. I'd only be able to use the system about 10 days per year x 2 or 3 years. Spending a fortune on a system isn't an option. That is why on an initial review, I like the Charles unit. They cost $640 and I could bring it with me next year. It would be easy to install also.

What is the reason for not recommending this option?

Oh yes, must be cheap, forgot that. I can't recommend anything cheap and am lucky enough to not have any experience with it. Well, there is that time I was learning that cheap is the path of pain but that was long ago A good system cost money and if that is not available, you can't get it for less. So, in your shoes I would not buy anything. Rather have nothing than cheap; spend the money on diesel, maintenance and parts for the genset instead.

A floating voltage is one that is not polarized by tying a conductor to ground and calling it "neutral". It creates a power feed as safe as not having a shore power connection at all.

[s/v Jedi]

Originally Posted by goboatingnow

I understand that but why not use a split winding on the isolation transformer and generate split phase directly ( silly system anyway , derived from Edison's DC system )

Dave

Because you might want to connect something in between the two, like a genset output or a charger/inverter. Most people complain that they only have one 120V leg on inverter which can only be solved by either two interlinked and synchronized inverters, or an auto-transformer.

Which brings me to the most important reason: balancing the two legs. With the auto transformer, everything in front of it has no balancing issues at all. The isolation transformer can do it's full 3.6kW on it's single 240V secondary winding. The genset can also be wired as a simple 240V single winding output that is always fully balanced (because the windings are in series). The inverter/charger becomes an effective 240V device and you only need one. Then finally, the auto transformer creates the split phase and takes care (absorbs) of any inbalance on the two legs. No power is lost because one leg is at it's max while the other is not.

[Palarran]

Great. Thank you Nick for the information and time. At least I know a few options now. Though besides being cheap I'd really like to know what is wrong with the Charles or similar solution. Does anyone else have an opinion in it?

[kellyp08]

Originally Posted by goboatingnow

Err , what about a charger inverter ?

Dave

Hi Dave

I have little experience with a charger inverter (except for using inverters to covert 12V DC battery power to 110-120V AC power to run a TV, computer, electric razor or hairdryer). If you have actually used a charger/inverter to change 240V 50 Hz from the dock to 120V 60Hz to power US spec air conditioners and refrigerators, I'd be VERY interested in your thoughts.

Thanks
Pat

[Saltyhog]

I've been thinking about whether I need an Isolation Xfmr. Need is obviously a relative term. Our boat is wired in typical US 115V - 30A -60Hz. I'd really prefer not to add the weight and bulk of an Iso-Xfmr. However we plan on some extended cruising and many of those locations will be 240V 50Hz. Not planning on spending much time in marinas, however there will be the occasional times where we need to or it is just too hot. I'm thinking of hurricane season in Grenada or the Rio Dolce. For those times, it would be *really* nice to be able to run the Air Conditioning. That is the *only* true need I have of an Iso Xfmr, as a step down xfmr. The isolation is a bonus, but with an ELCI and galvanic isolator, I think I'm ok. The rest of the boat is DC and I plan on having a universal voltage battery charger. Any small AC loads could be handled by an inverter. So, for those that have weathered hurricane season in hot places not having *your* power, is an iso-xfmr worth its weight in iron solely for running the air-con?

[Saltyhog]

Originally Posted by kellyp08

Hi Dave

I have little experience with a charger inverter (except for using inverters to covert 12V DC battery power to 110-120V AC power to run a TV, computer, electric razor or hairdryer). If you have actually used a charger/inverter to change 240V 50 Hz from the dock to 120V 60Hz to power US spec air conditioners and refrigerators, I'd be VERY interested in your thoughts.

Thanks
Pat

I'd be really interested in that too. That seems a perfect solution other than the fact that the inverter will be running pretty hard to power the air-cond, etc.
I have yet to find a universal AC voltage input charger-inverter. -Tom

[DotDun]

Originally Posted by Palarran

Great. Thank you Nick for the information and time. At least I know a few options now. Though besides being cheap I'd really like to know what is wrong with the Charles or similar solution. Does anyone else have an opinion in it?

As I stated above, I have no experience with the Charles unit, but lacking any data otherwise, my assumption is the Charles unit is an E-I design transformer whereas the Victron and Mastervolt units use a toroid core. Discarding money from the equation, I would go with a toroid, but I have to believe the Charles unit will perform as advertised (they simply don't advertise the more weight, lower efficiency, louder hum, etc.).

From Wikipedia - Transformer - Wikipedia, the free encyclopedia

Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level. Other advantages compared to E-I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see Classification parameters below). Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E-I types.

[Saltyhog]

Charles and Victron are *not* the only sources of transformers. Lots and lots of small companies that will wind anything you want. This is one example. It looks like it would fit the bill. Has medical grade specs regarding leakage, has the shield between windings, and is toroidal. I'm pretty sure that if you wanted, they'd give you additional taps on the secondaries to compensate for low dock voltage. Prices seem reasonable for what you're getting.
*Actually, the prices are totally un-reasonable, but only because of the unreasonably high price of copper at the moment.

[pbiJim]

Originally Posted by s/v Jedi

Soft start is done with relays and included with the Victron transformer.

Thank you for the link to that post. That was a most informative read.

That system is different from the soft starters that I have worked with in the past. The ones that I am familiar with can be found here - Sprecher + Schuh

[goboatingnow]

Originally Posted by kellyp08

Hi Dave

I have little experience with a charger inverter (except for using inverters to covert 12V DC battery power to 110-120V AC power to run a TV, computer, electric razor or hairdryer). If you have actually used a charger/inverter to change 240V 50 Hz from the dock to 120V 60Hz to power US spec air conditioners and refrigerators, I'd be VERY interested in your thoughts.

Thanks
Pat

No problems , multi voltage charger -> batteries -> 120 invertor -> AC 60hz power


Run AC , yes , but the costs are very large , you'd need a good Battery setup and big invertors and chargers , can be done with N+1 ganged invertors.


Dave

[pbiJim]

Just a few general comments here for people who don't have a strong electrical background:

Transformers:
Transformers can change the number of volts & amps from the input to the output. You can put 220vac 10 amps in & get 110vac 20 amps out (with a little loss) in the proper type of transformer. Amps & volts can change in the other direction too.

You can not change frequency with a transformer. If you put 50hz in, you will get 50hz out. If you put 60hz in, you will get 60hz out.

A transformer of the correct type can take in single phase 220vac or 480vac, etc & put out 110-0-110vac (aka a pair of 110vac circuits with a shared neutral). If you go from one hot of this output to the other hot of this output, you will have 220vac. This is standard US power configuration for use in houses & other typical civilian applications. Per NEC, the neutral gets connected to ground at the service entrance only (in houses). After that, separate wires get run for neutral & ground. Depending on loading balance, it is not unusual to see several volts of potential difference between neutral & ground once you get far away from the service entrance.

You can not get 3 phase out of a transformer that takes single phase in as primary power. You can use only a single phase off of a 3-phase supply.

Some transformers can electrically isolate the primary from the secondary & have only magnetic coupling between the two. Other types of transformers (auto transformers, buck/boost transformers) have primaries that are electrically connected to the secondaries & provide no isolation.

Inverters:
Inverters vary in function depending on which one you have. Some inverters are capable of producing 50hz or 60hz ac power, depending on how they are programmed. Others are one-trick ponies & only put out a single frequency.

Inverters usually don't care what frequency the incoming power is. They should always put out what they are programmed to put out as long as they are working correctly, they are not overloaded & they have sufficient supply power.

Most inverter based units don't put out real sign wave power. This isn't a problem for 90% of the equipment out there, but it can cause some issues with more sensitive equipment & some other inverters if they are used in the same system.

Inverters tend not to like heavy motor loads with high start currents or high voltage spikes. These are things that damage the output components of the inverters. If you plan to run motor loads, it is often prudent to plan to oversize your inverter a little so that it will have the capacity to handle the high starting currents that motor loads normally produce (6 x rated full load amps at locked rotor).

Motors:
You can usually run a 50hz motor on 60hz as long as you get the voltage right. It does not hurt the motor to do this. The motor will probably just run a little faster than it's nameplate RPM. If you run a 60hz motor on 50 hz, you can burn the motor. Some motors are rated 50/60hz. Others are not.

Motor loads generally suck up 6 times the full load rated amps on their nameplate, when they start from a dead stop. This is called locked rotor current or starting inrush current. A device called a soft starter can greatly reduce this inrush current, but makes the motor start up more slowly. A soft starter can greatly reduce the size of electrical supply that you need to run a motor load.

If you bought a motor based device like an air conditioner or a refrigerator in a country that has 50hz power, you can probably run it on 60hz power with no problems as long as the voltage is correct. The reverse is usually not true. US 110vac air conditioners generally do not last very long if you run them off of 50hz power that has been stepped down to 110vac with a transformer, even if the transformer was sized correctly to allow for the starting inrush current.

Putting Power Sources In Parallel:

DC in parallel
If you have multiple DC power sources of the same voltage, you can often put them in parallel with no problems. This is sometimes not true of chargers. Some smart chargers will have complicated sensing circuits that will not play well with other chargers that are put in parallel. You can put as many batteries as you want in parallel, as long as the voltages are the same.

AC in parallel
Do NOT put multiple AC sources in parallel unless you have special matching equipment. If you don't know what that equipment is, then don't even try it.

[kellyp08]

pbiJim..

Thank you for a very clear description of how isolation transformers and inverters work. I spent a year in the Balearics and figured out most of what you describe. What you say is right on the money!

Air conditioning and refrigerator 60Hz compressor motors will run on 50Hz but they are noisy, get hot and I surmised that this was not healthy for these motors. I thought about a buying and installing a high capacity inverter but they were expensive and I'd spent enough money on the project as it was. So I went to plan B:

I have a 12.5KW Westerbeke generator to run the AC (to cool down the cabin - took about 20-30 minutes) and can run the refer/freezer off 12V from the house system (8 AGMs/1160 AH) using shore 240vAC through the Victron 3.6W Isolation transformer to top-up the batteries.

So I am now back home in Maine without experiencing any electrical disasters. In retrospect, I wish that I had someone with your knowledge and experience who could have offered impartial advice on a cost-effective solution (providing brand names, model numbers and approximate cost) for converting 240V 50Hz dockside power to 120V 60Hz for on-board marine systems and appliances. This would be very useful in my opinion.

[DotDun]

FWIW, my MarineAir 60hz units run at 50hz. From the manual:

Ratings at 60 Hz. 50 Hz operation will be diminished by 17%.

Isolation transformers will typically handle inrush, inverters and generators are more prone to in-rush issues.

[Palarran]

DotDun,
I checked with Charles and their transformer is an E.I. unit. That unit still makes the most sense to me since it is 60 pounds and can fly with me next year. The weight isn't too much of an issue when your boats already at 50,000 pounds.

Also, the wiring would be very easy. Currently I have two 50 amp shore power connections on the boat (why? I don't know). I can take one of them and wire it into a breaker, then to the transformer and I'm done inside. I can use my current 50 amp cords to power it and just replace the male end with the 3 pin EU standard.

Did you buy your catamaran from TMC about 5 years ago?

[DotDun]

Originally Posted by Palarran

Did you buy your catamaran from TMC about 5 years ago?

Nope, bought almost 10 years ago from private owner.

I'm sure the Charles will do what you need. Good luck!