3 Phase to 2 Phase Marine Application

What is available and what is required? Voltage, currents? You could be right, unless...

It is an old Stamford 284HC I think it is 440V RMS 3Phase Serial Star.

It should in my view be okay to connect the generator output to give 220V RMS between the phases in parallel star connection but the control PCA I think needs to be changed.

The star earth is connected to the safety ground and there is also a galvanic isolator.

I think the loads need to be balanced for normal running or get a three phase inverter to charge batteries and run everything off of inverters or DC....the latter I prefer.

Using the existing generator to run a 3 phase inverter system to charge batteries and then re convert to whatever.

For me changing to delta from star involves rewiring the distribution board.

Dear Sir,

What do mean by " Serial Star Genarator & a parallel delta wired to give lower

voltage- Use terms which are normally used. Please let us / me to understand your

query fully.

Manroop.Chennai

You are confusing every one:

1- For you to have a neutral output, the generator will still have to be wired in star configuration for the lower voltage.

2- It seems that it is wired in star with 2 coils per phase put in series on each phase for higher voltage. To configure for lower voltage, then you make 2 start generators in parallel: you should have 12 ends coming out from the alternator. (sorry I don't know how to copy a sketch here) but suppose that Phase 1 coils are numbered A1,A2-A3,A4 and the same for Phase B and Phase C starting from the ends of each phase, B1,B2-B3,B4 & C1,C2-C3,C4 { A1,A2 (1st) coil in series with A3-A4 (2nd coil) etc...}

High volts Start will have all the A4-B4-C4 connected as Neutral while A1, B1 & C1 are the Output phases.

For Lower Volts: A2-B2-C2-A4-B4-C4 = Neutral while A1-A3, B1-B3, & C1-C3 are the phases

3- The distribution panel does not need to be reconfigured if it was properly designed except that the low voltage might draw higher currents per circuit branch if the same wattage as for higher voltage is required: Entirely dependent on the equipment using the power down the branches. Of course, the C.B. current tripping will be checked and replaced if necessary.

Confusing...ask me what you want and I tell.

1-Yes I know...delta removes star earth.

Does not delta in a six coil system have half the voltage of a star connection but twice the current ?

This is marine.....metal boats are floating sacrificial anodes when connected to voltages.

It is an old Stamford 284HC I think it is 440V RMS 3Phase Serial Star.

It should in my view be okay to connect the generator output to give 220V RMS between the phases in parallel star connection but the control PCA I think needs to be changed.

The star earth is connected to the safety ground and there is also a galvanic isolator.

I think the loads need to be balanced for normal running or get a three phase inverter to charge batteries and run everything off of inverters or DC....the latter I prefer.

Using the existing generator to run a 3 phase inverter system to charge batteries and then re convert to whatever.

For me changing to delta from star involves rewiring the distribution board.

Sorry but you wrote "Parallel Delta" in your submission...

Anyway, When the six coils are wired, every 2 in series per phase and the configuration is STAR, you have the high voltage between phases (maybe 440V or 415V. Check name plate). This is 3 phase high volts for a system requiring that voltage. You also have a neutral to ground for safety or for using to operate safety devices for protection. this can be grounded. Since it is alternating and the return is only for current within the boat, it does not (to my humble knowledge ) make the metal of the boat a sacrificial anode. DC voltage will be more susceptible to do that if there is a leak from the live pole (not grounded on the boat), or if the metal of the boat is used as a return to the DC battery or else.

IF you reconfigure the coils of the generator such that you form 2 STAR generators in parallel (as explained and maybe you meant), you will have 1/2 the high voltage and twice the current (The total Power kW or kVA will be the same as before...). The advantage is that you still have a possibility to connect a Neutral if required for the same reasons as before.

Of course, you can also configure the coils as two DELTA generators in Parallel and the Voltage between phases will also be Half the high one (220V). You will not have a neutral to use as such. BUT IF YOU INTEND TO CONVERT THE AC to DC USING A 3PHASE BRIDGE RECTIFIER, THEN YOU DO NOT NEED THE NEUTRAL. (In 2 x STAR parallel you can ignore the neutral).

Noe, for your STAR / DELTA Voltage ISSUE: If you configure as 2 x STAR with NEUTRAL, you will have an even lower voltage between a phase and the neutral which is 220 / 1.73 = 127V.

PANEL ISSUE: I did not undertand which panel you are referring to: If it is the Generator's Panel, meaning the Voltage Regulator etc, then you do not need to change anything usually because the maker does the connection using tappings on the coils in such a way that it does not interfere with later re-configurations. BUT PLEASE CHECK. This is not difficult and is easy to make sure that the voltage coming to the Auto-Voltage Regulator conforms with its name plate etc. More than that I can not help since I do not have any drawing of the wiring or details.

Best luck.

Thanks for your wonderful answer.

I believe all you say.

I now know it is 380 V output from a star configuration.

So all problems are solved it can stay as it is...the guy told me it was 415 V and wanted to know if I could make it 220/240 V system and get rid of the 3 phase.

But I now leave him alone as he wants to use the 20 year old cable (due to cost.)

The cable insulation when moved cracked like dry mud and he did not think this was a problem.

And to my humble knowledge.....

when a "shore line" is connected to a boat normally a safety earth is included and as the boats earth is its metal structures which will have a small potential difference between the boats "earth" and the generating station supplying the boat....I believe it why galvanic isolators are sold....but that is another question to post as I think they are just diodes in very expensive boxes !!

Thanks again.