3 phase generator question

lazza
lazza Solar Expert Posts: 336 ✭✭✭
HI

Can anyone tell me if this 3-phase generator can be converted to run as a single phase generator??

Thanks
LarryAttachment not found.
«1

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Larry, I think this is the manual for this alternator head:

    hb4 - hb2 manual_1.pdf

    There are wiring/configuration schematics at the end of the document. There is no single phase type configuration.

    And, from what little I know, I do not believe you can convert a three phase alternator to single phase (where you can use all "three phase" currents on a single phase 230 VAC circuit.

    The best you can do is connect the alternator into a Wye (or "Y" or star) configuration and have a common neutral/return with three hot wires that each will carry 1/3rd of the alternator's rated output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    BB. wrote: »
    And, from what little I know, I do not believe you can convert a three phase alternator to single phase (where you can use all "three phase" currents on a single phase 230 VAC circuit.
    You know all you need to know for this!
    It is possible to use a rotary converter (motor-generator) or AC-AC converter (rectifier plus inverter), but those will usually cost more than a new generator head.

    PS: I really laughed at that self-deprecating statement from you of all people. :)
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 3 phase generator question

    Actually that's not Bill's *ahem* field.

    :p:D
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    Actually that's not Bill's *ahem* field.

    :p:D

    OOOHHHH! :cry:
    SMA SB 3000, old BP panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Been doing stuff long enough that I have learned that as soon as I (or someone) makes a flat out statement that something can't be done--Often as not, somebody comes by with a neat way of doing it that I have never seen before.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: 3 phase generator question
    lazza wrote: »
    Can anyone tell me if this 3-phase generator can be converted to run as a single phase generator??

    No, it can't be converted to single phase. It's all right there on the nameplate. Starting at the top, you can use it single phase by connecting loads to one phase. That generator is 400V phase to phase in wye configuration, so it will be 231V phase to neutral. So obviously in delta configuration it will be 231V phase to phase, and 231 phase to neutral.

    In parallel wye it will be 200 volt phase to phase and 115 volt phase to neutral. In parallel delta it is 115V phase to phase, and phase to neutral.

    The only thing you have to deal with with a three-phase generator with single phase loads is keeping it somewhat phase balanced.
    --
    Chris
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    BB. wrote: »
    Been doing stuff long enough that I have learned that as soon as I (or someone) makes a flat out statement that something can't be done--Often as not, somebody comes by with a neat way of doing it that I have never seen before.

    -Bill

    Clarke's First Law (Arthur C. Clarke):
    When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

    But, just as relevant to Solar and other RE power is Asimov's Corollary to Clarke's First Law (Isaac Asimov):
    When, however, the lay public rallies round an idea that is denounced by distinguished but elderly scientists and supports that idea with great fervor and emotion -- the distinguished but elderly scientists are then, after all, probably right.
    SMA SB 3000, old BP panels.
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    HI

    Thanks for your replies. I thought that that last figure: I-ΔΔ was a way to configure the generator as a single phase generator? What does it actually signify.. ?

    I thought it may be the configuration mentioned under the section "Phase Conversion in Generators: (1) Reconfiguring Coil Connection" (http://www.dieselserviceandsupply.com/Generator_Phase_Conversions.aspx)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Well, I will be darned--There is a single phase (really split phase with a neutral) winding setup for this three phase alternator. On page 80, last diagram:

    http://www.sogagroup.com/FILES_UPLOAD/HB4 - HB2 manual_1.pdf

    Looks like it is rated for 50 amps @ 231 volts single phase @ 11.55 kVA rating.

    If this was a true single phase alternator, it would be rated at its full 20 kVA...

    So, as a single phase set, the output (and drive engine) would be 1/sqrt(3)=0.577 of "full" alternator rating.

    If 11.55 kVA is "worth while" for your installation--Then, yes it will work. It just does not supply the same amount of power as if it were wired to three phase loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    BB. wrote: »
    Well, I will be darned--There is a single phase (really split phase with a neutral) winding setup for this three phase alternator. On page 80, last diagram:

    http://www.sogagroup.com/FILES_UPLOAD/HB4 - HB2 manual_1.pdf

    Looks like it is rated for 50 amps @ 231 volts single phase @ 11.55 kVA rating.

    If this was a true single phase alternator, it would be rated at its full 20 kVA...

    So, as a single phase set, the output (and drive engine) would be 1/sqrt(3)=0.577 of "full" alternator rating.

    If 11.55 kVA is "worth while" for your installation--Then, yes it will work. It just does not supply the same amount of power as if it were wired to three phase loads.

    -Bill

    I am curious where you found the specification for 50A, 11.55kVA? It does not seem to be in the manual.
    Or did you just do a theoretical calculation based on the single winding specifications or the three to one phase conversion?

    I do like that they list an actual split phase 230 configuration, which is only possible because all of the 12 winding ends are brought out for access.
    SMA SB 3000, old BP panels.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    lazza wrote: »
    HI

    Thanks for your replies. I thought that that last figure: I-ΔΔ was a way to configure the generator as a single phase generator? What does it actually signify.. ?

    I thought it may be the configuration mentioned under the section "Phase Conversion in Generators: (1) Reconfiguring Coil Connection" (http://www.dieselserviceandsupply.com/Generator_Phase_Conversions.aspx)

    The statement at that URL about putting all of the coils in series to produce single phase is just plain wrong. It will indeed produce a single phase, but unfortunately it will be at zero volts. Or else it will be an inefficient, current limited, configuration in which you get an output voltage of twice the nominal voltage (i.e. twice the line-to-line voltage of a standard high voltage three phase delta configuration, but without a neutral. You would get more power from the single phase use of the delta or dual delta configuration of the same generator head.
    SMA SB 3000, old BP panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Inetdog,

    I was looking at Larry's/Iazza's first picture--The bottom line of the spec. sheet is 231 volts @ 50 amps... And confirming with a sqrt(3) factor difference and, what appears to be a 20 kVA power rating for the alternator...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: 3 phase generator question
    lazza wrote: »
    HI

    Thanks for your replies. I thought that that last figure: I-ΔΔ was a way to configure the generator as a single phase generator? What does it actually signify.. ?

    It signifies phase to neutral with the windings configured parallel delta.

    As I said before, the winding in this generator cannot be converted to single phase. Single phase European power requires a grounded neutral. Not a bonded neutral like US split-phase - a grounded neutral.

    Using the windings configured in parallel delta, pulling a single phase "hot" off each coil group, connecting a leg from each coil group together and calling it a neutral is a "hack" that prevents the generator from producing three-phase 400V power, but gives you single phase 230V 50Hz using only part of the winding. I do not recommend using it for European single phase 230V because it is not a grounded neutral and can't operate as one.
    --
    Chris
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    ChrisOlson wrote: »
    It signifies phase to neutral with the windings configured parallel delta.

    As I said before, the winding in this generator cannot be converted to single phase. Single phase European power requires a grounded neutral. Not a bonded neutral like US split-phase - a grounded neutral.

    Using the windings configured in parallel delta, pulling a single phase "hot" off each coil group, connecting a leg from each coil group together and calling it a neutral is a "hack" that prevents the generator from producing three-phase 400V power, but gives you single phase 230V 50Hz using only part of the winding. I do not recommend using it for European single phase 230V because it is not a grounded neutral and can't operate as one.
    --
    Chris
    Note that putting the windings into the standard series delta arrangement (Δ on the nameplate) will allow you to get the same 231V and the same 50A current by connecting your load only to one of the line-to-line connections, and you can also ground one of the winding ends to give you a true grounded return (not neutral in this case) European style single phase 230. Same power output too.
    The I-ΔΔ is an interesting way to get US-style split phase out of the generator, although with limited power capability. It also gives you two really strange phase and voltage connections using the remaining two terminals, sort of like a double high-leg configuration. :)
    SMA SB 3000, old BP panels.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: 3 phase generator question
    inetdog wrote: »
    The I-ΔΔ is an interesting way to get US-style split phase out of the generator, although with limited power capability. It also gives you two really strange phase and voltage connections using the remaining two terminals, sort of like a double high-leg configuration. :)

    Except that split-phase power is useless in Europe. It will allow about 1/2 the generator's normal capacity to be used on single phase without having three-phase output, but half the load has to be on each coil group. I think it's a "hack" that allows the generator to be used for single phase European power on a job site, etc. with a floating neutral, much like some generators built for the US market have a floating or non-bonded neutral.

    So basically, using it as single phase with the correct 230V 50Hz output for European power, will only allow you to use roughly 1/4 of the generator's capacity on each "leg" or coil group. Not a good option as far as "converting" the generator to single phase. You'd be better off to run the generator in the standard parallel wye configuration at 230/400 and use each individual three-phase leg to neutral for single phase power. That way, yes, you still get 400V line to line, but you get 230V line to neutral. And the wye configuration has a true neutral that can be grounded. Delta doesn't. You just have to leg balance the generator on single phase loads to get full capacity from it.
    --
    Chris
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    Mmm I'm lost!

    I have thought about having a 3 phase system with 3 different single phase lines. The problem is that it will be incredibly unbalanced, as only one phase would be used most of the time (without changing all the house installation's wiring). I understand that this is bad for a 3 phase system....
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: 3 phase generator question
    lazza wrote: »
    I have thought about having a 3 phase system with 3 different single phase lines. The problem is that it will be incredibly unbalanced, as only one phase would be used most of the time (without changing all the house installation's wiring). I understand that this is bad for a 3 phase system....

    Three-phase residential is not uncommon in some parts of Europe. While imbalance is not good for the transformer or a generator, it doesn't hurt anything as long as you don't overload the source. If you had three-phase to your home for three-phase appliances, you would likely rewire your home for more balanced single phase loads on the three-phase service. Then a normal 230/400V generator would be no problem at all.
    --
    Chris
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    Would unbalanced phases be more of a problem for the generator therefore, than for the 3-phase inverter set up?
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: 3 phase generator question
    lazza wrote: »
    Would unbalanced phases be more of a problem for the generator therefore, than for the 3-phase inverter set up?
    Someone has posted about a system that had 2 Inverters and a stand alone charger on the third phase before on here. Outback makes the GFX series that's probably perfect for that type of a small setup . I see posts on the Outback forums about 3 phase setups.
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    Looking at the I-ΔΔ configuration:Attachment not found.

    I understand that it's a the L1-L2 connection that gives you the 231V??

    For if it were the L1-N and L2-N connection then it would be like a 2-phase system.. no?

    Ohh what a headache- if my physics teacher hadnt bullied me at school.. and i'd carried on studying, i'd know all this :cry:
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Yep, you are correct. In the US/North America, we would call the "N" a neutral (transformer center tap) and connect that to earth ground rod/cold water pipe (and green wire ground too). Technically, we call it a "split phase" power system.

    We would put a circuit breaker on L1 and L2 leads only. The breakers would be independent if this was a pair of 115-120 VAC circuits. If we were powering a 240 VAC load, the two breaker handles would be "tied together" so if one leg was over loaded, the tripping of that breaker would also turn off the second leg too.

    In Europe, as I understand, you would simply ignore the "N" lead and bond L1 or L2 to earth/green wire ground (maybe), put a Fuse/Breaker on the "hot" leg and call it a day.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    Ok, that's good to know.

    Now i've been trying to rack my brains as to understand how this setup works. It's important because this generator will provide the generator input to a single phase inverter system... and the sine wave and quality of the power needs to be adequate.

    From what I can see... the 2nd and 3rd phases are in series and the voltages added, but the 1st phase voltage is subtracted? There's some kind of adding/subtracting of phase voltage wave forms going on...

    can anyone enlighten me with an explanation or graphical representation??

    my brain is smoking
    Larry
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: 3 phase generator question
    lazza wrote: »
    Ok, that's good to know.

    Now i've been trying to rack my brains as to understand how this setup works. It's important because this generator will provide the generator input to a single phase inverter system... and the sine wave and quality of the power needs to be adequate.

    From what I can see... the 2nd and 3rd phases are in series and the voltages added, but the 1st phase voltage is subtracted? There's some kind of adding/subtracting of phase voltage wave forms going on...

    can anyone enlighten me with an explanation or graphical representation??

    my brain is smoking
    Larry

    Because of the 120 degree phase shifts of the three windings, the voltage produced by 2nd and 3rd phase windings in series (adding the two voltage vectors) is identical to the voltage across the first phase winding. You just do not get to use their full power because the impedance will be twice that of the first winding and so they can only supply half as much current.
    To understand the rest of the connection, you can now ignore those two sets of windings and just look at the two isolated 1st windings, each of which produces 120VAC and in the connection you see produces a 120-0-120 split phase (single phase) 240V system just like a typical residential service. The voltage between the two ends of that series string is 240V.
    SMA SB 3000, old BP panels.
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    Ok great, that makes some sense to me- i'd love to understand the maths a bit more :confused:.. but maybe that's pushing my boundaries.

    So I take it that this setup, would provide a quality 240V sine wave for the inverter input. However, as the inverter output neutral will be ground-referenced... i wonder how this will affect the L1-L2 from the generator... Will the inverter simply ground-reference both its input and output neutrals?? OR will it leave L1-L2 from the generator floating?
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: 3 phase generator question

    I have a Mecca-Alt, 20 KW generator head that I think wires up like yours. The quality of the output is based on the AVR ( $1,000 ) and the governor & engine combination. It took awhile to get all the AVR settings correct, now it'll hold to utility grade output specs no matter how it's loaded at 240v @ 60 hz.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    From the manual, it appears you have to green wire/earth ground the genset according to your local electrical wiring requirements (at the main panel?). All of the alternator outputs are floating from the factory (unless somebody ground bonded the generator after the original installation).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    I spoke with Victron in Holland. They say a floating N input is not a problem for the inverter.

    They say that when the inverter is on the Earth-N is active, but when it's in charging mode that the Earth-N connection disengages and the system will be floating.

    I'm not convinced as the connection in the inverter of Earth-N seems permanent to me at the AC-out connection. So I predict that when connected to the inverter and the inverter is on, that the inverter grounds the generator AC-in neutral.... what does the forum think?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Do you have a link to the Victron Inverter you are thinking of using/connecting to?

    Some AC Inverters with AC input will switch the Ground/Neutral Bonding Lead with an AC Transfer Switch...

    In Spain, with your 230 VAC service--Do they "ground bond" the AC neutral from the utility feed (at the transformer, in the home/business, etc.) or do you expect the 230 VAC to be floating?

    The Generator is, sort of, a non-issue here. If the generator does not have a jumper from L(x) or Neutral to green wire/earth ground by the installer, then it is floating and "does not care" what happens "down stream".

    You just need to understand what is "expected" by your customer/local inspectors/local electricians for ground bonding (if any) of your local AC mains.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    Re: 3 phase generator question

    HI Bill

    There'll be no mains connection- just the generator support- the inverter will be the following: http://www.victronenergy.com/upload/documents/Manual%20-%20MultiPlus%205k%20230V%20-%20rev%2007%20-%20EN%20NL%20FR%20DE%20ES%20SE.pdf
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 phase generator question

    Larry,

    I am still interested in what is "expected" for single phase 230 VAC utility power in Spain (or where this system will be installed).

    Is the utility "neutral" bonded to earth ground (ground rod/water pipe) and the other lead is "Line" or "Hot"?

    Or do you expect that both single phase 230 VAC leads to be "floating"?

    And when you carry power through to the home outlets--If you have a "grounded neutral", is the 230 VAC socket polarized? (in the US, the outlets are polarized so that we always know which lead is Neutral and which is Hot (at least in new construction in the last 40-50+ years).

    Anyway, the way it appears is that you should "pick" one L(x) lead of 230 VAC lines and "earth ground" it (cold water pipe, ground rod, etc... Whatever is standard in your location). The other L(x) lead is "Hot" and should be carried through as the "L" lead for the AC inverter.

    The inverter has a transfer switch which will either use the L + Ground Neutral from the Generator (or AC mains), and when the inverter is supplying AC power, the Transfer switch with "ground reference" the Neutral leg using the inverter's "PE" ground as a reference.

    Assuming that your customer is "OK" with L+N (ground referenced Neutral, all fuses/breakers should be on L lead)--It seems like a safe and sane installation from what little I can see.

    I was unclear to me that the Transfer Switch could "switch" the Neutral's separately (usually all three "contacts" switch together)--So I don't expect any "fancy programming" issues.

    Again, based on what I understand from 1/2 a world away.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset