Grounding two (mains and generator) power feeds

On 5 Jul 2004 14:16:02 GMT snipped-for-privacy@ipal.net wrote: | On Sun, 04 Jul 2004 21:54:24 -0500 Jim Michaels wrote: | | On 25 Jun 2004 19:35:09 GMT, snipped-for-privacy@ipal.net wrote: | | | |>On Fri, 25 Jun 2004 00:53:05 -0500 Jim Michaels wrote: | |>

| |>| If you want massive functionality during an outage you could get a | |>| pair of :|

| |>They don't indicating the winding configuration on that. But I did find | |>another generator of the same size from Kohler, and it does use a double | |>delta type configuration, which is what I want to avoid. | | | | It is a true single phase generator. | | | | All the tech info is in the PDF specification sheet. The link is at | | the bottom of the main page. | | | | | | Kohler also offers a true single phase unit in 45kw (model 4Q10) | |

Plus, I may be having some occaisional use for three phase power. Given the cost of getting three phase from the utility would be high, and possibly very high, a generator would be a convenient way to get it when the usage is only occaisional.

On 5 Jul 2004 15:58:04 GMT, snipped-for-privacy@ipal.net put forth the notion that...

Why not use a rotary converter?

| On 5 Jul 2004 15:58:04 GMT, snipped-for-privacy@ipal.net put forth the | notion that... | | |> On 5 Jul 2004 14:16:02 GMT snipped-for-privacy@ipal.net wrote: |> | On Sun, 04 Jul 2004 21:54:24 -0500 Jim Michaels wrote: |> | | On 25 Jun 2004 19:35:09 GMT, snipped-for-privacy@ipal.net wrote: |> | | |> | |>On Fri, 25 Jun 2004 00:53:05 -0500 Jim Michaels wrote: |> | |>

|> | |>| If you want massive functionality during an outage you could get a |> | |>| pair of :|

|> | |>They don't indicating the winding configuration on that. But I did find |> | |>another generator of the same size from Kohler, and it does use a double |> | |>delta type configuration, which is what I want to avoid. |> | | |> | | It is a true single phase generator. |> | | |> | | All the tech info is in the PDF specification sheet. The link is at |> | | the bottom of the main page. |> | | |> | | |> | | Kohler also offers a true single phase unit in 45kw (model 4Q10) |> | |

I haven't found one I like. And you still have to add transformers to get all the voltages and phase angles right for 208Y/120 and/or 480Y/277. Most three phase generators produce it directly. The only ones I've seen that do what I want cost as much as a generator. I'd just be better off with a generator since it can also serve double duty as backup power, which I want to have anyway.

So the idea is to get a generator that can supply my backup power needs, plus supply three phase for occaisional three phase needs. Integrating that with the regular wiring will be part of what I am designing. But it has to also work with single phase utility power. There are a number of ways to do this that I am exploring. It may end up involving multiple small transfer switches. I'm still not sure of the best way to deal with some 240 volt single phase loads when getting 208 volts from the generator. But I don't want delta, so that means my choices are 208Y/120 or 240Y/139.

On 6 Jul 2004 00:05:46 GMT, snipped-for-privacy@ipal.net put forth the notion that...

The reason I mentioned it is I manufacture rotary converters, but they're all designed to operate on 220-240 volts. Getting all the other voltages you want out of a rotary isn't very practical cost-wise, for the reasons you mentioned. What is it you're designing, if I might ask?

| The reason I mentioned it is I manufacture rotary converters, but | they're all designed to operate on 220-240 volts. Getting all the other | voltages you want out of a rotary isn't very practical cost-wise, for | the reasons you mentioned. What is it you're designing, if I might ask?

A house, which will eventually have a detached garage, detached shop, and detached ham radio shack. You could call it a "personal campus".

You get 2/3 of the generator's 3 phase VA capacity which is normally greater than the prime movers power capacity to allow for non-unity power factors. Typical 60kw 3 phase genset has 72kVa generator section.

You still get all of the power available from the prime mover, if the generator is designed to provide appropriate VA capacity when in single phase mode.

The added cost of the select-able mode generator will easily be offset by the savings over the transfer switches, wiring, and boost/buck transformers needed by the three phase/single phase mixed system.

Remove SPAMX from email address

On Tue, 06 Jul 2004 22:55:26 -0500 Jim Michaels wrote: | On 5 Jul 2004 14:16:02 GMT, snipped-for-privacy@ipal.net wrote: | |>On Sun, 04 Jul 2004 21:54:24 -0500 Jim Michaels wrote: |>| On 25 Jun 2004 19:35:09 GMT, snipped-for-privacy@ipal.net wrote: |>| |>|>On Fri, 25 Jun 2004 00:53:05 -0500 Jim Michaels wrote: |>|>

|>|>| If you want massive functionality during an outage you could get a |>|>| pair of :|

|>|>They don't indicating the winding configuration on that. But I did find |>|>another generator of the same size from Kohler, and it does use a double |>|>delta type configuration, which is what I want to avoid. |>| |>| It is a true single phase generator. |>| |>| All the tech info is in the PDF specification sheet. The link is at |>| the bottom of the main page. |>| |>| |>| Kohler also offers a true single phase unit in 45kw (model 4Q10) |>|

|>The power factor applied to the 2 other phases is 0.5 in that case. |>You only get 2/3 of real power capacity. | | You get 2/3 of the generator's 3 phase VA capacity which is normally | greater than the prime movers power capacity to allow for non-unity | power factors. Typical 60kw 3 phase genset has 72kVa generator | section. | | You still get all of the power available from the prime mover, if the | generator is designed to provide appropriate VA capacity when in | single phase mode. | | The added cost of the select-able mode generator will easily be offset | by the savings over the transfer switches, wiring, and boost/buck | transformers needed by the three phase/single phase mixed system.

I'd still have 2 or 3 transformers getting the delta-delta power out of the generator unless that generator has a switch control system. While these generators can be re-wired for single phase, it's not just trivial to do that whenever you need to power up a three phase load. The smallest generator I've seen that incorporates such a switch is 60 kVA and only diesel (intended for trailer porting uses). The only practical way I see to get the single phase is to make that delta-delta with transformers. And that's what I'm trying to avoid with a 3-way balancing of circuits.

If your needs for 3 phase are that small then a static or rotary converter would seem to be a reasonable solution for the occasional 3 phase need. Also you could run your 3 phase (motors?) from utility power and not need to fire up the genny.

Or just replace the 3 phase motors with single phase units.

Even a second generator would seem simpler and cheaper than a complicated switching system and transformers.

This discussion seems to trying to hit a moving target. You should define your resources, needs, desires, and budget and then engineer from there. Remove SPAMX from email address

| This discussion seems to trying to hit a moving target. | You should define your resources, needs, desires, and budget and then | engineer from there.

That is what I am doing. What I post here is not the whole process, but rather, just pieces of it to get specific technical information. Unfortunately it is a tendency for people on Usenet to try to work out the whole solution for people, rather than simply analyze the effect and impact of a candidate solution. I think it has something to do with people wanting to have control, and even helping someone to make a decision by doing the deciding for them satisfies that. I intentionally post only parts of the problem to avoid getting answers that are too limited (e.g. just tell my what to do, not why). I want to know the why's (and why not's). Then I can figure out what will work for me (what works for someone else may not work for me because of something I could have left out even if I try to give all the info). And in this case, much of what needs to be known to make the decision isn't yet known, and is part of the design process itself. It's kind of like a "what if" process (you figure out things that maybe you could do, and explore whether or not it is feasible by first understanding as much as you can about it, then seeing if it can be fitted into the design process). So yes, it really is much like hitting a moving target (the designing process being what is moving).