Wiring my MEP-804a to run single phase

[cpstanley]

Let me start by saying I am new to this forum and am amazed by the knowledge of many on here. I recently purchased both a 004a and 804a and working/learning the machines has become an obsession.

That being said, I have read many threads and understand converting the 004a to single phase. However, I am unsure of how to wire my 804a to run single phase. I know it cannot be converted but would like to hook up a three wire configuration to either L1-L2-L3 (two wires) and another to ground. This will give me single phase power from the three phase generator. However, I have read a lot about balancing the load and am unsure of what that means.

Another questions I have is the position of the rotary knob. If I have it on the L1-L0 then what am i selecting? Is L-1 the only pole receiving power? I am using this generator as a whole house backup and have read myself crazy on how to do this.

Another option all together is to get a 803a but they are a lot more expensive from what I have found.

Any and all help is appreciated. I am not an electrician and am grasping for knowledge.

Thank you,

Chris

 

[DieselAddict]

If you connect it up that way it will be 208v. The power will be 120 degree out of phase instead of 180 degrees. That will be ok for most things but anything with a 240v motor will run hotter than normal. Any of the 120v loads will see normal power. I expect you already understand that you will at most get 2/3 the capacity of the 804 using it this way.

The labels on on the switch are indicating which terminals the reading on the gauges is between. L0-L1 means you are reading the volts and amps between those two terminals.

 

[cpstanley]

Great. Thank you for the information. Is there a "down side" to doing it this way? What about balancing the load? I also thought about runing some 120v outlets from the third leg to use externally. Possible?

 

[Suprman]

Its not good to have an unbalanced load like that. If you were using 3 phase power and tapped off for some single phase use thats fine. Just using the 2 legs only is not advisable. TQ gens have 10 wire head you cant convert them to single phase. MEP-803a 10kw gen is a great unit and will provide just as much power as you could get out of the 2x 120v legs on the 15kw.
Will

 

[DieselAddict]

Agreed that it isn't the best scenario. But in the world of you run what you got.. Thats how it goes. The reality is that in a residential backup situation we aren't going to run these machines hard or long. Sure, and imbalance is bad. Its worse for a machine that runs at high loads for long periods. Doing for a few hours (as most residential outages go) isn't that bad. Running it with NO load is worse in my opinion.

The other reality with residential is that most load is 120v. That is going to cause a lot of unbalance as well. Even if you have a single phase generator you'll likely see a lot of imbalance and more neutral current than one would like.

To answer the other question, I would absolutely run the unused phase for lights or garage fridges or whatever you can.

 

[NEIOWA]

What does unbalanced is bad mean? Short/medium/long term burn out the winding in generator? controls? other?

 

[Suprman]

I am not an expert on this but here goes. 120/208 3 phase has 2 120v legs and one 208 (the bastard) leg. The 2 120 volt legs can be used for single phase power. When 3 phase gens have convenience outlets they are usually powered via those legs. Only drawing off 2 of the 3 legs, you would only have a certain percentage of the rated power output. So you could end up overloading those outputs by drawing what you think is under the generators rated output. The regulation system may not work properly and there may be some type of protection on the generator that kicks in and shuts you down. Also the protection may not work properly and you could cause damage by overload. On a 12 wire stator head it can be re-wired for single phase use. 10 wire head cannot. The older mep004a is a 12 wire head and there is info on the internet where people have converted them to single phase. Figure you could get 8kw safely out of the mep804a just using the 2 120v legs. It would use more fuel running that load than the 10kw mep803a running the same or slightly larger load since the 15kw gen has a larger motor and is still spinning a larger stator.

 

[DieselAddict]

Its true that in a perfect world there would be no imbalance. Anytime you allow single phase loads on a multi-phase source you WILL have phase load imbalances. What this does is causes uneven heating in coils and higher neutral currents. Normally this is a bad thing. If the generator was wound such that each set of phase coils were organized into three quadrants each 120 degrees apart the uneven heating would be magnified. The way these things are actually wound is the winding stagger and the angular separation is based on the number of poles on the rotor. As an example if there were 3 coils that were 120 degrees apart the rotor would be 2-pole. If you have a 4-pole rotor the coils will be 60 degrees apart. What this does is more closely couple the coils from a thermal perspective. This gives you more resistance to the thermal problems that come from imbalances.

I've attached a graphic that gives you a good idea how the winding of the stator is done. This is for a motor but the basics are exactly the same.

Now.. The interesting part is even though the 804 is technically a 10 wire head it has the exact same windings as a 12 wire head. The only difference is that 3 of the wires are connected together inside the head instead of bring brought out. What the is interesting is this - it is theoretically possible to modify the stator to be a 12 wire setup. I've been looking around to get my hands on one (804 stator) to find out how hard this will be able to pull off. If anyone has one, even a blown one, send it to me.

 

[cpstanley]

Great information guys. Thank you. I have a guy interested in my 804a but will need to decide whether to convert my 004a or part with both and get a 803a. I love my 004a but it is big and noisy.

 

[Guyfang]

All one needs to keep a MEP-004A running is air, fuel and compression. And very few tools. Great running gen sets. Yeah, we always had a bit of leaky main seals. That's a White engine. But with minimal TLC, it should run for ever.

 

[storeman]

Now.. The interesting part is even though the 804 is technically a 10 wire head it has the exact same windings as a 12 wire head. The only difference is that 3 of the wires are connected together inside the head instead of bring brought out. What the is interesting is this - it is theoretically possible to modify the stator to be a 12 wire setup. I've been looking around to get my hands on one (804 stator) to find out how hard this will be able to pull off. If anyone has one, even a blown one, send it to me.

Hi Diesel,
I'm curious. Did anyone respond regarding the 804 stator? I'm thinking of fooling with an 804 also. Been a while since I've been on the forum but found this thread while searching about 804s.
Jerry

 

[Suprman]

It's my understanding that since it's a wye config you can use each of the 3 120v legs to neutral for single phase power as long as the load on each leg is relatively equal.

 

[DieselAddict]

Hi Diesel,
I'm curious. Did anyone respond regarding the 804 stator? I'm thinking of fooling with an 804 also. Been a while since I've been on the forum but found this thread while searching about 804s.
Jerry

No response. I'll keep looking around though. I won't be able to do any serious work on one if it falls into my lap till I'm back at home full time at the end of the year.

 

[storeman]

Understand. Deployed? USAF or Army?
Jerry

 

[DieselAddict]

"Rental" engineer. Doing an expansion in Hillsboro OR for a sterile products filling plant (biopharma).

 

[dav5]

It will be great when you are back home and have more time Chris. Are you still working on the final edition of a colored schematic and maybe an 831a controller?

 

[DieselAddict]

It will be great when you are back home and have more time Chris. Are you still working on the final edition of a colored schematic and maybe an 831a controller?

I'm really looking forward to it. I hate that I've not finished up the schematic. I need to get a bit of motivation to finish it.

Once I get home I'll be building a shop. When thats done I'll have the space and hopefully the time to do a bunch of generator experimentation. I have prototype controller for the 831 built. Finishing that project will be a priority in the new shop.

 

[Guyfang]

Everything comes to the man or woman with patience, (and time!!!!!!!!!!!)

 

[dav5]

You have your priorities right for sure a shop is soooo important. Good luck

 

[YohanM]

Its true that in a perfect world there would be no imbalance. Anytime you allow single phase loads on a multi-phase source you WILL have phase load imbalances. What this does is causes uneven heating in coils and higher neutral currents. Normally this is a bad thing. If the generator was wound such that each set of phase coils were organized into three quadrants each 120 degrees apart the uneven heating would be magnified. The way these things are actually wound is the winding stagger and the angular separation is based on the number of poles on the rotor. As an example if there were 3 coils that were 120 degrees apart the rotor would be 2-pole. If you have a 4-pole rotor the coils will be 60 degrees apart. What this does is more closely couple the coils from a thermal perspective. This gives you more resistance to the thermal problems that come from imbalances.

I've attached a graphic that gives you a good idea how the winding of the stator is done. This is for a motor but the basics are exactly the same.

Now.. The interesting part is even though the 804 is technically a 10 wire head it has the exact same windings as a 12 wire head. The only difference is that 3 of the wires are connected together inside the head instead of bring brought out. What the is interesting is this - it is theoretically possible to modify the stator to be a 12 wire setup. I've been looking around to get my hands on one (804 stator) to find out how hard this will be able to pull off. If anyone has one, even a blown one, send it to me.

Hello Diesel,

I have an MEP-804A at an electric shop because the Generator was blown, and I was wondering if you can provide more info on how you would pull out the other 2 wires to make it 12 wire head. I am trying to use this generator as a backup for my house and connect it directly to my panel.

Is there any technical data on doing this conversion that I can show the shop and have them do it?