MEP 804A RETAPPING

[rangerxp1000]

Has anyone tried retaping a 804 A unit from 3 phase to single phase,

 

[Scoobyshep]

Has anyone tried retaping a 804 A unit from 3 phase to single phase,

IIRC the head on the 804 is only 10 lead (T10, T11, and T12 are bonded internally) So without a head rewind you cant.

 

[Ray70]

Hundreds of discussions about the subject here on the forum, but as Scoobyshep stated it's pretty much impossible with the 10 wire gen head.

 

[Scoobyshep]

If you really really want to you can set the unit to 416 volt and use transformers. But that might be a touch excessive

 

[Guyfang]

I wish we could put this old wives tale to bed. Its not possible.

 

[jamawieb]

Yes Ive done it. Ive discussed it in the past. Its very simple. On my next conversion I will take pictures. Ive switched over around 20 804 and 805a's.

 

[Ray70]

Do you have a link to where you previously discussed your conversions?

 

[jamawieb]

Do you have a link to where you previously discussed your conversions?

Let me see if I can find it. It wasn't a thread I started. The idea came from SmokeStak where an individual talked about a Bar Diamond connection. Worked on the theory with some other guys and it worked. The only set back we had was the VR. The original VR reads off all 3 legs to generate power. With Kurt Klopp's VR development, it was a game changer because his VR on reads off of 1 leg. So with the conversion, you have to put in Kurts VR, the remaining conversion is completed on the reconnection board. Its actually easier to do than the older 004 and 005 models. I have logged several thousand hours on 804s so the conversion is very dependable.

 

[2Pbfeet]

Let me see if I can find it. It wasn't a thread I started. The idea came from SmokeStak where an individual talked about a Bar Diamond connection. Worked on the theory with some other guys and it worked. The only set back we had was the VR. The original VR reads off all 3 legs to generate power. With Kurt Klopp's VR development, it was a game changer because his VR on reads off of 1 leg. So with the conversion, you have to put in Kurts VR, the remaining conversion is completed on the reconnection board. Its actually easier to do than the older 004 and 005 models. I have logged several thousand hours on 804s so the conversion is very dependable.

Are the threads by WA Ross? E.g.

Generator Conversion

I brought a 3 phase generator cheaply thinking it would suit me better than a single. However I have found that three phase equipment for domestic use is prohibitive and I would like to convert the machine to single phase: a] Is this Possible? b] If possible how would I proceed?

www.eng-tips.com

Bar Diamond or Collins Connection for 10 Lead 1 Phase 120/240

One W.A. "Bill" Ross on the eng-tips forum seems to have invented this connection. I have never found it in any book or publication. However I have used it when a customer wanted 120/240 1 phase out of a 10 lead machine with T10/T0 all bonded together. It works great and what is even greater...

www.smokstak.com

He seems very confident of his views, and they seem supported by diagrams that don't look crazy to me, but I am not an electrical engineer. He does point out the 1/3 loss in KVA capacity.

All the best,

2Pbfeet

 

[jamawieb]

Are the threads by WA Ross? E.g.

Generator Conversion

I brought a 3 phase generator cheaply thinking it would suit me better than a single. However I have found that three phase equipment for domestic use is prohibitive and I would like to convert the machine to single phase: a] Is this Possible? b] If possible how would I proceed?

www.eng-tips.com

Bar Diamond or Collins Connection for 10 Lead 1 Phase 120/240

One W.A. "Bill" Ross on the eng-tips forum seems to have invented this connection. I have never found it in any book or publication. However I have used it when a customer wanted 120/240 1 phase out of a 10 lead machine with T10/T0 all bonded together. It works great and what is even greater...

www.smokstak.com

He seems very confident of his views, and they seem supported by diagrams that don't look crazy to me, but I am not an electrical engineer. He does point out the 1/3 loss in KVA capacity.

All the best,

2Pbfeet

That is one of the articles. I shared the conversion with Peter who owns Innovahightech because he was very confident that it could NOT be done. He contacted electrical engineers with Marthon and explained the conversion, to his surprise they confirmed the ability with my drawings. Rated output of the generator is still 15kw on the 804 and 30kw on the 805. But anything over that trips the overload. Usually on the 804 I can push them until 19-20kw before overload happens.

 

[2Pbfeet]

That is one of the articles. I shared the conversion with Peter who owns Innovahightech because he was very confident that it could NOT be done. He contacted electrical engineers with Marthon and explained the conversion, to his surprise they confirmed the ability with my drawings. Rated output of the generator is still 15kw on the 804 and 30kw on the 805. But anything over that trips the overload. Usually on the 804 I can push them until 19-20kw before overload happens.

Thanks for the deep due diligence on your and Peter's (@peapvp) part! It is nice to know that on the 804/805 sets that there is no loss in capacity.

All the best,

2PbFeet

 

[Guyfang]

Good news!

 

[peapvp]

That is one of the articles. I shared the conversion with Peter who owns Innovahightech because he was very confident that it could NOT be done. He contacted electrical engineers with Marthon and explained the conversion, to his surprise they confirmed the ability with my drawings. Rated output of the generator is still 15kw on the 804 and 30kw on the 805. But anything over that trips the overload. Usually on the 804 I can push them until 19-20kw before overload happens.

@jamawieb
I am getting old, when did I have this conversation with you and Marathon(?)
I can’t remember this conversation and just checked my email archives and my steelsoldiers pm

 

[Ray70]

What am I missing here?? Reading the articles ( 2nd one in particular ) it sounds like he's saying you can rewire the 10 lead generator into a "reversed" dogleg output, but then he goes on to say the output will be reduced by 1/3 and the voltage will be 208 not 240.
What's the difference between that modification and just running your single phase loads off 2 of the original 3 phases?
Does this modification give you less output current, at 208V BUT balance the 3 legs?
( This is why I'm more of a mechanic, not an electrician.... )

 

[jamawieb]

What am I missing here?? Reading the articles ( 2nd one in particular ) it sounds like he's saying you can rewire the 10 lead generator into a "reversed" dogleg output, but then he goes on to say the output will be reduced by 1/3 and the voltage will be 208 not 240.
What's the difference between that modification and just running your single phase loads off 2 of the original 3 phases?
Does this modification give you less output current, at 208V BUT balance the 3 legs?
( This is why I'm more of a mechanic, not an electrician.... )

Ray,
It does not reduce voltage by 1/3. Ive completed the conversion on over 50 804 and 805a's. You will get 120/240v out of the set. On the 804 you will get 16kw all day long. It will surge to 20kw. But after 10 minutes on anything over 16kw it will trip the overload.
Jimmy

 

[peapvp]

What am I missing here?? Reading the articles ( 2nd one in particular ) it sounds like he's saying you can rewire the 10 lead generator into a "reversed" dogleg output, but then he goes on to say the output will be reduced by 1/3 and the voltage will be 208 not 240.
What's the difference between that modification and just running your single phase loads off 2 of the original 3 phases?
Does this modification give you less output current, at 208V BUT balance the 3 legs?
( This is why I'm more of a mechanic, not an electrician.... )

Ray, hope you’re doing well.
There is two ends to these conversions, like a sausage which has two ends and you don’t want one open….

1. the first question which has to be clarified is, whether the genhead was constructed in such way that a zig zag or dogleg will give you a phase shift of 180 degrees in single phase 240 connection between L1 and L2 or not.
A standard 3 phase genhead is constructed in such way, meaning the coil arrangement in the armature, that there is a 120 degree phase shift between each phase
Some off these heads can be reconfigured with their leads to match the voltages but they will not do the required phase shift of 180 degrees.

The now famous YouTube videos of our esteemed member shows him demonstrating the 180 degree phase shift between the two phases with his oscilloscope.
I am not sure on how exactly this was accomplished and of what he was actually showing us in his video, but he might be correct.

2. Each coil in a 3 phase generator head is wound with a specific wire gauge which will determine the maximum current each coil can produce and is determined by current draw from any one phase to neutral ( 120V).
The voltage is determined by the amount of turns each coil has.
A three phase head has 3 pairs of coils, one pair for each leg.
Each pair can be connected in series to produce 416V or in parallel for 208V which will then double the current

let’s say we have a 15KW rating with a power factor of 1 ( ideal generator ) as example.
Then when we apply ohms law and use power, we can see that we get a maximum of 72 Amps @ 208V
Now we divide the 72 Amps by 3 and we get 24 Amps per phase in parallel;
208V x 24A = 4992 VA = 4.992 KVA or KW

this means each individual coil is rated for 2.5 KW and yield 5 KW in parallel or in series because of the higher voltage 416V x 12A = 4992 VA

on the xx2 and xx3 gensets the coils are rated for the highest current in single phase 120V configuration

for a xx4 this would be 41.66 Amps x 120V = 4999.2 KVA


so in the end you will loose the power from one coil pair whenever you are doing a conversion or when you connect only to two legs on a 3 phase configured genset.

I used a power factor of 1 rather then working in the actual power factor of 0.8 PF for demonstration purposes to make it easier to be understood for all the readers who do not poses a phd in electrical engineering.


The currents with PF 0.8 are
120V 52Amps per phase
208V 26Amps between two phases
416V 13Amps between two phases

 

[Scoobyshep]

The phase shift in a low zigzag works because of the addition and subtraction of the 3rd leg tapped to leg 2. (One rises as the other falls averaging two 120volt over 2 legs)

The head is arranged where the phases are 120 apart but when leg 2 is extended it ends up 180 out. Simple way (but crude) is to draw out the windings in wye. Lay your pen over the drawing and spin it over the neutral. Tip is north clip is south each leg is 120 out. Do the same with the zigzag. You'll see they are 180 out now.

As someone who has done this to a 004 and 005 I can say the o scope readings are accurate.

Sent from my SM-S908U using Tapatalk

 

[peapvp]

Ray,
It does not reduce voltage by 1/3. Ive completed the conversion on over 50 804 and 805a's. You will get 120/240v out of the set. On the 804 you will get 16kw all day long. It will surge to 20kw. But after 10 minutes on anything over 16kw it will trip the overload.
Jimmy

James, I hope you are doing well.

If the interested reader has read posts #16 and 17#, this reader maybe wondering on how is it possible that James was able to get 16KW since he should have gotten only 10KW or a little bit more.

The explanation is quite simple:

A Generator head can produce basically infinite power with a oversized voltage regulator and without any circuit breaker in use.

This brings us to Guy's ( @Guyfang ) experience with the ultimate Fireworks or better, the fireworks of all fireworks

This spectacle will go on until either the Genhead Winding's melt down and shorten/open up or the Voltage Regulator goes to Voltage Regulator Heaven


The MEP Generators receive their current feedback through current transformers for each leg.

To convert a Generator properly, then the entire circuit protection has to be adjusted.

In a three phase gesent like in the MEP's (exception xx2, xx3), the circuit protection was designed to sum all three phase together and a over current is therefor determined by the sum of all three phase currents or if any one of the individual phases exceeds this summed threshold.

In our example in post #16 we derived at 72 Amps for a 15 KW rated genset @ 208V as a summed current.

The trip point is usually set to 15% above this summed current => 83.5 Amps

If we are using two phases out only, then each phase can be loaded up to 41.75 Amps each, which summed up by two phases loaded,
is 83.5 Amps x 208V = 17,368 VA or 17.368 KVA / KW

However, this can create the following issues:

1. The Coils and Armature over heat during prolonged overload condition and can get damaged.
This heavily depends on the ambient temperature, i.e. doing this at -20F provides sufficient cooling of Genhead vs doing this at 120F in the Arizona Desert

2. As higher the load becomes, as more the Automatic Voltage Regulator has to labor and the output current to the Exciter Coil increases dramatically.
This becomes even more of an issue when the output voltage is set like to 240 VAC rather then 208VAC, as the AVR is being operated on the end of their limits. AVR failure is usually the consequence.

IMPORTANT:
The Power Meter on the front panel also sums the output current of all three phases as the circuit protection circuit does. The Power Meter will indicate a 100% Load in the above scenario even though the genhead is technically overloaded and may give the Genset Operator the wrong feel that everything is running fine and OK

My suggestion is as follows, regardless if conversion or only two phases are used:

1. Set Voltage output to only 220VAC and your AVR will kiss you

2. Stay below 66% on the Powermeter

3. Adjust the amount of turns on your CT winding's to trip at 70% load on Power Meter

 

[LuckeyD]

Good day Folks. Not a fan of making single phase from a 3 phase but here goes. OK, PM MEP never thought of after market. They made the 15TQG according to the requirements Docs and Fermont came up with using a modified Marathon 12 lead down to 10 main gen because of mistakes from GIs using a 12 lead main gen. Count the fingers and think a moment. Marathon did not care. It does have 12 leads if you take it apart, find the neutral bundle and manage to separate the right t winding coil end and then get them back together for what is left over and insulate. Good Luck. You will find 10 11 and 12 together and they put one cable out to the Neutral from them and 5 and 6 was for other reasons. To make a 120/240 out of this main gen is next to impossible, but it is wound so one may want to try making it a delta strap. You can make it a 120/240 if you go to Marathon, purchase a main gen with 12 leads out and strap it, (or get one for this purpose) then reconnect the voltage sensing to another terminal and you can do it all at the TB1 area. The wrapping of the current transformers using the 12 lead main gen is about the same as you normally expect. One of the contracted maintenance guys in BLD 601 in Bagram AB tried this for a village at the request of the JOC. Result, POOF! They called me thinking I had a magic wand since I got other stuff going said one of the star ranking guys. Gave the same answer as this and it got dropped. $$$$ The village did use the CARC painted engine top as a grill. Don't say nothin, it made that war lord happy with a little greased palm, we had no body bags. It is not a DED or AMMPS main gen. Oh, on those that normally switch, (5 and 10KW) they use a quad winding for shaping and control because of this stuff. (The Marathon engineer answer). Cheaper to get an APU already set up for this as he went on. Still not bad for last half of the 80s design. Hint, look at AMMPs Cummins ONAN main gens for this idea. AMMPS 10 and 15KWs use the same main gen believe it or not. Check the parts if you do not believe me. Much cheaper to use 3 phases, adj voltages to threshold ratings, and use the last phase on some dedicated circuits.120 becomes 126 and 240 becomes 236. Most stuff will still work.