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re-wiring my MEP-004a for different voltages, including single phase

trukhead

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-002 and -003 are selectable between single and 3 phase with one switch; its a pretty neat feature!

It isn't an efficiency issue; it is the limit of how much current each individual winding can carry. When pulling single phase off of a wye (3 phase) configured machine, you are pulling more current through individual windings than when the machine is configured for single phase.
Thanks for the explain!

For a 3 phase machine, does it have 3 windings 120 degrees apart to make 3 phase and for single phase the machine has one winding to make the sine wave up then down for 180 degrees each side of 0? I understand that on an electric motor there are more than just 2 coils but that is that to make magnetizm to spin the armature, not to induce current in fields?
Are these generators or alternators?
Does the winding on a generator or alternator resemble a typical electric motor?

sure is - maybe a little more :grin:

I've had mine loaded with 50 amps/leg & 240 volts output (pretty resistive load) for 1/2 hour with no issues (that would be 12 kw)
Cool, thanks for the heads up! Sounds like a n 003 is the one for me.:grin:

This is a fascinating thread:jumpin:
 
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sinkaferd

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hey sewerzuk, I'm a newby with a mep 018, but I have been tied to this thread all day with amazement and antipacitation for your success. I know very little about these, but it has been my pleasure just "rubbing elbows" with you and all who participated with questions and theories. I join everyone offering gratitude and thanks to you for your dedication and drive to make this venture a huge success!!!!! Excellant. sinkaferd
 

leedawg

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sewerzuk just had to say thank you so much for all the info!!! Hands down best thread of the year its the entire reason I purchased a MEP 005a.

I had one question with my digital multimeter I get open line when I take a reading across L1 and L3. The meter does not read 240 as I would think it would it reads it as open circuit. Perhaps something wrong with my meter I dunno. I get the 120v from L1-Lo and L3-Lo. The Meter on the panel reads the 240 however so im not to worried about it just curious why.

Second question how did you go about fixing your percent power meter? Did you just simply replace the gauge with a new one or is there a transducer or something that needs to be replaced as well when you do that?

Thanks again.

Lee
 

sewerzuk

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sewerzuk just had to say thank you so much for all the info!!! Hands down best thread of the year its the entire reason I purchased a MEP 005a.

I had one question with my digital multimeter I get open line when I take a reading across L1 and L3. The meter does not read 240 as I would think it would it reads it as open circuit. Perhaps something wrong with my meter I dunno. I get the 120v from L1-Lo and L3-Lo. The Meter on the panel reads the 240 however so im not to worried about it just curious why.

Second question how did you go about fixing your percent power meter? Did you just simply replace the gauge with a new one or is there a transducer or something that needs to be replaced as well when you do that?

Thanks again.

Lee
Not sure why you are getting zero voltage across L1-L3; especially since your installed voltmeter reads 240 when selected to that position. If that set was in my shop, I would clamp my oscilloscope across the 2 phases and make sure they were 180 degrees out of phase...

I placed 3 resistors acrosss the outputs of the current transformer. This reduced the % power meter reading, % current reading, and raised the trip setpoints. I have a picture and small discussion about it on post #90:
http://www.steelsoldiers.com/auxili...ges-including-single-phase-9.html#post1064322
 

leedawg

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Napa / CA
Not sure why you are getting zero voltage across L1-L3; especially since your installed voltmeter reads 240 when selected to that position. If that set was in my shop, I would clamp my oscilloscope across the 2 phases and make sure they were 180 degrees out of phase...

I placed 3 resistors acrosss the outputs of the current transformer. This reduced the % power meter reading, % current reading, and raised the trip setpoints. I have a picture and small discussion about it on post #90:
http://www.steelsoldiers.com/auxili...ges-including-single-phase-9.html#post1064322
Thanks for the reply. I understand this is how you corrected the gauges so they read more accurate to what the unit is actually putting out.

My problem is that the percent power meter is not working at all and I noted in one of your videos you said that you had a unit that also had this problem. I get a reading on the L3-Lo leg onn the ampmeter as well as the L1-Lo leg and the L1-L3 I get a very low reading on the amp meter. But all three of those positions I do not get any readings on the percent power meter. I took a video and switched between them so you can see what I am talking about. I am pretty sure im near 90 percent power due to the amps being put out. With my ring ampmeter (Fluke) I was measuring around 76 amps of current on each leg going to the panel.

Is there a tranducer or something that I need to replace to get the percent power meter working or is actually the gauge itself in the panel that is not working typically with these. Thanks so much again sewerzuk!

[media]http://www.youtube.com/watch?v=9zD10OnEKRw[/media]

Lee
 

sewerzuk

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Location
Seaside, OR
Thanks for the reply. I understand this is how you corrected the gauges so they read more accurate to what the unit is actually putting out.

My problem is that the percent power meter is not working at all and I noted in one of your videos you said that you had a unit that also had this problem. I get a reading on the L3-Lo leg onn the ampmeter as well as the L1-Lo leg and the L1-L3 I get a very low reading on the amp meter. But all three of those positions I do not get any readings on the percent power meter. I took a video and switched between them so you can see what I am talking about. I am pretty sure im near 90 percent power due to the amps being put out. With my ring ampmeter (Fluke) I was measuring around 76 amps of current on each leg going to the panel.

Is there a tranducer or something that I need to replace to get the percent power meter working or is actually the gauge itself in the panel that is not working typically with these. Thanks so much again sewerzuk!

[media]http://www.youtube.com/watch?v=9zD10OnEKRw[/media]

Lee
The basic way the circuit works is that the thermal watt converter (black box inside the control cubicle) takes an input from the current transformer and drives the gauges; if the ammeter and the wattmeter both are not working, then the gauges themselves are likely not the problem (although this isn't definitive). It is more likely either a bad current transformer, or a bad thermal watt converter.

You can check the meters with a voltmeter across their terminals; it should vary from zero volts at no load up to several volts at full load (I'm not sure of the exact value).

You can check the CT by disconnecting the secondary leads and checking resistance of the windings (should be just a few ohms).

The thermal watt converter is kind of a magic black box, with components potted in epoxy. It can't be easily repaired (although I'm sure there are some electronics gurus out there who are up to the task).

edit:
after watching your video, I had a few questions:
I'm wondering how you had the set loaded besides the air compressor? Assuming you had this wired up to your house with a semi-constant load?
also, did you do the complete single phase conversion, including moving the leads underneath the voltage reconnection board? Or did you just do the bus bar/jumper mod? The way the meters are behaving, it is possible that you either didn't move the small leads on the bottom of the board, or possibly placed them on the wrong terminals.
It appears that your ammeter is working properly...it looked like it jumped a bit when your compressor started, and seems to be showing about 50%. At 76 amps, you're putting out roughly 18kw, or a little over 1/2 the rated output of your -005a. So, it seems that your % power meter is the only one with the problem...
That means that your CT is working properly, so you can eliminate it from the troubleshooting. I would start by verifying that you placed the leads under the reconnection board correctly, then measure voltage across the leads to the % power meter, and then follow it back through the circuit to the thermal watt converter.
 
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leedawg

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Location
Napa / CA
=sewerzuk;1178276
edit:
after watching your video, I had a few questions:
converter.

Thanks for taking a look swerzuk.

Ill answer your questions. Yes I did your mod I connected T12, 10, 11 together with some really heavy battery cable from the bottom side. I then connected T12 to T2.

I then moved the three wires as described in your video. So that is probably why the volts and amp meter are working alright.

I actually disassembled the meter itself today even though it said not to open it and discovered that one of the really really fine copper springs that moves the needle back to zero and carries the current to the coil on the needle was broken so that explains why its not moving. On a positive note I am getting about 4-5 volts DC power out of the thermal watt converter at both the meters leads and at the terminals on the thermal watt converter so hopefully that means it is not bad. I just now have to track down a new percent power meter. Found one that is the exact match on ebay but they want 100 bucks for it. Seems a little steep to me. I made an offer of 50 on it we will see what they say. Monday I am going to call Delks and ask them what they want for it.

What do you guys think is a fair price on one of these would be. Mine was the A&M Instruments version.

To answer how it was loaded. It was also driving the house AC there is an AC unit on in the barn as well. Had 4 refrigerators going and a freezer as well. Put the cloths dryer on and the electric oven in the house. Other than that not to much more to put on it. I wish I had a load bank to really test this thing out but all the ones ive seen cost at least 1500 dollars or more so guess I will just have to turn lots of stuff on and put it under a real load.

Where did you obtain your load bank if you dont mind me asking? Just curious if you know of a place to get them for a bit less.

At 18kv I hopefully will not run into the wetstacking issue ive read so much about on these boards.

Alright ive said enough I fear will update later when I figure out more whats going on thanks again for all the help.

Lee
 

sewerzuk

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Thanks for taking a look swerzuk.

Where did you obtain your load bank if you dont mind me asking? Just curious if you know of a place to get them for a bit less.

At 18kv I hopefully will not run into the wetstacking issue ive read so much about on these boards.

Lee
You're probably fine with the load you have on it to prevent wet stacking; Ithink that the -005a is the perfect gen for your setup! It will handle some larger surges easily too; if you need to start an big electric motors on top of all of that load it won't complain about it.

I bought my load bank from a local generator repair guy; it was a unit that was permanently installed on a 300kW set to provide an automatic dummy load. It drew air through the heat coils with the radiator fan. The generator was pulled and replaced with something else, and the load bank sat outside for a number of years. It was designed to run only 480v 3 phase; I bought it for $300, added some expanded metal to keep body parts from touching the heater coils, added pockets for my forklift forks, and modified it for 120/208 3 phase and 120/240 single phase. It is capable of dissipating 300kW with 100% duty cycle.
It works good for the larger sets, but each heater provides about a 5kw load at 120/208 (a little more with 120/240), so it isn't good for testing smaller sets. I was thinking of modifying it by placing one bank of heater pairs in series to reduce their load...that way I could progressively load the -002's and -003's. But...I haven been able to purchase any for quite a while so I haven't had a reason to do the modifications.
I'm currently working on a 10HP Lister flywheel type diesel engine that I intend to set up with a 120/240 generator head...maybe I'll set up the load bank to test that thing when I get it finished.
 

leedawg

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I'm currently working on a 10HP Lister flywheel type diesel engine that I intend to set up with a 120/240 generator head...maybe I'll set up the load bank to test that thing when I get it finished.
I saw the video of you starting it up looks awsome!! Take some more video when you make more progress on it. I actually subscribed to your channel think I watched almost all your videos. My wife thinks im crazy. She does not see how watching all these youtube videos of a guy doing stuff is entertaining to me, I love it though :) Thanks again Sewerzuk.

Lee
 

leedawg

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Location
Napa / CA
Okay I just wanted to follow up.

I fixed my percent power gauge. You were right sewerzuk it was the the thermal watt converter. I actually had two problems the gauge itself had a broken conductor inside of it so it did not work right and in addition the thermal watt converter was having issues.

So I found a percent power meter on ebay replaced it and noted it still did not read while the generator was under load. I put in a new thermal watt converter and presto its all working well now. Here is a little video of it in action.

[media]http://www.youtube.com/watch?v=WpmHC10Uwm0[/media]

Thanks again for all the help.
 

sewerzuk

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Seaside, OR
Okay I just wanted to follow up.

I fixed my percent power gauge. You were right sewerzuk it was the the thermal watt converter. I actually had two problems the gauge itself had a broken conductor inside of it so it did not work right and in addition the thermal watt converter was having issues.

So I found a percent power meter on ebay replaced it and noted it still did not read while the generator was under load. I put in a new thermal watt converter and presto its all working well now. Here is a little video of it in action.


Thanks again for all the help.
Glad you got it working properly! That's a nice looking set you have; should be a good reliable backup generator for you for years.
 

deuceaid

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So…most of us with 3 phase MEP generator sets have wondered if it is possible to rewire the set for something other than 120/208 or 240/417v. Some have asked the question in the forum here and the consensus seems to be that it won’t work. I think it will.

*I am using one of my MEP-004a’s for testing, so the numbers I am posting are related to its power/current/voltage ratings.

Why re-configure? Well, many of the people who own these generators use them only in single phase, at 120/208v. According to the TM, this is permissible, and the vast majority of 240v appliances operate just fine at 208v. But…there are a few loads that don’t like 208v. And, you are limited to 100% of rated current for each phase; so unless you are sending power to 2 separate services, you can only get about 43A, or 9kW. Re-configuring the set for its intended use nets you more useable power, and provides more appropriate voltage for the loads.

I began thinking about the possibility of re-configuring my MEP-004a the other day, and spent a few hours reading through Steelsoldiers and Smokstak; although there were a few stories of a guy who knew a guy whose buddy’s brother-in-law rewired an MEP for single phase, I couldn’t find a single post by somebody who had actually attempted it. I went a step further, and wondered if it would be possible to wire the generator in a 3 phase delta configuration, thinking that 120/240 delta would be useful for the small shop with several large 240v 3 phase loads, and a requirement for a light single phase 120v load. So, I spent another few hours poring over the schematics. Here are the conclusions I come up with:

The MEP’s use a standard 12 lead generator head. That means that, from the generator’s point of view, pretty much any standard voltage is possible. The problem is in the generators instrumentation and control system…the current transformers for the ammeter and safety trips are designed around a 3 phase wye setup. There is no provision for single phase in how the CT’s are wired. However…this doesn’t mean that single phase isn’t possible, it just means that there might be a few “quirks” to deal with when running single phase. I think that all of the safety trips will still function properly, as they are all designed around current passing through the individual windings of the generator. It doesn’t matter how the load is placed on those windings…the cumulative current is what is important and that will not change. The wattmeter should work properly. I believe that the voltmeter will also work properly; it will indicate line voltage as designed and simply read 0 when switched to the phase not being used (for single phase). The ammeter should also indicate current…however it may be a little confusing. It may indicate actual line current, ½ line current, or 1/√3 line current depending on how the switch is selected and the method I choose to re-wire the generator. This is because of where the CT measures the current (it may be possible to re-wind the CT to work properly, but I’ll jump that hurdle if my re-wire actually works and produces useable power). The voltage regulator should also work properly; it is designed to provide 120v per winding and that is all that is needed to produce the voltages that I am aiming for. 480v 3 phase delta is not possible with this generator, as it requires 240v per winding. I believe the following configurations are possible:

3 phase:
1. 417/240v wye (adjustable from 348/200v up to 480/277v) This is a factory-installed voltage
2. 208/120v wye (adjustable from 173/110v up to 240/138v) This is a factory-installed voltage
3. 240/120v Delta (adjustable from 200/100v up to 277/138v) This does change how current flows through the CT’s and may cause problems with the overload trip and ammeter reading
4. 120v Delta (adjustable from 100v to 138v) I don’t think this is a very useful configuration…don’t know of too many 120v 3 phase loads. But, it should be possible. Same CT issues as 240/120v delta.

Single Phase (both 120/240v configurations produce the same power, just different methods of wiring):
1. 120/240v Double Delta (adjustable from 100/200v up to 138/277v) Same issues with the CT
2. 120/240v low zigzag, or dogleg (adjustable from 100/200v up to 138/277v) Same issues with the CT
3. 240/480v high zigzag (adjustable from 200/400v up to 277/554v) Don’t know how many single phase 480v loads are out there, but 554v might be useful for the guy trying to get a little more lightning length out of his Tesla coil. Same issues with the CT

There are a few issues to deal with and things to think about:
1. The cable size going to the main circuit breaker and to the load terminals is too small for the increased current that is possible during single phase operation. It should be upsized appropriately.
2. I believe that no additional current would be traveling through individual generator windings, meaning that you could get the full rated 15kW out of the generator at 120/240v single phase without exceeding the design limits of the windings (however, the overload trip will still limit you to the current ratings from 3 phase operation).
3. The CT 1-3 could be re-wound to indicate proper current on each “leg”. This would also affect the overload trip.
4. Re-winding the CT’s might indicate proper current; however the overload trip is still set to 130% of the 3 phase rated current; meaning that it will still trip at roughly 55A, even though 63A would be the 100% rated current for single phase 120/240. It may be possible to add a properly sized resistor inline with the overload trip relays, as they only have a very small amount of current passing through them. This resistor could be sized to adjust the overload trip to the new 130% rated current of 82A. Another option would be to increase the size of resistors R23, R24, and R25 in the tactical relay box. It also may be possible to remove one turn of the generator leads from the CT; this would change how the ammeter and wattmeter read, and it would also raise the overload trip setpoint by roughly 25% (this is the method I intend to experiment with).
5. L0 is internally bonded to ground in the generator; therefore it would be absolutely critical to remove this bond prior to starting up the generator in delta configuration. Failure to do so would result in a hardwired phase to ground short.
6. T10, T11, and T12 are bonded together under the voltage reconnection board. It is critical to remove/modify this bonding bar for any configuration other than Wye. Failure to remove it would result is a phase to phase to phase short.
7. The generator reconfiguration should be able to be completed all on the voltage reconnection board; a few jumper wires and buss bars would complete the reconfiguration. I’m hoping to come up with a VERY simple reconnection for zigzag; the other connections will require a bit more work. For that reason I’ll try the zigzag first, and if it works I may proceed to experiment with the delta configurations.

I am planning on attempting this in the coming few weeks with one of my -004a sets. Of course I’ll take all of the safety precautions; and I am prepared for the possibility that I may destroy some critical internal components with my meddling (although I don’t think this will happen…otherwise I wouldn’t be trying it).
I’ll set up the video camera when I first fire this thing up, just in case I manage to create molten copper and smoke instead of single phase power.
I think I have a grasp on the problems, pitfalls, etc. associated with this reconfiguration (albeit a loose grasp). I’m looking for input before I try this out…anything I’ve missed? Am I re-creating something that somebody else has already accomplished?

Attached some relevant schematics and diagrams...

edit 1: low zigzag re-configuration is complete; it works mostly as predicted. Details and a video on page 3
edit 2: additional reconnections have been made to correct issues with the installed voltmeter and voltage regulator. Details on page 4
edit 3: I plan to post the entire reconnection process here in this original post once all of the testing is complete
edit 4: here is the completed process:

[media]http://www.youtube.com/watch?v=YmF4Awr3uc4[/media]
I think most civian genset over 25 k are wired this way..
 

Augdog1964

Member
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Location
Richmond, IN
How do you tell?

Hey all...

How do you tell how many kws your home needs to run in a backup situation?

I am looking to pickup a 15kw or 30kw mil generator... but I want to avoid the problems of not loading the generator enough...

I am an electrical newbie at best... its magic isn't it?

Thanks in Advance!
 

SCSG-G4

PSVB 3003
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Dave,
Go around the house and look at the amps or the watts (usually lights, hair dryers, etc.). To convert watts into amps divide the watts by the supply voltage. Figure out exactly what you 'need' to run and add up all the amps of all those things. A MEP-003 will produce 104 Amps, a MEP-004 will produce about 155 Amps (15 KW). A 30 KW generator for a house of less than 8000 square feet is way too big. the other side of the coin is the amount of fuel you will be using - a 30 KW unit will probably drink four gallons of diesel an hour, whether it's running under full load, or just running one 60 watt lightbulb. How much do you want to spend on fuel and where will you store it?
 
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PeterD

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I tried to work this out, but one issue is that you have the problem that loads come and go in residential environments. I have an 'all electric' house, with electric heat. One day last spring I did a test and forced the heat on, and turned on everything I could control (no control over the fridges or freezers) and never got more than half load on the generator (a 15KW MEP004a)

Were I to suggest, unless you have a huge place, with an incredible power usage, a 15 KW set (MEP-004a) would probably be more than enough, and a MEP-005 would likely be too much.


 

sewerzuk

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Seaside, OR
Dave,
Go around the house and look at the amps or the watts (usually lights, hair dryers, etc.). To convert watts into amps divide the watts by the supply voltage. Figure out exactly what you 'need' to run and add up all the amps of all those things. A MEP-003 will produce 104 Amps, a MEP-004 will produce about 155 Amps (15 KW). A 30 KW generator for a house of less than 8000 square feet is way too big. the other side of the coin is the amount of fuel you will be using - a 30 KW unit will probably drink four gallons of diesel an hour, whether it's running under full load, or just running one 60 watt lightbulb. How much do you want to spend on fuel and where will you store it?
This is good advice; I think your current numbers are a little high though (unless you were showing numbers right before overload trip, or taking power factor into consideration). IMO, most residences have a PF closer to 1, so a 15kw set will only provide about 125A (at 120v) or 63A (at 240v). While fuel consumption does vary with load, the -005a will consume more fuel per KWh than an -004a will.
You also need to take into account starting surges...things like A/C units, refrigerators, and other larger electric motors will need a bit of extra generator power to start up. You can't run the generator at 95% load and expect it to handle starting the air compressor in your garage.
I tend to agree with PeterD; a MEP-004a should be more than enough generator for most houses. If you have a large house with all electric heat, electric hot water heaters, or large A/C units then you may need to step up to an -005a.
I run my house and shop on a single phase converted -004a; it will run the entire house (including electric dryer, blowers for my hydronic and wood furnaces, and oven/range) and all of the tools in my shop (air compressor, ironworker, heat, lighting, etc.) The only thing it won't run are my lathe and milling machine (I use a 30HP rotary phase converter for them, and the -004a can't handle the starting surge of a motor that large).
 
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Xiphiasman

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Woodland Hills CA
Rewires to phase 1 now can't field to flash

MEP-005 1987 phase conversion
after cutting my buss bar which was under the bottom voltage reconnection board, moved all wires and put everything back (triple checked placement) and all connection thanks Sewerzuk. Fired it up but could get it to flash the field. so not able to check if worked.
Looked in TM pp 138 sec 4-19 speed switch: checked Continuity & discontinuity OK
however possible reset button on top will not stay down (arrow in photo). does it reset? Am I missing something when flash the field, fuel and oil work & fault indicators
Thanks Matt
 

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sewerzuk

Member
524
10
18
Location
Seaside, OR
MEP-005 1987 phase conversion
after cutting my buss bar which was under the bottom voltage reconnection board, moved all wires and put everything back (triple checked placement) and all connection thanks Sewerzuk. Fired it up but could get it to flash the field. so not able to check if worked.
Looked in TM pp 138 sec 4-19 speed switch: checked Continuity & discontinuity OK
however possible reset button on top will not stay down (arrow in photo). does it reset? Am I missing something when flash the field, fuel and oil work & fault indicators
Thanks Matt

Did it work fine before you did the single phase conversion?
Does the generator continue to run after you start it, or does it shut down?
Any warning lights that can't be reset?
Do any of the meters read anything on any of the positions on the switch?
 

Xiphiasman

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Ran fine before conversion and runs great when I start it hasn't shut down on me
no warning lights even after a reset
only gauge that moves is the hertz when I hold the start switch up with power, max it reads is 50 hz and goes away when start is released
oil, fuel, temp gauges, amp, hour meter all work
no change when I switch transfer switch
 
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