Mep-003A Gen Head question

[Saunders]

Hello, I"m new to the forum here and had a question I hadn't seen addressed yet. I understand the Mep-003A has the ability to be switched and run to be either single or three phase. Is that simply because of the way it is wired to the VR or is the internal wiring in the gen head different?

What I was wondering, is if you had a bad generator head on a MEP-003A, could you use one from off a Mep-004 or 005? I understand the bellhousing would have to be adapted to fit, but are the internals the same other than being bigger sized?

 

[Isaac-1]

You can switch between different voltages because it is a 12 lead generator, switching is done by the reconection switch on the front of the power box. Generator ends from MEP-002a's and MEP-003a's will interchange, I think we even have a member or two here that have bought surplus generators from GL, etc. and found they had the wrong head (at least MEP-002a engines mated to MEP-003a generator ends). As far as using a generator end off a MEP-004 or MEP-005, anything is possible with enough engineering.

 

[Saunders]

I understand the switching function on the Mep-002/003a's and that they are 12 wire generators. What I was hoping to find out, is if simply mounting a Mep-004/05 generator head up to the Mep-003a would work the same since they are 12 wires as well. The 15kw and 30kw heads are obviously bigger, but are they internally wired different to where this idea wouldn't work?

 

[gimpyrobb]

Why are you asking? Do you have one and want to do this, or are we theorizing? Lots of work to look it all up...

 

[SCSG-G4]

Yes, BUT! Since the heads produce more power, more power MUST be put into them, more than a MEP-003 can produce, and far more than a MEP-002 can produce. Result - low frequency followed by motor failure. Even if you somehow limit it to the 10KW power output, the head, being larger will take more energy from the motor to spin, so fuel consumption will be greater. Another factor may be (I don't know about this) considered is the diameter of the heads - will the larger one line-up with the output shaft of the motor?

 

[Isaac-1]

I am not sure if the MEP-003a voltage regulator would be compatible with the MEP-004 or MEP-005 generator end, you would need to look up the exciter resistance and max amp loads in the TM's, then you would have to make an educated guess as there is no published output specs for the MEP-003a voltage regulator.

 

[Keith_J]

12 lead is 12 lead. Sure, the 003 engine could swing a 15 kW generator but probably only to 12 kW before the speed would drop below 1800 rpm. They are both 4 pole.

now, back the control lever stop adjustment for more fuel and it might work, until the injector cooling heat sink melts or cokes the injector. Indirect injected engine.

 

[Saunders]

Why are you asking? Do you have one and want to do this, or are we theorizing? Lots of work to look it all up...

Don't currently have one now. Was looking into bidding on a MEP-003A from GL. With the possibility of getting one with a bad head, thought if I could also pick up a 15kw head unit off a MEP-004, then I'd mount that up since the 003's seem to be in more demand than the bigger units. Thought maybe someone had already looked into this before. I know it'd be more practical to just get another 10kw head if needed, but thought I'd ask.

The other idea I was looking at was getting a 15kw head and mounting it to a Thermo King Yanmar (TK486) I have which has been stored and collecting dust. The engine is very low hours and puts out around 30hp or so at 1800 rpms. A guy I used to know did this same setup. He machined the adapter to fit the two, but I don't remember what VR or gen head he ended up using. I'll have to post the pictures, he did a professional job putting them together. However the idea of a complete already built -003A or 803A seems a little more cost effective and less time consuming than starting from scratch.

 

[Keith_J]

Unless the head is burned, any repair is simple. Rotating diodes and one bearing. That is all that goes wrong. Control system and engine are the other two that give the most fits.

 

[Saunders]

I guess the question I was trying to understand is, what makes a 12 wire generator head single or three phase, is it the voltage regulator attached to it and how it's connected, or are the windings inside setup differently? With all the aftermarket AVR's that are available, can any 12 lead generator head be setup as a single phase simply by installing the "right" voltage regulator?

 

[Saunders]

Here are some pictures of the Generator my friend had built using a Thermo King diesel he had lying around. If I don't score on a good MEP-003A or 803A, I may go this route too. It was enough work and time to where he didn't want to build another one, but It ought to be a fun project.

 

[rustystud]

OK Saunders, what you are asking for is an explanation of basic power generating principles. I will just give you a short explanation for now. A generator is wound with a number of coils. These coils and the way they are connected allow different phases of A/C voltage. The military uses a generator with 6 pairs of coils ( 12 leads out ) . These coils connected in different ways allow different voltage and phase. Either 120/208 Volts 3 phase 4 wire, 120 Volt 1 phase 2 wire, or 120/240 Volt 1 phase 3 wire . In the most common configuration 120/240 volt single phase 3 wire the leads are connected this way. T1 to T12 , T2 to T4, T3 to T11. T5 to T7, T9, and T6 (this becomes the ground point), T8 to T10. By turning the reconnection switch you will be changing the way the leads are connected to each other giving you these different configurations.
Hope this little explanation helps.

 

[Saunders]

View attachment 515455OK Saunders, what you are asking for is an explanation of basic power generating principles. I will just give you a short explanation for now. A generator is wound with a number of coils. These coils and the way they are connected allow different phases of A/C voltage. The military uses a generator with 6 pairs of coils ( 12 leads out ) . These coils connected in different ways allow different voltage and phase. Either 120/208 Volts 3 phase 4 wire, 120 Volt 1 phase 2 wire, or 120/240 Volt 1 phase 3 wire . In the most common configuration 120/240 volt single phase 3 wire the leads are connected this way. T1 to T12 , T2 to T4, T3 to T11. T5 to T7, T9, and T6 (this becomes the ground point), T8 to T10. By turning the reconnection switch you will be changing the way the leads are connected to each other giving you these different configurations.
Hope this little explanation helps.

After reading up on this, it's finally starting to make a bit more sense. What was throwing me off was, I had read that with a 3 phase generator, to use it as single phase you only get 2/3rds of the output. But I didn't realize how you wire it up makes the difference (wye, delta, zig-zag, ect).

 

[Isaac-1]

The 2/3rd output rule is only valid for some generator, some have enough extra copper in the windings to be rated for full output (or close) at either 1 or 3 phase. For example my Kohler 30ROZJ commercial diesel generator is rated at 33KW 120/240 single phase and 35KW at 120/208 3 phase wye, strangely though it is only rated at 34KW at 277/480 3 phase .