Mep 002a, 003a automatic starting

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bmwsyc

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I wanted to pick the brains of the more season folks (unlike myself) here. I am waiting on a 002a and I was wondering what the requirements for automatic starting would be. I might have a relatively low cost solution, but wanted to get the sequence down. This is what I have so far:

sense power loss

preheat

crank until oil pressure is up

continue to hold "start" to ensure flashing of the field?

cool down after power returns?

how much time do y'all think is needed for flashing after the engine starts? How much time is needed for cool down? (if any) I also was thinking that there could be a button that would "test run" for 30 minutes or something like that.

Thanks!

Chris
 
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Speddmon

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Chris,

Cranking until oil pressure comes up in itself is not really a good idea. You definitely do not want to keep cranking the engine for more than 10 to 12 seconds (15 MAX), or you will be replacing electronic components. If you are in the dead of winter, you could need to crank it several times until it actually stays running. Instead, I would use a multiple condition test. Crank until oil pressure comes up, but NOT MORE than 10 to 12 seconds. If no oil pressure after that amount of time, restart the preheat/crank process with at least 30 seconds between cranks. No more than 10 to 12 seconds per cranking session. Once you have achieved oil pressure, you'll need to have your system wait for about 10 seconds and re-check oil pressure, if you still have oil pressure, then more than likely your engine is running. Next, have your system check for generator output, if you have oil pressure and generator output after 10 seconds, then you are more than likely good to go. If you have pressure but no output, then have it flash the field for a second or two at max and re-check for generator output. Repeat this step 2 to 3 times if necessary. If everything checks good, then you should be good to go, if not, have a shutdown sequence initiated.

just my 2cents
 

PeterD

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For process of change overs, I'd recommend:

1. Power fails, start and switch over to generator.
2. Power is restored, wait one minute, then switch back to main power.
3. Continue to run generator for an additional five minutes, and reset this timer if the main power fails in the five minute period. (Of course, switch over to the generator on these secondary power failures).

I use simple industrial timers (I get them surplus usually) to do these time computations. Two timers (the one minute, and the five minute) are usually sufficient.
 

iam4thapack

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For process of change overs, I'd recommend:

1. Power fails, start and switch over to generator.
2. Power is restored, wait one minute, then switch back to main power.
3. Continue to run generator for an additional five minutes, and reset this timer if the main power fails in the five minute period. (Of course, switch over to the generator on these secondary power failures).

I use simple industrial timers (I get them surplus usually) to do these time computations. Two timers (the one minute, and the five minute) are usually sufficient.
Some electricians I work with here in NC who install and maintain generators have told me the NEC says a generator has to run for 15 minutes before re-transfer to utility after it has been restored. This may or may not be correct but I would suggest researching same.
 

Isaac-1

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There are several different NEC and code requirements for allowable starting / cranking or cyclic cranking times, as well as retransfer times once utility power is restored, however most of these are only for legally required emergency generators, not optional standby units. As to the cool down time, I know Kohler specs 5 minutes no load cool down for all of their generators and this is what their units with automatic controllers do, seems like a sane number to me. As I see it you have 2 options on the MEP-002's and similar generators, either modify the inputs to the existing control system or scrap the entire control system and replace it with universal controller that supports remote starting like this one from flight systems NFPA110 Compliant Genset Replacement Control Panel

Ike
 
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derf

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You could use a small PLC and have start/run/shutdown gen control for around $100, I would think. Something like an Omron Zen could probably be made to work, essentially making a "two wire start" meaning there are two wires and when they are connected, the gen will start and run.
Many transfer switches are programmable for grid/aux switching timing. Many have a "two wire" gen control circuit built in.
 

PeterD

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NEC has rules for generators. Some of the rules are difficult to meet. Most of the difficult rules to meet are for generators that are permanently connected, and don't apply to plug-in portable generators.

The most important requirement is, of course, the main transfer switch with any backup generator.
 

derf

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My 12.5kW 1100lb water cooled Kubota gen is portable.
I have a big, fat SO cable with twist lock connectors on the ends.
I have a manual transfer switch, though. I've installed a few auto transfer switches for other people but I can't justify the cost for myself. I'd rather be there, start the gen, and switch the load.
Plus, my gen may not handle my entire home load if the central AC, electric stove, dual electric ovens, and other smaller loads were all on at the same time. If the power happened to go off when almost everything was on and I had an auto switch then it might get tricky.
 

rosco

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Quote Speddmom above "If you have pressure but no output, then have it flash the field for a second or two at max and re-check for generator output. Repeat this step 2 to 3 times if necessary. If everything checks good, then you should be good to go, if not, have a shutdown sequence initiated."

What is "Flash the Field"? Is that like "polarizeing" the generator? Thanks Lee
 

Isaac-1

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Yes, the MEP series generators have a flashing circuit built in that is activated by turning the knob back to the cranking position, there is a safe switch that should prevent the starter from engaging while the engine is running.

Ike
 

Speddmon

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Lee,

Flashing the field is just a way of saying you are applying a DC voltage to the field windings of the generator head to start the generating process. And yes, another way to put it would be "polarizing".

The generator head is wound similar to a DC motor with a few variations...no brushes, rotating field rather than fixed and some other differences. But basically, for the generator to produce power you must have conductors (the wires) cutting through a magnetic field. The magnetic field is produced in the rotating field of the generator head with the application of a DC voltage and the large iron core of the field windings. Since the generators are self excited, the DC voltage is made and rectified in the stator of the head once the generator starts producing power. In order to start producing power, there has to be enough residual magnetism left in the iron core of the field to produce some voltage in the startor windings then the head starts to turn. If there is not enough magnetism in the core due to sitting for a long period of time, sometimes open diodes will cause a lack of generation also, or what ever the reason then you get no voltage produced. That's when you "flash" the field. You apply a DC voltage from the batteries to the field winding for a second or two and re-magnetize the iron core of the field so it produces it's own voltage once again. Typically, if you flash the field once or twice and still get no output, then you probably have some open diodes which are causing the field to lose it's excitation voltage.
 

dfullerpt

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I have a question regarding the exciter stator. Long story short I had to have the exciter stator rewound. I had marked the two leads off the military connector and existing stator leads on the terminal strip prior to them rewinding. Just picked it up and the leads on the exciter stator are not marked. Does it make a difference which lead they connect to on the terminal strip.

Not wanting to blow something when I start the generator back up.

Dennis
 

storeman

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NEC has rules for generators. Some of the rules are difficult to meet. Most of the difficult rules to meet are for generators that are permanently connected, and don't apply to plug-in portable generators.

The most important requirement is, of course, the main transfer switch with any backup generator.
FYI: I have two of Peter's auto start units controlling my two generators, (003a and 002a). They work flawlessly.
Jerry
 

Keith_J

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I have a question regarding the exciter stator. Long story short I had to have the exciter stator rewound. I had marked the two leads off the military connector and existing stator leads on the terminal strip prior to them rewinding. Just picked it up and the leads on the exciter stator are not marked. Does it make a difference which lead they connect to on the terminal strip.

Not wanting to blow something when I start the generator back up.

Dennis
It doesn't matter, the exciter rotor is turning so it develops alternating current which is then turned into DC (rectified) by the diodes on the rotor, this DC then makes the main rotating magnetic field.
 
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