Wanting to build a Generator set-Need some advise

I am a bit of a scientist and have been looking into filling my lab/shop with some equipment and powering the equipment. This message is about powering the shop/lab. Right now my shop/lab is empty but will have some equipment that will need some clean 120/220VAC (single phase 25 to 30 A), some lighting/appliance (120/220 VAC 20A), a 48 VDC 10A max power outlet, and three-phase AC to power a MIG/TIG welder (up to 3/8" steel), A Lincoln welder (like a K1297 size), A Vertical Mill (something like a Bridgeport series 1) and A Lathe (something like a Hardinge HLV-H) (228/240 VAC? Greater than 58 A, but less than 80 A). I will need to run the mill and lathe with CNC capability. My approach so far was to locate a 100KW military generator set but that has not been easy nor successful. So I thought perhaps I could build one to meet my needs. I thought first I could get a wrecked Dodge Ram Truck with a Cummins 6.1 L diesel engine. To control the RPMs I would use a digital module from RPMControl (RPMControl.com). To cool off the engine I would need a larger radiator and larger fan. I could use some input here. Where would I locate a generator head? Some equipment that need clean current are oscilloscopes, precision power supplies, motion control, etc. I heard that there are isolation transformers but does anyone know if there are some low-cost ways to do this for a 30 A circuit? Oh, before I forget, I would like to make this generator set work also as an emergency back-up for my home nearby my shop/lab. Does anyone know where I can find parts to build the switching system, the power transfer box, and the way to separate out the breaker box for the two purposes (emergency back-up and the daily 100 A service Shop/Lab)? I know the RPMControl modules can remotely start an engine so this aspect of the problem is partly solved with that module. Perhaps the module just needs to have a current sensor to switch it into a start mode. The back-up system circuit switch likely would need a timer to operate a switch to include the house and a sensor for disengagement of the house when the power is back on. IF anyone has any suggestions for sources of used equipment, generator set parts, or advice I am all ears (like Ross Perot said). Thank you in advance,

Assuming off grid.

Look up UBS , unintruptable BATTERY systems.

Best power made them back in the day.

Was basically an online style ups that was full time on line with a generator to charge batteries.

Get a large commercial ups system and build generator to charge batteries.

That way ups does hard part and genny is now intermittent run and output not critical as it only charges batteries.

Telco switch rooms have large in multi kw size ups that operate on -48 plant so building 48 volt battery plant solves that.

Plus -48 is Telco standard so equipment is readily available in trade surplus supply

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100KW seems rather large for your needs, and the fuel bill will kill you, unless your just filthy rich in which case just go buy a nice new diesel set. Building a gen from scratch is not going to be cost effective, there are sets out there begging for homes, and they can be had quite inexpensively on the auction market. I would suggest you visit the smokstak onan forum for advice.

Look to Generac or Kohler for starters.

Tom

might call these people and see if this inverter could be modified to enable bi-directional operation.

ie.. plug the inverter into your batteries, get a generator running, synchronize the two and plug them together.

15KW 48V 208V 220V Three Phase Inverter Charger Off Grid

15KW, 45KW surge for 2600 bucks.

you'll only need a shit load of lead acid batteries, or a small pile of good condition ones.

similar capacity but only single phase
12000 watt inverter charger - 12kw 48 volt inverter | AIMS Power

again, some hacking would be required to get bi-directional operation going. but it should be possible.


if you go with a three phase inverter and battery bank you don't need a generator head, you can use an induction motor instead. less efficient but no synchronization problems, and throttle modulation to control the power flow and battery voltage will be softer and more forgiving.

Building your own genset is nuts, why are you reinventing the wheel? There are used gensets everywhere. About 50 on ebay right now.

TDegenhart said:

Look to Generac or Kohler for starters.

Tom

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Generacs are sh*t, old Onans are reliable and will outlive you, new Cummins/Onans are questionable.

^^I wasn't thinking about the generators but the switch gear which is one of his concerns.

Tom

moonlight machine said:

Building your own genset is nuts, why are you reinventing the wheel? There are used gensets everywhere. About 50 on ebay right now.

Click to expand...

Because:
1. Pot is legal
2. OP doesn't want to leave a paper trail on purchase....

That transfer switch is quite simple to make. Very similar to motor reversing contacters but the AC line from the power company is the trigger rather than a Forward, Reverse and stop push buttons switches. 100K contacter set will be kinda pricey.

Spend some quality time doing load calculations. You will likely never start everything at once and equipment doesn't run full tilt at constant load.

Froneck said:

That transfer switch is quite simple to make. Very similar to motor reversing contacters but the AC line from the power company is the trigger rather than a Forward, Reverse and stop push buttons switches. 100K contacter set will be kinda pricey.

Click to expand...

Depends on is wanted of the switch. A manual transfer switch is quite simple, a three pole double throw switch rated for whatever current capacity is needed. It needs to have inductive load rated make and break.

Next up is an automatic system. There you will need voltage sensing relays and timers. The system I designed at GE was as follows. Voltage sensing relays to detect phase loss/phase failure on the main system. An output would trigger a pneumatic time delay on dropout that would tell the engine generator to start. Sensing relays would detect the output and after a suitable time delay to allow the generator to be stable, would transfer the load to the generator. The main voltage sensing relays would monitor the main power and after a suitable delay for stability, would initiate a return to the main power system.

Simple and straight forward. The key was the voltage sensing relays. They need to be differential and adjustable for operational band. The transfer switch itself was mechanical held.

This was in the 1970's so the equipment I had to work with would not be the same today, but the logic is the same.

Tom

Pathogen said:

Spend some quality time doing load calculations. You will likely never start everything at once and equipment doesn't run full tilt at constant load.

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And, protracted running of a diesel generator at very light load is inefficient and not good for the engine
Wet Stacking - Why It's Important to Load Bank Your Diesel Generator

I have no idea what Utah state government is like or how far off the edge of everyone's field of awareness your location is, but some states' governments would take an active and unfavorable interest in someone putting a large diesel genset, especially one without current emissions controls, online for ongoing extended 'baseload,' not occasional backup, use. In saying that, I am not wishing it on you or anyone else, just mentioning it in the interest of helping avoid large investments of time/money/effort followed by unexpected surprises.

Voltage relays are available from Granger as another OP in another topic pointed out. Time delay relays are rather common so the trigger for the transfer action should not be hard to make.

Here is some ideas get you started.

asco power transfer switch - Google Search

Then there is HGR,

Used Machinery & Industrial Equipment | HGR Industrial Surplus

I would look at the Katolight generator. John Deere industrial diesel.

Tom

I would like to thank the original poster for starting such and enjoyable thread here. This will be going on for weeks,
probably. It has all the ingredients for a bang-up discussion. Whatever you do, do *not* decide to connect your shop,
and the NC equipment, to utility power, abandoning the prime mover genset project.

That would effectively shut down this wonderful discussion, with all the ins-and-outs of off-grid power generation.

I think if off the grid one can't beat a PTO unit so a very useful tractor is the power source. and then add one or two throw away
gas 3000 or 4000 wt for when lower power will do.
Winco W15PTOS - 15 kW Tractor-Driven PTO Generator 515/540 RPM

WINCO-30PTOC4-03 | Acme Tools

On the grid you can't beat the grid.

We are running fish camp,Ontario on a 3000 throw-away and I am running kellyroadcamp.com on a 5000 wt Honda.

I knew a fellow who ran himself broke with running a diesel gen set, when most of the time he only needed 1/10 that power.

diy? a wrecked chevy volt. The generator is the size you need, crazy efficient 4 cylinder engine, already tied together. Also get the battery (480 vdc) to smooth it out.

memphisjed said:

diy? a wrecked chevy volt. The generator is the size you need, crazy efficient 4 cylinder engine, already tied together. Also get the battery (480 vdc) to smooth it out.

Click to expand...

i forgot to mention that, there are people who have done such a thing. some just run a 12v inverter off of the lead acid battery, and the car auto restarts to charge the main battery which feeds the 12v battery through a converter.

if you do mess with the main battery.. some hybrid cars have a voltage doubler between the battery and the main motor. the battery is typically 200-300 volts and the motor about double that. reason for this is because battery reliability and power density drop as the number of cells increases beyond various limits. also its difficult enough as it is to build circuit breakers and fuses for high voltage dc so i'm assuming that is another reason for the car companies to have incorporated voltage doublers after the battery.. they are often integrated in the battery package as one unit, but i'm assuming the circuit breaker is on the battery so you should still be able to get to that directly without taking the whole thing apart.


200-300 volts may not be enough to run a vfd directly and for efficiency and reliability reasons i would suggest people tap the battery directly rather than the ~500 volt bus after the voltage doubler, also for safety reasons.

there are various ways to fool a 240vac vfd into running from 200 volts dc directly, and you will need a transformer after the vfd to remove the common mode problem anyways because a 200-300 volt bus only gives you a maximum of 141 to 212 volts ac, a 120/208 to 240v center tapped delta transformer is probably the way to go if you can reconnect the 120/208 coil as 120v delta. you can ground the center tap and get your residential 120/240v supply, and you have 240v 3p at the same time.

you will need to ground the car somehow otherwise the common mode voltage generated by the vfd will cause the car to float up and down at say, 100vac at the pwm frequncy.. according to the ratio of capacitance of the transformer and the capacitance of the car in air.. you will probably get shocked touching the car if it isn't grounded.

a 120/208 to 120/208 isolation transformer with the primary reconnected delta and driven by the vfd is another way to go, only gets you 208 3p though.

We went to look at a wind mill set that was for sale in northern Michigan. The blades were perhaps 6" radius(or larger) and ran voltage to a battery that had come from a ship. Battery was about 4" high and perhaps 4' wide by 6" long. He was running a good size house with it. Reason for selling was that the grid had come close enough to tie into and you can't beat the low price of the grid.

Whole set up $600. He had much more into (thousands) is but nobody was interested and he wanted it gone..Yes it is gone now.

My kellyroadcamp is not that of elevation high and to be useful for me I would have had to build a very high tower to get into decent wind. Plus I most often don't need much energy except for running the welder and I need that on rare occasion.