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How to power small off grid three phase machines?

That advice is wrong. Diesel fuel is the same as heating oil, but with anti-waxing and metallic lubrication additives and it is road tax free. Diesel fuel and heating fuel will last indefinitely. Heating fuel will require a can of anti-waxing additive if the fuel is exposed to temperatures below about 4 C. Propane on the other hand will not vaporize in very cold temperatures. I use heating oil with additives successfully in my my generator and forklift and have been be for many years
This is wrong too, at least sometimes. I heat the shop with off road (No road tax) diesel . I fill my 120 gallon diesel tank with the same. Every time it’s delivered I ask the guy if it’s the same as home heating oil. He says they both come out of the same tank and are used interchangeably. Not sure if this is the case everywhere.

I’m in a similar situation with my power. I bought a 20kw trailer mounted generator (Wacker Newson G25) about 10-15 years ago. Wonderful machine. A little thing to watch for in buying a bigger generator is how fast does it run? Most bigger diesel generators have a 4 pole generator head and run at 1800 rpm. This is pretty low speed generally inherently pretty quiet and these machines commonly go 20k+ hours trouble free. Most gas/propane/ natural gas generators run at 3600 rpm. Probably not always but it seems most commonly this is the case. These are much louder and I don't think live as long. Many welders run 3600 rpm too because they’re trying to get as many hp as they can squeeze out of a given engine size. I like the slower machines. Seems like they’re almost at idle.

I have machines with several year old diesel fuel in them. Never had a problem with it going bad.

I don’t have any diesel equipment with emission controls. Hope what I have outlives me so I don’t need to experience that.

Old takeout diesel standby generators with very low hours are pretty common on the used market. This isn't a bad way to go. Most have very low hours.
 
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This is wrong too, at least sometimes. I heat the shop with off road (No road tax) diesel . I fill my 120 gallon diesel tank with the same. Every time it’s delivered I ask the guy if it’s the same as home heating oil. He says they both come out of the same tank and are used interchangeably. Not sure if this is the case everywhere.

I’m in a similar situation with my power. I bought a 20kw trailer mounted generator about 10-15 years ago. Wonderful machine. A little thing to watch for in buying a big generator is how fast does it run? Most bigger diesel generators have a 4 pole generator and run at 1800 rpm. This is pretty low speed generally inherently pretty quiet and these machines commonly go 20k+ hours trouble free. Most gas/propane/ natural gas generators run at 3600 rpm. Much louder. Many welders run 3600 rpm too because they’re trying to get as many hp as they can squeeze out of a given engine size. I like the slower machines. Seems like they’re almost at idle.
Diesel fuel from gas stations, depending on where you are, is not the same year around. In cold weather, the fuel is slightly thinner in viscosity and has a different additive package which includes anti-waxing additives. Summer diesel is a bit thicker and does not contain anti-waxing additives. Heating fuel although the same as you stated may or may not have anti-waxing additives. It is this reason, that I always order the additives when I order the fuel. I have 6000 liters of fuel storage and this fuel may stay in my storage tank for a number of years before it is consumed. The additive, which is available from every company that sells heating oil is inexpensive and is cheap insurance. As a side note, I also use diesel fuel in my car and I get better mileage per liter in the summer than in the winter by about 2 to 3% because of the higher energy content in the summer. fuel. You are also correct with your comment on engine speed. I bought a 10' shipping container and converted it to a gen set house. This allows plenty of weather protection, noise reduction and maintenance space when required. I feed house power to the container for lights and utilities and then run the genset output to a switch over facility at the street power connection cabinet in the house.
 
If you have solar and batteries, there are some inverters that can be interconnected to produce 3 phase. I am trying to recall the brand, but I did a demo setup back at the Consulting Co for a customer. You connected the outputs, of course, and there was a control cable harness as well to get them in sync.

Worked well.
I have been considering doing exactly this. Sol Arc and SolarEdge are two inverters that can either be connected together for 3phase or are just a 3 phase inverter. I have one solaredge on the house now and I would not recommend it if you want to anything other than "normal grid tie". The solarc ones can do grid tie and in an outage be off grid so you still have power, neighbor has one of those. They were not on the market when I did mine :( I am sure there are many other brands now as well.
This would be a great way to convert single phase to 3 phase and also have some UPS protection in the event of a power outage, limited only by battery bank size. You would not even have to have solar panels, the battery bank could be charged of the 240 single phase grid power and then put out 3 phase.
 
If you have solar and batteries, there are some inverters that can be interconnected to produce 3 phase. I am trying to recall the brand, but I did a demo setup back at the Consulting Co for a customer. You connected the outputs, of course, and there was a control cable harness as well to get them in sync.

Worked well.
Outback Power systems, for one. Expensive, but quality equipment usually is.
 
Outback does both now, the fxr/vfxfr series is programmable for 7 different modes. Capable of managing a battery bank, generator, the grid, the loads and solar charge controls. True sine wave, stackable for 3 phase. 200 page programming manual, ugh, but exhaustive. UL approved, legal to gridtie in all 50 states. (Possible exceptions Vermont and California.) Excellent customer service and a very good company sponsored user forum. I've installed 3 and they've been troublefree once I got the programming worked out.

Flies in the ointment..... A 3kW single phase inverter is about $2K by the time the accessories and the programming/monitoring box arrive. It's a significant cost, but when considering the overall cost of the system, less than a battery bank and more durable. And they really don't like being overloaded very long, so need to be carefully sized for starting motors.

It could be that a single FXR inverter could power an RPC. I bet someone in the user forum would know, or at least have some knowledge to offer.

And the disclaimer: My only connection with them is as a satisfied customer.
 
No RPC is required if the gen set is 3 phase in the first place. Yes you can use a 3 phase gen set to power single phase loads as long as you do not exceed the max current limit of any of the three phases of the alternator. In that light, you should size the gen set accordingly. My 25 kva diesel genset powers my entire house and my 3 phase machine shop without issues.
They already have the RPC , works fine. You don’t want to run more generator than you need or more often than necessary for economical reasons
 
Propane will store longer diesel but I have diesel going on 12 years and still usable. Diesel has a higher energy density than propane which means that you use less fuel and have more power.

This is what I do
Solar array charging a battery bank.
Inverter tied into battery providing power.
Small diesel generator providing extra battery power.

The inverter will provide clean power and handle the surge. Solar will charge batteries and feed inverter, generator will load up when clouds hit.

Propane generators are low quality and low grade not designed for continuous use.
Diesel generators are heavier duty designed for loooong hours.
 
We have a 3 phase 3hp lathe and 2hp mill. They do not run at the same time. Right now they are powered through a 10hp RPC. on grid power.
We are at the very end of a dead end with sketchy reliability when the wind blows hard. Every time it goes out I wonder if it is ever coming back on....

What is the best way to power up these machines when grid power is gone?
Buy a three phase generator and power them up directly?
Buy a big single phase generator to start the RPC?
Use a smaller RPC?
What sort of output would we need?
Most of the replies will work and work well. I have a total off grid shop 30kw 3 phase solar. I went with victron because of at starting of the electric motors it will produce 45kw for starting skva.
I also have a diesel generator for my larger loads 20-40hp that is on a transfer switch.
My only suggestion is make sure you have adequate skva for your situation. A lathe that the motor starts with no load and then a clutch takes a lot less current at start up than a lathe that the motor is started and stopped to run the spindle. You also need to consider the other things that might be on or cycling on and off like a air compressor etc
 
Lots of good advice above.

I'm running a shop off of both and RPC and a diesel generator. Of the 7 generators that I have here on the farm, 5 are diesel, one gasoline and one liquid LP.

From a cost standpoint, grid power is your least expensive solution. Minimal capital investment and operating cost.

For your stated situation, I'd look into a good, used diesel generator that has been removed from standby service. I have purchased several from my local utility provider. These low hour units (typically 300 - 1000 hours) were used as standby units for remote offices and were removed when they either aged out (around 20 years old) of the office grew and needed a more powerful unit. The 35KW Liquid LP generator that is my house standby unit had 360 hours on it when I bought it and was 22 years old. I paid 3K for it 3 years ago. Same generator last year was 4K, and a trailer mounted diesel 20KW unit with 300 hours was 5K - all utility surplus.

Typically any 12 wire alternator can be rewired to provide either 208, 240 or 480 3 phase, or 240 single phase. I'm not aware of any that will allow you to pull both single phase with a neutral and 3 phase off of the generator at the same time. You'd need a transformer wired in with a center tap to provide the neutral for your single phase needs.
 
...From a cost standpoint, grid power is your least expensive solution. Minimal capital investment and operating cost.

Depends on how far from the utility he is. Around here it's somewhere around $50,000/mile, if the neighbors grant the utility ROW's.Then there's the $30 monthly service charge, which is the cost of a decent battery bank. So a lot depends on initial installation cost.

I'm not badmouthing utilities - the do a pretty good job at keeping the power on. But if there's an icestorm or a fire somewhere else on the system, you could be without power for a couple weeks. (DAMHIKT). If it's your own system, you have the capability to keep he power on.
 
Ive been involved with a couple of these .......no high tech at all.........one solution is a genset fuelled by a wood gas producer ,if you have access to free firewood ........one small problem is that simple gasoline engines are no longer as freely available as they once were ...........another solution for the mechanically inclined is steam power ......build your own boiler (slightly illegal most places,but you are off grid ) and either make a steam engine,or repurpose an IC engine.
 
Depends on how far from the utility he is. Around here it's somewhere around $50,000/mile, if the neighbors grant the utility ROW's.Then there's the $30 monthly service charge, which is the cost of a decent battery bank. So a lot depends on initial installation cost.

I'm not badmouthing utilities - the do a pretty good job at keeping the power on. But if there's an icestorm or a fire somewhere else on the system, you could be without power for a couple weeks. (DAMHIKT). If it's your own system, you have the capability to keep he power on.

I thought that the OP indicated that he already had grid power; just that it was unreliable...
 
I thought that the OP indicated that he already had grid power; just that it was unreliable...
Yes, that is the case.
On another note, but related- does a VFD require less power? Would I be ahead to get a 3hp VFD to power the lathe, and another one to power the mill? I did note some of the newer Taiwan variable speed lathes are equipped with a VFD from the factory- they can be wired single or three phase input.
 
I think that any power consumption differences will be negligible.
Not sure where this is coming from if you are comparing a RPC vs. VFD. RPC is running constantly and consuming power, a VFD idle power would be about 10X less. VFD's have a high efficiency around 97%. In addition you would have to size your power generation to be able to start the RPC. Smaller single phase input VFD's to 5 Hp are fairly common and cost effective alternative to drive a 3 phase motor off of single phase. If you are just running a small mill or lathe intermittent, a VFD would be more efficient than an RPC.

 
Not sure where this is coming from if you are comparing a RPC vs. VFD. RPC is running constantly and consuming power, a VFD idle power would be about 10X less. VFD's have a high efficiency around 97%. In addition you would have to size your power generation to be able to start the RPC. Smaller single phase input VFD's to 5 Hp are fairly common and cost effective alternative to drive a 3 phase motor off of single phase. If you are just running a small mill or lathe intermittent, a VFD would be more efficient than an RPC.


Fair question. Here is where I'm coming from. If the OP asking the question is a hobbiest, I'm presuming that the lathe will only be operated on a very limited basis. If he/she only uses it an hour or two per month, the electric differences will be negligible - ie a few bucks a month. This is based upon the premise that the RPC will only be running for the couple of hours that the lathe is needed, and not that the RPC will be running 8 hours a day.

On the other hand, if the OP is a commercial shop that will operate the lathe for several hours a day, then by all means a VFD is a more cost effective solution from an OpEx standpoint.
 








 
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