Industrial 3 phase 10-30 kVA UPS as inverter in an off-grid machine shop

aefriotaefriot Registered Users Posts: 5
I am thinking of building my workshop with 3 phase power. I'm looking for the pros and cons to using a large-ish industrial UPS to supply power to my machines.

First...I do not currently have 3 phase requirements. I do not currently have the motors to supply power to the machinery. Though, used/NOS 3 phase motors are very cheap to find. As I understand, 3 phase motors provide more power more efficiently than do 1 phase motors thereby lowering the rated motor HP requirement. So, I'm thinking even if the UPS inverters are not as efficient as purpose-built, off-grid inverters, I still might use less battery power for the same work output.

I am most likely the only one using the shop, so only one machine would be operating at one time. Auxiliary motors that might be operating while machining are air compressor and dust vacuum/fan.

I know I can operate a generator while machining and use a smaller inverter for low power devices like lighting and hand-held tools, but I want to look at the possibilities of using battery power and recharge with solar, wind and conserved energy. I try to use less fossil fuels if I can afford the time or money.

I know I am forgetting to include all the information I should, but I want to get the topic started.

Comments

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    There are off-grid inverters which are stackable in a 3-phase config.  Personally I'd look to use those rather than a UPS (which would be designed for grid-connected standy use).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,574 ✭✭✭✭✭
    Are you in California?  Take a look below and info you might address is the why, when, where, & budget.

    https://solar.schneider-electric.com/solution/commercial-off-grid-solar-2/


    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 31,182 admin
    It is all about your loads (peak Watts, kWH per day, location for hours of sun per season, etc.).

    Need to do a paper sizing of the system first.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,099 ✭✭✭✭✭
    if you are only using 1 phase motors, don't use a 3 phase inverter or genset.  The loads will not balance well, and you won't be able to get full power from 1/3rd of the windings.  With balance issues and inverter may only give 1/6 power on a single leg
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • aefriotaefriot Registered Users Posts: 5
    While the equipment that can be found at Schneider is very good equipment, I will never, in my realistic dreams, be able to afford their equipment...even used. I am happy to live with other's cast offs because I spend more time doing what I like rather than being a "cog in the wheel" so to speak.

    I am in Northern NY. Nice sun March through maybe November. For the house, we run a generator maybe 24 hours during summer if we use AC AND too many electric cooking appliances. Otherwise, we have far more power than we use. December to February we average maybe 8 hours per week as we cook and heat with wood. 20 gallons per year has been about average since we upgraded to MPPT charge controllers.

    The UPS I am thinking of using is one that is being replaced because of a growth in the business and network. I am definitely not purchasing new equipment. I can purchase the UPS at a considerable discount. This is the only way we could afford to do something of this size.  Also, older, well-maintained 3 phase equipment can be purchased at very reasonable prices because businesses want newer equipment and individuals do not usually have access to 3 phase power. Also, many do not know of phase converters. If I operate with what most consider odd-ball equipment, I can fill my shop and do more much cheaper than others can.

    As far as the workshop. I know the difference between 1 and 3 phase. I know 1 phase will not properly power a 3 phase motor and 1 phase motors will unbalance the environment. This is where I am looking for the reason why I should not power my shop with a used 20kVA 3 phase UPS that I can purchase the entire system with charger, inverter, rectifier, main cabinet and 2 auxiliary battery cabinets with batteries. I'm sure the batteries have expired. I do have a resource for commercial deep cell tow motor batteries as replacements.

    I could stack inverters of the correct feature to get 3 phase, but try to find them at a comparable price to what I can obtain the UPS (sub $500). 

    The 3 phase UPS will only be switched on when a machine is to be used. A 1 phase inverter will supply enough current for lighting and smaller electric hand tools.

    Now, leaving out the PV panels and charge controllers. I know how to figure power requirements. Is there a reason why an industrial 3 phase 20kVA UPS should not be preferred over a 1 phase workshop configuration? Will it be too inefficient? Be too noisy (at 55-60db)? Will it make neighbors laugh at me? Just kidding about the neighbors...let them. Will it not give me the correct 60Hz cycle? I don't know what else can concern me, that's why I come here, to learn the how and why. What do I need to know about the UPS to help determine if it is suitable?

    I hope I have included enough information without giving too much irrelevant information.

    Thank you

  • mike95490mike95490 Solar Expert Posts: 9,099 ✭✭✭✭✭
    The biggest problem with a 3 phase inverter, is loading it properly.  using just one phase, Absolutely limits you to 1/3 power, and maybe even less.  Trying to balance all the phases is going to be needed.   Even really great split phase inverters only manage 50% phase imbalance.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    I'm not sure what "commercial deep cell tow motor batteries" are, exactly. 

    Typical UPS batteries aren't designed for frequent deep cycling.  I'm guessing a "tow motor" battery may be designed to provide high current for a short time, and get recharged promtly?  If so, it likely has lots of thin plates to maximize reaction surface area for high current discharge, and may not last in a true deep cycle application.  In your application (short use of high current motor loads at times when batteries can be quickly recharged) they may work though.

    How much does the UPS weigh?  A 20kva stacked inverter system might weigh something like 1000lbs (big, heavy transformers).  If significantly lighter, the inverter may be a different design?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,574 ✭✭✭✭✭
    To me, as a business person, it is all about the budget. That is why I ask this long before spending time. On the forum it is fine for wishful thinking.

    The OP is best served by using a genset and the utility as primary power source.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • aefriotaefriot Registered Users Posts: 5
    The UPS will only power 3 phase motors on saws, lathes, planers, mills etc.  I believe proper loading should not be an issue, should it?

    The tow motor batteries I write of are from pallet jacks and forklifts. Most equipment I buy have 24V (12-125-11), 625Ah, 1200lb batteries. Granted, they are used, but still have plenty of life left for what I need. I am not a professional, full-time machine/woodworking shop. I do these things to make what I need for myself and for fun.

    The UPS main cabinet weighs about 1175 lb.

    Most won't want to deal with the weight, but I have the equipment to move it all around safely.

    The UPS default battery voltage is 288V. I would need 6 of the aforementioned batteries to attain this. Charging these batteries would be done through MPPT controllers each across 6 cells. 12 MPPT controllers would be required. But I am getting away from my intended topic. So far, I haven't read anything to dissuade me from this venture.

    Thank you for your input thus far.

  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    Forklift type batteries can work well.  Buying used, I'd want to do some load testing.  They can last a long time if looked after, but...

    At 1175#, the inverters likely do have big transformers.  AFAIK, some UPS have designs ("high frequency") that are lighter and more efficient, but may not be so good with big motor loads.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • MarkCMarkC Solar Expert Posts: 194 ✭✭✭
    aefriot said:
    The UPS will only power 3 phase motors on saws, lathes, planers, mills etc.  I believe proper loading should not be an issue, should it?

    The tow motor batteries I write of are from pallet jacks and forklifts. Most equipment I buy have 24V (12-125-11), 625Ah, 1200lb batteries. Granted, they are used, but still have plenty of life left for what I need. I am not a professional, full-time machine/woodworking shop. I do these things to make what I need for myself and for fun.

    The UPS main cabinet weighs about 1175 lb.

    Most won't want to deal with the weight, but I have the equipment to move it all around safely.

    The UPS default battery voltage is 288V. I would need 6 of the aforementioned batteries to attain this. Charging these batteries would be done through MPPT controllers each across 6 cells. 12 MPPT controllers would be required. But I am getting away from my intended topic. So far, I haven't read anything to dissuade me from this venture.

    Thank you for your input thus far.

    First, I'm not an electrical engineer, so the concerns that I've had using the larger UPSs may/may not be valid - and may not even be applicable to your quest.  I considered using a 10k APC/Schneider UPS to produce 240 VAC single phase energized with the ~380 VDC battery of my Nissan Leaf.  As these large UPSs (not sure of yours) use a "center tap" on the DC side (+/- 196 VDC) AND this center tap is directly connected to the neutral on the AC side (I have the electrical schematics), I was most concerned about DC potentials around any external equipment and the Leaf's high voltage systems (A/C, DC/DC converter to the 12 volt system, etc).  Using totally isolated Lead Acid batteries probably would not be a concern?  

    Like you I can get very cheap UPSs as they are mostly "throw-away" when the batteries go bad or need a minor repair.  I do have the 48 VDC/220 VAC UPSs in operation.with good results and a 196 VDC to 240 VAC unit that is energized by a Prius.
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • aefriotaefriot Registered Users Posts: 5
    Thank you for your input. I have seen others have had negative experience with a small UPS tripping while powering even small circuits with mild surges. I can understand those systems not being optimal, but sometimes adequate for smaller loads like lighting even though they may not be very efficient. People sometimes have to begin somewhere and UPS devices can be found for cheap. I never tried or read about something this big and powerful so I look for those who have experience.
    The one thing I can also add is that my 3 phase tools should not be high draw startup, but may require higher power during use when I hog on the lathe, saw thick hardwood or plane wider boards.

  • MarkCMarkC Solar Expert Posts: 194 ✭✭✭
    Yes, the 3000 kVA units work fine for lights, ceiling fans and refrigerators (at least a medium sized one).  I would not recommend going much above 50-60% wattage loads however.
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • aefriotaefriot Registered Users Posts: 5
    Oh, it's not going to be used for lighting, ceiling fans or refrigerators. Lower current devices (lighting, fans, sanders, portable routers, sawzall, circular saw, hand drills, etc.) will be on a smaller 3kW (6kW surge) inverter. The large 3 phase inverter will only be turned on for the larger lathes, mills, CNC router/plasma table, shear, press, etc. Most likely the welders will be generator only.
  • BB.BB. Super Moderators, Administrators Posts: 31,182 admin
    I have done a few systems with rotary phase converters (just a 3 phase, Wye wound preferred--its seems with some sort of starter--Originally used a cord around the spindle, later just another small single phase motor+belt+hinge to bring up to speed, and even the capacitor start + voltage controlled relay). 

    Have run 70 year old 3 phase 10 hp turret lathe, to full CNC with DC Drive, etc. originally setup for three phase power. For the CNC, just rewired the controller/power supplies to run from the true single phase, and ran the rest of the stuff off the phase converter.

    Personally, I would suggest a single phase 10kWatt (or larger, as needed) system and use a rotary phase converter (or even capacitive start for the "dumb" machines--Especially if they are clutched drives--Motor always runs, clutch to spindle).

    You can also look at VFDs (variable frequency drives)--Setup for single phase input, 3 phase, variable frequency/voltage output (although, induction motors driven with VFDs can have a higher failure rate--Because most (all) VFDs are basically square wave/modified square wave output? Don't know).

    Anyway... Just a paper design with a 48 VDC battery bank (if you have a 288 volt or other battery configuration, adjust as needed).

    Say 15 kWatt AC inverter... At 48 VDC, that would be around 1,500 to 3,000 AH battery bank (assuming flooded cell lead acid batteries) to supply surge power to inverter "reliably".

    Next, say you run production runs/long cuts/etc. And you use 7.5 kWatt for 8 hours per day (knowing your actual/required loads, very important--You could end up with a way oversized system, or undersized that does not do what you need)... Assume 2 days stored energy, and 50% maximum discharge (usually a good optimum starting point for planning)... Such a bank would be:
    • 7,500 Watts * 8 hours * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge * 1/48 volt batt bus = 5,882 AH @ 48 volt battery bank
    So, that gives you a battery bank of 1,500 AH minimum to 5,882 AH @ 48 volts on a 50% loaded 15 kWatt inverter running 8 hours per day

    And there is sizing the solar array... First, charging based on size of battery bank. 5% for backup power, weekend/sunny weather minimum. 10% to 13% to 20% for full time off grid operation (again, using FLA batteries--Others batteries can have different results). Say 5,882 AH @ 48 volt battery bank and 13% rate of charge:
    • 5,882 AH * 59 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 58,590 Watt array (on the large side)
    And then looking at hours of sun per day by season. Try Albany NY, fixed array:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Albany
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 47° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.09
     
    3.89
     
    4.40
     
    4.46
     
    4.67
     
    4.92
     
    JulAugSepOctNovDec
    5.02
     
    4.91
     
    4.56
     
    3.88
     
    2.83
     
    2.73
     

    Lets use 3.88 hours of sun (October) for "generator break even month":
    • 7,500 Watts * 8 hours * 1/0.52 off grid system eff * 1/3.88 hours = 29,738 Watt array "October break even"
    And sizing the MPPT charge controllers... Say use 80 Amp @ 48 volt MPPT controllers:
    • 58,590 Watt array * 0.77 panel+controller derarings * 1/59 volts charging * 1/80 amp controllers = 9.6 ~ 10 MPPT charge controllers
    Not saying the above is the proper design for you needs (still too many unknowns)--But it does give you some quick design rules to pencil out a few different systems and see what is needed, and how changes in your needs/assumptions can change the design.

    And when you get to larger systems, there are other components out there that may do you better (cost/maintenance) vs just a bunch of "residential" components tied together.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.