Sizing start & run capacitors for 100hp 3 Phase motor - Page 4
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  1. #61
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    Just for the sake of craziness and as a data point, here’s a 100HP ABB VFD soft starting a 200HP 3ph Toshiba motor using single phase household power.
    240V 1ph stepped up to 480V 1ph then into the VFD via 14 gauge extension cord.



    I’m in agreement with Thermite that a VFD would be well suited to the original poster’s 50HP hydraulic pump, especially if you could run it off the DC bus and avoid conversion losses.


    If you wanted, you could soft start the 100HP motor with a VFD, and then cut out the VFD and apply line voltage, but seems messy and overly complicated.
    Probably be better to get a 75KW 3ph alternator or motor generator set and drive the motor with the VFD, so you could tune the whole system, but this is also more complicated and less versatile than just powering the 50HP pump/load motor directly with a VFD.

    YouTube

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    is a 75hp idler motor more appropriate for a 50hp load?

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    A one way clutch, something like you would find in an automatic transmission would work so you weren't constantly driving the pony motor.

    Cheap, readily availible, and reliable.

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  5. #64
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    Quote Originally Posted by triumph406 View Post
    A one way clutch, something like you would find in an automatic transmission would work so you weren't constantly driving the pony motor.

    Cheap, readily availible, and reliable.
    Battery-bank environment right close, be tempting to use an IC engine starter that already has an actuating solenoid and a to-speed throwout mechanism.

    You'd not want to gear it down much if at all, nor have to do.

    100 HP AC motors don't have squat in the way of compression-stroke load compared to a Hemi or Diesel frog-jerky maker.

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  7. #65
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    An error in my previous post. (Now past the edit cutoff.)

    Quote Originally Posted by neilho View Post
    ....You will need to adjust that factor downward if it's for gridtied.
    Should read "if it's for remote."

  8. #66
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    Quote Originally Posted by JST View Post
    The first advantage of a battery system is "brown-out" protection. There are clouds, and output drops like a stone when clouds cover the sun for short times on partly cloudy days. Even in Florida....

    The other advantage is "regulation".... batteries tend to keep a system regulated to their voltage, through the action of the charging system, which tracks the battery voltage. Otherwise you may have fauirly large changes in voltage..

    The batteries are a reference, a current sink, and a source for short times of no sun, even if they are not extremely large capacity. Of course the more capacity the better.

    This is a much more complex system than I believe is being understood... It needs careful evaluation for what is wanted, vs what is probably going to be provided by the system under the various choices of configuration you have available as choices.

    You might want to consider a grid tie system where the PV is the prime source, if you can get powerco approval for such a large system that may turn from a source to a sink in a few seconds (they hate that). In that way you have continuity through the powerco grid power when there is no sun, and generated revenue when there is solar input.

    I am still a bit unclear about what you expect from your proposed system. From the various statements made, I think it sounds as if it will not be able to do what may be expected, for a number of reasons, the largest of which is the variability of the power source (solar), which can drastically change in a few seconds. You need something to stabilize that.
    ".
    The powerco may be accepting inputs from many small solar systems (15kW max, typically), but they are usually scattered around, so that some may be shadowed, but others are not ("diversity"). The average tends to even out reasonably.

    You will have one large array, and no averaging over a large area. When you are shadowed, all your power is reuced, you have no "diversity". And, if I understand your statements, also no plan to stabilize output to cover your loads when you are shadowed.
    There is no-grid at the location, that's not an option. Sizing a battery bank to keep this setup going for 25-30 minutes if there's shade can get costly.

    There are micro-inverters that can be strung together for large voltages, there's even a few coming out soon that will allow up to kW from 1 micro-inverter that can be strung together. So instead of having a micro-inverter on each panel, a group of one to six strings can be sent to a micro-inverter. I don't want to post the link here since I am not advertising for them.

    The hydro doesn't have to work full time, no person or thing will be injured if the machine has 10-15 minutes to just stop; and start up again some time later. If it stops for a week, that would cause some issues.

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    Quote Originally Posted by thermite View Post
    I'd STILL go VFD for the 50 HP. You really, really gain from ability to slow-ramp it as to essentially eliminating starting inrush TOTALLY as a hammer on the PV's inverters.

    AND THEN.. same again, VFD for the next LARGE unattended load, same reason.

    AND THEN.. much smaller RPC for smaller 3-P loads. Which might be used only when a two-legger is actual at the site.

    Given the KINDs of things as can go wrong?

    Maintenance helicopter or hovercraft should have an IC-engine driven welder/generator or gen set on the chopper or boat. Or truck. Or Mars lander. Wotever.

    Regardless.

    SOL if the PV array or inverters are what has gone pear-shaped, needs fixed.

    NO local power atall! Can't even re-charge cordless HAND tools!

    There is 1 large idler that will power all downstream smaller motor loads. There are many things that can go wrong, which I'll be responsible for, I'd like to get feedback on all the things that can go wrong and be prepared vs not thinking about something and getting caught behind the eight ball.

    You are correct, No grid to fall back on.

  10. #68
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    Quote Originally Posted by neilho View Post
    90 kW is a very large array for a single offgrid user.

    What JST and others have said, politely, I'll say bluntly, having installed and used these things for over 40 years. You don't understand your proposed PV system.

    You need to calculate your loads and usage realistically, then output (in kWh annually) from your panels, realistically. 93kW is just output at Standard Test Conditions. (See here for Standard Test Conditions for PV's.) They almost never exist in real life. There's also the local factor, too. Average ambient temperature, cloud cover, hours of sunlight, solar exposure, etc, etc. There'll be a local solar developer in your area that knows this, based on data from past installations. Installers, less likely. You will need to adjust that factor downward if it's for gridtied.

    Since this will be a remote system, not connected to the grid, you'll manage it in a much different way than if it were gridtied. In a gridtied installation every watt hr of generated energy is used onsite or goes into the grid. (Less inefficiencies, of course). In remote systems, the goal is to have power available at all times, with storage for overnight and cloudy days. The ideal is to have the battery bank at near full charge by noon on a sunny day, taper charge and feeding a dump load after that. More on this if you're interested.

    A battery bank with 3phase inverters is the best way to manage large loads. Lead acids are still the biggest bang for the buck. Li-ion is silly for a stationary application, in spite of all the PowerWall marketing. Get the biggest cells you can to avoid imbalances, in your case forklift size.

    Inverters from mfgers like Outback are stackable for 3 phase. Use a different inverter for your single phase loads, possibly even an inverter for each load. Inverters are very reliable these days - the industry standard warranty is now 10 years.

    Someone familiar with a remote system as large as you're proposing will be hard to find, but you need them and they'll be worth it. You're looking at a $100K PV system installed, minimum.

    And (if I haven't offended you already ) please, please give us an overview of your system and its intended purpose. Without it we won't be able to give you the best advice. Garbage in, garbage out.

    I don't take any offense and like the feedback.

    93kW is an oversized system for my purpose.

    The large idler motor is 75kw which is 2:1 ratio vs the motor that will actually do the work is only rated for 37kW; which
    93kW * .85 is about 79kW; still more than I need but any panels that don't produce 85% over 25 years are under warranty for replacement.

    The system is just pumping water to spread over a large area, if water isn't pumped for a few hours, days, things should be fine.

    It's a fairly simple project as far as what's needed to get accomplished. The solar is a whole bag of its own things;

    You could expand more on the battery system; I would not use Li batteries as they can explode and one bad cell is all it takes for a runaway situation. The Lead acid batteries are going to need to be replaced ever 3-5 years... That costly in time and labor; or maybe not.


    I was leaning towards a 3 phase inverter; lets say I do get rid of the 100hp idler, how many additional inverters will I need for a 50Hp hydro system as well as some 3 phase machining/ shop tools?

  11. #69
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    Quote Originally Posted by thermite View Post
    Ahem... now that we are down to the proverbial "brass tacks"...?



    MY take (Dominant-Carrier Global Telco of the many-small-islands flavour)...

    is that our poster is one member of a team. Someone ELSE - or several - DOES have a klew. Or so one may hope.

    He's just fixated on "selling" a higher-up on RPC's being more durable than dirty-beach-sand.

    Could was. Or maybe not-so-much?

    But it isn't even remotely germane to this environment.

    That's the bedrock. The rest ain't my rice-bowl.

    Our supply boat only hit an island twice a year? It carried up to a year's worth of Diesel fuel. In case the bugger SANK before a replacement could be arranged, next go.

    BFBI, but the phone and telegraph worked and Carefree and Wifeless, Able & Tireless got paid.

    BTW.. More than one tribe of "middleman" in the world. Got medium-Voltage Dee Cee off a battery pile? Tap points? DC motors still exist. So do Hydraulic load-sharing goods.

    Ever heard the term "no single point of failure"?
    There is no team, there is no grid. It has to be done. The more pitfalls I can learn about, the more pitfalls I can avoid.

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    Quote Originally Posted by Bill Simmons View Post
    Lots of good information coming to you.

    And JST is correct regarding my suggestion of 480V from a single phase inverter (and that is what I was thinking) is a no go. But he got me doing just a little more research.

    480 three phase is readily available with solar. With three phase 480 (or 240) and the system just got simpler as no RPC is required and those other 3 phase loads are easily handled. A vfd (or possibly some other soft start method) would still be needed to start 50 hp motor.

    As has been stated by others with far greater experience than I (I have only done 2 grid tie solar systems) without either grid tie or batteries the operation of this system will be tied to the whims of mother nature in addition to the schedule of the sun.

    I agree that a professional with experience in solar power generation and distribution should be consulted as there is a vast amount of information (not yet provided) to be digested to come up with the best solution.
    Two complications, there are no professionals where this will be installed. There are no skilled solar installers, the good news is there is a lot of sun.

    The 3 phase 480v with soft starters does seem like the most practical solution to this.

  13. #71
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    Why not just use DC motors run off panel voltage, ( no vfd or rpc) seems that is what you are trying to do with this RPC? Am I correct that if the sun is shining you want the hydro motor turning? And if the sun is shaded for a bit the motor will slow or stop and restart when sun returns, this is all OK?
    Instead of one 50hp hydro pump can you have five 10hp pumps? Or?
    Some sort of voltage control so the motors are not fed until voltage is enough to start them might be needed, not sure what that would be...

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  15. #72
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    I am not saying your solar system is not sized appropriately but I think you are overly optimistic about its output level. My home solar system is 20 panels rated at 320 watts each for a total of 6.4 kW. I seldom see 5 kw and that is only at noon. I only once saw an output approaching its rating. My understanding is that occurs when some form of an atmospheric lens dumps extra sunlight onto the panels.

    The test conditions for a solar panel do not match the real world. The irradiation is stronger than the sun and it is at a temperature much lower than you will ever see in Florida.

    Unless you have at least one axis of tracking the output will fall off pretty quickly either side of noon. You might want to explore tracking.

    Unless you have a lab to test the panel, you will never know if the performance has dropped the during the warranty period and unless the company giving the warranty creates some form of trust to pay warranty claims, they most likely will not be around to replace the panel (which will no longer be available in the size and shape of your present panel) in 15 plus years.

    A suggestion of using multiple pumps was thrown out there. You should explore this. Smaller pumps are easier to start and you could have some flow during cloud cover and before 10 am and after 3 pm (actually you may have to wait till noon to start that large motor unless using a VFD).

    I have an irrigation system with four pumps in a large tank. This is not for power purposes but to handle large differences in needed flow rates for drip vs large sprinklers. Pressure is monitored and control is done by a PLC. You could have a similar system where the number or size of the pump(s) running was controlled by a system monitoring a sun sensor (small solar cell).

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    All good feedback, Newbea.

    Lacking more specific knowledge of your situation I'll make a few assumptions and estimates.

    A crude way to estimate PV output is to multiply average hours of full sun/day x STC peak rating of the panel. Florida varies a bit, but seems to be between 5.3 and 6.2. (See here, also a guide for estimating the rest of the system). Taking an average of 5.75, x 93kW = 535kWhrs/day average. More in the summer, obviously, but presumably a good load match since irrigation requirements are higher in the summer.

    93kW is a large installation with hundreds of panels. They'll be configured in strings, essentially multiple installations. Very good for reliability and shading, since output of one string isn't affected by bad panels/shading in another string. Directly feeding a DC pump with panels is a great idea - there are pumps out there designed for that. One pump/string would be good for reliability of the system: One pump or string down is a low percentage of the total system. Tanks are cheap compared to batteries. A battery bank w/inverters to run the workshop tools seems essential to me, though.

    9-12 years is a more reasonable life expectancy for lead acids. Life expectancy depends primarily on maintenance, secondarily on total charge/discharge cycles. Equalize charging every two weeks (most battery chargers for PV systems can be programmed to do this) helps a lot, as do desulfators and automatic watering systems. Regular corrosion checks are helpful too. There are a lot of lead acids on the market designed for remote PV systems - mostly they have thick plates with more room at the bottom for debris. Trojan batteries are good for smaller banks - their L series are for PV systems and have an optional automatic watering system. A Trojan L series bank installation I did 12 years ago is still working, though not well - maintenance has been indifferent, at best. Solar One HUP batteries (1700Ahrs @24V, 2700lbs each) are well regarded. 7 year free replacement warranty, 3 year prorated. Shipping these things can be spendy, but Trojan ships free to distributors, so if there's one near you, that may be the way to go.

    Used panels are available, too. Last I checked, an eBay seller had Sunpower 315W panels for $100 each, guaranteed output. If you want to go new, the Federal tax credit still applies to the installed cost of the entire system. Panels, racks, batteries, inverters, wiring, installation, the whole shebang. You do have to have enough income to generate a fed tax liability, but the credits can be rolled over.


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