Solar Powered AC Motor

You need at least 5 -8 Kw to get the motor started.

Talk to solar power guys for the correct set-up.

You realize you're looking at somewhere between $5k and $10k for panels + electronics? What would the pay-back period be?

No John. I don't think it would be this much expensive. Solar Panels are available here at under US $ 0.76/watt. An inverter rated at 10 kVA is available at under $ 800. If someone could tell me how to upload pic, I could upload the picture of the motor then

http://cr4.globalspec.com/blogentry/12466/How-to-Post-Pictures

I've found that posting images you have on your computer (rather than posting links to images on other websites) to be more reliable. All you need to do is copy the image from the other site and save it (in e.g. jpg format) on your local drive, then follow the instructions.

...and if the facility is needed to support human life in there, it needs some sort of backup for when it is cloudy/rainy/snowing.

Consider the cost of not having it as well: the cost of arranging funerals is rising too.

No backup needed since the miners will be working in day-light only.

What happens when it get cloudy/wet/snowy, then?

The generator is always there. I shall not use solar panels on a cloudy day at all. But all this discussion is digression. Let us focus on designing the solar power system :)

solar begins its cycle as DC, you'd have to run it through an inverter to get AC, and that has losses, just use a DC MOTOR and save time and hassle

Yes. An inverter is needed to convert it into DC and I have different quotes from different manufacturers. Would still want to go with the AC motor though. Just need some design calculation example.

"The in rush current falls off as a function of speed. So, if the fan starts rather slowly then the simple solution is to over design with a big honking inverter. But that pushes the issue to how the motor was made. So, yes it would work.....until the motor fails".

Please clarify

Sorry about the slang. By "big honking inverter" I mean "extra large capacity".

If the strongest part of your system is the supply, then the motor will be the weak link in the chain of parts.

At 3 hp and 3400 RM that's well within the range of having the electric motor replaced with a small high efficiency single cylinder diesel running the fan via either direct drive or a simple belt drive that allows the engine to run at it's optimal efficiency speed.

To me this would be the cheapest and most fuel efficient method to go with.

As for fuel costs most small single cylinder diesel are not all that fussy about what grade of fuel they get once up to operating temperature. As long as its clean they tend to be happy with most any blends of diesel fuel and used oils or ethanol.

I have a small Petter AC1 that will will start and run on a mix of 80% used oil and 20% E85 fuel without issues.

Thanks for the reply. But I want to go clean. And doesn't matter how much expensive the system comes out to be. I just want it designed. Any useful links will be helpful

"I just want it designed"

I submit that, in the end , you will use nothing offered here.

That is why I gave a minimal answer.

All too often, people come here and ask the forum to design something for them and when the time comes to purchase a system, since the requester has no idea if (or why) a given design will work, they simple go to the solar power purveyor who designs the system, based on what is selling best/has the highest profit margin at the time. "doesn't matter how much expensive the system comes out to be" means you will get the best system the seller can sell you. (I don't think you really mean this)

But, it's an interesting exercise for those who want to dabble in advising others on their favorite way to do something.

Good luck.

Although it never happens, (people coming back to let the forum know how they did something) let us know what you do in the end.

"doesn't matter how much expensive the system comes out to be". No, I do not mean throwing all the money to get the best system that the power purveyor can supply. I wrote that so that we can start discussing what power losses and other factors we have to take into account when building such a system. Problem is, a power purveyor or an energy expert for that matter is not present for miles in the place where I live.

LOL and well put!!!

Fair enough but saying you don't like the high fuel prices but want to go with a system that will cost you even more in setup and operating costs doesn't make sense to me.

In my experience 'going clean' is too much of an excuse for justifying spending a lot of company money that could be put to better use elsewear.

As has been suggested so far a Solar power system capable of running a 3 hp electric motor the way you want for the reasons you imply would cost around $15,000 US dollars. Whereas a basic 6 hp industrial Diesel engine would cost around $1000 and do the same job while only running at half load.

On top of that the remaining $14,000 if put against diesel fuel at an equivalent of $10 US dollars per gallon would run such an engine for 12 hours a day for roughly 260 grams of fuel per hour or about 12 hours per gallon.

Based on that for $14,000 worth of fuel at $10 a gallon that would give you a run time of around 1400 work days or 3.9 years of working 12 hours a day 7 days a week. On a five day a week work schedule that would take you to well past 5 years. 10 if your fuel cost $5 a gallon.

Granted without solid numbers relating to your actual cost for fuel and how many hours a year your mine runs I am only guessing.

Still by the numbers even when heavily weighted to try and favor the Solar power apprch the direct diesel engine powered blower system still comes in at competitive or superior.

GA You beat me to it!!! It would work fine and probably be quite cheap, economical to run and the original fuel tank can be used for supply AND keeping the original system as backup!!!! Far cheaper than Solar!!!

Since Solar is usually designed to first charge a battery bank, you can probably get away without the startup generator, the batteries with a proper inverter package will do that for you. Plus you will have a safety margin in the extra capacity of the batteries, do not save money on those either, they are crucial to safety issues. ( Miners opearting only in daytime / sunlight is a red herring since the mine is by definition underground. ) You might ask your supplier again about $ inverters $ to supply 3 phase power, for the inrush suggested by LYN ( kudos ). Also remember the solar array will need to be oversized to allow for less than perfect conditions of daylight and still supply the minimum KW. I hope you will keep the diesel genset on site as an emergency source for solar maintenance issues / faults.

As an aside, the starter on the genset is most likely battery driven, so no UPS should be required there, and your statement to please not suggest DC motors is a willingness to endure the losses of the inverters to go back to AC from the Solar DC output. Your Genset should also be able to drive a DC control directly as well, so DC drive should still be an option to consider. What were your disadvantages to DC ? In my humble opinion, this system would be better off with as few conversions as possible for reasons of reliability and efficiency, and if cost is not really a concern DC is not going to be that different in price anyhow.

I would highly recomend taking your specifications and requirements to the engineers who will be contracted to set up the solar array and have them offer their designs for the implementation of this setup. DO NOT consider this to be an on site - do it yourself project, lives are in the balance whether you like to consider that or not.

A DC motor is less-efficient and requires more frequent maintenance. Also it is more bulky. Finding a dc motor with this much RPM is another problem.

Money solves all problems, excuse my sarcasm, no offense intended.

a Brushless DC motor perhaps, with a belt drive to change RPM ?

Actually, now that I think of it, a golf cart dc motor is about 3hp and uses only 36 or 48 volts. They are notoriously low maintenance in the most rugged of conditions; seems like an ideal fit to me, they are also high RPM. the single phase controller would be simpler, and the solar array would not be as high a voltage either, batteries as well. If you had a small wind turbine ( and a little wind ) you could charge overnight as well.

Think about DC again.

Nope. Golf cart batteries don't last.

Think about a round of golf.

Drink beer. Hit the ball, drive 50 yards, stop. Drink beer. Hit the ball, swear profanely, drive 40 yards, stop. Drink beer. Hit the ball, throw club while swearing profanely, drive across fairway drinking beer, stop. Retrieve club, drink beer, drive back to ball, if you can find it. Drink beer.

By now, you have to pee. Drive back to clubhouse drinking beer and pee.

I'm too drunk and tired to go on, so I'll take a nap now.

"Nope. Golf cart batteries don't last."

Well if you use more than 6 or so they do!

Standard battery capacity curves and motor power draw charts should be able to say exactly how large of battery set would work.

As far as the DC is less efficient than AC thats a weak excuse at best. Modern motor design for both in the 3 HP range are for all purposes equal. If anything by the time inverters/VFD units are included on the AC motor its going to be a little less efficient than the direct connected DC motor.

To me more of the OPS reasoning sound more like either he is greatly misinformed or just wants justification to spend a lot of money to power a simple small blower system.

I wasnt really talking about the batteries as much as the DC motor, but yes thats sort of true if they are the ONLY power source. In sunlight conditions, the Solar grid would be expected to take the load, and the batteries would be temp storage for the startup surge. The batteries are fairly robust ( they can handle a lot of swearing ) but the OP was for a power setup to 3 phase AC 3hp. Any battery on the solar array would be a deep cycle, and the golf cart was given as an example of such a battery.

None taken. Have started thinking about the DC as an alternate option but wondering what will be the cost of buying one and a belt drive. But still, if say I have a large ac motor with a VFD, and now I have to connect it to solar, how would I take the power losses and starting current into account to choose my charge controller and inverter etc.

Probably, DC motor is the best solution as for now. But what if I had a large ac motor, replacing which would have been very expensive.

How good you design your solar system, it will always be critical for the purpose you want to use it. Get your miners good alarms down there and tanks with oxygen for emergency. (read frequently air shortage)

Look at the graph below and you will see what to expect from a 5kVA solar system with infinite load storage capacity.

5 kW will not even let you operate the 3 HP for 2 hours per day in the best circumstances.

To give you an estimation or a design, you need to come up with details, other than the motor you will run. The time determines your kWh needed and when.

Without battery back up, you will end up nowhere close to what you expect.

The best possible installation that I have installed and is running, has 15.000 Watts panels and 12,000.00 Ah@6 Volts battery back up to run a 4 Hp pump for 24 hours during the summer and has only capacity for maximal 18 hours during winter.

The cost price with panels @ 0.65/Watts, a high voltage battery (220 Volts X 1.41) and a 3 phase inverter/converter ran up to $56,000.00. The Lithium battery has been stolen once already. ($18,000.00)

The backup is very important.

The picture gives you the production with the green bars (month of October)

Count on 1/3 now in Januari.

Good luck. D.

Do you use the generator for other things, other than the motor in question? In other words, is it running, supplying current to other aspects of your operation? Why not have your diesel generator power a power converter to keep the batteries charged, regardless? That makes things simple. You will still need a failsafe, in the event of an inverter failure.

What you will want for this system, is to determine the current spike on initial startup for the motor. Disregard all other power factors at this time, if the motor draws 2KW at run, but needs 8KW to start, you are going to need, at a minimum, an 8KW inverter. Startup current is your most critical factor.

Determining this can be as easy as reading a data graph, or using instruments to graph and read this peak value.

Once you have that value, you will want to match it to an inverter that has a MINIMUM ability to produce this current.

You will also want a sine-wave inverter, which will be quite costly, compared to another form of modified- wave inverter that will cause the motor to heat up and fail, due to an impure waveform causing electromagnetic harmonics within the (field) coils of the motor.

Once you have the inverter selected, you will need to shop for solar panels, which need to be able to supply the necessary running current to the inverter, but ALSO to charge, and maintain a reserve of current within the battery banks.

In other words, if the inverter wants 5KW of DC current to keep the motor running, it is a good policy to have 7.5KW of solar panels at a minimum. This is to compensate for efficiency deficiencies in the solar panels, as they will not often be placed at optimum. In other words, those 7.5KW "Capable" panels might likely be only putting out 6KW, realistically, if you are lucky.

You will want to invest in a system that tracks the sun, to rotate the panel arrays (There will be more than one) into the sun at all times. These are not cheap.
Once you have the inverter, the panels, the arrays, and the trackers, you will need to purchase a good power regulator. These will prevent the solar panels from overcharging and cooking your batteries. You may need to separate the solar arrays, and add charge controllers to each one, individually (Each array). It is better to have a few arrays, in the event one fails, you still have the others, rather than having one large one, that if it fails, you are totally down.

Once you have the inverter, panels, tracking arrays, and charge controllers, you will need to select batteries to take the charge, and supply the inverter.
The more batteries you have, the more panels you will need to keep them charged. However, the more batteries you have that remain charged, the bigger backup you will have in the event of a solar panel malfunction, or extended cloudy days.

Lead- acid batteries are very plentiful, as they are also in most cars, and RV's. You may want to check into large electric forklift batteries. They can be had for a reasonable price, and offer significant reserve power.

In my estimation you may be looking at a 48V+ system, maybe higher. But it is definitely do- able, especially if you run a power converter from your diesel generator, and charge the batteries that way, in the even of a deficiency.

Sorry for the spacing, the formatting is acting up.

Thank you. Can you please suggest any instruments that can help me plot the voltage and current curves so that I get the peak starting current.

OP was to abandon the diesel generator due to high fuel costs.

THEN to spend many thousands of dollars on a huge solar array to run one motor.

Cost not a large concern, but then, why worry about the cost of fuel in the first place.

Theres more than one non-sequitur in this thread.

Because the solar panel powered motor will eventually prove to be cheaper in the long run. According to my estimates the Solar System cost will break even in no more than 1 years. 2 years at more than max. I shall paste my estimates soon.

Does this Solar System of your include all the planets? moons? Hey just obtaining a short outburst of laughter at your expense sir.

I think you are pretty correct when you state that there really is not a starting current issue, since the start-up should well be covered by the existing diesel genset you have, then after you turn that off to save money, the solar power panels /inverter etc. pick up the load. If that is what you intended, then right on, good show, and all that jolly rot.

Solar guys are dreamers, and than they start using it.

I have walked that road also.

More investment again, good business

Would love to see estimates.

I have many clients that over- estimate the solar production of a set up. Most of them by 2 to 2.5 times.

Good info, sounds to me to be "par for the course".

In Germany they have found that windmills, on average, generally only produce electricity for about 30% of the time (if they are lucky!).......but the owners planned for 100%!!!!

Scotland, which can be quite "Windy", plans for 28% to be a good average I once heard on a TV program!!

It might be interesting to hear from other areas.....

GA. I find it strange too..... We are not alone!!! Also, he comes over as unfriendly too....

Yep I'm third to agree with that.

So far what is know is there is a 2.2 KW fan a 600 watt fan and 2000 watts of lighting.

To me this sounds like a very small mine plus the concern over the 2.2 KW fan system but no concern about how the additional lights and other fan that make up the other 60% of the total load makes no sense to me.

The total load so far is less than 5 KW's which in diesel genset terms suggest that if the loads are managed properly a 6 KW genset system should be more than sufficient. Now from that the fuel consumption issue makes nearly no sense at all unless a massively oversized genset is being used and if so that in itself to me does not warrant going to an outrageously expensive and high maintenance solar based system.

To me that says that a much smaller genset with proper power management is what is needed and little else.

I would also like to know what the guy is mining.

Good post, I have similar thoughts....

Think you're getting your wires crossed. The "600 watt fan and 2000 watts of lighting" is from Musthafa, in post #39, not alihussain.syed (the OP), who is only fretting about his 3hp fan motor.

Well we are waiting on usable information from you conversation tends to drift a bit.

Where are your numbers on your electrical system so that we have actual data to work with?

So far you seem convinced that a solar based systems is whats best yet you have given zero usable information to back up your claim. On top of it s multiple people here who are active solar power users and system designers have given basic hands on testaments that heavily suggest that you don't have much if any of your facts correct.

By the way I would drop the pissy attitude real fast. It may get you what you want with your employees but here you're nothing more than a demanding ignorant nobody and can easily be treated as such.

Careful with how you make your next post. It could easily become your last!

I have reported him to Admin.

I may be being a bit simplistic. Drive the fan direct off the diesel. Get rid of the generator and motor.

BTW how do you operate a mine in daylight? As I recall they tend to be a bit dark.

Mines are dark irrespective of the day time. I operate them when it is day outside with bulbs inside the mine for the miners to work.

It is very essential to introduce a variable speed drive with the motor. This reduces the huge starting current issue of the motor.

Any solar supplier can guide you the exact requirement depending upon your load demand and the available exposed area to sunlight. And of course, sufficient initial capital also is a must.

Currently, I am operating a 6KW PV system which is used to power up some lighting load as well as some fan coil units of the HVAC system.

Dear Musthaafa, Can you please approximate the total load of your HVAC system. How much watts for the lighting and how much for the fan. What equipment do you have excluding the solar panel. Information would be greatly appreciated

I have 2000W lighting and 600W Fan coil unit. there is no starting current issue because the fans are alway on.

Apart from PV panel, we have Charge Controller and Inverter, and a supporting grid connection.

"there is no starting current issue because the fans are alway on" - were they on when delivered/installed?

it is continuously running equipments. It shuts down only for maintenance.

What charge controller and inverter are you using. A link to their datasheet will be very helpful. Thanks for helping out in deciphering the 'something' language. Regards

Ali,

you can brows for any charge controller having an output of controlled voltage of 48 Volt, cause if you really want to go with the solar system, you need an inverter of 48 Volt DC input and 380 Volt AC out. And the panel bank capacity will be not less than 50 KW if you are not using a soft starter. If you use soft start the panel capacity will be reduced tremendously.

Since we are not utilizing this thread for promoting any particular product, I don't like to be a brand ambassador for the brand I am using.

Solar Provider(pty)ltd We inport inverters that use dc solar power to convert it into ac. It can be used to power any 220 or 380v

Solar Provider Tell me , is it a 220 or 380 motor? Wat kw power do u need? i can help greensie101@gmail.com

It is 220/380 V, 2.2 kW, three-phase, 3-hp motor. Other details are in some Chinese/Korean language which I cannot understand. Still I am writing it down. It might make some sense to someone in this thread.

something 60C/S

something 112S

something S/60 A

something 3402 RPM. This one I understood :).

something 8.6/5.0 A.

something 60C/S is the frequency 60H/z

something 112S is the Service Factor

something S/60 is the starting current or LRA

something 8.6/5.0A is the full load current FLA at 220V/380V

do you still need to go with the conventional starter?

Wind is also solar energy, so put that to work too. In fact, you could use a windmill to turn the fan drive directly, then disengage when the wind drops out. The solar idea is good in areas where there is seldom any cloud cover, latitude is low relative to equator, provided you follow the advice offered by the real gurus in here on the topic. You should oversize the power inverter/battery bank so that start-ups are well covered, for undervoltage will ruin your 3 HP motor.