Diy wind generator capacitor help

[Overachiever]

I have a 500 hp ac induction motor and  I need help figuring out capacitance. It's 3 phase 2300 volts at 120 amps. I used a calculator on Google for capacitance and said I need 195 ufd but read a lot of people using 250 ufd per hp. I'm also wondering do i hook them to the wires or use slip rings/bushings on the rotor. Some people say it has to hook to the rotor some say it has to be the wires. This is for a grid tie wind turbine but I need it to power up to be inspected before I can be grid tie.

[bigrockcandymountain]

Hmm the pros will be here shortly but i will start with what i think i know.

A 3 phase induction motor has no slip rings etc to the rotor. 

It also takes no capacitors to start.  It is 3 phase.  Capacitors might help start if it is a high torque start but just spinning up to test i would think they aren't needed.

This may not apply to that big of a motor.

How big a turbine are you thinking?   

[dnix71]

bigrockcandymountain   How big a turbine are you thinking?   
Way too big. 500 hp is about 370 KW, enough to run 35 to 40 homes.

It would take 5kw just to make the thing idle.

[Frank S]

  I'm not one of the pros and am not an expert for sure.
 iff 500 hp is not a type"O" then that sounds to me like you might have something like the GENERAL ELECTRIC FRAME 509LS 3PH 2300V 3575RPM 500HP AC MOTOR
 If so that thing weighs 3500 lbs and could be rewired to many different configurations if you wanted to. But due to its size your will most probably need a tower that is in the 120 to 200 ft tall range  You will probably need  a gear box to step up the RPM from the turbine to the motor  without knowing how much out put you are expecting that motor used as a generator at near its full potential on a properly sized tower and turbine could power a small community 

[SparWeb]

Not the first time this has been suggested.
https://www.fieldlines.com/index.php/topic,149559
That didn't go anywhere.

And for the same reasons, I have to discourage this idea again.  This is not a newcomer's starting point for a wind turbine.
It also does not lead to a practical professional wind turbine.  Anyone with professional experience in this field would not be asking questions about choosing capacitors and using slip rings or not.  From this I deduce that you do not have any knowledge or experience with high voltage AC equipment.  Without that, you are likely to hurt yourself, or someone else.

I applaud the ambition, and if you could focus your attention on a more practical use, and one much more likely to succeed, such as hydro, then we can help you much more sensibly.  But you'll still need professional help on-site for the electrical safety and to build a very large dam.

[Overachiever]

.

A 3 phase induction motor has no slip rings etc to the rotor. 

It also takes no capacitors to start.  It is 3 phase.  Capacitors might help start if it is a high torque start but just spinning up to test i would think they aren't needed.

How big a turbine are you thinking?

Yeah would have to add them. I would think unless you have a permanent magnet rotor you would need something to energize the field at first then yeah probably won't need it unless it loses it field again.. Was planning on about 65 foot with 20ft diameter blades but....

 
 iff 500 hp is not a type"O" then that sounds to me like you might have something like the GENERAL ELECTRIC FRAME 509LS 3PH 2300V 3575RPM 500HP AC MOTOR
 If so that thing weighs 3500 lbs and could be rewired to many different configurations if you wanted to. But due to its size your will most probably need a tower that is in the 120 to 200 ft tall range  You will probably need  a gear box to step up the RPM from the turbine to the motor  without knowing how much out put you are expecting that motor used as a generator at near its full potential on a properly sized tower and turbine could power a small community 

It's a type E 7110cs frame at 1175 rmp and weighs 3000. I expected to get around 250 to 275 kwh since I thought to get output you take hp x 746 and then x about 80% to get at frequency output. I think I can mange about 120 ft tall tower but have to double check.

[Overachiever]

Not the first time this has been suggested.
https://www.fieldlines.com/index.php/topic,149559
That didn't go anywhere.

And for the same reasons, I have to discourage this idea again.  This is not a newcomer's starting point for a wind turbine.
It also does not lead to a practical professional wind turbine.  Anyone with professional experience in this field would not be asking questions about choosing capacitors and using slip rings or not.  From this I deduce that you do not have any knowledge or experience with high voltage AC equipment.  Without that, you are likely to hurt yourself, or someone else.

I applaud the ambition, and if you could focus your attention on a more practical use, and one much more likely to succeed, such as hydro, then we can help you much more sensibly.  But you'll still need professional help on-site for the electrical safety and to build a very large dam.

You're not wrong. I have no experience with anything of this nature and this is really big project for a newbie, but I'm smart enough not to do the dangerous parts by myself. I can put up the tower and run the lines but will have the electric company connect to anything live. Thanks for the warning though I'll double check my safety plans and make sure nothing can go wrong bad enough that could even result in a near miss. As for hydro I'm not against it but not a lot of places nearby I can set that up and no idea how heavy a flow I'm looking for.

[Frank S]

20 ft diameter blades is not going to get you anything near the kind of Kw you are thinking maybe 50 or 60 ft diameter might get you half of what you want. but I don't have my calculator any more.
 the tower is going to need to be massive and with deep roots there have been small 17 ft diameter 10 to 15 kw generators blown over with a 14 ton concrete footing.

[SparWeb]

No no no.
We are talking 20 METERS diameter, not feet to get 200kW plus out of it.
You are talking about a wind turbine design that will require very modern materials (composites), a 12 meter long autoclave, a machine shop that can manufacture a center hub about 4 feet across and a motor-driven yaw bearing system also several feet across.  The rotor assembly will weigh a ton (or more, not exaggerating!) and will require a special bearing system of its own.

This is an 80KW wind turbine with 18 meter blades:

[Frank S]

No no no.
We are talking 20 METERS diameter, not feet to get 200kW plus out of it.
You are talking about a wind turbine design that will require very modern materials (composites), a 12 meter long autoclave, a machine shop that can manufacture a center hub about 4 feet across and a motor-driven yaw bearing system also several feet across.  The rotor assembly will weigh a ton (or more, not exaggerating!) and will require a special bearing system of its own.

This is an 80KW wind turbine with 18 meter blades:

  Yes and most of the research I've done shows the rotor diameter ( blade tip to blade tip) ranging from 27 meters for a 200 KW to 33 meters or more for a 300 KW with tower heights from 33 to 44 meters in height
 the gear boxes IE step up transmission of 1:33 to 1:48  the nacelle weights with blades installed can be more than 15 tons.
 Not saying it can not be done. If I had the pockets for it and the motor I would be sorely tempted since I own my wind rights and there is a community  of about 25 homes within a 3 mile radius

[Overachiever]

The tower and and then the blades were gonna be my next sets of questions but you guys already helped a lot with your information. I have a guy who is going to build the blades out of carbon fiber maybe make the full tower out of it if that works. I planned on digging four deep holes to put the legs of the tower in the ground and filling it up with concrete since I heard bad things about a concrete slab for the base. I was also wondering is it possible to have the gearbox and motor on the ground? I know you lose efficiency but is it bad enough to outweigh the ease of access to the main system and losing weight from the top?

Back to the main topic real quick though. What should I use to energize the field? Would attaching a car battery to each phase wires for a few seconds or minutes be good enough? Thanks again for your help so far though. If I rushed in and bought the 65ft tower I would've wasted a lot of money.

[Frank S]

 I'm not quite sure you have fully grasped the scale of what you are thinking about doing.
 in order to even think about putting the generator and gear box on the ground first you would need some sort of drive system  capable of transmitting the horizontal rotation power from the turbine to the ground, which would require a right angle gear box mounted at the top of the tower and a long shaft to the generator on the ground a drive system of this type would likely weigh more than simply mounting the several tons of the generator and the transmission in the nacelle either way you are looking at a nacelle the size of a medium sized car at the very least. Not only are you going to require the step up transmission but the hub the turbine is to be mounted on must be large enough to not only mount the balds on but to house the pitch control mechanism these blades are going to weigh a few tons each. your 3000 lb motor that you want to use as the generator is one of the lighter components of the system.
 you will need to hire a civil engineer for the foundation but before he will be able to help you you will need an industrial design engineer with mechanical engineering background and a structural engineer to help with the design of the tower and several gearing systems for the generator the pitch and the yaw systems also an electrical engineer to to incorporate everything together.
 Since there are many manufactures of turbine systems of the size you are contemplating much of this has already been done it would be a matter of reverse engineering to incorporate everything together.
 http://www.komaihaltec.co.jp/english/renewable_energy/pdf/KWT300_Brochure_2.pdf

https://www.umass.edu/windenergy/sites/default/files/downloads/pdfs/Small_Wind_Power__Wright__May06-1.pdf
 
https://repository.tudelft.nl/islandora/object/uuid:a0835edc-f436-40f7-9c7e-ff3b92c0ada3/datastream/OBJ

Just to give you a few things to study.

[joestue]

If the motor is scrap your best option is building a direct drive wind turbine on the order of 20 foot diameter using perhaps a 4" thick stack of the stator laminations. (you might be able to make 10 of them from that motor?) each tooth or every other tooth gets wound with its own coil.. and the number of magnets is on the order of 2 less than the stator teeth (which for that motor might be 54 to 72.)

-----

basically torque follows the cube of the windspeed and the cube of the rotor diameter. a lot of work has been done to build gear boxes for wind turbines and in the end they ended up just building 40 foot diameter direct drive generators.. using brick sized neodymium magnets.
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simply throwing gears and shafts together might work.. until some vibration you didn't think about destroys it. a right angle gear box on the turbine and the motor on the ground is at least 3 exposed seals. thermal expansion of the vertical shaft needs to be accounted for. vibration of that long shaft is a problem.


one option might be to use a large truck differential for your right angle gear box at the top of the tower. you could easily send a shaft through the differential to operate the variable blade angle mechanism.. which will probably be required to get the turbine to start up in low winds due to friction in the gearboxes.

but i don't know what the practical limits of a large truck differential would be for blade diameter. also depends on definition of "large"

[Mary B]

No way will carbon fiber work for a tower that size. Steel, lots of it are going to be needed.

[Frank S]

If the motor is scrap your best option is building a direct drive wind turbine on the order of 20 foot diameter using perhaps a 4" thick stack of the stator laminations. (you might be able to make 10 of them from that motor?) each tooth or every other tooth gets wound with its own coil.. and the number of magnets is on the order of 2 less than the stator teeth (which for that motor might be 54 to 72.)

-----

basically torque follows the cube of the windspeed and the cube of the rotor diameter. a lot of work has been done to build gear boxes for wind turbines and in the end they ended up just building 40 foot diameter direct drive generators.. using brick sized neodymium magnets.
---

simply throwing gears and shafts together might work.. until some vibration you didn't think about destroys it. a right angle gear box on the turbine and the motor on the ground is at least 3 exposed seals. thermal expansion of the vertical shaft needs to be accounted for. vibration of that long shaft is a problem.


one option might be to use a large truck differential for your right angle gear box at the top of the tower. you could easily send a shaft through the differential to operate the variable blade angle mechanism.. which will probably be required to get the turbine to start up in low winds due to friction in the gearboxes.

but i don't know what the practical limits of a large truck differential would be for blade diameter. also depends on definition of "large"

 If someone wanted to go the large truck differential route it should be one of the ones with planetary gears in the hub like the large Mercedes heavy duty buss rear ends but the practical turbine diameter is still going to be limited to the amount of blade flex due to the distance from the center shaft to the hub flange Also differentials are designed to transmit torque to the hub not not the other way around.
 Turbine diameter could be increased by extending a large shaft from the hub outward and adding large bearing there. again there are practical limits.
 Another obstacle as was mentioned is how to keep a 100+ foot long shaft rotating true. this could probably be done by making shorter shafts and using u joints and carrier bearings but every connection is another potential for more problems. but it would allow for the final reduction to be at the ground. Another thing to consider is every connection every bearing every  gear set adds to the parasitic load to be overcome before the turbine can even begin to spin.
 Then there is the speed control blade pitch and lock down which has to be done at the hub of the turbine otherwise the force of the wind will destroy it.   

[JW]

Back to the main topic real quick though. What should I use to energize the field? Would attaching a car battery to each phase wires for a few seconds or minutes be good enough? Thanks again for your help so far though. If I rushed in and bought the 65ft tower I would've wasted a lot of money.

If the motor is 3 phase it does not need a start or run capacitor. The same should be true when you generate, actually a 3 phase motor will make power when it reaches the name plate RPM.   

[joestue]

Also differentials are designed to transmit torque to the hub not not the other way around.

The gear teeth are ground on one side with a lower pressure angle than the other. i recall reading 7 and 25 degrees for hypoid gears. so you're going to need to carve the blades so they spin in the right direction to load the gear teeth the right direction.

they still work backwards but maybe 2/3rds the strength.