Build a 48 VDC Generator with a 50 hp electric motor

[deckart]

You can select any type of motor. I'm going to spin it at a varying RPM and with a varying torque. The combination of torque and RPM will be capable of 50 hp intermittently. I can limit the maximum RPM but lower is better as I can leave out a gearbox.

No different than what they probably use in a wind type generator.

What all is required to covert this rotational energy @ 48 vdc with an electic motor?

 

[anorlunda]

Wrong units on your question. You don't convert energy to volts, you convert mechanical energy to electric energy. Volts are not energy.

Is this homework? If so, it should be posted to the homework forum.

 

[deckart]

Wrong units on your question. You don't convert energy to volts, you convert mechanical energy to electric energy. Volts are not energy.

Is this homework? If so, it should be posted to the homework forum.

No, this isn't homework. I am converting rotational energy to electric power @ 48 vdc.

 

[anorlunda]

You must specify how much power. Power is voltage times current. 48 volts and zero current is zero power. If you don't understand that, I'm afraid you will not be able to understand any better answers to your question.

 

[deckart]

50 hp

 

[deckart]

You must specify how much power. Power is voltage times current. 48 volts and zero current is zero power. If you don't understand that, I'm afraid you will not be able to understand any better answers to your question.

I'm not using the electric motor to turn a generator, I'm using a hydraulic motor. I want to convert the electric motor to a generator.

 

[anorlunda]

The generic term for DC generators motors is Dynamo https://en.m.wikipedia.org/wiki/Dynamo.

Some types can be used as generators or motors without modification. Therefore you must be more specific. Do you want to design a motor yourself ? Do you want the make/model of a motor to buy on EBay? Do you need only the name of the type of motor? What to you mean by "what is required?"

 

[deckart]

The generic term for DC generators motors is Dynamo https://en.m.wikipedia.org/wiki/Dynamo.

Some types can be used as generators or motors without modification. Therefore you must be more specific. Do you want to design a motor yourself ? Do you want the make/model of a motor to buy on EBay? Do you need only the name of the type of motor? What to you mean by "what is required?"

I want to buy a manufactured motor.

Can I simply buy a 48 vdc, 50 hp motor and spin it?

 

[jim hardy]

Do you understand my question now?

A question well stated is half answered.

You can select any type of motor.

I select a permanent magnet DC dynamo.

I want to convert the electric motor to a generator.

A DC dynamo will act as either a motor or a generator, just the directions of current and torque reverse.

What all is required to covert this rotational energy @ 48 vdc with a motor?

A mechanical coupling between your hydraulic motor and your dynamo, a device to control speed, and a sturdy mount.


Just what is your question?

 

[anorlunda]

http://www.ebay.com/itm/WIND-TURBINE-GENERATOR-3-6HP-AMETEK-PERMANENT-MAGNET-DC-GENERATOR-MOTOR-PMG-PMA-/221958095876?hash=item33adbbc404:g:x1oAAOSwxN5WX98k

That is the suitable kind. You just need to find a bigger one.

 

[deckart]

Looking at a Baldor catalog, 48 vdc might be too low for a large motor.

A question well stated is half answered.

I select a permanent magnet DC dynamo.

A DC dynamo will act as either a motor or a generator, just the directions of current and torque reverse.

A mechanical coupling between your hydraulic motor and your dynamo, a device to control speed, and a sturdy mount.Just what is your question?

I'm trying to select the appropriate dynamo for this application. I can design everything up to the dynamo. I was told on another thread that the best way to get power back to the grid is begin at 48 vdc and use a proper inverter. Once I select the dynamo I can size the hydraulic motor. But my expertise ends at the dynamo shaft.

 

[jim hardy]

I was told on another thread that the best way to get power back to the grid is begin at 48 vdc and use a proper inverter.

Have you looked into that claim?
Induction generator has the nice feature it won't backfeed into a dead grid and electrocute a lineman, like a simple inverter can..

In your shoes i'd try to cultivate experts like Anorlunda by sharing more details of your experiment.

Like a dynamo, an ordinary induction motor will induction generate by simply overspeeding it slightly. Plus it has no brushes and is cheap. But that might need a gearbox.

It's a helpful bunch here, just you got to prime the pump and be polite.

old jim

 

[deckart]

Have you looked into that claim?
Induction generator has the nice feature it won't backfeed into a dead grid and electrocute a lineman, like a simple inverter can..

In your shoes i'd try to cultivate experts like Anorlunda by sharing more details of your experiment.

Like a dynamo, an ordinary induction motor will induction generate by simply overspeeding it slightly. Plus it has no brushes and is cheap. But that might need a gearbox.

It's a helpful bunch here, just you got to prime the pump and be polite. Revisit post 7 ?

old jim

Thanks Jim. Didn't mean to come off impolite. I'm having trouble asking the right question.

Basically, I have up to 50 units of mechanical/hydraulic HP I want to convert and put on the grid. I've done the bulk of the conceptual design on the mechanical/hydraulic side and I'm trying to at least nail down the generator motor. Once I have those specs I can finish sizing the hydraulic motor and coupling. If there is a minimum RPM then I can configure the hydraulics to store the energy and release it to the hydraulic motor when there is enough to get it up to speed.

Just hammering out the details but I have very little knowledge of electric motors beyond what is required to drive a pump.

 

[russ_watters]

50 hp is 37 kW. That's a pretty powerful system (mechanically and electrically) for a novice to undertake. It will be complex, dangerous and expensive. You can't design it just by getting vague/disconnected one-liner questions answered.

I'm using a hydraulic motor.

You aren't using anything yet, are you? Have you purchased this hydraulic motor? What is the make/model of it and where is it getting its hydraulics? [Edit; oh, this is your wave power thing]

Does your house even have a big enough electrical service to handle this? Have you talked to your utility about setting up the metering/service?

I think you may need to hire yourself an electrical engineer if you want to have much of a chance of this working.

 

[deckart]

50 hp is 37 kW. That's a pretty powerful system (mechanically and electrically) for a novice to undertake. It will be complex, dangerous and expensive. You can't design it just by getting vague/disconnected one-liner questions answered.

It's just a matter of scale. I've designed much larger and more powerful systems. This is relatively simple other than the fact I've never created electricity before :)

 

[deckart]

50 hp is 37 kW. That's a pretty powerful system (mechanically and electrically) for a novice to undertake. It will be complex, dangerous and expensive. You can't design it just by getting vague/disconnected one-liner questions answered.

You aren't using anything yet, are you? Have you purchased this hydraulic motor? What is the make/model of it and where is it getting its hydraulics? [Edit; oh, this is your wave power thing]

Does your house even have a big enough electrical service to handle this? Have you talked to your utility about setting up the metering/service?

I think you may need to hire yourself an electrical engineer if you want to have much of a chance of this working.

I haven't sized the hydraulic motor yet, I need to get the RPM range. I'm designing something on a slightly larger scale than a single household. Targeting remote villages on the AK coast. I won't be hiring an electrical engineer anytime soon. I want to have a solid design laid out for the generator platform before I begin soliciting an electrical engineer. Otherwise, like yourself, I'll be talking to people who will be just be rolling their eyes at the whole concept.

This thing is getting designed and costed to the last bolt. But, I need to specify the generator motor.

Thanks for your input, Russ.

 

[russ_watters]

I don't see how you can size the generator until you've gotten the hydraulic motor (and maybe even tested it).

And fyi, the eye rolling you are getting is mostly about your approach. This is a serious project and you don't seem to be approaching it very rigorously.

 

[deckart]

I don't see how you can size the generator until you've gotten the hydraulic motor (and maybe even tested it).

And fyi, the eye rolling you are getting is mostly about your approach. This is a serious project and you don't seem to be approaching it very rigorously.

What is your "rigorous" recommendation? I'm not sure what you mean by "your approach". You start with an abstract concept and work out the details.

The hydraulic motor is determined by the output specifications, not the other way around. Cmon, Russ. You don't specify components without the application parameters. The hydraulic motor output depends on the gen motor input RPM range and torque requirements.

FYI, I expect this will cost much less than an equivalent kW wind turbine generator system.

 

[russ_watters]

What is your "rigorous" recommendation? I'm not sure what you mean by "your approach".

All we see are the disconnected bits and pieces and half-finished thoughts posted here. I sincerely hope there is more detail than we are seeing. Have you made any drawings/schematics? Have you designed the wave energy harvester? An electric generator is a common thing, but a wave power harvester would be quite an invention. All I've seen of that was a couple of hypothetical numbered pulled out of the air - nothing about how to capture it.

The hydraulic motor is determined by the output specifications, not the other way around. Cmon, Russ. You don't specify components without the application parameters. The hydraulic motor output depends on the gen motor input RPM range and torque requirements.

No, since this is an experimental power generation project, the driver is the amount and type of available power: the flow rate and pressure of the water. At this point, that part of the system should be functioning. Then you select a hydraulic motor based on that input, then a generator to match the motor and electrical requirements.

FYI, I expect this will cost much less than an equivalent kW wind turbine generator system.

Highly unlikely but in either case, have you priced-out any of the components yet? The actual wave energy gathering device in particular. It's the "special sauce" in this recipe.

 

[deckart]

All we see are the disconnected bits and pieces and half-finished thoughts posted here. I sincerely hope there is more detail than we are seeing. Have you made any drawings/schematics?

No, since this is an experimental power generation project, the driver is the amount and type of available power: the flow rate and pressure of the water. At this point, that part of the system should be functioning. Then you select a hydraulic motor based on that input, then a generator to match the motor and electrical requirements.

Highly unlikely but in either case, have you priced-out any of the components yet? The actual wave energy gathering device in particular. It's the "special sauce" in this recipe.

Yes, I have the general schematic completed but the components aren't yet specified. See attached. But, you see my point, you want to see details. That's what I'm working on.

I agree, there are a lot of half-finished thoughts here. I'm debating whether I should just put this up as a PF group project or not. If there is actually something that's patentable in the system, I'd be killing that ability by publishing it in a public forum. I haven't seen any designs in my research that take my approach. So, I'm asking questions that don't reveal the entire "sauce" recipe. There's a buoy, a mechanical to hydraulic conversion, a simple hydraulic system, and a gen motor. From that gen motor the interface to the grid is no different than with any other generator system. Probably nothing patentable here but I want to make sure I can put something out there first.

I don't want to debate hydraulic design with you but, you don't create a hydraulic system (or any system) and then try to make it work on an application. The application defines the system components. Then prime mover, the "input", is the ocean wave action, the application is the gen motor. Moving on from that...

I haven't done a lot of costing yet but based on the simplicity of the system and the fact that most of the components are "off-the-shelf", I can say with confidence that it will be cheaper to construct and maintain than a wind turbine equivalent. A buoy is cheaper than a set of precisely engineered props, for example.

 

[anorlunda]

https://en.m.wikipedia.org/wiki/PowerBuoy
https://en.m.wikipedia.org/w/index.php?title=Wave_power

Have you checked what others more qualified have done in this field? If not, it's pretty arrogant to think you have a patentable idea that they didn't think of first.

if you trivialize the difficulties, you won't get far. That dampens our interest in answering your questions.

 

[deckart]

https://en.m.wikipedia.org/wiki/PowerBuoy
https://en.m.wikipedia.org/w/index.php?title=Wave_power

Have you checked what others more qualified have done in this field? If not, it's pretty arrogant to think you have a patentable idea that they didn't think of first.

if you trivialize the difficulties, you won't get far. That dampens our interest in answering your questions.

Yes, I've checked. Those designs are mostly exotic and expensive. It's not arrogant to think you have an original idea. If I thought that way I wouldn't have gotten my first patent. Difficulty depends on perspective. The part I'm designing is not very difficult to me. The part that is difficult for me is the gen motor. I'm here because there are people here who would not see this part as difficult.

I'm hoping to find a like-minded individual who happens to specialize in the electrical side that could suggest a gen motor for this application.

Jim Hardy would use a dc dynamo. That gives me something to research.

If more details are needed, please let me know.

 

[CWatters]

Most countries have strict rules on how you connect generators to the grid. For example you must usually disconnect from the grid automatically when the grid goes down due to fault. Otherwise you might electrocute the engineer working to solve the problem. This is probably why someone suggested you use a battery and a proper inverter - a professional inverter should deal with any local regulatory issues.

However 50HP/37kW at 48V implies a current of 781 Amps! I suspect it will be hard to find an inverter that will do that. I think most inverters in that power range will be designed for higher voltage/lower current.

Here in the UK any generator over about 4kW requires a three phase connection and special permissions but perhaps three phase grid connections are more common where you live?

Edit: Your generator might be capable of delivering 50HP but your battery charger will only draw what the batteries can handle. There will be a time when the batteries are full and cannot accept 50HP so your system needs to handle that situation.

 

[deckart]

Most countries have strict rules on how you connect generators to the grid. For example you must usually disconnect from the grid automatically when the grid goes down due to fault. Otherwise you might electrocute the engineer working to solve the problem. This is probably why someone suggested you use a battery and a proper inverter - a professional inverter should deal with any local regulatory issues.

However 50HP/37kW at 48V implies a current of 781 Amps! I suspect it will be hard to find an inverter that will do that. I think most inverters in that power range will be designed for higher voltage/lower current.

Here in the UK any generator over about 4kW requires a three phase connection and special permissions but perhaps three phase grid connections are more common where you live?

Edit: Your generator might be capable of delivering 50HP but your battery charger will only draw what the batteries can handle. There will be a time when the batteries are full and cannot accept 50HP so your system needs to handle that situation.

Yeah, that's A LOT of current. 48V doesn't seem to be a practical voltage. I see Baldor has dc electric motors that are 500 V. I don't know how the wind generators do it. More Googling to do on that.

And for interfacing the grid, it would be in the same fashion as a wind generator. Those are common enough and standardized that I'm not going to try to reinvent the wheel on that end of it.

 

[jim hardy]

I don't know how the wind generators do it. More Googling to do on that.

And for interfacing the grid, it would be in the same fashion as a wind generator. Those are common enough and standardized that I'm not going to try to reinvent the wheel on that end of it.

AWEA is a resource you should mine

https://www.awea.org/files/FileDownloads/pdfs/AWEA_Electrical_Guide_to_Wind_Turbines.pdf

early wind generators were induction machines. Way simpler, and you just might find a surplus induction motor lying around.
https://en.wikipedia.org/wiki/Induction_generator

 

[deckart]

AWEA is a resource you should mine

https://www.awea.org/files/FileDownloads/pdfs/AWEA_Electrical_Guide_to_Wind_Turbines.pdf

early wind generators were induction machines. Way simpler, and you just might find a surplus induction motor lying around.
https://en.wikipedia.org/wiki/Induction_generator

That's excellent information! Thanks, Jim!

 

[Averagesupernova]

Why don't you start on a smaller scale? You cannot expect to design and get this project working in one shot. Ever hear of proof of concept? It seems you don't understand the relationship between watts, volts, amps, horsepower, etc. If you started on a smaller scale I think you might learn enough so that you would not rely so heavily on the people here that are not giving you the answers you desire. This goes along with what one of my favorite members here on PF that says: "A question well stated is half answered." Likewise, start at an easier scale and answers to your questions will become obvious. Some answers you will like, some you may not.

 

[deckart]

Why don't you start on a smaller scale? You cannot expect to design and get this project working in one shot. Ever hear of proof of concept? It seems you don't understand the relationship between watts, volts, amps, horsepower, etc. If you started on a smaller scale I think you might learn enough so that you would not rely so heavily on the people here that are not giving you the answers you desire. This goes along with what one of my favorite members here on PF that says: "A question well stated is half answered." Likewise, start at an easier scale and answers to your questions will become obvious. Some answers you will like, some you may not.

Thank you. I had actually started at a single home scale. However, people around here that have ocean front property don't really have a need for it. A friend, who lives in AK, spoke to me about the electricity problems they are having in the coastal villages up there. Some of the communities have wind generators but are also having maintenance issues. So, that's the scale I'm targeting. I've designed a mousetrap that can convert the wave energy to a mechanical, rotational, energy. But that's the limit of my expertise.

I do understand the relationship between watts, volts, amps, and horsepower. I don't understand electricity generation. 48 VDC is out, the amperage is excessive at such a low voltage.

The theory is the same regardless of scale and I've worked with larger scales of power. I've just never generated electricity.

Take on the problem with me. :) I have up to 50 units of hydraulic/mechanical HP available for a generator to make use of. I say 50 HP to provide a target, it really is dependent on wave conditions and could be higher but I've built in a provision to limit this in the hydraulic circuit. With the schematic I've provided so far, when the system is saturated, it goes into "float" mode and does not accept any more energy input.

 

[jim hardy]

again you're skimpy on detail.Are you locked into a single machine?
Does hydraulic imply low RPM ?
An alternator would relieve the need for an inverter, simplifying maintenance.

Searching for "low RPM alternator"
turns up whoever's bribed google
here's a 10 kw 50 RPM permanent magnet three phase unit
http://www.xindaenergy.com/10Kw-50r...Generator-for-vertical-wind-turbine-p205.html

here's an old line manufacturer that makes generators for industry
http://www.emersonindustrial.com/en...ernators/power-alternators/Pages/default.aspx
number of poles you'd want is
(3600/RPM of your torque supply ) X 2 and it has to be an even integer
ie
3600 rpm = 2 pole
1800 rpm = 4 pole
900 rpm= 8 pole
720 rpm = 10 pole

I used a 150 kw Kato machine for our simulator, found it well made and reliable
how 'bout that - Emerson bought them.
http://www.emersonindustrial.com/en...s/katoengineering/Pages/Kato-Engineering.aspx

good luckIf this is a "Red Green" project, a dozen truck alternators could make your 800 amps DC

check your PBS listings...

 

[deckart]

again you're skimpy on detail.Are you locked into a single machine?
Does hydraulic imply low RPM ?
An alternator would relieve the need for an inverter, simplifying maintenance.

Searching for "low RPM alternator"
turns up whoever's bribed google
here's a 10 kw 50 RPM permanent magnet three phase unit
http://www.xindaenergy.com/10Kw-50r...Generator-for-vertical-wind-turbine-p205.html

here's an old line manufacturer that makes generators for industry
http://www.emersonindustrial.com/en...ernators/power-alternators/Pages/default.aspx
number of poles you'd want is
(3600/RPM of your torque supply ) X 2 and it has to be an even integer
ie
3600 rpm = 2 pole
1800 rpm = 4 pole
900 rpm= 8 pole
720 rpm = 10 pole

I used a 150 kw Kato machine for our simulator, found it well made and reliable
how 'bout that - Emerson bought them.
http://www.emersonindustrial.com/en...s/katoengineering/Pages/Kato-Engineering.aspx

good luckIf this is a "Red Green" project, a dozen truck alternators could make your 800 amps DC

View attachment 93706
check your PBS listings...

Red-Green Show! My wife and I watch that all the time! This is not such a project but, I love the reference!

Ok, this gives me something to work with, thanks again.

 

[deckart]

again you're skimpy on detail.Are you locked into a single machine?
Does hydraulic imply low RPM ?
An alternator would relieve the need for an inverter, simplifying maintenance.

Searching for "low RPM alternator"
turns up whoever's bribed google
here's a 10 kw 50 RPM permanent magnet three phase unit
http://www.xindaenergy.com/10Kw-50r...Generator-for-vertical-wind-turbine-p205.html

here's an old line manufacturer that makes generators for industry
http://www.emersonindustrial.com/en...ernators/power-alternators/Pages/default.aspx
number of poles you'd want is
(3600/RPM of your torque supply ) X 2 and it has to be an even integer
ie
3600 rpm = 2 pole
1800 rpm = 4 pole
900 rpm= 8 pole
720 rpm = 10 pole

I used a 150 kw Kato machine for our simulator, found it well made and reliable
how 'bout that - Emerson bought them.
http://www.emersonindustrial.com/en...s/katoengineering/Pages/Kato-Engineering.aspx

good luckIf this is a "Red Green" project, a dozen truck alternators could make your 800 amps DC

View attachment 93706
check your PBS listings...

Jim, help me out on the details that are needed. I know I'm not asking the question correctly. I'm not sure how to ask it other than I want to convert up to 50 mechanical horsepower to grid ready 37.3 kW. This is a bridge I don't know how to build. What I don't understand is the kind of loading I will need to design to. When working with mechanical rotary applications I'm used to designing to loads and RPM/velocities that are predefined.

<101 electrical theory
What I've come to believe is that an electric motor is a generator when rotated in the opposite direction. So my vastly limited electrical brain thinks I should design to a 50HP, 1750 RPM, "off-the-shelf" electric motor and have the "sparky's" wire it up and make it work. That gives me a fixed torque (assuming there is a fixed load?) and from there a fixed hydraulic motor displacement. I could design the hydraulics to do that but it would be in intervals as the hydraulic energy was accumulated and then delivered to the hydraulic motor. So far, I've read that wind generators do this but don't store any of the energy when the wind velocities aren't there. Shutting down when the wind velocities where too low and then coming on line when they pick up. But they are able to work with varying wind velocities/rotor rpm after a minimum is reached.

So, a couple of my questions are, "will there be a constant load?", and "what is the RPM range?". I'm still confused on where the load comes from. In order to get a load from the grid, don't we need a higher voltage? This is where I'm in the weeds.

The hydraulic associations I have are:
voltage = pressure
current = flow
In order to get flow you need a pressure differential.

(What's required to get the AC sine waves synced up to the grid is a whole nuther topic.)

I see that my inquiries are all over the place, and that's why I'm here. I really appreciate your input.

 

[jim hardy]

wow you're starting from scratch on electric machinery? Brave man.

You need a mental image before jumping into formulas.
Here's a primer on alternators that'll show how one works, and what are the major pieces

the "Alternator" is also known as "Synchronous Machine"
it has a rotating field made of electromagnets as in that video, or of permanent magnets and is easy to understand.

What I've come to believe is that an electric motor is a generator when rotated in the opposite direction.

Actually direction stays the same, it's torque that reverses - hence direction of energy flow.

That gives me a fixed torque (assuming there is a fixed load?)

It's a triad - power, speed and torque
in utility work we always lock speed at 60 hz , so power and torque are in proportion
the electric machine is equally happy providing power to or extracting power from the electric grid to which it's connected
by convention positive power flows into the grid

and from there a fixed hydraulic motor displacement.

Displacement ? I'm ignorant on hydraulics - volumetric fluid flow rate? I'd think that'd be f(rpm) not f(torque)

I could design the hydraulics to do that but it would be in intervals as the hydraulic energy was accumulated and then delivered to the hydraulic motor.

overriding clutch perhaps? I learned about them from my '53 Ford overdrive.

So far, I've read that wind generators do this but don't store any of the energy when the wind velocities aren't there.

Wind generators extract wind energy only when it's there. Somebody else has to store it.
A friend of mine in Colorado is trying to build a windfarm adjacent a pumped hydro plant, that'd save a lot of coal late at night when they're using electricity to pump water uphill instead of heating bathwater and running clothes dryers.

Shutting down when the wind velocities where too low and then coming on line when they pick up. But they are able to work with varying wind velocities/rotor rpm after a minimum is reached.

Newer wind uses clever electrical tricks to allow variable mechanical speed at fixed frequency.
For now think of fixed speed generator and one-way torque device , like that overriding clutch.(or is it over-running? I'm no Mechanical engineer)

"will there be a constant load?",

If your generator is small compared to local grid then you can push power into it without changing speed, so load is determined by your driver..

I'm still confused on where the load comes from. In order to get a load from the grid, don't we need a higher voltage? This is where I'm in the weeds.

Have you and your kids ever played with magnets on a table? The one under the table will drag one on top of the table around, to their great amusement? It's not much of a stretch to think magnets could transmit rotary torque, hence power.
The power is transmitted through an electric machine by magnetics

so you need to adjust your thinking to torque and angular displacement at operating RPM, just as if that magnetic coupling inside the machine were a spring.
Cavaeat - that's for alternators like in the video...

Your thinking was derived from DC and your analogies are okay
but AC adds angular displacement to all the math

Anorlunda wrote an "Insights" on generator/grid interaction.
It's a "beautifully self regulating system". Old timers used Mother Nature's propensity for a balance in their designs.

whew

one step at a time
and we took several

Train your search engine - search on keywords from articles and check out wikipedia's references

old jim

 

[anorlunda]

I'm not sure how to ask it other than I want to convert up to 50 mechanical horsepower to grid ready 37.3 kW. This is a bridge I don't know how to build. What I don't understand is the kind of loading I will need to design to. When working with mechanical rotary applications I'm used to designing to loads and RPM/velocities that are predefined.

You are asking random questions without the educational background to understand the answers. You refuse to hire an engineer. I think you're a disaster waiting to happen. Even in remote Alaska, there are laws and codes designed to ensure safety of the public, that you stubbornly ignore. I think that we on PF should refuse to participate in a project that could kill people, until you follow the advice already given, "Hire an electrical engineer."

 

[deckart]

You are asking random questions without the educational background to understand the answers. You refuse to hire an engineer. I think you're a disaster waiting to happen. Even in remote Alaska, there are laws and codes designed to ensure safety of the public, that you stubbornly ignore. I think that we on PF should refuse to participate in a project that could kill people, until you follow the advice already given, "Hire an electrical engineer."

I assure you that only electrical professionals will be wiring this up. No laws will be circumvented during installation and operation. No humans will be harmed by designing this system. My inquiries are aimed at specifying the generator so that I can design around it on the platform. Once the generator is in place, the electrical engineers will have a known entity to work with when interfacing the grid. I'll have a known entity to size the hydraulic interface. And, I'll be able to provide an accurate costing of the entire platform, less the electrical grid interface costs. No need to insult me or beat me up for not having the educational background.

 

[jim hardy]

"Hire an electrical engineer."

@deckart
You'll do that before the project gets into much detail.
I don't mind helping you become mildly conversant in the basics so you'll be better able to pick one.
Codes exist for good reason and you'll need knowledgeable help.I've seen from the ferryboat windmills in some small SE Alaska settlements and i wondered how they're kept running.
If as you said earlier maintenance is an issue - you need simplicity. Look for an engineer who appreciates that.
old jim

 

[deckart]

@deckart
You'll do that before the project gets into much detail.
I don't mind helping you become mildly conversant in the basics so you'll be better able to pick one.
Codes exist for good reason and you'll need knowledgeable help.I've seen from the ferryboat windmills in some small SE Alaska settlements and i wondered how they're kept running.
If as you said earlier maintenance is an issue - you need simplicity. Look for an engineer who appreciates that.
old jim

Thanks, Jim. I've got the design down to a single cylinder used as the pumping mechanism, a wire rope pulley system to reduce the travel and increase force to the cylinder, and a hydraulic motor (yet to be specified). That's the extent of the moving parts. Sheave bearings are probably going to be the biggest wear item. Simplicity is definitely key to making this a usable system.

I've already learned great deal from your posts. I'm not trying to become an electrical engineer, just understand the fundamentals. Now I understand the relationship between the number of poles and RPM!

 

[jim hardy]

That's fair. One needs vocabulary.

Have you accepted that in a constant speed system torque determines power?

When you run across the term induction generator don't throw up your arms...
In induction generator the rotor''s magnetic field is produced by a slight relative difference in speed between rotor and the grid. Like a very few percent .
Example - a 4 pole induction generator tied to a 60 hz system has a nominal speed of 1800 RPM. But - at exactly 1800 there is no relative speed difference to create a rotor field , so no torque can be transferred.
So an induction generator will be driven slightly off synchronous speed.
At 1801 RPM it will transfer some power into the grid
at 1799 it RPM will draw some power from the grid
That speed difference is called "slip" and is what creates the rotor's field.
Slip is typically less than 5%.

Just like a synchronous machine or a DC one, an induction machine is equally happy as a generator or a motor.
Induction machines have a speed-torque curve that looks like this

which came from here and you ought to digest the whole article
http://www.purduecal.edu/cpmi/NSF%20Courses/ECET-212/CLASSPRESENTATION/InductionMotors.pdf

The only useful range of speed is that steep part right around synchronous and that's where you'll operate

look at some induction motors around your house and note rated RPM
most of them will be four pole
difference between rated and synchronous is slip
1760 would be 40/1800 = 4.4% slip, typical
1650 would be 8.3%, which is a lot
1785 would be <1% which is tight

if you used them as generators those speeds would be 1840, 1950 and 1815

so your hydraulic motor will operate , after accelerating the machine, over the small range of slip speed 1800 to say 1840
which for first approximation purposes is constant speed. Again, torque determines load.

Work it in your head..

We had a recent thread about wiring a washing machine motor.
https://www.physicsforums.com/threads/trying-to-wire-a-washer-motor-to-power-a-grain-mill.833300/
I wired one for multispeed,
when i selected from high speed to low it visibly jumped on my bench as the rotor slowed down returning its inertia to the grid by generator action. But it wasn't big enough to make the power company's generators overspeed...Such tinkering though gives one that intuitive feel he needs in order to believe what the equations say.
We learn by doing - so keep plugging.

old jim

 

[deckart]

It's a triad - power, speed and torque
in utility work we always lock speed at 60 hz , so power and torque are in proportion
the electric machine is equally happy providing power to or extracting power from the electric grid to which it's connected
by convention positive power flows into the grid

old jim

From what I've learned so far (that video was very good), I'm going to size the hydraulic motor to a 120-400 RPM generator (alternator). I don't need to fully understand how it is loaded but from your statement I'm going to assume that most of the hydraulic energy will be converted to 60 Hz AC with the appropriately sized generator and the grid will readily accept it after it is conditioned to the correct phase and voltage. Knowing that much, I can let an electrical engineer specify that actual generator. Thanks for the help.

 

[jim hardy]

I'm going to assume that most of the hydraulic energy will be converted to 60 Hz AC with the appropriately sized generator and the grid will readily accept it after it is conditioned to the correct phase and voltage.

Generators in parallel are like pumps in parallel, you need some sort of governor or inherent torque-speed characteristic that tends toward stability.
Hopefully this thing is small compared to your whole grid.

old jim

 

[deckart]

Generators in parallel are like pumps in parallel, you need some sort of governor or inherent torque-speed characteristic that tends toward stability.
Hopefully this thing is small compared to your whole grid.

old jim

It will be smaller but in some of these villages it may not be by much. There are so many small grids out there.
http://www.iser.uaa.alaska.edu/Publications/2012_07-RS-EnergizingAlaska.pdf

 

[russ_watters]

Yes, I have the general schematic completed but the components aren't yet specified. See attached.

Good! I'm pleasantly surprised.

But, you see my point, you want to see details.

My advice from here is that you focus on the details of the cylinder. That's the unique part of this and the part who's performance drives everything else.

I'm debating whether I should just put this up as a PF group project or not. If there is actually something that's patentable in the system, I'd be killing that ability by publishing it in a public forum...

Probably nothing patentable here...

I disagree. People have been working on wave power for a very long time, trying to make it viable. If you have a unique way to collect it, it would certainly be patentable.

...you don't create a hydraulic system (or any system) and then try to make it work on an application. The application defines the system components. Then prime mover, the "input", is the ocean wave action, the application is the gen motor.

If the prime mover were a gas engine selected from a catalogue, sure. But because the wave power system is custom and its output is unpredictable, you may find you've selected components that don't match what it gives you. You're spending time/effort (here) on the easy/everyday parts and not on the key piece of your device.

 

[russ_watters]

Why don't you start on a smaller scale? You cannot expect to design and get this project working in one shot. Ever hear of proof of concept? It seems you don't understand the relationship between watts, volts, amps, horsepower, etc. If you started on a smaller scale I think you might learn enough so that you would not rely so heavily on the people here that are not giving you the answers you desire. This goes along with what one of my favorite members here on PF that says: "A question well stated is half answered." Likewise, start at an easier scale and answers to your questions will become obvious. Some answers you will like, some you may not.

I wholeheartedly agree. And in particular you will demonstrate whether the wave power harvesting piece actually works and what it can do. That's the toughest part of this. After that, scaling it up is not difficult.

You'll also save time/effort/money -- and risk. And you'll set yourself up with a system you can patent while working on scaling it up.

 

[deckart]

I wholeheartedly agree. And in particular you will demonstrate whether the wave power harvesting piece actually works and what it can do. That's the toughest part of this. After that, scaling it up is not difficult.

You'll also save time/effort/money -- and risk. And you'll set yourself up with a system you can patent while working on scaling it up.

Definitely. I can certainly make a micro version of it for proof-of-concept. Drive a small automotive alternator and battery. A 12V inverter and run a 1000W light bulb on the buoy indefinitely. Showing it working will definitely help get buy-in for the useful, larger, scale version that will actually pay for itself.