Varying Speed AC Generator to Steady DC

[Soul21]

Thanks for clarifying. As a person with limite knowledge in the field, I appriciate the patience.

I have done a lot of research on wind turbines. They do control blade pitch to manage speed, but they generator do turn at varying rpms. It might not be noticeable by the blade speed, but the gearbox ratio makes slight differences in blade bigger differences at the motor. That is why most make AC to DC back to AC.

So my generator is an alternator without the internal control of the the rotor field. I am curious to learn more about that and how it is implemented in AC machines (like the one I have) to make them be an "alternator"

 

[Nigel Goodwin]

Thanks for clarifying. As a person with limite knowledge in the field, I appriciate the patience.

I have done a lot of research on wind turbines. They do control blade pitch to manage speed, but they generator do turn at varying rpms. It might not be noticeable by the blade speed, but the gearbox ratio makes slight differences in blade bigger differences at the motor. That is why most make AC to DC back to AC.

So my generator is an alternator without the internal control of the the rotor field. I am curious to learn more about that and how it is implemented in AC machines (like the one I have) to make them be an "alternator"

Essentially an alternator spins a magnet (rotor) inside a coil (stator), this produces an AC voltage in the coil. A dynamo spins a coil (rotor) inside a magnet (stator), and the power is collected from the rotor via brushes, which also provide a simple rectification, producing a DC output.

In either case the magnet can be either a permanent magnet, or (more usefully, as you can control it) an electromagnet.

 

[Soul21]

Further reading on modern wind turbines I have found that most use DFIG. So they are using induction generator which I don't believe are alternators. Is that correct?

 

[Diver300]

Further reading on modern wind turbines I have found that most use DFIG. So they are using induction generator which I don't believe are alternators. Is that correct?

I'm not sure that there is a common term for the generators found in wind turbines. It a very specialist device, so few people outside of the industry will have heard of them. I didn't know what a DFIG was until I looked it up just now.

The names people use often depend on the application. For instance:-

Controlled field dc generator, with rotating power windings and a commutator, fitted to a car - "Dynamo"

Controlled field ac generator, with stationary power windings and a rectifier, fitted to a car - "Alternator"

Permanent field ac generator, with stationary power windings and a rectifier, but also possibly with ac loads, fitted to a motorbike, outboard motor or lawn mower - "Alternator"

Permanent field ac generator, with stationary power windings, fitted to a pushbike - "Dynamo"

 

[rjenkinsgb]

Further reading on modern wind turbines I have found that most use DFIG

They are a slip-ring type alternator; the power output is AC, only the regulation feedback is via the AC-DC-AC path.

From the definition on Wikipedia:

Electromagnetic generators fall into one of two broad categories, dynamos and alternators.

• Dynamos generate pulsing direct current through the use of a commutator.
• Alternators generate alternating current.

In other words, any power generator that directly produces AC output is by definition an Alternator.

Your existing generator IS an "alternator" - just one without feedback regulation, which makes it very difficult to do anything practical with.

It's the feedback regulation that matters.

 

[ChrisP58]

What are you using for the turbine? What is the cfm for each pressure value

Currently unknown. Working to get a meter on it. Rough estimate is somewhere around 5,000 cfd

My question was to know what device you're using to convert the linear airflow into the rotational force needed to turn the alternator.

 

[Soul21]

My question was to know what device you're using to convert the linear airflow into the rotational force needed to turn the alternator.

A small turbine expander

 

[Soul21]

This post gets to why I was avoiding alternators.

https://www.reddit.com/r/ECE/comments/g6lbm

If my motor is an alternator then why can't I deploy the feedback regulation to it?

 

[Nigel Goodwin]

This post gets to why I was avoiding alternators.

https://www.reddit.com/r/ECE/comments/g6lbm

If my motor is an alternator then why can't I deploy the feedback regulation to it?

The answers are all in your link, why don't you read them?.

Exactly what 'generator' do you have?, not all alternators have electro-magnet rotors that allow regulation, and the power wasted in energising the magnet is why they tend not to be used on wind mills.

 

[Soul21]

I have read them. It seems there are conflicting opinions to that link in this thread. I am just trying to understand why. Specifically, if the link says alternators aren't appropriate (inefficient and made for to be belt driven), then how might I go about using my motor.

Alternator and Generator Comparison | Otherpower

www.otherpower.com

 

[Nigel Goodwin]

I have read them. It seems there are conflicting opinions to that link in this thread. I am just trying to understand why. Specifically, if the link says alternators aren't appropriate (inefficient and made for to be belt driven), then how might I go about using my motor.

Alternator and Generator Comparison | Otherpower

www.otherpower.com

Have you ever told us what you've got?, but you appear to be confusing 'alternators' with 'car alternators'

 

[Soul21]

The prime mover is pressurized air (150 psi - 190 psi). The generator is a 240 v 60hz 10 amp motor (wanco AB20L) The load below is a test load 120v 500 watt heater.

The real load will be a bank of 12 volt batteries wired to be 24 volt. I am struggling to understand why the frequency/rpm remains the exact same even though the prime mover is increasing.

With load:
150 psi / 55 volts / 0.9 amps / 33 Hz
170 psi / 78 volts / 2.1 amps / 33 Hz
190 psi / 112 volts / 4.1 amps / 33 Hz

Without load:
150 psi / 85 volts / 37 Hz
170 psi / 168 volts / 47 Hz
190 psi / 235 volts / 59 Hz

Yep - right here. I must be, but the suggestions in this thread were for car alternators.

 

[rjenkinsgb]

If my motor is an alternator then why can't I deploy the feedback regulation to it?

1: There are dozens of variations in types and construction of alternators, with different capabilities and specifications.

2: The speed/frequency are too low to run an external PSU to convert to 24V - and most common motors are not designed to be run above synchronous frequency & may fail if forced to run overspeed.

3: You have not yet provided technical details on the motor you are using! As I mentioned earlier in the thread, the make and model you mentioned can only be found in YOUR posts.


Re. vehicle alternators - the thread you refer to is about small, low output, DIY wind turbines. The mechanical losses in running a V-Belt drive & the high speed needed would reduce output compared to some other alternator types.

You do not have that problem - you have a quite high power mechanical drive system & the relatively trivial loss from the step-up drive is far compensated by the electrical simplicity and the vehicle alternator being designed to function over a wide speed range.

The end efficiency would likely be as good as the existing motor and PSU setup; as you eliminate one electrical conversion stage.

 

[shortbus=]

In all of the TS's postings he never gives information on what he has, either here or on AAC. He said earlier -

As a person with limite knowledge in the field, I appriciate the patience.

But when given advice to a way of doing what he wants he refuses because he knows better.

The above still points me to him taking air pressure from somewhere that doesn't belong to him, to give him some electrical power. He's not willing to just use the power that comes from when the air pressure is high, but wants it all the time. For what time and money he is spending he could buy a small gas powered generator and had electric for the months he has wasted on his "project".

 

[Soul21]

3: You have not yet provided technical details on the motor you are using! As I mentioned earlier in the thread, the make and model you mentioned can only be found in YOUR posts.

Its an older model wanco, that currently isn't on the website. Here are some of the details, happy to provide any more you need. If you call Wanco they will provide info for the model

V: 240
W: 2400
Hz: 50 (got this wrong earlier)
Phase 1
RPM 3000

 

[Soul21]

Re. vehicle alternators - the thread you refer to is about small, low output, DIY wind turbines. The mechanical losses in running a V-Belt drive & the high speed needed would reduce output compared to some other alternator types.

You do not have that problem - you have a quite high power mechanical drive system & the relatively trivial loss from the step-up drive is far compensated by the electrical simplicity and the vehicle alternator being designed to function over a wide speed range.

The end efficiency would likely be as good as the existing motor and PSU setup; as you eliminate one electrical conversion stage.

Thank you, that helps me understand. Which is my point of being on this forum.

In all of the TS's postings he never gives information on what he has, either here or on AAC. He said earlier -

But when given advice to a way of doing what he wants he refuses because he knows better.

The above still points me to him taking air pressure from somewhere that doesn't belong to him, to give him some electrical power. He's not willing to just use the power that comes from when the air pressure is high, but wants it all the time. For what time and money he is spending he could buy a small gas powered generator and had electric for the months he has wasted on his "project".

This does not, and has gotten to the point of you trolling. I have a learned a lot from the back and forth of this thread. If you could overlook this thread and not derail it, that would be appreciated.

 

[rjenkinsgb]

Its an older model wanco, that currently isn't on the website. Here are some of the details, happy to provide any more you need. If you call Wanco they will provide info for the model

V: 240
W: 2400
Hz: 50 (got this wrong earlier)
Phase 1
RPM 3000

That still does not give any useful info on the motor type - can you post a photo of the actual motor data plate?

Is it actually a motor or a purpose made generator?

 

[shortbus=]

This does not, and has gotten to the point of you trolling. I have a learned a lot from the back and forth of this thread. If you could overlook this thread and not derail it, that would be appreciated.

Your saying I'm the troll? You are not willing to share many things, things that may get your project up and running. Things like -
1.Where is this unreliable air source coming from? I've worked at many different places, and they all had compressed air. But the air was a constant pressure, not high one time and low the next.

2. What is the type of turbine that is going to drive your "generator"? You claim to have something but give no information on what type or style. That would be the first thing to talk about before the "generator". The driver is always the place to start when designing something like this. Too small of turbine on a large "generator" with a light pressure may not even be possible. You don't give the information.

There are more but those are the main ones, ones that would give you more real information.

Doing things like your posting are are one mark of a troll, not some one guessing at what your up to.

 

[JimB]

OK guys, let us just hold this discussion of who may or may not be a troll, and consider this thread from a few months ago:

Electronic Speed Control of a Generator

I am trying to better understand methods that can electronically control the speed of a generator (specifically). The generator will be spinning using mechanical energy generated by air through a pipe. The electricity will be sent to a load or battery bank. I thought a VFD might be the...

www.electro-tech-online.com

Looks sort of familiar doesn't it?
Lots of questions from those trying to help, but not much information coming back from the guy with the problem.

JimB

 

[Soul21]

Providing no helpful information and derailing focus continuously is absolutely being a troll. You have probably posted on my threads over 20 times over 2 years. The first two posts you made an attempt at being helpful. Since starting discussions on these forums I have designed, built, obtained a patent, sold a unit, and preparing to sell more. I will have this issue solved here or with the help of a paid electrician. I come here first because I like to learn. I have made progress and will continue to.

As far as information anyone is looking for I am happy to provide anything relevant. My prime mover is compressed gas that has variable inlet and outlet characteristics. I am not the owner of the compressed gas, but the owner has purchased the first unit from me in an effort to continue getting it to market. The turbine information I gave is all that I will give. I do not believe any more information is needed to solve the problem I am addressing on this thread. That's the last I am going to reply to Shortbus.

Refocusing. The problem I am trying to address is the if I can charge a bank of 12 volt batteries (wired to be 24 volt) using the machine I have with variable speed and output.

Converting to DC using diode bridge and then a buck converter seems to be where I have landed, but open to any other suggestions. If an car alternator is the better solution then thats what I will use moving forward. Is a 24 volt car alternator the best path or something like an axial flux generator? I would like to figure out the best solution before getting into iteration #2.

That still does not give any useful info on the motor type - can you post a photo of the actual motor data plate?

Is it actually a motor or a purpose made generator?

Happy to share pictures. If there is something specific I can call Wanco and get that information. They are very helpful. Currently the second unit purchased will have the AB30T on it. The customer like the idea of AC due to the long line run from gernator.