Low Speed PM Alternators

[wind4Reg2]

For me I know I won't have the time to build my own PM alternator, so I will be purchasing one.
It seems there are a ton of choices out there and lots to choose from on Amazon and Alibaba as well as other sites.
It looks like most are manufactured and sold by Chinese companies and the prices are fairly low for the claimed outputs. It is obvious that there is a lot of noise out there and some outlandish claims and I am doubtful of many of these. My concern is buying the wrong one, having it fail after a short time due to quality issues, or having really low power output, not being able to source parts, etc. I was looking at 150 - 900 RPM and 1KW - 4KW ranges.
It would be great if there was some kind of resource that did reviews on these, was fairly current with what was being sold online, so that you could be reasonably confident about what you were buying. Most of what I have been able to find in terms of reviews are for something that isn't even sold anymore.
Also if there are North American manufacturers that provide a good quality low speed PM alternator that others have had luck with, I would be interested to see who they are as well.
Also if there is some crappy Chinese windmill (maybe has bad or too small blades or a poorly functioning VAWT) but has a solid alternator that could be utilized, I am not against buying the unit and removing the alternator and tossing the rest if the price is right. Anyone have some suggestions?

[SparWeb]

Simplest answer is to look through the last year's worth of posts by Mackenzie71:

https://www.fieldlines.com/index.php?action=profile;area=showposts;u=6750

I think the rest of your question really outlines the obstacles against what you're looking for (and why some of us resort to motor conversion and custom fabrication ourselves).
-China fabricates cheaper than NA and Europe by a factor of 5
-price pressure is so low that very few consumers are willing to pay for quality/durability in anything (shoes, electronics, etc.)
-Fabrication of copycat parts means there is low/no integrity in the product you buy
-When there are more copycats than the originals...

Look at all the stuff in your house/apartment.  Ask yourself how much of it would be there if it cost 5X more than what you paid for it.  That's how much it would cost for everything in the world to be made by its own designer, by people paid a wage that can support their family, in an area not poisoned by the materials they use, for a company that will accept responsibility for the product they sold you.

How dare you ask for so much!

[bigrockcandymountain]

A couple questions. What is your project?

Does this unit need to be outside in the weather?
 Is it going to get rectified to DC?

What voltage output is required?

The reason most of us build PMA's instead of buying is exactly the problems you mentioned.  The ones on the market are pretty poor.  Honestly, i would rather hire a machine shop to convert a 3 phase induction motor to permanent magnet than buy what i see on the market. 

A user called skid has a thread under hydro where he bought a pretty decent pma manufactured in china with pretty similar specs to what you are after.  It did fail in his extremely harsh conditions, but i think it was an ok unit. 

https://www.fieldlines.com/index.php/topic,148325.0.html

[JW]

For me I know I won't have the time to build my own PM alternator, so I will be purchasing one.
It seems there are a ton of choices out there and lots to choose from on Amazon and Alibaba as well as other sites.

This sounds like a VAWT project, not sure if savonius or darrieus.

You should contact DanF and have a custom PMA built for your application.

https://www.otherpower.com

Atleast that way you will get the stator right

[JW]

https://www.otherpower.com/contact_op

[Adriaan Kragten]

I have rather good experiences with the Chinese brand Hefei Top Grand which supplies a large range of axial flux generators for which the generator housing is rotating around the shaft. I have bought the small type TGET165-0.15kW-500R and I have tested this generator for a 12 V battery load. The measurements are given in my public report KD 595 which can be copied for free from my website: www.kdwindturbines.nl at the menu KD-reports. The maximum power at 500 rpm is lower than according to the manufacturers specification but the generator is well designed and it has functioned for more than four years now in one of my small wind turbines. I have also investigated the possible use of a bigger generator of this brand type TGET260-0.5kW-350R but I have not measured it. A problem with all these generators is that the characteristics are given for a resistor load but if you use it to charge a battery, you will get completely different characteristics. In chapter 6 of my public report KD 676, I have tried to derive the characteristics for a 24 V battery load from the given characteristics for a resistor load.

[mbouwer]

Can we say:

Low speed generators are simply not available and way too expensive?

You just have to build it yourself.

[Adriaan Kragten]

I don't agree with this statement. It is difficult to find a good quality commercial available PM-generator with a reliable specification but it isn't impossible. The point is that serial manufacture in China will always result in a much lower price than if you make one generator for yourself.  And even if you can make a good generator for yourself, you need a sophisticated test rig if you want to know the generator characteristics. Especially for big generators, this test rig will be expensive with respect to the value of the generator. A manufacturer can use the test results obtained on one generator prototype for thousands of supplied generators so the measuring costs are relatively low.

But the problem is that most manufacturers have no good idea about the matching in between the generator and a certain wind turbine rotor and therefore they test the generator in the wrong way. I have even heard of suppliers which first measure the open DC voltage at a certain rotational speed. Next they measure the short-circuit current at that rotational speed. Next they multiply the measured open voltage and short-circuit current and claim that the result is the maximum electrical power at that rotational speed. This is absolutely wrong. One should measure the loaded voltage and the loaded current. The real maximum power at the given rotational speed is less than halve the value which is specified so buyers of generators which are measured in this wrong way are always very disappointed.

Hefei Top Grand measures the loaded voltage and loaded current but they still specify a too high power for the small generator which I have tested. It might be that this is because they have measured only generators of medium size and that they scale down the result for small generators. But small generators have lower efficiencies than bigger ones and so the specification for small ones will be too optimistic. Another reason might be that they have measured the AC voltage and AC current. If the generator winding is rectified, you will have losses in the rectifier which are relatively large if the battery voltage is low.

[JW]

The point is that serial manufacture in China will always result in a much lower price than if you make one generator for yourself.

Only if you are dealing with production volume. A one-off has to be tested with empirical standards. Can we at least see a picture define the application. 

[mbouwer]

Adriaan Kragten,

You don't agree with the statement that we ca'nt buy a generator for our small windmills.

And the next moment you clearly explain that we ca'nt buy a generator for our small windmills.

In my opinion we must talk and think how to make progress to design and build small windmills.

[Adriaan Kragten]

I thought that I made myself clear. Most Chinese manufacturers supply rubbish but this isn't the case for Hefei Top Grand. They supply a large range of nice axial flux PM-generators which are technically Okay and which have a very low sticking torque because they have no iron in the coils. You should go to their website and look at the specification for each type. You can transform the given characteristics for a resistor load to the load of your rotor-generator-battery combination using the method which I give in KD 676. But if you have selected a certain type, you can only be sure that the characteristics are really matching for your load, if you buy one and test it like I did in KD 595.

[Adriaan Kragten]

The point is that serial manufacture in China will always result in a much lower price than if you make one generator for yourself.

Only if you are dealing with production volume. A one-off has to be tested with empirical standards. Can we at least see a picture define the application.

I have designed and tested several PM-generators made from asynchronous motors. The method is described in my public report KD 341. Measurements for such a generator with frame size 90 and a lengthened stator stamping are given in public report KD 78. An about similar PM-generator using a cheaper Indian housing with frame size 100 and a standard stator is described in public report KD 503.

The generator which I have used in KD 78 has cost me about € 500 to be manufactured. First you have to buy a standard motor (I have used the standard winding for the tests). Next a friend which had a lathe and a milling machine made the new 4-pole armature but this armature wasn't for free. I bought the neodymium magnets and the glue and glued the magnets in the armature myself. The generator was tested on an accurate test rig of the University of Technology Eindhoven and I have paid about € 300 to use it. So the total costs to get one tested prototype were about € 800 in 2001.

The generator of Hefei Top Grand for which the measurements are given in KD 595 was ordered directly at the manufacturer and the cost of transport and tax were even higher than the original fee (the total costs are specified in KD 595). However, some types of Hefei Top Grand can also be ordered at Alibaba or at a similar company and then the costs of transport are much lower. 

[Bruce S]

Can we say:

Low speed generators are simply not available and way too expensive?

You just have to build it yourself.

I have to partly agree with Adriaan on this one.
They are available , through alibaba or AliExpress . However the way too expensive in terms of purchase price versus usability stands as a true statement too.

Building a small scale genset is also much more fun :-) and a great learning tool.

Cheers
Bruce S