Ceramic vs Neo

[Yianie123.]

Can a 2"x2"x1" ceramic magnets replace 2"x1" x 1/2" Neo magnets.  The cost difference can nearly 80%

[MattM]

Straight off the google... "The magnetic field typically produced by rare-earth magnets can exceed 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla."

So a definitive no.  But double your magnets and... Maybe.  Other factors come into play because scaling the design may be much more expensive than simply paying for neodymiuns.

[Yianie123.]

Does anyone have any experience building a PMA with ceramic magnets? Can you please share your results.

[MattM]

Go back 30 pages plus on the Wind subforum and they were common.

[kitestrings]

Hugh Piggott has written recently about his experiences with building using ceramic magnets.  I believe the motivation in his efforts are due to corrosion that can be a real challenges with Neo's in coastal areas (like Scoraig).  If you google his Blog you will find it.

Also, Chris O., on this site has built several turbines with ceramics.  Good luck, ~ks

[Yianie123.]

Thank you all your responses.  I did look 30+ pages and could not find anything.  I will check Hughs page

[kitestrings]

Try this:

https://scoraigwind.co.uk/2020/07/f-series-wind-turbine-designs/

I haven't re-read this, but I believe he is saying that some of the newer ceramics are closer than in the past to neo's, and offer better resistance to corrosion.  ~ks

[Bruce S]

Do a search for ChrisOlson , Flux{RIP} or Hugh on here.
All were big into using Ferrite (Ceramic) magnets and the reason put forth were sound. Hugh & Flux were mainly due the at-the-time hard to get Neos and the issue with corrosion. Chris posted a lot about the temperature issues and Ceramic being able to withstand higher heat and they're kinda self-limiting.

Bruce S

[MattM]

Thank you all your responses.  I did look 30+ pages and could not find anything.  I will check Hughs page

Ferrite Gen with a Classic 150 (ChrisOlson)
https://www.fieldlines.com/index.php/topic,146180.0.html

Transiant Thermal Modeling of an Axial Flux...
https://www.fieldlines.com/index.php/topic,148581.0.html

Design for ferrite, high voltage, MPPT and chain drive
https://www.fieldlines.com/index.php/topic,148526.0.html

Sourcing ceramic magnets for Piggot's 2F
https://www.fieldlines.com/index.php/topic,148487.0.html

A small, inexpensive first windmill project?
http://www.fieldlines.com/index.php/topic,140546.0.html

lets talk alternator design
https://www.fieldlines.com/index.php/topic,147259.0.html

[joestue]

https://www.fieldlines.com/index.php/topic,147259.msg1015975.html#msg1015975

with regard to this claim in the above post:
This below photo is for a single stator ferrite generator, designed for MPPT, that produces 3.0 kW @ 1,200 rpm and peak 4.2 kW @ 1,500 rpm.  It is right on 90% power efficient at 3.0 kW output.  It is 13.8" in diameter and also weighs 22 lbs.

I'm assuming there are two magnet disks, for a total of 44 pounds, plus the single stator coil.

modern hvac fan motors are getting 1hp at 1250 rpm, out of 6 cubic inches of ferrite magnets in a 56 frame motor. my last experiment with such a motor as a generator produced around 200 watts output at 800 rpm with a significant voltage drop. my guess is the inverter drive send a lot of leading power factor current into the motor, to get the required torque. the coils are 4 ohms, 2.5 amps at 50 volts 3 phase, 80 volts open circuit.

In any case, you can do the mental math yourself. 1hp out of a 56c frame.. vs 4-5hp out of something with 16x2x2 (times 2 stators) cubic inches of magnets.

[Mary B]

https://www.fieldlines.com/index.php/topic,147259.msg1015975.html#msg1015975

with regard to this claim in the above post:
This below photo is for a single stator ferrite generator, designed for MPPT, that produces 3.0 kW @ 1,200 rpm and peak 4.2 kW @ 1,500 rpm.  It is right on 90% power efficient at 3.0 kW output.  It is 13.8" in diameter and also weighs 22 lbs.

I'm assuming there are two magnet disks, for a total of 44 pounds, plus the single stator coil.

modern hvac fan motors are getting 1hp at 1250 rpm, out of 6 cubic inches of ferrite magnets in a 56 frame motor. my last experiment with such a motor as a generator produced around 200 watts output at 800 rpm with a significant voltage drop. my guess is the inverter drive send a lot of leading power factor current into the motor, to get the required torque. the coils are 4 ohms, 2.5 amps at 50 volts 3 phase, 80 volts open circuit.

In any case, you can do the mental math yourself. 1hp out of a 56c frame.. vs 4-5hp out of something with 16x2x2 (times 2 stators) cubic inches of magnets.

Motor specs have no direct correlation to generator specs... one may work well, the next a cogging piece of junk that barely produces... and you can't compare an air core alternator to an iron core motor in any way... apples to oranges...

[joestue]

Motor specs have no direct correlation to generator specs... one may work well, the next a cogging piece of junk that barely produces... and you can't compare an air core alternator to an iron core motor in any way... apples to oranges...

Do you have a better explanation to explain why 3kw divided by 128 cubic inches of magnets at 1250 rpm is pretty similar to 200watts divided by 7 cubic inches?

(neglecting the fact that a 56 frame motor delivered that power at 780 rpm?)

[Adriaan Kragten]

If you compare generators made of asynchronous motors of different size, you have to compare generators with the same armature construction and with the about the same calculated flux density in the air gap. Then you will find that there is about a certain ratio in between the maximum torque level and the nominal motor torque. For all PM-generators wich I have built and measured, the peak torque of the generator was higher than the nominal motor torque (see report KD 78, KD 82 and KD 200). If you know the characteristics of a certain size, the characteristics of a bigger size can be predicted rather accurately if the armature construction is similar and if the stator winding has the same nominal voltage.

Comparing powers is more difficult than comparing torques. Powers can ony be compared for the same rotational speed.

[Yianie123.]

Thank you all for your comments.  Their really appreciated.