# AC rotor modification proposal patent



## parasole (Jun 27, 2013)

Hi AC motor experts,

found this patent application describing a radical modernization of an AC motor, to me it looks promising, although may be wrong. What is your opinion about?
Probably it would be possible to perform such modification even in home workshop environment and instead of all cage to wire up cooper winding?

http://patentscope.wipo.int/search/en/WO2011002334


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## parasole (Jun 27, 2013)

parasole said:


> Hi AC motor experts,
> 
> found this patent application describing a radical modernization of an AC motor, to me it looks promising, although may be wrong. What is your opinion about?
> Probably it would be possible to perform such modification even in home workshop environment and instead of all cage to wire up cooper winding?
> ...



By time being, having no any feedback from you folks  I did get in touch with the author of this invention and he did provide me some data…

According to his input, right now there is one more patent application with claiming of even better improvements, however he is not willing to open the details until having his rights protected.
In short, here are the numbers I did obtain, they looks to be to good to be real, however from what I understand looks to be the real ones, obviously these are comparison data with stock industrial motor taken as basis for modification:

Starting torque +90% 
Minimum torque +100%
Maximum torque increased by 80%
Short term overload capability 400%
At 300% overload the motor is having same level of loss as regular one at 23%
Much better Power factor and Efficiency
Less heat dissipation and energy consumption, at the given power by 30%

Quite interesting, considering that it is possible to modify the stock AC motor rotor by DIY. He explained me that for testing purpose the rotor aluminum cage was etched in strong alkaline solution (NaOH; KaOH) then, did a new winding by using cooper bars.

Any comments on this?


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## PStechPaul (May 1, 2012)

I thought I had replied to your post but either I am mistaken or my reply plopped into the bit bucket. I read through the patent but I did not really understand much of it. However, it seemed as if the rotor was constructed to have shorter magnetic paths and the windings were changed from the usual end-to-end squirrel cage to one where multiple insulated conductors were used. This would be the same ampere-turns but perhaps there was some other benefit. It may also be that some stator windings were used to produce current in the rotor without necessarily causing torque.

This may be similar to the concept of separately inducing a current in a set of rotor coils and then using rectifiers to produce DC in the rotor coils and thus approximate the characteristics of a PMAC motor. 

I am familiar with the operation of AC induction motors and other types, but I am by no means a magnetics expert. I doubt there is much room for improvement of ACIMs except for using copper in the rotor (which is one method used for premium efficiency motors), and optimizing the entire motor for use at higher frequencies such as 400 Hz, which is already commonly used for aerospace applications. 

When I get more time I'll read through the patent again and try to understand it. Also I would like more detailed performance figures rather than percent improvement as you provided. We need to know what we are comparing to, including actual size and weight, and what sort of controller is being used.


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## PStechPaul (May 1, 2012)

Those figures do look impressive, but I am surprised that the standard motor was as inefficient as it was measured to be. I had some problems viewing the patent which is apparently Russian, and the translation was confusing and missing the illustrations except on a separate page. 

The original efficiency of the motor was 82.5%. Just replacing the aluminum rotor bars with copper might reduce the resistive losses by 25-50% so the efficiency might be increased to 87% or even 92%. Losses should increase by the square of current (or torque), so a motor with 8% losses at 1x would have 32% losses (68% efficiency) at 2x and 72% losses (28% efficiency) at 3x.

The first test was 10 N-m or 1.35x, but current more than doubled for the stock motor, while it was 1.2x for the new design. So this contributed largely to the relative loss of efficiency. The second test with 2x torque shows a 6.25x increase in current for the stock motor, and 1.85x for the new version. The third test was 2.7x torque for the stock motor and 3.2x for the new design, with current 6.6x and 2.4x respectively. 

One puzzling difference is the 2.0A no-load current for the standard design compared to 4.5A for the modified version. This may explain the non-linear characteristic of the current for the modified design, which may have more inductance as indicated by the lower no-load and rated load power factor.

Here are figures for a 4 pole 3 HP Baldor motor which has similar nominal efficiency but not nearly so much worse performance at 150%:

*Load Characteristics at 200 V, 60 Hz , 3 HP*
% of Rated Load---25----50----75---100---125---150---S.F.
Power Factor------32----53----66----73----78----81----76
Efficiency-------79.6--87.4--89.4--89.7--89.5--88.3--89.6
Speed (rpm)------1791--1783--1775--1766--1756--1745--1760
Line Amperes------6.1--6.99--8.24--9.84--11.5--13.5--10.8​


These figures seem much more reasonable. There may very well be some major improvement with the new design but the comparison seems to have unfairly disadvantaged the standard design.


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## parasole (Jun 27, 2013)

PStechPaul said:


> Those figures do look impressive, but I am surprised that the standard motor was as inefficient as it was measured to be. I had some problems viewing the patent which is apparently Russian, and the translation was confusing and missing the illustrations except on a separate page.


Sorry for my older post you have answered to, I did want to modify it and deleted by mistake.

So, the information is coming from the author, I did only the translation.
As of my understanding the tested motor is the regular industrial motor which is of old technology, mean is not a modern high efficiency one. he is mentioning that changes would work in same manner for the new high efficient motors.

Regarding the patent, sorry for confusion, now it is clear why no one reacted, by providing the link I was thinking there is both, Russian and English version, my fault, attached will find the correct one.


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