Electric Motor Secrets

[Schpankme]

machined smooth

... my stator core with the inner surface machined smooth.

Hello Jetijs,

What method was used to smooth (finish) the core inner surfaces ?

- Schpankme

[Jetijs]

They stacked the stator core in a lathe and used a very sharp cutting tool with small passes, a little bit deeper each time till the surface was smooth
Jetijs

[theremart]

Hand dryer to use the DC12 motor

Air jet dries hands at 400mph 16/11/2006

Dyson’s new product – a hand dryer that claims to be more hygienic and efficient than its rivals – could be the first in a series of technologies to use its digital motor. Lou Reade reports

James Dyson’s latest concern is not his school for engineers, but something much smaller: your hands. Just as he re-thought the way that vacuum cleaners work, so his company has now devised a hand dryer that works differently to conventional products.
Instead of using hot air to evaporate water from your hands, the Airblade uses a high-speed ‘sheet’ of unheated air to force excess water off the surface – rather like air jets in a car wash. Dyson claims it is more hygienic, more energy-efficient and far faster than existing products. The company spent three years and £10m on the development.
“It will dry your hands in 10 seconds,” says Dyson design engineer Paul Finn-Kelcey, who worked on the Airblade.
The technology at the heart of the dryer is Dyson’s digital motor, which spins at 100,000rpm. To date, the motor has only been used in the DC12 vacuum cleaner, which is sold in Japan.
The motor generates enough pressure to force air through a 0.3mm slot, which runs for the length of the dryer. There are actually two slots: one is relatively straight and dries the palm side of the hand; the other is bent into the shape of a ‘3’ and dries the back of the hands and knuckles.
“The aperture in the middle of this one is about 0.7mm,” he says. “It’s because you need more air to dry that part of the hand.”
The twin-headed vent that delivers air to the slots is made from glass-filled polypropylene, while the slots themselves are made from a composite material.
Dyson says that the Airblade overcomes all the problems that it identified with existing dryers – they are unhygienic, take too long to dry hands and are expensive to run.
First, it ensures that incoming air – which will be blown across freshly washed hands – is clean by drawing it through a Hepa filter.
The method of recycling water is also ingenious. Water that has been removed from the hands is caught and fed through an iodine filter. This clean water then drips onto a piezoelectric crystal about the size of a 10p piece. This fast-vibrating element acts as a nebuliser, converting the water into a puff of vapour which is blown back into the atmosphere.
All components are contained in a die-cast aluminium housing. Internal and external parts have an anti-microbial coating to maintain hygiene.
The Airblade removes excess moisture from the hands – enough for them to feel ‘dry’ – in 10 seconds, around a quarter of the time that it takes a conventional dryer to do the same job. This is the first source of energy saving, says Dyson. The other is that the Dyson motor is only 160W, compared with 240W for a conventional dryer.
“The energy saving is a combination of these two factors,” says Finn-Kelcey.
Inevitably, a patent wrangle has reared its ugly head. Mitsubishi of Japan has had a product called the Jet Towel on the market for a number of years, and recently launched the product in the US. Mitsubishi has accused Dyson of copying its design. Dyson has responded by saying its design is radically different and more effective – and intends to challenge Mitsubishi’s claimed drying time of three to six seconds.

Series start
The Airblade is likely to be the first in a series of products that rely on the Dyson motor.
Since launching the DC12 vacuum cleaner in Japan over two years ago, Dyson engineers have continued to refine the motor.
“We’re constantly trying to improve it,” says Finn-Kelcey. “The electric control system is being improved and we’re also trying to make the circuit board smaller.”
However, he says there are “more steps to go” before the motor can be put into the next product.
“Within two years, you will see lots of other products that use the Dyson digital motor,” he says. “We have more engineers working on the next generation of this motor than on any single product.”


Motoring on
Conventional motors use brushes, fixed magnets and commutators, but these are absent from the Dyson motor.
The company says that this makes it more long-lasting – giving it a typical lifetime of 1500 hours or more. Its lighter weight means it can rotate at 100,000rpm.
“A conventional motor might be able to manage 40,000rpm,” says Finn-Kelcey.
According to Dyson engineers, the motor is likely to feature heavily in future Dyson products, becoming almost a core technology for various products.
The motor’s embedded software gives it diagnostic abilities, allowing it to manage energy efficiently and safely. Problems can be communicated back to a call centre via the internet.
“We are focusing heavily on the next generation of the motor,” says Finn-Kelcey
Dyson is keeping very quiet about specific applications, but it seems likely that an improved version of its motor will be a crucial part of emerging products.
“If we can make the motor smaller and more efficient, this would make smaller products more feasible,” he says.


Author
Tom Shelley

[theremart]

Question to Peter about Electric Motor Secrets

Hi Peter,

In the video you had a coil that you used to run a motor. This motor would pull the metal into the center of the coil then release.

You strenghten the power of this coil by putting as I recall a ring around the coil and then a lid on top of the coil, then stated you could futher increase the efficiency if you had not glued down the coil to the mount.

My question is, how did you make the ring? Could an iron cup do the same thing? I wanted to test this with my SSG, but I did not know if it would have the same effect on my coil.

Thanks.

Mart

[Peter Lindemann]

Iron Ring

Hi Peter,

In the video you had a coil that you used to run a motor. This motor would pull the metal into the center of the coil then release.

You strenghten the power of this coil by putting as I recall a ring around the coil and then a lid on top of the coil, then stated you could futher increase the efficiency if you had not glued down the coil to the mount.

My question is, how did you make the ring? Could an iron cup do the same thing? I wanted to test this with my SSG, but I did not know if it would have the same effect on my coil.

Thanks.

Mart

Mart,

The outer ring was made of two different diameters of clear plastic tubing, defining the outer and inner walls, and a flat donut section to define the bottom. These pieces of plastic were super glued together. Once dry, the area in the ring was filled with iron shavings from an engine rebuild shop. These iron filings were compressed down as tightly as possible and super glue was pours on top to form a sealed upper surface.

All I was trying to do was create a magnetic path back around the coil that would be better than the air. Adding the iron plate on the top helped too. If I could have completed the iron pathway around the bottom of the coil also, the torque would have increased dramatically for the same electrical input.

A properly sized iron cup could work. But this is not going to make your SSG run better. That is a different system altogether.

Peter

[theremart]

RE: Iron cup

Thanks.

Are there plans that you have of the motor in the video that I could take to a CNC shop and have them make one? Did you just take one of the patents and make the motor yourself?


There seems that there would be a market for these custom motors were they to be made, as the Amish who make their own power, and those people out in the middle of no where.

Also, I have purchased a 5HP Baldor motor, I am in process of making it a Roto Verter. I have seen others at otherpower.com put neos on the shaft inside the motor. Is there a conversion that you would recommend for changing this motor from a standard motor into one that harnesses the back EMF or helps efficiently?

Thanks

[Peter Lindemann]

Answered in an Earlier Post

Thanks.

Are there plans that you have of the motor in the video that I could take to a CNC shop and have them make one? Did you just take one of the patents and make the motor yourself?


There seems that there would be a market for these custom motors were they to be made, as the Amish who make their own power, and those people out in the middle of no where.

Also, I have purchased a 5HP Baldor motor, I am in process of making it a Roto Verter. I have seen others at otherpower.com put neos on the shaft inside the motor. Is there a conversion that you would recommend for changing this motor from a standard motor into one that harnesses the back EMF or helps efficiently?

Thanks

Theremart,

Please read the entire thread. I have answered these questions at least twice before.

Thanks,

Peter

[theremart]

RE: Answers

Theremart,

Please read the entire thread. I have answered these questions at least twice before.

Thanks,

Peter

Wow, I did not realize the depth of what is on this forum. From the first message, i found that the link to where an off the shelf motor is modified by removing the windings, and cutting it square.

Thanks for pointing me where I can find this information. And sorry for not doing it sooner.

Mart

[theremart]

Making the no EMF motor

I am looking for suggestions for cutting the plates on the rotor of a DC motor so they are square like the motor Peter has demonstrated.

My first thought is to use a saber saw with several blades the coating on the plates does eat the blades...

Another thought I had is to use an abrasive wheel or a torch. The torch seems like a bad idea, but I am open to what methods other people have found to work.

From what I am seeing no modification is needed for the coils in the walls of the motor housing.


Thanks.

[Peter Lindemann]

Abrasive Wheel

I am looking for suggestions for cutting the plates on the rotor of a DC motor so they are square like the motor Peter has demonstrated.

My first thought is to use a saber saw with several blades the coating on the plates does eat the blades...

Another thought I had is to use an abrasive wheel or a torch. The torch seems like a bad idea, but I am open to what methods other people have found to work.

From what I am seeing no modification is needed for the coils in the walls of the motor housing.


Thanks.

Dear Mart,

Yes, the silicon-steel laminations are pretty tough. You need a thin, high speed abrasive wheel in an electric drill to cut through them. There are a number of other considerations to keep in mind when modifying your series wound, universal motor. The first is whether the rotor has an EVEN number of segments or an ODD number of segments. I've seen them with either even or odd. Obviously, the ones with an EVEN number are going to be easier to BALANCE after the modification. Second, make sure you cut off and remove all of the copper windings on the rotor. Just disconnecting them from the commutator or removing the brushes is not enough. All of the copper windings are short circuited together and will cause back EMF drag on the rotor unless they are removed.

The size of the air-gap between the rotor and the stator will determine the total amount and efficiency of mechanical energy production. Although it is not exactly true, the rule of thumb is that if you cut the air-gap in half, the torque should double. When modifying an off-the-shelf motor, modifying the air-gap is impractical, unless you save the stator and make a whole new rotor piece. But that is a bigger project. The motor I show on the YouTube films has an air-gap of .021 (twenty-one thousandths of an inch). Just so there is no confusion, that is .0105" (ten and a half thousandths) per side. With this air-gap, I have measured the mechanical energy production at about 30%. So, choosing an off-the-shelf motor with the smallest air-gap helps a lot. Even so, at high speed, this motor will go OU as the total ON TIME of the commutator approaches the inductive current rise-time of the coils. As the motor speeds up, the total percentage of electrical energy recovered rises as well. At 2500 rpm the electrical recovery is about 25%. This suggests that the motor will go OU at about 7000 rpm, or at the speed where the electrical recovery exceeds 70%.

The plastic wheel the motor turns has the little magnets in it to operate the magnetic reed switch, but also doubles as a calibrated dynamometer that is exactly one foot in circumference. The motor is capable of very high speed, so I have embedded the magnets in the wheel so they don't go flying across the room. At the speeds this motor can turn, this danger is very real, as I actually threw the magnets off the wheel three times before finally embedding them this way!

What you are building is a simple demonstrator of the principles of the motor, where the stator acts as the inductor in a DC-to-DC forward converter, and the rotor responds passively to the changes in flux of the inductor.

Good luck with your experiments!

Peter

[elias]

Dear Peter

I recently found an old vacuum cleaner and took the motor out as you can see in the attachment. I was planning to see if I can turn it into an attraction motor. What do you suggest? The airgap of it is around 0.015" as I measured several times to get sure. Fortunately the number of segments are Even would make balancing it easier. But I don't know if the stators are fine for this. How much do you recommend me to cut and shape the rotor?

Thanks in advance

[Peter Lindemann]

Shaping the Rotor

Dear Peter

I recently found an old vacuum cleaner and took the motor out as you can see in the attachment. I was planning to see if I can turn it into an attraction motor. What do you suggest? The airgap of it is around 0.015" as I measured several times to get sure. Fortunately the number of segments are Even would make balancing it easier. But I don't know if the stators are fine for this. How much do you recommend me to cut and shape the rotor?

Thanks in advance

Elias,

Yes, the vacuum cleaner motor is an excellent place to start. The main drawback of these two-pole stators is that the outer edges of the pole faces get so close to each other. This limits the width of the rotor to the width of the space between the stator poles. The reason is that the rotor must be just at the beginning edge of one of the pole faces and be attracted into alignment during the power stroke. If the rotor is wider than the space between the stator poles, then when the fields come ON, the rotor is attracted forward, but is also attracted backward. This geometry partially negates the forward mechanical energy you are trying to produce.

You can see in the design that Jetijs is building right now, how this problem has been eliminated by selecting a better geometry for the stator that includes stator poles that are only 70 degrees of arc.

One thing you could do is TRY to cut some of the outer lips off the stator poles. This is very difficult because the silicon steel is murderously tough material and dulls saw blades easily. The other issue is to do all of this AND protect the coils that are currently in place. One little nick from an errant saw blade and the coils can be ruined.

So, it just depends on how much work you want to do. The simplest thing to do is to cut the rotor down to the width of the space between the stator poles (or a little bit wider) and leave it at that. Get your first model going, and do more extensive work on your second one.

Good luck,

Peter

[theremart]

RE: help about converting motor

Dear Peter,

THANK YOU

[elias]

butterfly rotor

Thank you very much Peter, I got it. Modifying the stators was risky, so I shaved my rotor.

I shaved my rotor like a butterfly for testing. What do you think about this. Also I want to place my timing magnets on the commutator wheel, is that Ok?

Regards

[Peter Lindemann]

Rotor Modification

Thank you very much Peter, I got it. Modifying the stators was risky, so I shaved my rotor.

I shaved my rotor like a butterfly for testing. What do you think about this. Also I want to place my timing magnets on the commutator wheel, is that Ok?

Regards

Elias,

Nice job on the rotor. But according to what I said in my last post, you have still not taken enough segments off the rotor. Currently, you have 6 segments on each side, but the width of the space between the stator poles looks like it is about 4 segments wide. You can try it like this, but you will find that cutting the rotor back to 4 segments will allow better performance.

You can try to place the magnets on the commutator wheel, but I don't think it will work, unless you are going to trigger the circuit with a Hall-Effect device. If you are planning on using a magnetic reed, like I do, you will need to get the reed switch away from the magnetic field of the stator coils. The magnetic reed has to disconnect for the fields of the stator to turn off. If the reed is IN or near the field of the stator, it may latch ON and not turn off when the little magnet goes away.

Plus, with the magnets outside of the motor, it is easier to find the best placement for the magnetic reed for proper sensitivity and ON time.

Keep up the great work.

Peter