1946

Item 1946

DESIGN: Electrotor-SloMo - Rotorhead - Synchronization - Magnetic Coupling (Magnetic Gear)

Objective:

To provide a means of synchronizing a pair of intermeshing rotors using permanent magnets, which do not consume electrical power.

Disadvantages:

When the rotors are in synchronization there will be a large radial force on the two rotors attempting to pull them together.

If the rotor-to-rotor flux bars are in 180º pairs they will oppose each other and the above loading on the axial bearing will not exist.

It appears that the length of the steel between the magnets on each rotor does not affect the magnetic force. (test on a couple of bolts of 1" long and 4" long)

Could laminated steel meaningfully improve the magnetic connectivity between the two rotors?

Concerns over back Iron and Laminations between Rotors:

Eddy current losses.

Weight of Steel.

Thought:- Will sheathing the flux paths in aluminum, copper, or some flux barrier reduce the eddy current losses and allow for lighter bars?

On alternative 1 the magnetic attraction between the two rotorhubs will put an additional loading on the main bearings.

Drawing - Alternative 1:

Drawing Notes:

An alternative arrangement on the above may be to have a solid fence of laminates between the segments of the two rotors.
'Balance point' is used below as the azimuth where the magnet holder is subjected to equal torque in both directions.

It appears that the 'balance point' for the motor's rotor is ⁺/_- 7.5º.
It appears that the 'balance point' for this aero-rotor is ⁺/_- 15.0º.

Iron backing yokes or Halbach close the flux and the torque is transmitted by the angular displacement between the two rotors and the iron flux carriers between.

Drawing - Alternative 2:

Drawing Notes:

On the sketch; A is flux path #1 and B is flux path #2 ----------->

Have a pair of flux ring around each rotor. On both rotors one flux ring has its flux gaps located opposite all the negative magnets and its other flux ring has its flux gaps located opposite all the positive magnets

Each of the two flux rings are joined by their own flux path to the ring with the opposite polarity on the other rotor.

This results in all the magnets contributing to the synchronization of the two rotors at all times.

The two (or more) steel flux paths that connect the two rotors could serve double-duty as structural members of the Frame.

_____________________

Might these magnets share the same flux ring that the power magnets do on their respective rotors?
Consider using the flux bars as part of the structure of the Frame.

Initial Considerations:

The weight and cost of the magnets is high considering that only 1/6th of them are functioning ant a time.

Directions of Rotation: The electric motors will set and maintain the two rotors to turning in the required direction.

Consider the pros & cons of adding more flux paths between more magnets and reducing the weight and strength of existing flux paths, backing iron and magnets.

This method is a consideration for eliminating a mechanical coupling, if it is better from the perspective of reliability, weight, cost, etc.

Alternatively this method might be considered as a means of assisting the electric and the mechanical means of synchronizing the two rotors.

Regenerative braking: Would it be advantageous to include the regenerative braking for use on the leading rotor when the 'out of sync' exceeds a certain angle?

Magnetic Coupling: To compliment the synchronized motors. See paper notes.

Re Intermeshing configuration. Very few of the magnets would be functional at a give time. This may represent an excessive wasted of cost and weight:

US Patents:

6,841,910 ~ Magnetic coupling using Halbach type magnet array
US Patent search on ["Magnetic Coupling" AND "permanent magnets" AND synchronization] had 81 hits

US Patent Applications:

20100028176 ~ ROTARY PUMP WITH COAXIAL MAGNETIC COUPLING

US Patent Application search on ["Magnetic Coupling" AND "permanent magnets" AND synchronization] had ?? hits

Since the magnets are on the aero-rotor this idea should work fine for:-

No-power autorotation

When power is being delivered to only 1/2 of each rotor.

It will not deliver equal torque (and thereby equal blade pitch) if only one motor is powering. However with duplicity in each of the two rotors this should not be a problem.

Another Consideration:

To add additional power to the motors:

Consider wrapping the six flux bars between the two rotors with copper coils and powering them electrically with a 2-phase current that is synchronized with the primary power circuit.

Outside Information:

Neodymium-Iron-Boron Magnet in Electromechanical Applications. See section 2.2 Magnetic Couplers. Have copy on E;drive

Permanent Magnet Couplings: Field and Torque three-Dimensional Expressions Based on the Coulombian Model

Notes:

Should one rotor advance and then physically 'push' the other rotor this push might temporarily decrease the electrical torque of the pushed rotor, which would decrease the pitch of the pushed rotor, which will allow it to accelerate; perhaps. Albeit with a slight loss of thrust; perhaps.

Remember the rotors MUST retain synchronization if there is a loss of power in one or both rotors.

This is a critical argument for total electrical redundancy; in each motor, or,

Redundancy due to two motors and a 100% mechanical interconnection.

This idea would also be applicable to the coaxial configuration.

The attraction was significantly less when testing the above using an iron bar and magnets on either side then the attraction was when just using the two magnets.

Possible improvements;

The contact surface area of the iron bar was not as large as that of the magnets, and one end of the iron bar was curved which would give an air gap.
Perhaps giving the iron bar a smaller x-sectional area will increase the attraction.
Perhaps using laminates will increase the attraction.

Concern: This idea may not work as well, if yaw is to be accomplished by opposed longitudinal pitch where outward roll of both the rotors provides blade-blade clearance.

Rough notes related to Magnetically Permeable Pole Pieces:

See Patent 3,378701 Magnetic Transmission Figure - 1A. Have hard copy.

'Soft ferrite' does not retain significant magnetization whereas 'hard ferrite' magnetization is considered permanent.

Excessively Fast Change Possibility:

The maximum pitch change on the blades will be < 15º. The reasons for a sudden large angular change might be; a loss of power in one or both rotors and the fast application of full throttle. Both would change the torque before the RRPM. This 15º change in pitch will be the result of a 4.83º physical change in the motor-rotor to hub and this equates to a 57.96º electrical change. Is this too much?

Wild Idea:

Wrap each of the flux bars in the top drawing with a coil of copper wire. This should provide the assemblage with the ability to provide torque to both rotors, while still providing synchronization.

This assemblage could be modified for 3-phase, or even higher phases.
This assemblage would likely only drive a segment of 360º mechanical disk at a given interval in time.

Concern:

The additional magnets represent an increase in parts and some degree of decrease in safety.

Alternative Idea:

The following is an alternative idea that may be preferable to the ones on this page.

DESIGN: Electrotor-SloMo - Rotor - Synchronization - PM Electromagnetic Coupling

Initially displayed: August 29, 2010 ~ Posted to Eng-Tips: August 30, 2010 ~ Last Revised: Friday, August 26, 2011

The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.