by

Codrin-Gruie (CG) CANTEMIR & Adrian MUNTEANU

TM: Ralph JANSEN

10 MW Ring MotorOSU-NNX14AL87A

By

Codrin-Gruie (CG) CANTEMIR & Adrian MUNTEANU

NASA TM: Ralph JANSEN

This work was sponsored by NASA under the Hybrid Gas /

Electric Propulsion subproject of the Advanced Air Transport

Technology Project, previously known as the Fundamental

Aeronautics Program Fixed Wing Project.

The purpose of this project is to significantly reduce the thrust

specific fuel/energy consumption.

Acknowledgement

Why CAR?

• 4 World Speed Records for Electric Vehicles currently at 348 mph

• Plethora of high power electric drives

Prior this program

The study suggests 13 MW at 5400 rpm (max N1) for a total weight under 700 kg (1540 lbs).

This is already 11.2 hp / lbs some 40% better than required

However, there are 2-3 major issues which were revealed only towards the end of the study

Target: CFM-56

The target is a 60 percent reduction relative to a baseline Boeing 737-

800 aircraft with CFM56-7B engines in the 2030 to 2035 time frame.

Project Goals

• Direct driving of the LP shaft with no gears • 10 MW continuously at 5000 rpm (20000 Nm continuous torque)

• 8 hp/lb

• No permanent magnets• An induction motor will be way more forgiving in case of failure while flying

• No nacelle distortion

How?

• Ring VCSWC or Variable Cross-Section Wet Coils (2 new technologies)• Cooling

• Efficiency

• Power Density

• Distributed Power Electronic (new technology)• Cooling

• Power Level

• Control

• External rotor (known technology)• Rotor integrity

• Implementation of VCSWC

• Power density

• Jet-engine integration

By marrying 3 new technologies in the same machine with the accent on

fabrication and integration while optimization has only a marginal role

Variable Cross-Section TechnologyPatent Pending

• Ring Motor

• Ring Coils

• Reversed construction

VCS unfolded

Just for the sake of facilitating intuition, the coil depicted is only formed in the first slot (with 4 turns) and unformed for the remaining 4 turns (which should fit in the adjacent slot).

As shown, in order to form the coil, the winding process commences in the middle. Technologically the conductor is no longer of a wire type but moreover is a ribbon with some material removed for the portions of the coil located in the slot (it can be water or laser cut from a sheet). As visually presented, the last turns have a higher length outside of the slot -obviously the increased cross section has subsequently a major impact in increasing the overall efficiency. In this specific design, the total stator resistance can be decreased 60% over conventional coils.

WC (Wet Coil) TechnologyPatent Pending

Although it may be not intuitive, a column of water with the height of 10 cm (approximately 4”) located at a diameter of 1.65m (65”) and spinning at 1200 rpm will generate a pressure of roughly 10 bar (145 psi) in addition to what the resin own density generates.

It should simply acknowledge the fact that centrifugation may be a much more effective technology in electric machine construction than VPI

VCSWCPatent Pending

It did work at the first attempt

How to design?

• A conventional design (considered convergent) - as seen standard in electric machine design - would be highly dependent on statistical numbers from similar applications. The problem is that for this specific application such statistical numbers do not exist (or at least we are not aware of any).

• Most likely, a classic convergent design approach will be prone to missed design opportunities. Albeit it might work, nothing will guarantee the proximity of an optimum.

• Optimizing the design process at an incipient stage is more important than optimizing the design results

• So, we designed… divergent

10 MW Design Space Exploration (DSE)

• In this DSE the numbers of poles and the air-gap speed (the motor diameter) are varied considering the same base speed and a minimum shaft efficiency of 96% (with the aim to assess weight and practical ability to fabricate).

• All the motors are designed to function at 5000 rpm base speed, as will be consistent with the LP shaft of CFM 56 (typically runs between 4800 and 5200 rpm).

• From a practicability point of view, the numbers of poles is considered between 12 and 24 (30) and the air-gap speed vary from subsonic to supersonic in a ratio close to 1/2.

• As a general practice, for a given pole number, between 6-8 candidates have been preliminary designed and simulated and only the most representative 4 have been considered.

• In principle for a given number of poles, the higher the air-gap speed, the shorter the motor length and aspect ratio.

• Due the large variation in the motor configurations, it is not possible/practical/optimum to hold all the other parameters the same e.g. number of slots/turns and/or magnetic and electric loads and rated values. Rather, for each candidate the individual design was tuned as most appropriate and therefore the shaft performances vary slightly.

Four Families

The study is based on 46 designs and simulations from which 18 have been selected as consistent with the goals of the study. Just for orientations, the CAD models are presented above.

Example:12-16-20-24-30 poles family (500-667-833-1000-1250 Hz) des=1000 mm

• Variant 06_250mm_5000rpm_13000V - 12 poles / 500 Hz

• Rotor outer diameter = 1150 mm

• Rotor inner diameter = 1006 mm

• Stator outer diameter = 1000 mm

• Stator inner diameter = 800 mm

• Axial length = 250 mm

• Stator slots = Z1 = 108

• Rotor bars = N2 = 132

• Air gap tangential speed: v = 262 m/s

• Results:

• I = 564 A Uf = 13000 V cosφ = 0.463

• s = 0.006M2 = 18970 Nm P2 = 9.926 MW

• pFe = 130 kW pCu = 124 kW

500 Hz

667 Hz

833 Hz

1000 Hz

1250 Hz

0

1

2

3

4

5

6

7

8

9

1000 mm1200 mm

1400 mm1600 mm

Po

we

r d

en

sity

[h

p/l

b]

Power density 8-9

7-8

6-7

5-6

4-5

3-4

2-3

1-2

0-1

• Results show a peak performer mostly because of magnetic loss behavior

• Due to the general scope of this study, an average-to-good magnetic material was desired, particularly M330 35A for which in-house test values are available. It should be acknowledged that better materials are commercially available (as Cogent NO 005), but there are offered without a full set of magnetic proprieties and the risk of erroneous results was considered important.

First Layer of OptimizationMaterial Selection - Conductor

• Cu-Cu

813 kg

• Cu-Al

773 kg

• Al-Al

724 kg

Second Layer of OptimizationGeometry

Trapezoidal stator slots

From 724 kg to 707 kg

Trapezoidal stator slots and trapezoidal rotor bars

From 707 kg to 665 kg

First Implementation: 770 KgApproximately 8hp/lb

Grey - unchanged parts

Off-the-shelf CREE SiC Mosfets

and cold plates

Details

Cooling is implemented in the booster’s blades

VCSWC at its best

Third Layer of OptimizationMagnetic Materials - Performance 10.9 hp/lb

• 24_poles_190mm_43200V_2mm_dd_Al_rotor_CoFe

• Rotor outer diameter = 1282 mm

• Rotor inner diameter = 1204 mm

• Stator outer diameter = 1200 mm

• Stator inner diameter = 1020 mm

• Axial length = 190 mm

• Stator slots = Z1 = 144 - Al

• Rotor bars = N2 = 172 - Al

• Air gap tangential speed: v = 314 m/s

• I = 275

• Uf = 43200 V

• M2 = 26435 Nm

• P2 =13.792 MW

• pFe = 360kW

• pAl = 101 kW (51kW-stator si 50kW-rotor)

Forth Layer of Optimization 11.2 hp/lbsNumber of phases

A six phase system may be implemented if each coil is independently controlled without the need to change the hardware. Two systems of 3 phases spaced at 90 degrees is the most advantageous combination having a clear gain over a conventional 3 phase system

If each coil is independently controlled, it is

possible to implement a 4 phase system at 90

degrees with only 18 poles. Overall the power

decreases, however the efficiency increases

over 97% mostly because the frequency

decreases.

Independently controlled coilsCustom modules

A module containing 6 H bridges, each independently fused and a build in radiator is proposed. Such modules may be build around existing transistors. The radiator may be the positive or negative terminal

Independently controlled coils3-6 kV configuration

The modules can be connected in series and will be symmetrized by the machine reactance

Independently controlled coilsImplementation in the midbox

Grey = unmodified parts

14 MW Electric Boost

How we built the first demonstrator

29

Technology Readiness

An unique toroidal winding machine was designed and built at OSU. In principle it can be fully automated / robotized opening the door for mass production

VCSWC fabrication technology was conceived and successfully demonstrated by OSU recently. It is expected that VCSWC technology will provide the best power density for a price under anything existing today, just because:

1. Does not use permanent magnets,

2. Does not use copper, 3. Uses the minimum

quantities of magnetic materials/kW

4. It can be FULLY AUTOMATED

Today apple to apple

Modular configuration in order to allow different combinations in future

350 kW10000 Nm801 lbs.

245 kW7000 Nm2130 lbs.

Favorite quote

“ Motor-vehicles, automobiles and even aircrafts never appealed to me, but rather

theirs creators”

Henri-Marie COANDA