IEEE Electrification Magazine - December 2014 - 20

Turn-to-Turn
Insulation

Dedicated
60° Half-Phase
Sector
A∅

Outer Conductor

Phase
Separators
Two Phases
Per Slot

Inner Litz Conductor

C∅

B∅

B∅

C∅

Toothless
Laminations

Identical
Rotor Assembly
Magnetic Gap

A∅

Phase
Separator

Ring-Wound Stator
(Optional Variable-CrossSection Conductor)

Conventionally Wound
Stator

(a)

(b)

Figure 2. The toothless ring-type PMM.

drawback is the difficulty in cooling copper. The toothless
machines have been the dominating machines for highspeed applications until recently, primarily due to excellent
rotor stiffness and low air-gap sensitivity, allowing for
superb foil and magnetic bearing integrations. However,
progress in the area of foil bearings diminishes this advantage. Hence, the use of the higher-power-density tooth-type
machine is gaining momentum.
Figure 3 shows a radial and axial cross section of a typical two-pole, tooth-type PMM. This machine appears to
have the best future and will most likely replace most of
the toothless designs. Figure 4 shows the basic geometry
differences between four- and two-pole machines.
Four-pole machines use four C-shaped magnets instead
of one cylindrical magnet used in two pole machines. The
total amount of magnet for a four-pole machine is smaller.

The flux in two-pole machines is split in two magnetic circuits, while the flux in four-pole machine is split in four magnetic circuits. As a result, the four-pole machine requires
much less back iron to close the magnetic circuit. The conclusion is that the four-pole machine is much smaller and
cheaper. On the other hand, the four-pole machine presents
twice the fundamental frequency, which may penalize the
power-conditioning power electronics. The same tendency
remains when transitioning to generators with higher numbers of poles.

examples of High-Performance
Power-Generation Systems

A typical example for a high-performance EPGS is the
Honeywell PTMS for the Lockheed Martin Joint Strike
Fighter (JSF) aircraft currently in production and service.
Following a research and development program, an HRPMM was
selected to be incorporated on the
same shaft of the gas turbine engine
and a cooling turbine. The rotating
group uses oil-lubricated ceramic
ball bearings. The maximum operating speed is 62,000 r/min. The rotating group is shown in Figure 5. The
system delivers up to 140-kW, 270Vdc conditioned power.
Another example of a high(a)
(b)
performance EPGS is the system
developed as part of the NASA
Figure 3. The tooth-type PMM: the (a) radial and (b) axial cross sections.

20

I E E E E l e c t r i f i c ati o n M agaz ine / december 2014



Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2014

IEEE Electrification Magazine - December 2014 - Cover1
IEEE Electrification Magazine - December 2014 - Cover2
IEEE Electrification Magazine - December 2014 - 1
IEEE Electrification Magazine - December 2014 - 2
IEEE Electrification Magazine - December 2014 - 3
IEEE Electrification Magazine - December 2014 - 4
IEEE Electrification Magazine - December 2014 - 5
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IEEE Electrification Magazine - December 2014 - 46
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IEEE Electrification Magazine - December 2014 - 48
IEEE Electrification Magazine - December 2014 - Cover3
IEEE Electrification Magazine - December 2014 - Cover4
https://www.nxtbook.com/nxtbooks/pes/electrification_december2022
https://www.nxtbook.com/nxtbooks/pes/electrification_september2022
https://www.nxtbook.com/nxtbooks/pes/electrification_june2022
https://www.nxtbook.com/nxtbooks/pes/electrification_march2022
https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
https://www.nxtbook.com/nxtbooks/pes/electrification_march2021
https://www.nxtbook.com/nxtbooks/pes/electrification_december2020
https://www.nxtbook.com/nxtbooks/pes/electrification_september2020
https://www.nxtbook.com/nxtbooks/pes/electrification_june2020
https://www.nxtbook.com/nxtbooks/pes/electrification_march2020
https://www.nxtbook.com/nxtbooks/pes/electrification_december2019
https://www.nxtbook.com/nxtbooks/pes/electrification_september2019
https://www.nxtbook.com/nxtbooks/pes/electrification_june2019
https://www.nxtbook.com/nxtbooks/pes/electrification_march2019
https://www.nxtbook.com/nxtbooks/pes/electrification_december2018
https://www.nxtbook.com/nxtbooks/pes/electrification_september2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2017
https://www.nxtbook.com/nxtbooks/pes/electrification_june2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2016
https://www.nxtbook.com/nxtbooks/pes/electrification_september2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2016
https://www.nxtbook.com/nxtbooks/pes/electrification_march2015
https://www.nxtbook.com/nxtbooks/pes/electrification_june2015
https://www.nxtbook.com/nxtbooks/pes/electrification_september2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2014
https://www.nxtbook.com/nxtbooks/pes/electrification_june2014
https://www.nxtbook.com/nxtbooks/pes/electrification_september2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2013
https://www.nxtbook.com/nxtbooks/pes/electrification_september2013
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