Change on the way as insulated powders press ahead

Change on the way as insulated powders press ahead

Revolutionary changes in the way designers conceive electric motors in automotive, domestic and industrial applications are on the way with the introd...

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Revolutionary changes in the way designers conceive electric motors in automotive, domestic and industrial applications are on the way with the introduction of insulated iron powders...

N

ew ground

is waiting

broken

in the area

motive

and

applications

other

to be of auto-

magnetic

say two North

American material powders, machine

researchers. systems combined design

future

Ferromagnetic

using with

principles

motor

designers

will be able to

iron

specify

lower-cost,

more

new electrical

motors

and other

electrical

QMP’s

Claude

insulated

mean

that

in

efficient

Gelinas

devices,

say

and Donald

Brydges. In their

Insulated

paper

for automotive SAE2003

in Detroit,

insulated

iron

their

they

powders

AC or pulsed find

iron powders

applications,

given

developed

DC applications

niche

in low-frequency

applications

such

motors

or sensors.

These

which each

from

pure

iron

the particles other

Among these

using

neering

materials

are

powder

in from

dielectrics.

attributes

of

is the possibility

their

ing them

auto-

as accessory

are insulated different

the interesting materials

for

may soon

motive

produced

at

say that

composition

of engi-

and process-

to specifically

meet

application

requirements. The iron particle

size may be varied

well as the amount certain

cases,

even replace

of thermoset

a lubricant

as

resin.

In

can be added

or

the resin in order

to ease

pressing. New

motor

iron powders

designs provide

for automotive

used in power

dows,

sunroofs

tions

Figure I. Port of on electric motor moulded born insuloted magnetic composite powder

32 lvAR June 2003

-

accessory

those

that

dimensional

seats,

and fans.

take advantage and thermal

the iron powders,

0026-0657103 02003

using

insulated

technical

resulting

solutions

motors

such as

antennae, They

win-

are solu-

of the threeproperties

of

in smaller,

Elsevier Ltd. All rights reserved.

lighter motors

with

higher

torque-to-weight

ratios

and less cop-

per in the windings. The automotive savings

that

waste.

industry

can accrue

long production

runs

Smooth

atomised

iron powder

tromagnetics. has long

from that

surface

near

aware

net shape

powder

finish

been

metal

and high

of the cost

forming

parts

used to electrically

insulate

resins

of choice

and lubricating

the iron particles

for these dielecdielectrics

are

and to provide

and

allow

efficiencies

is the material

Thermoset

- minimal

among

them. Insulated

iron powders

engineered

or dielectromagnetics

for soft magnetic

applications

fields where high permeability, desired.

These

materials

mance gap between

the properties

in the development ty requirements,

material

formulations

combined

property-application systems.

of ferrites input

relationship High-purity

with

magnetic

and low losses

are

to fill the perforand those

variables

of dielectromagnetics

tions. These factors,

iron-resin

high induction

can be engineered

nated steels. Some of the design

are specifically

in alternating

of lami-

to be considered

are application and processing an understanding

propercondi-

compressible

also CVKVD

of the

have led to the development and highly

with Superheated Gas Technology for finer, cleaner spherical powders - PVD - Rapid Quench Techniques

of

water-

Dental Amalgams H2 Storage 7.2

-

Magnetic

alloys

Catalysts Brazing alloys Hard-facing Trials/R&D 6.4 300

I

I

I

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I

400

500

600

700

800

tools facility

900

Compacting Pressure, MPa

Fig 2 Effect of compacting pressure on the density of TR bors pressed from the three composite moteriols.

metal-powder.net

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June 2003

d”

$

45

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6.9

6.8

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7.3

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7.1

Density, g/cm3

171

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A

16-

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B c

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13

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6.9

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_

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Density,

Figure 3. Effect of density on the stripping ond sliding ejection pressures of iz7mm thick TR bars pressed from the three composite moteriols

adequate

strength

less affected plastics,

providing

Finally, reduce

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posite

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A is an iron-resin 11 5683

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three

typical

Their

formulations

characteristics

material

called

material

requiring

ATOMET die-wall

of com-

are as follows:

EM-l.

That

lubrication

is a relfor

metal-powder.net

compaction.

After

pressing,

parts

are

&red at 2OOoC in air to cross-link resin and attain

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B is a lubricated called FLOMET prietary

iron-resin EM-l.

lubricant

ever die-wall

lubrication

C is an iron-dielectric

during

after low-temperature

restricted

compaction

80

heat This material

for pressing

but, unlike

100

as well as an

350%.

suitable

that

acts as a

insulator

typically

120

at 160°C

material

lubricant

is particularly

140

is less critical.

are cured

differs in that the dielectric

plex shapes

a pro-

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strength

parts

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It contains

and can be used when-

and mechanical The pressed

the

strength.

com-

60

A and B, is

to AC applications

at 50 - 60

Hz. These free-flowing apparent 3.05g/cm3

density

between

and require

heat treatment mechanical

powders

after

metal

and

6.8

6.9

a low temperature

and magnetic

dent on their density, powdered

2.80gicm3

compaction.

such dielectromagnetics c_

40 6.7

have an

properties

7.2

.

to any other

part.

I

’ Figure 4 Effect of density on the mechonicol strength of TR bors for three materials cured in for 30 minutes. A at 2o0°C. B at 16oY and Cat 350°C.

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Density, g/cm3

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June 2003

The compressibility composite

1200 E k s 1 s .Z > 'E rn .z u

ing transverse

1000 -

'.B

plotted

\

\

800 -

'._

about

A

200 0 6.7

and sliding

of the 12.7mm-thick

6.8

I

I

I

I

6.9

7.0

7.1

7.2

The

of

strip-

for the ejecTR bars

2 as a function

are of the

density.

C ____-- ___------___ I

in density

pressures

in Figure

slightly

the iron-resin

at 800MPa.

tion

B and

were

than

ping

is

materials

a difference

0.05gicm3

plotted

bars,

a lubricant

with

by press-

(TR)

1. The

compressible

material

600 400 -

contain

more

obtained

rupture

in Figure

C that

of the three

materials,

The pressures ejection

7.3

Density, g/cm3

to the other or lower with

to start

vary

from

the

one mix

but are, in all cases,

than

those

conventional

40MPa

typically

as low

obtained

PM mixes

30MPa

of about

7.0g/cm3.

at a density

The pressures Figure 5. Effect of density on bulk resistivity of the three moteriols as determnined on TR bars cured in air forgo minutes. A at 22oY; B at 160°C and C ot35oY.

required

of the bars

required

to

to slide the bars

out of the die are very similar

for the

three

the densi-

mixes

and increase

ty or compacting cal strength trated

exhibits

values, with

values,

independent

about

55MPa.

(below

and values

at densities

of about

Electrical between

low-density made their

from strength

insulation

is needed

particles

to minimise

and it is possible

to evalu-

ate insulation

by measuring

bulk

cal resistivity

- the one that

results

the combination phase

(iron)

to

100 MPa.

the iron

currents

above

It is also possi-

7.0 gicm3)

C to increase

values

are

of material

can be reached.

material

eddy

which

dependent

ble to resin-impregnate parts

A B

The strength

as 1lOMPa

7.2g/cm3

material Material

of the density

C is very density as high

of the

up to

no lubricant.

the lowest

almost

is illus-

3 as a function

are obtained

contains

The mechani-

materials

The highest

125MPa, that

pressure.

of these

in Figure

density.

with

electrifrom

of the conducting and the insulating

phase

(dielectric). The bulk resistivity rials,

as determined

four-point ment

method,

function materials than

contact

_

C: 400uR

to the 100pR

C, which

is also less density

4 as a

more

resistive as

value for material dependent.

A and B are thus adequate up to at frequencies while material

low-frequency

a

measure-

to 1000pQ

opposed

few KHz,

mate-

The resin-containing

A and B are much

applications

june 2003

direct-current

is given in Figure

of density.

material

Materials

Figure 6. A commercially ovoiloble brushless servomotor. The overall length ond mass of this motor is obout one third of the troditionol lomination design.

of the three

on TR bars using

applications

for

up to a

C is suitable - 50Hz

for

to

6OHz.

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I_

MEETING

your

EXPECTATIONS

The effect of density on AC losses at 1

.

Tesla measured

at 60Hz and 400Hz for

the three materials

(3 Y < 2

14.0 0 w A

13.5 13.0

fs z m s

The AC losses decrease with an increase

A

A B c

is shown in Figure 6.

in density for all materials. attributed

This can be

to a decrease in the hysteresis

loss. Magnctisation

becomes

powdered materials

as density increases

easier in

because of the higher magnetic

12.5 -

higher permeability

induction,

and lower coercive

force.

12.0 -

The improvement

in DC characteristics

with an increase in density translates

‘Z 2

11.5 -

a decrease of hysteresis

z 6.7

I

I

I

I

I

6.8

6.9

7.0

7.1

7.2

portion

into

of the

core loss. Losses are the same for materials A and B and approximately

7.3

cent lower for material

the 350°C heat treatment

Density, g/cm3

12 per

C. This is due to

reduced the hysteresis

that slightly

loss in this

material. At densities

above 7.0g/cm3, losses in

these materials

are about low/kg

and 70 W/kg at 400Hz.

at 60Hz

The fact that the

AC losses are proportional

to the frequen-

cy and not to its square is a good indication that the insulation

.g

=

280 -

eddy currents

C which has a lower

C

However,

rials depends

of insulation

but also on specimen

I

I

6.8

I

6.9

I

materials

induction

of eddy currents

7.0

Depending

I

7.1

7.2

induction

7.3

that

nated Figure 7 Effect of density on the magnetic induction ond maximum permeability applied field).

has approximately

permeability

is

properties

were measured

field of 120

A/cm (1500e) diameter 0.635cm tional

5.26cm

outside

inside diameter

The induction

to the density

by

is propor-

and not greatly

by the mix formulation.

However, affected

by 4.34cm thick.

affected ability

at an applied on toroids

while the maximum

increases

with density

by composition

This is exhibited

38 WRJune 2003

materials

(120

A/cm

permeit is also C, which

_

15 per cent higher

at a given density

C is too conductive

for the

results

attrib-

parts

losses

high in these materials

a low temperature

heat treatment

effect on their magnetic

Here, even at a temperature

and

has a propas

are

They where variations

force in mate-

tions.

rial C is reduced

15 per cent -

especially

of their stable

under

the isotropic

properties

in ignition

the hood

375 A/cm versus 415 A/cm for materials

motors,

alternators

A and B.

sensors

and relays.

and

to be cost-effeccoil applica-

can be used in small DC brush

in

to tem-

applications.

have been shown

They

as dropbetter

by redesigning

show

automotive

They

parts much

they are subject

in-cabin

tive and reliable

at low

Even if they can

laminated

perature

low as 35O”C, the coercive by about

domi-

They

modification,

are obtained

situations

hysteresis

to

previously

to take advantage

properties.

Indeed,

are just starting

frequencies.

existing

utable to stress relief during the 350%

beneficial

field

for use in AC applications

ins without

than

A and B. This is partly

are relatively

with

it may be found

by steel laminations.

intended

heat treatment.

erties.

and processing.

in material

permeability

dimension,

applications

replace and maximum

on the part

materials

to medium

induction

the

increases

cross-section.

material

These

shown in Figure 5. Magnetic

that

in the part

and frequency,

penetrate

on magnetic

In low

it is known

application.

Density, g/cm3

The effect of density

mate-

or resistivity,

geometry.

resistivity

an increase

160 6.7

that the induc-

in composite

not only on the frequency

and the extent

180-

and

resistivitp

it is known

tion of eddy currents

Z

is efficient

remain low, even in material

motors,

and brushless and generators,

speed

metal-powder.net