nanocrystalline cores
Current Transformers with nanocrystalline cores - Metering.com
Current Transformers with nanocrystalline cores - Metering.com
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Current Transformers with<br />
<strong>nanocrystalline</strong> <strong>cores</strong>
Power Measurement<br />
MeasurementErrors<br />
Exact power value<br />
P true<br />
= U ⋅ I<br />
⋅ cos φ<br />
Measured power value including errors<br />
P meas<br />
( 1−<br />
F( I)<br />
) ⋅ ( φ + ϕ ( I)<br />
)<br />
= U ⋅ I ⋅ cos<br />
− P<br />
P<br />
meas true<br />
Error ∆P<br />
[% ] = ⋅100<br />
P<br />
true<br />
5<br />
4<br />
3<br />
Power error DP [%]<br />
2<br />
1<br />
0<br />
-1<br />
-2<br />
-3<br />
-4<br />
-5<br />
0,1 1 10 100<br />
Primary current I prim [A rms ]<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 2
Power Measurement<br />
Functional principlesof currenttransducers<br />
Shunt resistor<br />
Hall Effect sensor<br />
Pickup coil<br />
sensor<br />
Current<br />
transformer<br />
with fluxconcentrating<br />
pole pieces<br />
withgapped laminated<br />
core<br />
„Rogowski-Coil“(no core)<br />
gapped laminated core<br />
withgapped ferrite core<br />
with ferrite core<br />
with optimised<br />
toroidal VAC core<br />
D complexjoining<br />
technology<br />
D no galvanicseparation<br />
D lowoutputvoltage<br />
D outputdriftsovertime<br />
D high offset, high T-drift<br />
offset extensive<br />
compensation<br />
D lowoutputsignals<br />
D needsintegrator<br />
C securegalvanicseparation<br />
C high dynamicrange<br />
C insensitive to external<br />
magneticfields(closed core)<br />
Dominant<br />
technology<br />
D high susceptabilityto external<br />
magneticfieldsforfield-detecting<br />
measurementmethods( shielding) differentiation bymaterial<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 3
Toroidal Core CTs – CT Design<br />
Fundamental Formulae<br />
↑<br />
I prim<br />
I sec<br />
Burden<br />
resistor<br />
R B<br />
Toroidal soft<br />
magnetic<br />
Primary<br />
Secondary core<br />
current<br />
conductorwinding<br />
Material:<br />
• permeabilities<br />
• core losses d,<br />
µ = ⋅<br />
' ''<br />
µ s<br />
+ i µ s<br />
''<br />
µ<br />
s<br />
δ =<br />
'<br />
µ<br />
s<br />
tan<br />
• saturationinduction B sat<br />
Current ranges<br />
Errors<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 4
Toroidal Core CTs – CT design<br />
Maximum primaryAC current<br />
I sec<br />
I prim<br />
2<br />
ω ⋅N<br />
B<br />
N prim<br />
=1 N sec<br />
R<br />
sat<br />
B U<br />
sec<br />
⋅<br />
B Imaxrms<br />
≈ ⋅<br />
R<br />
ω = 2π ⋅<br />
f<br />
R Cu<br />
Primary current range increases with<br />
Current range :<br />
2<br />
R = R Cu<br />
+ R B<br />
‣ highersaturation induction B sat<br />
crystalline, amorphous and <strong>nanocrystalline</strong><strong>cores</strong> (B sat<br />
> 1T) superiorto ferrites (B sat<br />
~ 0.4T)<br />
ˆ<br />
A<br />
Fe<br />
‣ increased corecross section A Fe<br />
drawbacks: highercost, biggercomponent, A Fe<br />
↑⇒R ↑ ~ √ A Fe<br />
‣ decreased winding resistance RCu<br />
exhaustavailable windingspace<br />
Mostly R Cu<br />
>> R B<br />
, withR Cu<br />
~ N sec<br />
² ⇒ R ~ N sec<br />
², increasingN sec<br />
does notextendprimary currentrange.<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 5
I sec<br />
I prim<br />
N prim N sec<br />
R B U B<br />
R Cu<br />
ω = 2π ⋅ f<br />
R = R Cu<br />
+ RB<br />
Errors improve with<br />
Toroidal Core CTs – CT design<br />
Errors<br />
Phase<br />
error:<br />
Amplitude<br />
error:<br />
ϕ( I)<br />
≈<br />
F(<br />
I)<br />
≈<br />
FOM =<br />
arctan<br />
−sinδ<br />
R<br />
ω L<br />
⋅<br />
R<br />
ω⋅L<br />
‣ higherpermeabilityµ<br />
µ↑⇒L ↑, crystalline, amorphous, <strong>nanocrystalline</strong><strong>cores</strong> (µ > 100000) superiorto ferrites (µ<<br />
15000)<br />
R<br />
ω⋅L<br />
‣ lowercorelosses (amplitudeerror)<br />
amorphous and <strong>nanocrystalline</strong><strong>cores</strong> superior to crystalline<strong>cores</strong> and ferrites<br />
≈<br />
ρ<br />
µ<br />
Cu<br />
‣ decreased winding resistance R Cu<br />
exhaustavailable windingspace<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 6
Toroidal Core CTs –Materials<br />
Non-DC-tolerantCTs<br />
0,60<br />
0,40<br />
0,20<br />
High-perm crystalline(C), amorphous(AM) and <strong>nanocrystalline</strong> (NC) <strong>cores</strong><br />
Phase error j [°]<br />
crystalline<br />
ULTRAPERM 10<br />
<strong>nanocrystalline</strong><br />
VITROPERM 500 F<br />
amorphous<br />
VITROVAC 6025 F<br />
AM, NC: no load<br />
dependence of<br />
phase error<br />
0,00<br />
Amplitude error [%]<br />
~ (bigger)<br />
ferrite<br />
AM, NC: Low<br />
amplitude errors<br />
Losses !<br />
-0,20<br />
I prim [A rms ]<br />
0,1 1 10 100<br />
Easy error compensation requires independence of L, tan δ on load and temperature + stable production<br />
processes with low tolerances for µ and tan δ.<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 7
Toroidal Core CTs - Material selection:<br />
Non-DC-tolerantCTs<br />
accuracy<br />
very high<br />
high<br />
High current range + low errors<br />
Amorphous high-µ VITROVAC<br />
Nanocrystallinehigh-µVITROPERM<br />
80%NiFe ULTRAPERM<br />
medium<br />
high-µ ferrite<br />
toolow<br />
50%NiFe PERMENORM<br />
3% SiFeTRAFOPERM<br />
primarycurrent<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 8
Toroidal Core CTs – CT design<br />
Maximum unipolar current<br />
I sec<br />
I prim<br />
N prim N sec<br />
R B U B<br />
Current range :<br />
Iˆ<br />
DC max<br />
=<br />
π<br />
µ<br />
0<br />
.<br />
Bˆ<br />
sat<br />
⋅<br />
µ<br />
l<br />
Fe<br />
ω = 2π ⋅<br />
f<br />
R Cu<br />
Unipolar current rangeincreases with<br />
‣ highersaturation induction B sat<br />
crystalline, amorphous and <strong>nanocrystalline</strong><strong>cores</strong> (B sat<br />
> 1T) superiorto ferrites (B sat<br />
~ 0.4T)<br />
‣ lowerpermeability µ<br />
lowµ low L generally higheramplitudeand phase errors<br />
‣ increased corelength l Fe<br />
highercost, biggercomponent<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 9
Toroidal Core CTs –Materials<br />
DC-tolerant CTs<br />
6<br />
Low-perm<strong>nanocrystalline</strong> core<br />
basically no loadand<br />
temperature dependence<br />
easy compensation<br />
85°<br />
5<br />
4<br />
Phase error j [°]<br />
25°<br />
3<br />
2<br />
Phase and amplitudeerrorshave to becompensated; compensation<br />
easy, if errorsdo notvarywith temperatureand load<br />
1<br />
0<br />
-1<br />
Amplitude error [%]<br />
25°<br />
85°<br />
0,1 1 10 100 1000<br />
I prim [A rms ]<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 10
Toroidal Core CTs - Material selection:<br />
DC tolerant CTs<br />
accuracy<br />
very high<br />
high<br />
High unipolar current range + low errors<br />
Nanocrystalline low-µVITROPERM<br />
Amorphous low-µ VITROVAC<br />
newlow-µ<br />
VITROPERM variants<br />
medium<br />
low-µferrite<br />
toolow<br />
50%, 80%NiFe, 3% SiFe<br />
primarycurrent~ unipolar current<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 11
Furtherdevelopmentof material basis:<br />
‣ New low-µ<strong>nanocrystalline</strong> VP alloys<br />
Toroidal Core CTs – New developments:<br />
Low-perm VITROPERM <strong>cores</strong>, integrated CTs<br />
smaller<strong>cores</strong> (OD)<br />
<strong>nanocrystalline</strong> material<br />
costsavings<br />
Design of application-specific and customer-specific components_<br />
‣ Integration of CT fore.g. 3 phase applicationsinto 1 component<br />
easierassembly<br />
costsavings<br />
Customer-specificdesigns<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 12
Integrated seamlessprimary conductor<br />
‣ radial through ID of core<br />
‣ connection to meterbasethroughblades<br />
Toroidal Core CTs –New developments:<br />
CT with integrated primary conductor<br />
Picture to visualizeconcept<br />
optimizedcoregeometry (ID smaller)<br />
less expensivecopper bar<br />
costsavings<br />
CurrentTransformers with<strong>nanocrystalline</strong> <strong>cores</strong> 23.02.2009 Page 13
Change language