Toroidal Core

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Toroidal Core

Description

Permanent Magnets Ltd. supplies tape-wound 80% NiFe Toroidal Cores to industries requiring High Metering Accuracy (HMA) current transformer cores. 80% NiFe has High permeability, Low magnetization in higher inductions and High saturation flux density. By properly heat treating in a controlled hydrogen atmosphere furnace, (to a soft magnetic anneal) we maintain close control of the magnetic properties over a broad range of flux densities which permits the most economical and efficient design of your transformer. The Toroidal wound cores are made robust by finishing them with varnish coating with or without plastic casing. They are available in comprehensive range of sizes.We offer a range of wound cores from minimum 1” [25 mm] inside diameter to maximum 47.25” [1200 mm] outside diameter, using 80% NiFe foil thicknesses ranging between 0.004” [0.1 mm] and 0.014” [0.36 mm] . Core height is available from .200” to 2” [5-50 mm] .

Material Properties

Magnetic & Chemical Properties
Properties Measurement Unit 80% NiFe7
Permeability Permeability AC
Bs Tesla 0.751
Br Tesla 0.42
Hc 2(A.m)-1 Tesla 0.35
µ4 4 Tesla 550000
µ max Tesla 570000
Permeability AC
µ4z5 70000
µz86 -
µmax 95000
Core loss (W/Kg-1) 0.015
Chemical Composition % Ni - 78%-81%
% Mo - 4.5%-6%
% Si - 0.05%-0.4%
% Mn - 0%-0.5%
% C - 0.01%
% Fe - Balance
Physical
Properties 		Density (g.cm -3) 8.7
Specific Heat (J.Kg-1.˚C-1) 460
Thermal conductivity W.m-1.˚C-1 19
Mean CTE between -50 & +200˚C ˚C-1 12.10-6
Electrical resistivity µΩ.cm 60
Curie Point ᵒC 420
Coefficient of magnetostriction at Saturation ∆l / l - 1-3 x 10-6
Melting temperature ᵒC 1450
Saturation Induction Tesla -
Hardness Hv 325
In Cold worked
condition 		UTS MPa 1050
0.2% PS(Cold Worked) MPa 1030
Elongation % min 3
In Annealed
condition 		Hardness Hv 160
UTS MPa 650
0.2% PS MPa 280
Elongation % 35
Grain Size - 8

Key:

  1. Practical saturation measured for H = 800 A/m.
  2. Remanent induction Br and coercive field Hc measured from H = 80 A/m.
  3. Practical saturation Bs and Remanent induction Br measured for H = 800 A/m.
  4. Measured for H = 4 mA/cm (peak value).
  5. Sinusoidal excitation field H = 4 mA/cm (peak value).
  6. Impedance permeability for B = 0.8 T.
  7. Measurements made on 35X26X0.34 mm ring specimens after annealing in Pure
    & Dry Hydrogen for 4h at 1170°C followed by cooling at 200°C/h.
  8. Practical saturation measured for H=5000A/m.
  9. Core loss W/kg at 1.5T at 50Hz=3.90 max.
  10. Typical operating frequency - 50 hz to 400hz

Dimensions and tolerances:

DIMENSIONS AND TOLERANCE
Outer Diameter (mm) Tolerance (mm) Inner Diameter (mm) Tolerance (mm) Height Tolerance (mm)
< 10 ± 0.4 < 10 ± 0.3 ± 0.3
< 25 ± 0.5 < 25 ± 0.4 ± 0.4
< 50 ± 1.0 < 50 ± 0.5 ± 0.5
< 80 ± 1.25 < 80 ± 0.75 ± 0.8
< 100 ± 1.5 < 100 ± 0.8 ± 0.8
< 160 ± 2.0 < 160 ± 1.3 ± 1.5
< 200 ± 2.5 < 200 ± 1.5 ± 1.5
< 320 ± 2.5 < 320 ± 2.0 ± 2.0
NOTE: General Cutting gap tolerance will be ± 0.5mm

Applications

Current measurement for:
  • Automotive
  • Aerospace
  • Medical
  • Renewable energy

Testing

As a standard practice PML checks Toroidal core (before cutting) for magnetic properties by tracing the B-H properties of the core itself. Below are results of a sample core

Sample Core Geometry
  • Outer Diameter - 160 mm+/-2mm
  • Inner Diameter - 110 mm+/-1mm
  • Height - 30 mm+0.2 /- 0.0 mm

Application Toroidal core Hysteresis Loop Diagram

Ind Pk(T) Permeability Loss/kg (Wt) H EffPk (A/cm) H RMS (A/cm) Ind RMS (T) Hc (A/cm) Br (T)
0.1 127150.24 0 0.0083 0.0059 0.0672 0.0019 0.02
0.2 144038.48 0 0.0134 0.0095 0.1378 0.0073 0.0868
0.3 158385.11 0 0.0188 0.0133 0.2102 0.0125 0.1708
0.4 164657.89 0 0.0242 0.0171 0.277 0.0166 0.2839
0.5 115868.36 0.0061 0.1674 0.1183 0.352 0.0204 0.3449
0.6 41492.51 0.015 0.3746 0.2649 0.4307 0.024 0.3815
0.636 14717.2 0.0183 0.4492 0.3176 0.4591 0.0253 0.3947
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