Transformer Design Intro Core Material
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Design on SMPS Transformer (Topology and Material Selection)
Typical locations where cores are used
Core Material • Purpose of the core is: – To reduce the magnetizing current. (For topologies such as Forward, Bridge etc we need the magnetizing current to be as small as possible. For fly-back topology, though the magnetizing current is used to transfer energy, the size of the transformer will be very large to get the required inductance if a core is not used.) – To improve the linkage of the flux within windings if the windings are separated spatially. – to contain the magnetic flux within a given volume – In magnetic amplifier applications a saturable core is used as a switch.
Core Material • Different types of material used for cores – Iron – Silicon Steel – Nickel-Iron – Iron-Cobalt – Ferrite – Molybdenum – Met-glas
Core Material • Salient characteristics of a core material are – Permeability – Saturation flux density – Coercive force – Remnant flux – losses due to • Hysteresis • Eddy Current
B-H loop of a magnetic material
B-H Minor loops
Core Material • The power loss is a function of frequency and the ac flux swing and is given by the equation
• P = K1 * (frequency)K2 * (Flux Density)K3 • Typical power loss for different material are given below:
Material Type Phillips, Ferrite 3C90, µ = 2300 Phillips, Ferrite 3C81 µ = 2700 Phillips, Ferrite 3F3 µ = 2000 Phillips, Ferrite 3F4 µ = 900
Loss (mw/cm^3) 110 220 120 10 @ 200 G,500 KHz 180 @ 1000G,100KHz 1600 @1000G,500KHz
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type
Loss (mw/cm^3)
EPCOS, Ferrite N27, µ = 2000
231.5
EPCOS, Ferrite N67, µ = 2100
68.57
EPCOS, Ferrite N87, µ = 2200
50.7
Met-glas, 2714 AS
105
Met-glas , Powerlite, C core
840
Met-glas , Micolite µ = 245
560
Met-glas , Micolite µ = 270
630
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type Moly Powder Permalloy µ = 12
Loss (mw/cm^3) 870
Moly Powder Permalloy µ = 60
360
Moly Powder Permalloy µ = 200 Magnetics , Material K µ = 1500
1440 110
Magnetics , Material R µ = 2300
70
Magnetics , Material P µ = 2500
125
Magnetics , Material F µ = 3000
225
Magnetics , Material H , µ = 15000
2200
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type Magnetics Tape wound Supermalloy Magnetics Tape wound Square-Permalloy Magnetics , Material P µ = 2500
Loss (mw/cm^3) 870 360 125
Magnetics , Material F µ = 3000
225
Magnetics , Material H , µ = 15000
2200
Frequency = 100 KHz ; B = 1000 Gauss.
Performance factor
Typical locations where cores are used
Core Material • Purpose of the core is: – To reduce the magnetizing current. (For topologies such as Forward, Bridge etc we need the magnetizing current to be as small as possible. For fly-back topology, though the magnetizing current is used to transfer energy, the size of the transformer will be very large to get the required inductance if a core is not used.) – To improve the linkage of the flux within windings if the windings are separated spatially. – to contain the magnetic flux within a given volume – In magnetic amplifier applications a saturable core is used as a switch.
Core Material • Different types of material used for cores – Iron – Silicon Steel – Nickel-Iron – Iron-Cobalt – Ferrite – Molybdenum – Met-glas
Core Material • Salient characteristics of a core material are – Permeability – Saturation flux density – Coercive force – Remnant flux – losses due to • Hysteresis • Eddy Current
B-H loop of a magnetic material
B-H Minor loops
Core Material • The power loss is a function of frequency and the ac flux swing and is given by the equation
• P = K1 * (frequency)K2 * (Flux Density)K3 • Typical power loss for different material are given below:
Material Type Phillips, Ferrite 3C90, µ = 2300 Phillips, Ferrite 3C81 µ = 2700 Phillips, Ferrite 3F3 µ = 2000 Phillips, Ferrite 3F4 µ = 900
Loss (mw/cm^3) 110 220 120 10 @ 200 G,500 KHz 180 @ 1000G,100KHz 1600 @1000G,500KHz
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type
Loss (mw/cm^3)
EPCOS, Ferrite N27, µ = 2000
231.5
EPCOS, Ferrite N67, µ = 2100
68.57
EPCOS, Ferrite N87, µ = 2200
50.7
Met-glas, 2714 AS
105
Met-glas , Powerlite, C core
840
Met-glas , Micolite µ = 245
560
Met-glas , Micolite µ = 270
630
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type Moly Powder Permalloy µ = 12
Loss (mw/cm^3) 870
Moly Powder Permalloy µ = 60
360
Moly Powder Permalloy µ = 200 Magnetics , Material K µ = 1500
1440 110
Magnetics , Material R µ = 2300
70
Magnetics , Material P µ = 2500
125
Magnetics , Material F µ = 3000
225
Magnetics , Material H , µ = 15000
2200
Frequency = 100 KHz ; B = 1000 Gauss.
Material Type Magnetics Tape wound Supermalloy Magnetics Tape wound Square-Permalloy Magnetics , Material P µ = 2500
Loss (mw/cm^3) 870 360 125
Magnetics , Material F µ = 3000
225
Magnetics , Material H , µ = 15000
2200
Frequency = 100 KHz ; B = 1000 Gauss.
Performance factor
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