Electronics > Beginners
EI375 steel laminate primary transformer calculation
gkmaia:
If there are any transformers experts here I would love to learn more about how to wind the primary of my transformer to suit 220v without saturation.
The basic thing is it has to be the EI357 laminates/coil former.
If I could get some help to fill these values and understand them that would be great.
I am using to calculate my primary http://dicks-website.eu/coilcalculator/index.html
Maximum magnetic flux density in core: Bmax = 1.3.
I do not know the BSAT so I am going for an average. Is it ok?
Effective cross section area of one core: Ae = 1900mm2
The core has 10/10/19mm
Effective permeability of the core: μe = Dont know how to get those values bellow
μr = relative permeability of the core material.
le = effective length of the magnetic path in the core
g = length of the air gap (measured in same unit as le)
Inductance factor for one core: AL = 230 nH/n²
Value has been collected from TECH11 pdf attached.
Jwillis:
BSAT and Effective permeability are dependent on core material.Core material greatly determines the maximum flux density of the magnetic field.
gkmaia:
I believe core material is silicon steel. But that is all I know.
Jwillis:
The relative permeability is around 5000–10,000 for silicon steel and 1.5 Tesla at 50Hz.
First off we need the parameters of you transformer
Power rating
Voltage levels (primary and secondary)
Currents on both sides
Primary and secondary coils wire diameter/size
Iron Core area
Numbers of turns (primary and secondary)
Calculate core area Ai=1/4.44fBmTe
Ai= area of core
F= operating frequency
Bm= magnetic flux density
Te= turns per volts
So we can say that Te=1/4.44fBmAi assuming its single phase . 3 phase would omit the 4.44
Total number of turns = turns per volts x primary side voltage
VA rating = (Vs x I)/0.8
Primary current = I1= VA / Vp
So to prevent over saturation I1 = VA/ (efficiency x Vp) Typical efficiency of EI transformers is around 80-95%
Copper has a current density approximately 2.3 A per mm square
Current Density= I/A I being the primary amperage and A being the copper area. so Primary conductor size is A1=Primary Amps/Copper Current Density =minimum size of conductor in mm approximately.edit: this may be wrong
gkmaia:
--- Quote from: Jwillis on August 04, 2019, 05:07:59 am --- The relative permeability is around 5000–10,000 for silicon steel and 1.5 Tesla at 50Hz.
First off we need the parameters of you transformer
Power rating
Voltage levels (primary and secondary)
Currents on both sides
Primary and secondary coils wire diameter/size
Iron Core area
Numbers of turns (primary and secondary)
Calculate core area Ai=1/4.44fBmTe
Ai= area of core
F= operating frequency
Bm= magnetic flux density
Te= turns per volts
So we can say that Te=1/4.44fBmAi assuming its single phase . 3 phase would omit the 4.44
Total number of turns = turns per volts x primary side voltage
VA rating = (Vs x I)/0.8
Primary current = I1= VA / Vp
So to prevent over saturation I1 = VA/ (efficiency x Vp) Typical efficiency of EI transformers is around 80-95%
Copper has a current density approximately 2.3 A per mm square
Current Density= I/A I being the primary amperage and A being the copper area. so Primary conductor size is A1=Primary Amps/Copper Current Density =minimum size of conductor in mm approximately
--- End quote ---
Thanks so much Jwillis. I really appreciate your help. Your answers are bellow.
Power rating
2W @ 110v
Voltage levels (primary and secondary)
Primary 110V
Secondary A 2.9V
Secondary B 15V
Currents on both sides
Primary current 0.018A
Not 100% precise about the secondaries so I will base it on primary ratio.
Secondary A 0.59A
Secondary B 0.13A
Primary and secondary coils wire diameter/size
Secondaries 32AWG
Primary 38 AWG
Iron Core area
10mmx10mmx19mm
1900mm2
F= operating frequency
60Hz
Maximum magnetic flux density in core: Bmax
1.5 Tesla
Numbers of turns (primary and secondary)
I will have to unwind it to get these values. But before doing that would be good to know where are we heading so I can make sure I understand what our goals are.
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