6.FOR OPERATIONAL CHARACTERISTICS

FOR RESISTANCE

r_p= L_mtpT_p/a_p

  Where =0.021 H mm²/m

                d=mean diameter of primary =265.825mm

                 L_mtp=length of mean turns of primary= d = 835.11mm

Now, r_p=((0.021*835.11)/1.5393 )*2310 = 26.317 ohm

For secondary winding, r_s= L_mtpT_s/a_s

   d_s=mean diameter of LV =192.38mm

   L_mts= d_s = 604.37mm

 r_s= ((0.021*604.37)/70.8)*50 = 8.96 *10^-3ohm

 Total resistance refers to primary winding

   R_p  = r_p + r_s(T_p/T_s)²

        = 26.317 +8.96*10^-3(2310/50)² = 45.44 ohm

PU resistance = (I_p*R_p)/ V_p

                        =(3.787*45.44)/11000 = 0.0156 ohm

5.DESIGN OF HIGH VOLTAGE WINDING

Primary line voltage (V_l)=11000v                           

For high voltage delta side,primary phase voltage V_p=11000

Number of turns per phase of primary,T_p=(V_p/V_s)*T_s

                                                                         = (11000/250)*50

                                                                         = 2200 turns

Tapping ±2½%, ±5½%

Total number of primary turns for providing tapping=1.05*2200

                                                                                                =2310 turns

Selecting cross-over type of winding(from table)

Now, for cross-over type:

             Number of coil=voltage level / (800 to 1000)

                                        =11000/845 ≈13

Using  12 separate coils ,

  Number of turns per coil =2310/12 = 192.5 turns/coil

   Voltage per coil = 11000/12 =916.66 volt/coil

Taking 15 layers per coil

   Turns per layer =192.5/15 =12.83 13 turns per layer

 25 turns for first 10 layer and 27 turns for remaining  5 layers

High voltage winding current (phase current)

              I_p =125*10³/3*11000 =3.787A

Current density for LV winding = 2.35A/mm²

Taking current density of HV winding 10% greater than LV winding =1.1*2.35

                                                                                                                     =2.585A/mm²

Now, Area of primary conductor,a_p=I_p/

                                                                =3.787/2.585 =1.464mm²

For cylindrical conductor ,a_p= d²/4

                                                d= _p/

                                                   =1.365mm

From table :

Taking conductor of diameter,d=1.4mm(bare conducter)

From table: selecting a conductor of fine insulated cover having diameter=1.575mm

Now,modified  area of insulated conductor = d_new ²/4

                                                                                         = ²/4

                                                                                          = 1.5393 mm²

Actual value of current density =3.787/1.5393 = 2.46A/mm²

Axial depth of one coil = 15 * 1.575 mm

                                          =23.625mm

Total axial depth of HV winding

        L_cp=no of coil *axial depth of one coil +spacing *no of coils

             =12*23.625+12*5

              =305.7mm

Clearance,on each side of winding ,=(Height of window - L_cp)/2

                                                                  =55.65mm

Let the insulation between layers =0.3

Radial depth of HV winding =15*1.575+14*0.3

                                                    =27.825mm

Thickness of insulation between LV and HV winding

I.e. width of duct ,a=5+0.9*kv

                                =5+0.9*11 =15mm

Inside diameter of HV winding =(outside dia of LV winding +2*15)

                                                         =238.08mm

Outside diameter of HV winding =( inside dia of HVwinding +2*47.475)

                                                            =238.08+2*47.475

                                                               =333.03mm

Overall dimension

    Width of frame ,W= (2*D+a) = 0.7815 m

     Height of frame,H= H_w+2*H_y = 0.73 m

4.FOR DESIGN OF LOW VOLTAGE WINDING

No of turns /phase ,T_s= (v_s/ph)/E_t

                                        =(433/ )/5.031

                                        50

Secondary phase current ,I_s= (125*10³)/(3*433/ )

                                                  = 166.62A

Area of secondary conductor ,a_s= I_s/ _s

                                                          =166.62/2.35

                                                           = 70.92mm²

Using helical winding and considering 4-strips in parallel with two layer having 25 turns each layer.

We have, area of each strips = 70.92/4

                                                     = 17.73 mm²

From table: with nearly equal area taking the dimension of each strip 6.5*2.6 mm²

Total area of conductor = 6.5*2.6*4   =67.6mm²

Actual current density , _s= 166.67/67.6

                                               = 2.465mm²

Taking insulation 0.5mm

The dimension of each strip =7mm*3.1mm

Axial depth of one turn =2*7+1

                                           =15mm

Radial depth of one turn = 2*3.1+1

                                              =7.2mm

For helical winding ,taking one extra turn in axial depth

Total turns per layer =25+1= 26

Total axial depth of Lv winding ,L_cs= 15*26

                                                              =390mm

Now, clearance of each side winding  = (Ht of winding –L_cs)/2                                                                              

                                                                  = (417-390)/2 = 13.5mm

As minimum clearance is 6mm, thus the arrangement is acceptable .

Total radial depth of Lv winding (b_s)  =No of layers *Radial depth of each turn +

                                                                       Insulation between layers

                                                                    =2*7.2*0.5

                                                                     =14.9mm

inside diameter of LV winding = d+2*thickness of insulation betⁿ core &winding

                                                       =174+2*1.5

                                                        =177mm

Outside diameter of LV winding,d_outer=d_inner+2*Radial depth of LV

                                                                   =177+2*14.9

                                                                    =207mm

Mean diameter of LV winding =(d_inner + d_outer )/2

                                                        =(177+207)/2

                                                         =192.15mm

Mean length of LV winding =  *d_mean

                                                  =192.15*

                                                   =603.65mm