CABLE SIZE CALCULATION
{Fg - Grouping Factor ( From A7(h) If more than one circuit}
Example:- If Connect load is 6KW, 2 C PVC non-armoured cable cliped on wall, ambient temperature is 40 C and Power factor is 0.85.
If Load is Single phase
Load Current Ic = Ic = P/V * p.f. = 6000/1.732 * 0.85 = 30.6A
Circuit Break Size = 32A ( Next One Higher Value)
Cable Size = CB x 1.15 /Ft * Fg = 32 * 1.15/0.87*0.85 ( From above Table the value of Ft and Fg )
= 49A
From A7(c) Cable Size = 2C x 10mm2 ( One next higher value)
Voltage Drop Calculation
Ic x L x ( mV/A/m)
Vd = ----------------------
1000
From Table A7(a) for 70 C Thermoplast PVC non-armoured Cable "mV/A/m = 18"
So 30.1 x 22 x 18
Vd = ------------------- = 7.9 so %age Vd = 7.9 /230 = 3.4 % ( which is less than 4% nominal Value)
1000
- ALWAYS REMEMBER {LOAD <CB< CABLE}
- Calculate the Demand Load or Connected Load Ic = P/1.732 * V * p.f.
- Choose the Next Size of Circuit Breaker In = ( CB =Ic).
- Cable Size = (CB x 1.15) /(Ft *Fg)
{Fg - Grouping Factor ( From A7(h) If more than one circuit}
 |
| Grouping Factor |
 |
| Temperature Correction Factors |
 |
| mV/A/m - VALUES |
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| Power Factor Calculation |
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| Voltage Drop Calculation |
Example:- If Connect load is 6KW, 2 C PVC non-armoured cable cliped on wall, ambient temperature is 40 C and Power factor is 0.85.
If Load is Single phase
Load Current Ic = Ic = P/V * p.f. = 6000/1.732 * 0.85 = 30.6A
Circuit Break Size = 32A ( Next One Higher Value)
Cable Size = CB x 1.15 /Ft * Fg = 32 * 1.15/0.87*0.85 ( From above Table the value of Ft and Fg )
= 49A
From A7(c) Cable Size = 2C x 10mm2 ( One next higher value)
Voltage Drop Calculation
Ic x L x ( mV/A/m)
Vd = ----------------------
1000
From Table A7(a) for 70 C Thermoplast PVC non-armoured Cable "mV/A/m = 18"
So 30.1 x 22 x 18
Vd = ------------------- = 7.9 so %age Vd = 7.9 /230 = 3.4 % ( which is less than 4% nominal Value)
1000
