Answer Posted / shirish

Theory for Cable Sizing.
From Ohms law, the voltage drop in an electrical conductor is
V = I R
where
I = Current, amps
R = Resistance, Ohms

The electrical resistance can be derived from the properties of the conductor material.
R = ρ L / A
where
ρ = Resistivity, Ω mm2 /m
L = Length, m
A = Cross sectional area, mm2
Watch the units in the above equation.

The resistance can also be expressed in terms of the material conductivity (ψ) which is just the reciprocal of the resistivity.
R = L / (ψ A)

Table 1. Typical material electrical conductivity
Material Conductivity, ψ
Copper 58
Aluminium 36
Mild Steel 7.7

Combining Ohms law with the resistance expression, we get.
V = (I L) / (ψ A)

Now, we can define an acceptable voltage drop in a conductor. I have calculated the voltage drop that was used in several published tables and get around 5.5 Volts.
We could therefore re-arrange this equation to give the cable size. But cables come in standard sizes measured in mm2. In addition, you also need to consider the maximum current for each cable size.

Table 2. Conductor sizes and maximum currents
Cable Size, mm2 1.5 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300
Maximum current, A 13 21 28 36 46 61 81 99 125 160 195 220 250 285 340 395
So, the theory is relatively simple, let us now see how to use the program.

how to calculate the loss tangent of electrical cables

2035

---

How to calculate the time setting for star connection in star delta starter? For example 10KW 3PH Induction motor.

2596

---

sir,in our plant we r using SATEC PM172E power reading meeters in HT panel side it is monitoring the MB data smart viewer(sever).but last one week we did not get readings inthe server only available in meeter.tell me how communicate meter and server. and also what steps we take for checking.

2196

---

What is difference and reason b/w -48V BTS system and 24 V BTS system. Plzzzzzzzzz tel me.

2190

---

When a square wave is applied to primary of a transformer then what will be output wave form of secondary ?

2054

---

how to generator maintenance (A Check, B check,Etc)

2267

---

how works inductive &capacitive sensors?

1935

---

Usage of flywheel diode in relays

1886

---

WHAT IS THE DIFFERENE IN ACTION OF MCB,MCCB,RCCB

2390

---

What is the technical difference between On delay timer and a Star delta timer?

1584

---

why asa method ZPF method is more accurate than ASA method?

5775

---

How to size Air Circuit breaker (ACB)? What is the most important factors?

2205

---

we have 15 ampere variyac but we want 30 ampere variyac what we do

1898

---

what is breathing?

1779

---

132/66kv sub-station procation ?

2231

---