cable size

On the right of the screen see "Searach This Forum'. There are many answers to this question.

Use Ohms Law. If you can not work out this problem, you do not have the experience to be working on this project. Get someone to help you.

It is true. If you don't have experience, it is better to get some one to do it for you. Don't take the risk as it involved High Voltage of 11KV. Any voltage above 1000 V, you need to have the charge-man or someone who qualified to handle these projects.

Anyway, 1^st you got to use the power formula to calculate your total current of your motor.

Formula : P= V x I x 1.732 x P.F (0.85)

Current (I) = Power/(V x 1.732 x 0.85) = 2,000,000 / (11,000 x 1.732 x 0.85)

Motor Current (I) = 132.5 Amp

Now, look into the Cable data's books and search for the "Current Rating for 8.7/15KV Armoured XLPE cable" table.

You have to decide what cable to used. If it is a single core cable or 3 core cable. Look at the table and find your motor current there and on the left column you will find the cable size.

For example, your motor rated is 132.5 amp and in the current table, there is no single core cable for 132.5 Amp but the next value is 50mm sq. which is able to withstand 235Amp.

For the 3 core cable, there is a cable of 25 mm sq that has the capacity of 145 amps laying in air and 140Amp laying in the ground. Now you have to decide whether this cable is suitable to use or not as your faults level and your voltage drop is not included in this initial calculation.

The next value is 35mm sq where the cable can carried the current of 175A in air and 170A in ground.

After you have decided what type of cable to use and the sizes, then, with the cable sized you need to check again at the "Electrical Characteristics for the armoured cable" In this table it has the AC resistance, Reactance and Capacitance value for single core and 3 core.

These values will determine the voltage drop of your cable by the formula.

For AC circuits, where AC resistance and inductive reactance are considered, the following is the IEEE Std 141 exact voltage drop formula.

where:

Vd = Voltage drop (Line to Neutral)

V = Voltage (source)

I = Current in amperes (A)

R = AC Resistance

X = AC Reactance

distance (L) is considered from the Resistance & Reactance Tables

where Ohms per unit / 1000 * L in same unit = R or X

θ = Angle of Phase Offset = Arc Cosine (device or circuit Power Factor)

Line to Line is computed by Line to Neutral VD / Sqrt(3).

You have to consider the "Correction Factors for Various Basic Ambient Temperature" table for your cable.

You see it is not easy to do all these calculation as you need an expert to do it for you.

According to Calculation of Simon, I propose you should use copper cable 75mm sq.