Discussion in 'Homework Help' started by ElecNerd, Jan 2, 2011.

1. ### ElecNerd Thread Starter New Member

Jan 2, 2011
20
0
Hi People, new to this so thought I would give it a go .

I am currently completing revision for 3 phase theory and in the process am completing some example questions. Due to lack of support/teaching from the lecturer I am having to look a majority of the info up myself...

I am currently trying to calculate the power dissipated in one phase of a Delta connected load comprising of a resistor of 10Ω per phase and a line voltage of 650V. In addition to this I need to calculate the total power dissipated.

Im not really looking for answers as such as thats not going to assist in the long run however I do not have even the basic calculations and formulas for this...

2. ### edgetrigger Member

Dec 19, 2010
133
19
In delta connection line and phase voltage are same. Just v*v/r will give you thw wattage per line. Thrice that is the total power.

3. ### ElecNerd Thread Starter New Member

Jan 2, 2011
20
0
Hi thanks for that does that mean that the calculations are the same as that for a Star connected load then?

Also your formula please could you clarify this for me in terms of the * you have used...sorry for the simplicity

4. ### edgetrigger Member

Dec 19, 2010
133
19
* is multiplication symbol.

It is not same for star connection.

Anyways, the basics are as under

VL is line voltage
Vp is phase voltage

IL is line current
Ip is phase current

For Star Connection

Line current = Phase Current
But Line Voltage VL = √3 Vp

For Delta Connection

Line Voltage = Phase Voltage
But Line Current IL = √3 Ip

5. ### ElecNerd Thread Starter New Member

Jan 2, 2011
20
0
Thanks a lot for your assistance. Am I right in that...

Ip = 650/10 = 65A and therefore
IL = 1.732 x 65A = 112.53A

From this I have calculated the power dissipated within 1 phase (red) as...

650 x 650 / 10 = 42250
Therefore power dissipated in red phase = 42250W

and 42250 x 3 = 126750W = Total power dissipated.

Thanks alot

6. ### edgetrigger Member

Dec 19, 2010
133
19
Yes, it is correct.

7. ### ElecNerd Thread Starter New Member

Jan 2, 2011
20
0
Thanks a lot for all your assistance its appreciated