# Percent Voltage Drop

### Help Support Engineer Boards:

#### Rajan

##### Member

To find the voltage drop percentage for 1 phase and 3 phase, do we divide both by 480V?

#### Sam_

##### Member
3Ø - 480:

Vd-Value * sqrt(3)
480

1Ø - 277/480

Vd-Value
277

#### akyip

##### Member
To be a bit more clear and accurate about 3-phase voltage drop, you have to be consistent about whether you are using line-to-neutral or line-to-line voltage drop.

If you are doing line-to-neutral voltage drop, you have to calculate as a percentage of the source line-to-neutral voltage (e.g. 277 V).

If you are doing line-to-line voltage drop, you have to calculate as a percentage of the source line-to-line voltage (e.g. 480 V).

So that means you can't mix and match L-N and L-L voltage. Meaning you cannot do a line-to-line voltage divided by 277 V or a line-to-neutral voltage divided by 480 V in this problem.

#### Rajan

##### Member
To be a bit more clear and accurate about 3-phase voltage drop, you have to be consistent about whether you are using line-to-neutral or line-to-line voltage drop.

If you are doing line-to-neutral voltage drop, you have to calculate as a percentage of the source line-to-neutral voltage (e.g. 277 V).

If you are doing line-to-line voltage drop, you have to calculate as a percentage of the source line-to-line voltage (e.g. 480 V).

So that means you can't mix and match L-N and L-L voltage. Meaning you cannot do a line-to-line voltage divided by 277 V or a line-to-neutral voltage divided by 480 V in this problem.
As Sam replied:

1) 3Ø - 480:

Vd-Value * sqrt(3)
480

2) 1Ø - 277

Vd-Value
277

3) What about 1Ø - 480?
Is this formula below correct for 1Ø - 480?
To calculate for Vd-value, do we use 1Ø formula?

Vd Percent= Vd-Value X100
480

#### Rajan

##### Member
3Ø - 480:

Vd-Value * sqrt(3)
480

1Ø - 277/480

Vd-Value
277
Hi Sam,

1) 3Ø - 480:

Vd-Value * sqrt(3)
480

2) 1Ø - 277

Vd-Value
277

3) What about 1Ø - 480?
Is this formula below correct for 1Ø - 480?
To calculate for Vd-value, do we use 1Ø formula?
View attachment 23158
Vd Percent= Vd-Value X100
480

Replies
1
Views
276
Replies
1
Views
194
Replies
7
Views
486