Can you work this out

[lofty84]

what is the maximum permitted voltage drop of a cable supplied from 400v three phase.

a.11.5v
b.6.9v
c.20v
d.12v

I know the answers c but I dont know what the formula is to get there.

does anyone know

 

[Notsosmart]

Thus nominal voltage for 3 phase which used to be 415V is now 400V

5 % of 400 is 20 but each line is 240 so its 12 volts

(230v) Yes but the implication is that the load is distributed across three phases so the 20Volt stands.

 

[Guest123]

The OP reads "a cable supplied form 400V three phase" i.e a three phase load so I stand by my previous post.


Also 12V is incorrect anyway as ALL calculations are based on the nominal Uo of 230V = 11.5V.

 

[Risteard]

Yup I know, anything up to about 256V.

It shouldn't exceed 253V. (230V +10%/-6%)

 

[pevvers]

It shouldn't exceed 253V. (230V +10%/-6%)

Yeah, but it was just a voltage from the top of my head, and I have seen it that high.

 

[Risteard]

Yeah, but it was just a voltage from the top of my head, and I have seen it that high.

Not disputing that you encountered it - just pointing out that they shouldn't be transmitting that voltage!