voltage drop.

[ELZ4742]

evenin all!

could someone perhapes explain why, in the volt drop tables (mv/a/m) they give you 3 options - R X Z. which one dya use ?

also is design current the current capacity of the cable?

been too long...

 

[ricicle]

The 3 figures quoted are for the resistance, reactance and impedance components of the volts drop.Without the need for complex maths you can use the largest figure which give you a worst case scenario.

 

[ELZ4742]

is that based on 1m length on said cable?

 

[rlc]

is that based on 1m length on said cable?

Yes the quoted values are based on normalised values of 1 for current and unit length i.e per amp per meter - this equates to 18milli - ohms per meter of resistance for a 2.5mm^2 from the table....

so for a 2.5mm^2 :

1m @1A = 18mV drop
1m @ 2A = 36mV drop

or

[email protected] = (28.4 * 18E-3) * 3.6 = 1.84Volt drop (A-B)

in circuit analysis terms the cable represents a lumped resistance equalling 0.5112ohms:

_____VdropA-B
A......<----------........B
-->---|======|-------

 

[securespark]

mV/A/m.


You take the volt drop reading, multiply it by the design current and the circuit length, then put it all over 1000 to give volt drop for the circuit.

Eg, you have 10.5kW shower running 25m. Is 10mm² cable OK, assuming no other correction factors?

10.5kW = 45.65

45.65 x 25 x 4.4 (? off the top of my head)
--------------------
1000

Equals: 5.02V dropped, which is within 4%.

 

[securespark]

Bah!!

 

[rlc]

Bah!!

.....Used to express impatient rejection or contempt

???

 

[bernardgreen]

Bah!!

.....Used to express impatient rejection or contempt

???

Actually old chap, its is what posh sheep say

 

[ELZ4742]

lol

thanks for that fellas