ECN Forum Forums General Topics of the Trade General Discussion Area Electrical Abbreviations

Hi

I am studying to be an electrician and keep coming across various abbrevitions that i dont fully understand. Please could somebody explain to me what the following abbrevitions mean.

Uo
Uoc
Ib
In
Iz
It
P

also are there any books that focus on electrical calculations,abbreviations etc

Vo= Volts out, or output
Voc= Open circuit voltage
Ib= current in "B" phase
In= current in neutral
It= total current
P= power
Z=impedance(not sure about Iz)

Iz is the current flow through an impedance.

Hi there topsparks, and welcome to ECN.

I see from your profile that you're in London, which from the abbreviations you are quoting I take to be London, England and not London, Ontario.

The current references listed have specific meanings according to the British IEE, and the subscripts they use aren't particularly logical:

Ib = Design current of circuit

In = Rating of protective fuse or circuit breaker

It = Tabulated current rating of cable, i.e. the basic cable rating from the tables

Iz = Rating of cable in specific situation, i.e. after the application of correction factors for temperature, grouping, etc.

You can see some notes and worked examples relating to these at this link: http://www.tlc-direct.co.uk/Book/4.3.9.htm

The adoption of the symbol U for voltage is another of those amendments the IEE made to "harmonize" with common European standards. A subscript "o" is commonly used to refer to a nominal level, hence the use of Uo to refer to the nominal supply voltage.

Interesting, Paul.
Thanks for the explanation!

topsparks,Welcome to ECN, mate!.
Anymore abbreviations that you are unsure of, or anything else related to electricity?.

hi all

thanks for the nice warm welcome, ive been reading these forums for some time and am very impressed so i thought it time to join.

pauluk you are right i am in london england .
when you say design current, is that the maximum amount of current for that circuit or the estimated current flow

Redsy Uo and Uoc are with a U and not a V, does it mean the same thing = Volts?

in a domestic installation i assume Uo would be the voltage at each socket/light etc, but with or without load?

open circuit voltage i assume to be the voltage without any load(not swithed on)but measured where?

Thanks everyone for the input, exactly what i wanted, just a few bits that i need to clear up.

cheers

Topsparks,

The nominal voltage is simply the voltage that you write on signs and design appliances for. In the UK it's 230V or 230/400V. It cannot be measured, but in theory it is without load on the panel (consumer unit).


If there is no load, there is no voltage drop and the voltage will be the same everywhere.

For some reason, U appears to be used for voltage and V for potential in Europe. The Americans use V for both, I think.


[This message has been edited by C-H (edited 09-26-2003).]

V is used in North America—while some older references use E, as in E=IR.

Here are two definitions of nominal voltage:

A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.

and

Voltage by which an installation or part of an installation is designated.

{Why is it I always have to go back and edit my posts? Why can't I write it right the first time? }

[This message has been edited by C-H (edited 09-26-2003).]