I want to measure the wire/cable size to determine the cross-sectional area like mm2 or AWG. How I should take the measurement or know what is size of wire...

Thank you for your kind assistance.

 

AWG stands for American Wire Gauge. This can be found in any Machinery's Handbook, Engineering Tables Book, any shop tools & measurement supplier like Mitotoyo, Brown & Sharpe, L.S. Starret etc. or a Mechanical Engineer's handbook. or search the website under "AWG". The circular mils can be found in any electrical handbook also.

 

Respondng to M. Abdul Raheem's Apr 13 query. Assuming the cable is
3-phase, then:

1) Make a reasonable determination of the circuit length (L) of the cable, in meters.

2) Make a reasonable determination of the temperature (Ta, °C) of the environment in which the cable is located (air, ground, etc):

3) Assuming "load" is disconnected, then short-circuit one end of the cable. Make three Ohm-measurements from the opposite end. Determine the
average phase-phase resistance (Ra) of the three wire pairs, A-B, B-C, & C-A (or R-S, S-T, T-R).

4) Convert the resistance above by the following relationship,
R@20° C = Ra x [ 254.5 / ( 234.5+Ta) ] x [ 2000/L], in Ohms/km

5) Then wire-size area is calculated as,
mmq = 17.2 / R@20°C

Please note:
The above procedure is valid for copper conductor material. But, the formula ignores adustments for "stranded' conductors. The "worst-case"
multiplier is (ca.) 1.12.

Alternative Method.
A method is available using current injection. Contact me if you are
interested.

Regards,
Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected])

 

Dear Raheem,
Wrap the wire say 10 turns or 50 turns (depending on guage), closely spaced, on say a pencil. Then measure the total length and divide by number of turns.

If the guage is 'low' enough, the dia can be measured with a vernier. This is assuming that proper wire gauges are not available for measurement.

Otherwise wire gauges are available which have holes punched through them. The wire can be inserted through the correct hole and wire guage can be found out.

Tomy Zacharia

 

Dear Phil Corso, PE

I too wanted to know the way of measuring the conductor size by physical means. For a circular conductor I use to measure the diameter of the conductor using a vernier. Then based on this dia, i used to calculate the cross sectinal area of one conductor. Then I multiplied with the No. of strands to obtain the total cross sectional area of that core. I am not sure if I am right.

Similarly for stranded conductor (sector shaped), I used to insert a lug (whose size has been embossed in terms of Sq.mm in the lug itself)Then based on the freeness/ closeness with the lug size that fits in that core condcutors, I used to identify that cable as 35 SQ.mm or 50 Sq.mm and so on. Though I have my doubts hereto, i adopt this practice as my senior guided me this way. Whats more interesting is that I find for the same size, If I take a copper lug the id is different than the alu. lug, though the embossed sizes over the lugs indicate the same size. Please note that I am talking about alum. condr, armoured LT UG cables and the lugs I am talking abut are for crimping and not soldering types.
Can U please calrify what is the correct method of measuring the size of cables.

 

Responding to Ramesh's Dec 18, 5:00pm query... If your question is "What is the alternative method", then:

Par 3) Instead of using an ohmmeter, connect each pair of conductors to a stable DC source, say 5-10 V, and measure the current. Calculate the average current for the three phases. Using Ohm's Law (for the uninformed an 'ohm is an Englishman's 'ouse) calculate the resistance.

Par 4) Because the material is aluminium, change the factor 254.5 to 248.0, and the factor 234.5 to 228.0.

Par 5) Change factor 17.2 to 28.3.

Ramesh, please note... this method is approximate because there is no way to know the impact of the twist-factor. But, if you are working with commercial metric wire sizes, the procedure should be adequate. Please keep us informed of your progress.

Regards,
Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected])