Power Electronics: Why the voltage supply is always a multiple of 11?
For e.g.: Normal household supply is of 220 V, Supply voltage in high tension wires is of 11KV, 22KV, etc.
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Anuj Sharma
Anuj Sharma
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The form factor of an alternating current waveform (signal) is the ratio of the RMS (Root Mean Square) value to the average value (mathematical mean of absolute values of all points on the waveform). In case of a sinusoidal wave, the form factor is approximately 1.11.
The reason is something historical. In olden days when the electricity becomes popular, the people had a misconception that in the transmission line there would be a voltage loss of around 10%. So in order to get 100 at the load point they started sending 110 from supply side.
This is the reason. It has nothing to do with form factor (1.11).
Nowadays that thought has changed and we are using 400 V instead of 440 V, or 230 V instead of 220 V.
Also alternators are now available with terminal voltages from 10.5 kV to 15.5 kV so generation in multiples of 11 does not arise.
The Basic Idea behind a desired transmission voltage was still the form factor. In ancient times when we needed to use 10 kV at destination, simply multiplied the form factor to it Say 1.11X10=1.11 =11KV aprox.(we had taken 10% losses as standard thumb rule) similarly for 30 & 60 KV.
Form Factor = RMS voltage/Average Voltage For AC sine wave Form Factor is 1.11.
Now a days when, we have voltage correction systems, power factor improving capacitors, which can boost/correct voltage to desired level, we are using the exact voltages like 400KV in spite of 444KV

The First Mobile Phone: Motorola DynaTAC 8000X (1983) 

List of countries by number of mobile phones in use

Rank	Country or region	Number of mobile phones	Population	# of phones as % of population	Last updated date
-	World	Over 6.8 billion	7,012,000,000[1]	87	2013[2][3]
01	China	1,150,000,000[4]	1,349,585,838[5]	85.21	April 2013[4]
02	India	867,800,000	1,220,800,359[6]	70.72	30 April 2013[7]
03	United States	327,577,529	310,866,000[8]	103.9	June 2013[9]
04	Brazil	265,741,000	192,379,287[10]	134.2	June 2013[11]
05	Russia	256,117,000	142,905,200[10]	155.5	July 2013[12]
06	Indonesia	236,800,000	237,556,363	109.28	September 2013[10]
07	Pakistan	125,012,860[13]	178,854,781[14]	69.90	May 2013[15]
08	Japan	121,246,700	127,628,095	95.1	June 2013[16]
09	Germany	107,000,000	81,882,342	130.1	2003[17]
10	Philippines	106,987,098	94,013,200	113.8	October 2013[18]
11	Nigeria	114,000,000	165,200,000	69	May 2013[19]
12	Bangladesh	106,000,000	148,090,000	68	www.btrc.gov.bd,july2013
13	Iran	96,165,000	73,973,000	130	February 2013[20]
14	Mexico	92,900,000	112,322,757	82.7	Dec. 2011[21]
15	Italy	88,580,000	60,090,400	147.4	Dec. 2013[22]
16	United Kingdom	75,750,000	61,612,300	122.9	Dec. 2013[23]
17	Vietnam	72,300,000	90,549,390	79	October 2013[24]
18	France	72,180,000	63,573,842	114.2	Dec. 2013[25]
19	Egypt	92,640,000	82,120,000	112.81	Egypt Ministry of Communications & IT, August 2013[26]
20	Thailand	69,000,000	65,001,021	105	2013[27]
21	Turkey	66,000,000	71,517,100	92.2	2013[28]
22	Ukraine	57,505,555	45,579,904	126.0	Dec. 2013[29]
23	Spain	55.740.000	47 265 321	118.0	Feb. 2013[30]
25	South Korea	52,510,000	48,580,000	108.1	2013[31]
25	Argentina	56,725,200	40,134,425	141.34	2013[32]
26	Poland	47,153,200	38,186,860[33]	123.48	2013[34]
27	Colombia	49.066.359	47.000.000	104.4	2013[35]
28	South Africa	59,474,500	50,586,757	117.6	2013 GSM African Mobile Observatory report [36]
29	Algeria	33,000,000	35,000,000	94.2	2013[37]
30	Taiwan	28,610,000	23,197,947	123.33	September 2013[38]
31	Kenya	28,080,000	42,000,000	71.3	2013[39]
32	Venezuela	27,400,000	28,200,000	98.0	2013[citation needed]
33	Peru	33,000,000	30,000,000	110.0	Oct. 2013[40]
34	Romania	22,800,000	21,438,000	108.5	March 20[citation needed]
35	Canada	26,543,780	34,466,423	74.1	Q3 2013[41]
36	Morocco	36,550,000	31,968,361	113.6	Q1 2013[42]
37	Netherlands	20,000,000	16,515,057	121.1	Nov. 2013[43]
38	Australia	21,260,000	21,179,211	100.4	Jun 2013[44]
39	Saudi Arabia	46,000,000	27,137,000	169.5	Jun 2013[45]
40	Malaysia	30,379,000	28,250,000	106	2013[46]
41	Chile	21,000,000	17,094,270	122.9	Dec. 2013[47]
42	Nepal	18,240,670	26,620,020	68.5	Mar. 2013[48]
42	Ethiopia	18,000,000	85,000,020	21.8	Dec. 2013[49]
43	Guatemala	17,571,895	14,713,763	119.4	Jun. 2013[50]
44	Sri Lanka	17,359,312	21,000,000	80.95	Dec. 2013[51]
45	Ecuador	15,900,000	14,300,000	111.18	Jan. 2013[52]
46	Portugal	13,400,000	10,562,178	126.87	November 2013
47	Hong Kong	13,264,896	7,008,900[53]	187.9	Nov. 2013[54]
48	Belgium	11,822,000	10,414,000	113.6	2013[citation needed]
49	Hungary	11,833,000	10,020,000	118.3	Sept. 2013[citation needed]
50	United Arab Emirates	11,540,040	8,264,070	139.6	Nov 2013[55]
51	Sweden	11,194,000	9,103,788	122.9	(July 2012 est.)
52	Bulgaria	10,655,000	7,600,000	140.2	2008[48]
53	Israel	9,319,000	7,310,000	127.5	2008[48]
54	Denmark	7,000,000	5,543,819	126.2	February 2008[56]
55	Azerbaijan	7,000,000	8,900,000	78.7	November 2009
56	Jordan	6,010,000	5,950,000	101.0	March 2010[57]
57	Singapore	7,289,000	5,076,700	143.5	December 2010[58]
58	New Zealand	4,620,000	4,252,277	108.6	2008[59]
59	Estonia	1,982,000	1,340,602	147.8	April 2009[citation needed]
60	Lebanon	2,720,000	4,224,000	64.4	Oct 2010[60]
61	Lithuania	4,940,000	2,955,986[61]	167.1	End of Q2 2013 (Tentative)[62]
62	Cuba	1,300,000	11,200,000	11.6	December 2011[63]
63	North Korea	2,000,000	24,451,285	8.3	April 2013[64]
64	Panama	6,900,000	3,405,813	202.5	July 2013[65]