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
Upvote • 48 upvotes by Saurabh Suman, Mohit Nanda, Amit Raul, (more)
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
For e.g.: Normal household supply is of 220 V, Supply voltage in high tension wires is of 11KV, 22KV, etc.
Want Answers30
Comments1+
Write Answer
11 ANSWERS
30 WANT ANSWERS
11,195 VIEWS
EDITS
Anuj Sharma
Anuj Sharma
Upvote • 48 upvotes by Saurabh Suman, Mohit Nanda, Amit Raul, (more)
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
