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Why AC Needs More Insulation Than DC at Same Voltage Level?

AC Needs More Insulation Than DC for the Same Working Voltage Level

For the same working voltage, the potential stress on the insulation is less than in case of DC system than that AC system. Therefore , a DC line requires less insulation.

In other words A DC System has a less potential stress over AC system for same Voltage level and power rating, this is why AC needs more insulation than DC system?

Why AC needs more insulation than DC for the Same Working Voltage Level?

Let’s explain in detail..

When we talk about DC, let say 220 Volt DC, it means the maximum value (peak value) of the voltage is 220V, but when we talk about 220 Volt AC (As in our home distribution system = single phase AC Supply = 220 V AC or 110V AC in the US), then it is basically 220 RMS (Root Mean Square = √2) value, i.e. it is the RMS value of 220V AC.

The peak value of AC voltage is equal to √2xVRMS = 1.414 x VRMS (where √2 = 1.414)

In other words. The peak value of AC voltage = VRMS / 0.707

Now, in our case, The peak value of 220V AC = 220V/0.707 or 220V x 1.414 = 311V AC peak.

Its mean 220VDC = 311V AC peak. That’s why AC Voltage needs more insulation than DC voltages for the same rating of Voltage and Power.

In addition, 220 Volt AC can reach to its peak value of 220/0.707 = 311V peak. Its Mean 220 Volt AC RMS reaches to 311 Volts peak and again to -311V peak in one hertz (Hz) of frequency (where frequency = cycles/Sec).

That’s why AC needs more insulation than DC.

Click image to enlarge

Why AC needs more insulation than DC?
Why AC needs more insulation than DC?

As shown in the above diagram, RMS value of AC voltage is below than its peak value and we have to provide the insulation for the peak value or maximum voltage, not for the RMS value. And in DC systems, RMS value and peak values of voltages are equal.

Now, you have a clear understanding of the need for more insulation in AC system as compared to the DC system for the same working voltage and power rating.

Moreover, there are more factors in AC voltages like Corona effect, Skin effect etc and we will discuss them in detail in next posts.

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  1. Muhammad Amir says:

    this is why AC needs more insulation over DC system. I ma clear now. Thanks for sharing

  2. James iverson says:

    Thanks for taking the time to discuss this, I feel strongly about it and learning more on this topic. If possible, as you gain expertise, would you mind updating your blog with more information? It is extremely helpful for me. Insulation contractors Calgary.

  3. Electrical Technology says:

    Thanx for Your appreciation. we will do our best. once again thanx

  4. mike bonar says:

    You have added here an interesting question and appreciable answer of it. Thanks for sharing this informative post.

    1. Electrical Technology says:

      Thanx Dear

  5. Tom Hardy says:

    So if I need some extra wiring installed with my insulation? do you offer a service where I can get both done?

  6. Anonymous says:

    Great post. I did not know that ac needed more insulation. Thanks

  7. Anonymous says:

    Why the potential stress on the insulation is less in DC plz reply

  8. Great article. Keep up the good work!

  9. Essam Hassan says:

    Well done (Electrical Technology), but I have here two questions:
    1. Why we normally name the 220Vac as an RMS voltage?
    2. Why we are using (Root Mean Square of 2), why not 4 or 5 or ….. ?

  10. Really awesome! Thanks!

  11. Assalamu alikum brother..i feel so much happy bcoz u r spending ur valubale time for updating these posts..i complited my masters but again in some areas iam so much weak..but by d grace of allah aftr founding ur site most of my doubts r clarified..thanx a lot brother…finally one muslim doing this much good by running this site…keep it up brother…in sha allah i will remember u in my dua always..take care

    1. Electrical Technology says:

      Thank you so much for appreciation…

  12. Armando Medel Trujillo says:

    Excelente información

    1. Vasant Annasaheb Mane. says:

      Thanks for this interesting information.

  13. Vinod yadav says:

    Very good explanation . Thank you sir

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