# confused about maximum current on ac mains

Discussion in 'General Electronics Chat' started by nepdeep, Dec 19, 2012.

1. ### nepdeep Thread Starter Member

Sep 14, 2011
139
0
Hi,
1. What is the maximum current delivered by the electric mains supply?
2. If I use the transformer to step down 220 to 20 for example...how do i determine the maximum current at primary and secondary side...let us say secondary side is connected to caps and regulator...do we consider the output current from the regulator as the current on secondary side..

bit confused with no hints....please enlighten me

2. ### mkbutan Senior Member

Sep 30, 2008
270
16

as you said it the TRANSFORMER
It depends on the TRANSFORMER Winding the rating are mention on every Transformer
say 250μA/500μA/.../1A/2A/5A and so on.......

3. ### MrChips Moderator

Oct 2, 2009
12,227
3,280
The maximum current delivered by the transformer will depend on the size and construction of the transformer. If you provide the model number and the rating that is written on the transformer we may be able to better inform you.

As an example, let us say the transformer steps down from 220VAC to 20VAC. This is approximately 10:1 reduction.

Then if the transformer is rated at 1A on the secondary, the primary will take 0.1A.

That is, power in is equal to power out for a 100% efficient transformer.

4. ### nepdeep Thread Starter Member

Sep 14, 2011
139
0
thanks for the suggestion...i still didnot get...what is the maximum current our mains can supply...does it depend on transformers rating...for eg...if ..just if...the transformer is rated with maximum current 10[A] on primary and our setup is 220 V to 22 V and current is 100A on primary and 1000[A](??really) on secondary side....can our mains ac supply deliver that current...??

what is the maximum current ratings of our 220V mains??

5. ### MrChips Moderator

Oct 2, 2009
12,227
3,280
These are two separate issues:

1) How much current the transformer can supply

2) How much current can your mains AC supply deliver.

The answer to (2) is easy. Go to your fuse box and look at the rating on the fuse or circuit breaker.

If the rating is 40A, then the maximum power delivered before blowing the fuse is 220V x 40A = 8800W.

Now to answer (1), 8800W = 20V x 440A.

Can the transformer deliver 440A?
That would have to be a mother of a transformer - read: a very big transformer.

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6. ### mkbutan Senior Member

Sep 30, 2008
270
16

ha ha ha
that MOTHER TRANSFORMER with 440A will blow up my state (GOD SAVE US)

I think Mr. Nepdeep is not asking the right Question?????
or he must be asking how much Current he can draw from his MAIN's (METER)
which I think is about 20A-50A then Mr. Nepdeep can take about the same current for his Transformer

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7. ### nepdeep Thread Starter Member

Sep 14, 2011
139
0
Mr.Chips...that is exactly what i wanted to know....i was not sure if i was clear about my question....but thanks a lot...every word provides answer to my curiosity...and as per the mother thingy....i just wanted to konw the ideal values....may be like you said 400A rated transformer doesnot exist...thanks...again..

8. ### BReeves Member

Nov 24, 2012
412
64
Look on the power pole outside your house, that big round thing is a ~400 amp transformer

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