Hi,
can I connect the primaries of 2 transformers to the same main outlet as shown in figure?

Thanks

 

yes, don't forget to fuse the input line.

 

Yes, Ideally separately fused and not exceed 1800Va total.
Max.

 

It depends what the ratings are for your outlet and transformers. The transformers must not draw more current than the maximum the outlet can safely provide.

 

Yes you can... just make sure to verify with a voltmeter that the polarity of each transformer is as shown in your figure.

 

Forgot to add, the transformers are rated for 3A each.

 

Also, you can add transformers in parallel in case you need more current

 

Also, you can add transformers in parallel in case you need more current

Only if they are identical transformers.

 

Only if they are identical transformers.

A very important detail that I forgot to mention... thanks for clarifying...

 

A very important detail that I forgot to mention... thanks for clarifying...

And phased right!
Max.

 

Also, you can add transformers in parallel in case you need more current

I am bit confused - isn't the way I have added them in parallel? Do you mean the secondaries can be connected in parallel? In the figure above the secondaries on are series, right?

 

Ok, thanks.

One more question, can I add 2 primaries in series with ratings of 110/40V and 110/12.5 to reduce the voltage coming out of the 110/40V transformer? I will be using only the output from the 40V secondary.

 

I am bit confused - isn't the way I have added them in parallel? Do you mean the secondaries can be connected in parallel? In the figure above the secondaries on are series, right?

Yes, in your figure the secondaries are in series. AND if you need more current, you can add parallel transformers to that array. Under the condition that they're identical and phased right, as has been already stated.

 

Ok, thanks.

One more question, can I add 2 primaries in series with ratings of 110/40V and 110/12.5 to reduce the voltage coming out of the 110/40V transformer? I will be using only the output from the 40V secondary.

What's the output voltage that you'd like to obtain ?

 

I am bit confused - isn't the way I have added them in parallel? Do you mean the secondaries can be connected in parallel? In the figure above the secondaries on are series, right?

Your diagram shows the DC in series, if you connect the secondaries (AC) in parallel or series , you will have to phase them correctly.
Not necessary when connecting series or parallel on the DC side.
Max.

 

What's the output voltage that you'd like to obtain ?

I would like to reduce to about 28V on the secondary.

 

Your diagram shows the DC in series, if you connect the secondaries (AC) in parallel or series , you will have to phase them correctly.
Not necessary when connecting series or parallel on the DC side.
Max.

Would this eliminate the need for 2 rectifiers, since the secondaries are center tapped, I could create a virtual ground on the dc side.

 

You will need to series up one half of one secondary and wire it in series with the other 12.5 to get close to the 28vdc.
Wire them up in SERIES and measure the voltage, if less that 12.5v, swap one pair, then connect to a Bridge rectifier and the caps.
It should result in around 26-28v.
Presuming you want a single supply?
Max.

 

You will need to series up one half of one secondary and wire it in series with the other 12.5 to get close to the 28vdc.
Wire them up in SERIES and measure the voltage, if less that 12.5v, swap one pair, then connect to a Bridge rectifier and the caps.
It should result in around 26-28v.
Presuming you want a single supply?
Max.

The primaries are in parallel and the secondaries are in series but we use only half of one secondary.

So we get 12.5V + 6.25V = 18.75V ac.

DC = 18.75 * 1.41 = 26.5V

In this case does it matter if the transformers are not identical?

Thanks

 

In this case does it matter if the transformers are not identical?

Thanks

No, just that the Va rating applies to the lower rated one.
Max.