Transformers in Multisim: Building a 240V to 15V Full Wave Rectifier

[nnis13]

Is there a normal transformer(not the center tapped transformer) in multisim that i can use to built a full wave recifier that will transform 240V @ 60Hz AC to 15V @ 60Hz AC.I am not very familiar with analog circuits and multisim and i cannot seem to find one.

If anyone can help, he/she is welcomed.

 

[Live2Learn]

You don't need a rectifier to transform AC to AC. You probably mean 240 AC rms to 15 Volts DC. If this is the case then your secondary winding should produce a sine wave whose peak voltage is 15 volts or equivalently, a sine wave whose rms voltage is 15 divided by the square root of 2.

I think a center tap is necessary for a full wave rectifier using 2 diodes. Unless you want to use a bridge rectifier requiring 4 diodes. In this case you do not need a center tap. If all you have is a transformer with a center tap then use that transformer without anything connected to the center tap.

 

[nnis13]

You don't need a rectifier to transform AC to AC. You probably mean 240 AC rms to 15 Volts DC. If this is the case then your secondary winding should produce a sine wave whose peak voltage is 15 volts or equivalently, a sine wave whose rms voltage is 15 divided by the square root of 2.

I think a center tap is necessary for a full wave rectifier using 2 diodes. Unless you want to use a bridge rectifier requiring 4 diodes. In this case you do not need a center tap. If all you have is a transformer with a center tap then use that transformer without anything connected to the center tap.

I am sorry i mean a full wave bridge rectifier and not a full wave rectifier.
I tried putting a center tapped without connecting the ground but it doesn't work.

 

[Live2Learn]

The disadvantage with using a bridge full wave rectifier is that the negative side of the bridge is a "hot ground" relative to the AC ground (neutral) and these two grounds cannot be connected. You could be inadvertantly connecting these two grounds through an oscilloscope connection. If this is the case than you'll have to use two separate scopes with separate ground connections. I know it would be convenient to use only one scope to probe the AC input to the bridge on channel A and probe the rectified full wave signal on channel B but I don't see an easy way to do this.

 

[nnis13]

The disadvantage with using a bridge full wave rectifier is that the negative side of the bridge is a "hot ground" relative to the AC ground (neutral) and these two grounds cannot be connected. You could be inadvertantly connecting these two grounds through an oscilloscope connection. If this is the case than you'll have to use two separate scopes with separate ground connections. I know it would be convenient to use only one scope to probe the AC input to the bridge on channel A and probe the rectified full wave signal on channel B but I don't see an easy way to do this.

I have builded the circuit(bridge rectifier) with the center-tapped transformer without connecting the ground to the center tap and is working, but is there a normal transformer in multisim that i can use in order to achive the same result.

I haven't found any so far.
If anyone can help , he is welcomed.

By the way thanks Live2Learn for the info

 

[sophiecentaur]

Why do you want to use a centre tap with a bridge rectifier? It's not necessary. Just use a single secondary winding, connect it correctly to the bridge and you will get what you need.

 

[nnis13]

Why do you want to use a centre tap with a bridge rectifier? It's not necessary. Just use a single secondary winding, connect it correctly to the bridge and you will get what you need.

Yes that is exactly what i want to do, but i can't find one in multisim.
I you know the reference code of one please post it here.
Thanks for replying by the way.

 

[sophiecentaur]

Multisim should be able to cope with just not connecting the centre tap (as suggested above). Why not try that?

 

[nnis13]

Multisim should be able to cope with just not connecting the centre tap (as suggested above). Why not try that?

Yes i already said that i have done that, but i have to do the circuit with a normal transformer in order to show the difference in circuit design between the 2 circuit models.
(It's an assignement)

 

[sophiecentaur]

You miss my point. What is the difference between a centretap transformer with the centre tap disconnected and a transformer without a centre tap?

 

[nnis13]

You miss my point. What is the difference between a centretap transformer with the centre tap disconnected and a transformer without a centre tap?

I think it's you the one who is missing the point. I know there is no difference ,but i have to make this assingment with a normal transformer, do you understand now or not.

 

[sophiecentaur]

I understand - and so should any teacher who has given you the assignment, that they are the same so why should you need to include a 'special' transformer that has no centre tap? Leaving out the centre tap produces just what you want. Have a bit of confidence and, if necessary, explain what you have done. The result will be correct. Who could complain?
Simulations are supposed to be there as our servants- not as our masters.

If that's not good enough then do the full analysis without the simulation. It 'used to be' quite possible.

 

[Live2Learn]

I think the assignment may be challenging you to research the procedure for creating a custom component within multisim.

Check out:

http://zone.ni.com/devzone/cda/tut/p/id/3173"

I would approach this by copying the information of the existing transformer (the one with the center tap) and seeing what changes I can make to create the custom transformer.

Perhaps a quick and dirty solution is to edit the symbol information to get rid of the center tap.

Let me know how it goes, I too am interested in learning how to do this because many real world transformers have more than two windings and several taps.

 

[sophiecentaur]

Would we be having the same conversation if the task were to use a potentiometer with the wiper disconnected in place of a fixed resistor? How would we deal with a multitap transformer of the kind that used to be used to adjust for various European mains voltages?
As an exercise in electrical theory it is pretty trivial and not worth getting worried about so, I agree, it may be meant as a programming challenge.