transformed voltage

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wyatt

Senior Member
just trying to learn. is there and diferance betwen 120v split phase and 240v steped down to 120v. I would think that the wave form would be diferant
 

charlie

Senior Member
Location
Indianapolis
Re: transformed voltage

I don't know what you mean by 120 V, split ? unless you are talking about a 120/240 V secondary from a 1? transformer. If that is the case, you would have 120 V from either ? to the neutral and 240 V from ? to ?.

The other configuration would be a single voltage on the secondary side of the transformer. In other words 120 V from ? to the grounded point. To do this from 240 V, you would use a 2:1 ratio transformer to step down from 240 V to 120 V.

Is this what you are talking about? :D
 

wyatt

Senior Member
Re: transformed voltage

yes this is what I am talking about. If you could see the two on a scope would they be the same or differant this comes from me useing 110v items overseas on a transformer. (I know the Hz is lower) but here there is as I understand it. no EMF on the neturel side the transformed one would have EMF though steped down to 120v
 

charlie

Senior Member
Location
Indianapolis
Re: transformed voltage

They would be exactly the same on a scope. I don't understand the term EMF and how it is used. I am assuming it means electromotive force. The grounded point on either transformer would have no EMF as it is grounded. However, if you are getting away from the Code and talking just theory, grounding or earthing the transformer does nothing for the circuit performance, it is only for high voltage pulses.

I do not really understand what you are asking. :confused:
 

wyatt

Senior Member
Re: transformed voltage

Thanks Charlie don't mean to gaet off track just tryin gto learn a little more I have never been one to be happy knowing that it works but needing to know why.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Semi-Retired Electrical Engineer
Re: transformed voltage

I must advise you that you are not being very clear in expressing your question. From what I think you are saying, you are really talking about three different signals.
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Start with a single phase transformer, with a primary voltage that we don?t need to know. The secondary voltage, from end to end, is 240 volts. Center tap this secondary, and ground the center point. The first signal is from the right hand side of this secondary to the center point (i.e., to the ground).</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">The second signal is from the left hand side of this secondary to the center point (i.e., to the ground).</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Now consider a different single phase transformer. This one has a primary voltage of 240 volts. The secondary voltage, from end to end, is 120 volts. There will be no center tap on this secondary. Connect one end of this secondary to ground. The third signal is from the ungrounded side of this secondary to the grounded side.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">Now connect all three signals to an oscilloscope. Tweak the settings until all three hit the zero voltage point at the same moment in time.

What you will see is that signals one and two will be ?opposites? from each other. One will be going up (positive) at the same time that the other will be going down (negative). The third signal will be identical to signal one (or to signal two, depending on how you did the tweaking).

Does this answer your question?
 

wyatt

Senior Member
Re: transformed voltage

Thanks for your time I'm learning more. In my mind I thought that the 240 to 120 transformer only had a peak voltage of o to 60v with a diferance of 120v between the two ends. and that the other transformer had a 120v from center point to peak and 240v from end to end. and that ther may have been a deferance between the two types. I have a lot to learn, thanks for your inputs
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Semi-Retired Electrical Engineer
Re: transformed voltage

Originally posted by wyatt: I thought that the 240 to 120 transformer only had a peak voltage of 0 to 60v with a difference of 120v between the two ends.
In one sense, you are right about this. There is a voltage of ?0 to 60V? from one end to the center. But for this type of transformer, we do not connect a wire to the center. We only connect wires to the two ends, and we get 120V for our efforts.

As a side note, let me suggest you try to avoid using the word ?peak,? until your training has come along a bit further. That word tempts people to talk about RMS, and the square root of two, and effective DC value, and a host of other terms that you will come to understand in time. Let?s call that a ?homework assignment?: :D Try to find out (from somewhere other than this Forum ? although I know our members would be glad to help) what the difference is between ?peak? and ?RMS.?
 
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