Transformer secondary windings

T

tomato

Member
Location
NY
Occupation
Retired bus mechanic
Can somebody explain about the secondary winding on a pole transformer going to a house. Is it 120 total across the coil with a neutral center tap?. Or does it start at zero and make its way to 120 across the coil.
 
We are allowing this thread, it is for educational purposes and not "how to"
 
As normally connected, and shown in @ron 's diagram, there is a 240V coil with a center tap. The RMS voltage from either 'hot' end of the coil to the center tap is 120V. So you get 120V 'hot' to neutral and 240V 'hot' to 'hot'.

-Jonathan
 
To add, the center-tapped 240v secondary is electrically identical to two separate 120v secondaries that are wired in series.

Most utility transformers are made with two 120v secondaries that can be connected in series (for the 120/240v we're discussing) or in parallel (for 120v with full capacity).
 
ron said:
View attachment 2574737
Click to expand...
So if the phase starts at leg 1, being positive, 120 volts,it will go to leg 2, building up and reaching 240 volts. then, it starts the other half of the phase by reversing its polarity going back to leg 1 on a negative polarity starting with 120 volts on leg 2, until it reaches leg one at 240 V negative polarity?. It’s really not that important that I totally understand this, I was a New York City transit Authority bus mechanic for 30 years and we always worked with DC current. This A/C is really interesting stuff.and lethal. The more I keep learning, I find out the more I don’t know.Thank you for all of your replies.
 
Since it is all technically theory, there is no "right or wrong" way to look at it, but I think you may find this easier. Start at the neutral which is your reference voltage meaning it is zero. The sine wave representing voltage goes positive or up to the peak of A then goes down (negative) back to and through zero to a negative peak of B, then back up (positive) to zero and repeats.

To throw a wrench in it, 120 volts isn't the peak, it is 170 volts or 120 volts time the square root of 2, because sometimes the voltage is greater than 120 and sometimes it is less than 120. So it was decided that they would rate AC as the equivalent work done by DC.
 
You must log in or register to reply here.
Top