What is a Transformer? An Electrical Transformer Tutorial

The basics of how transformers work, where to shop for step down mains transformers, and how to wire one up to mains voltages. European and North American wiring is discussed. DO NOT FORGET TO ADD A FUSE. Finally, a quick example of AC to DC conversion in an unregulated dual rail power supply. Watch the followup video on diodes and AC to DC conversion here:
Example transformer:
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46 thoughts on “What is a Transformer? An Electrical Transformer Tutorial”

  1. That center tap looks like it could come in handy. Could I potentially use MOSFETs to turn DC to AC and step it up at the same time via a center-tap transformer?

  2. the neutral wire is definitely not 0 volts but it's connect to the earth so you would get a shock when you would touch the "live" wire

  3. you said transformer only work on ac what about flyback transformers and a zvs with centre tapped primary through a ferite can run a HV mot

  4. I understand that I can use a transformer to take the output of a pure sine wave inverter to convert 120 vac to 240 vac with a center tap so I can run 220 vac devices.
    However can I take two independent 120 vac pure sine wave inverters and hook them up to a single transformer to produce 220 vac split phase to run 220 vac devices?

  5. In the nearly 6 years since this was made, I'm sure someone's already pointed out that the character from Commando isn't Solly, it's Bennett. Just before he 'lets off some steam'. 🙂 After which, Arnold made his way to 'da choppa'.

  6. Hey Afrotechmods, i have a small transformer in my mobile charger! on the case of charger it says output is 5volts dc and 1amp does that means the transformer transforms 240V ac to 5V ac and gives 1amps?

  7. I notice in the diagram that the diode on the bottom is facing the opposite way. Doesn't make sense to me. Is it right?

  8. How come that the primary side can be plugged into the mains voltage without any current limiting resistor or feedback diode (when unplugging from mains) since it is just a coil. Has it something to do with the impedance of the coil and the voltage being AC? Because to me it just looks like shorting the mains wiring with a coil.

  9. if the input voltage supply changes does the output voltage of the transformer changes to? or the output supply is fixed

  10. Ever since I was a kit transformers had always been a mystery to me! Thank you for the explanation! I got smarter now! **I subscribed**

  11. You warned not to use transformers scalped from other machines (old transformers).  Please explain why.  What do I need to do to look for or watch out for if I want to use them?  Also, I repeated this over and over to hear it, but is the Vout 18 Volts DC after passing thru the diodes and caps?  Do I need to go through a voltage regulator circuit to clean up the Vout @ 18 V DC?  Or is the voltage still AC and needs to go through a bridge rectifier?   Thank you.  Also, I don't have an oscilloscope like you do to check things out.  I have to rely on my multimeter for any readings.

  12. if rhere is no indication on transformer then how to identify in multimeter which one is primary and secondary?

  13. How is a properly rated transformer able to be plugged in straight to the mains without burning up?
    If you just took a straight bit of copper wire of the caliber used in these, I'm pretty sure it would go yellow hot and melt apart, if not trip a breaker first.

    Light bulbs are a small bit of wire, coiled up as well, and look at how hot they get.

    Is it something to do with magnetic impedance? The coil has to be tuned properly to be connected directly to mains? So for example you couldn't use a 10 turn primary because it would be too weak?

  14. If you turn it round, and connect the mains to the secondary, and the scope to the primary, do you just get a puddle of metal?

  15. man I wish you were a friend or a neighbor! …or even better, I could just download your brain into mine…n instantly understand this stuff in detail the way you do…

  16. I noticed you used a 117V on a 120+V mains supply…do you just have to get a transformer rated "close enough" to 120V or does buying a 117V vs a (I don't know) 148V {if that even exist} give you a benefit for heat/efficiency/etc.? …THANKS ..I know I'm a dumb ass…but I'm trying to learn N UNDERSTAND n not just memorize the Lego parts that work because they were already pre built in something else. THANKS AGAIN! ..I know some of my questions may seem stupid at the moment, sorry about that….

  17. isn't the "second" 12V below the ground the -12V?
    So why you don't tell that simply we get +12V and -12V in the output? Do you have any reasons for that?

  18. what about those tiny phone chargers D:. do they use inductors at high frequency instead of huge ones;?

    I would assume they're a rectifier bridge with a switch step down

  19. How come the two waveforms are in opposite polarity in the last setup? What's the factor the influences that outcome?

    Thank you in advance.

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