Mains Voltage Power Transformers
Battery Eliminators, Power Packs and Mains
Adapters etc. are names given to products that are
made to provide a DC supply from the Mains Supply.
Even in Equipment like a computer or radio a power
supply block is required. Step down 50/60 Hz
transformers are used to give isolation from mains
and to obtain a lower voltage. SMPS designs are
more popular as can give more power in a smaller
size and dont heat up. Mains Power Packs with 50Hz
Transformers are still popular for audio and some
product safety sensitive applications, as they are
more isolated, reliable and EMI-RFI
Supplies Section - ideas on how
Transformers are used in making Power Supplies and
Low Frequency Power Transformers are used to step
down mains voltage of 230V or 110V to safer
voltages like 12V and 6V. The core is made of
laminations of a Conditioned Alloy of Iron. The
windings are Enameled or Insulated Copper Wire.
They provide both Isolation and Safety while
Scaling the Voltage and Power.
In Switch Mode Power Supplies the Transformers
and Cores are High Frequency
Coils Transformers in SMPS.
Series and Parallel Connections in
Observe the Dot-Polarity. When windings are in
parallel the current capacity doubles. When windings
are in series the voltage doubles. (or adds up).
Wrong dot polarity in series connection just
cancels the voltage and a small residual imbalance
voltage remains. If wrong polarity connection is
done in parallel, then a short circuit or overload
Hysteresis - Charles Proteus Steinmetz - See
how he made the Hot Transformers and Motors Run
Mains Adapter 230V AC 50 Hz to Rectified DC
- How is a small power transformer used to
Center Tap Transformer
This is when you need to build a symmetrical dual
supply like +12V and -12V supply for an opamp
design. This is also good for a two diode full
wave rectifier. But when you make a dual supply
use a bridge and the center tap is ground.
If you use just two diodes then one winding may
be loaded more than other. That may not be good
for long term transformer life. The core may get
A more accurate reference on transformers is
Hook Up Data on Transformers from Hammond
Types of Transformers
- Split bobbin assures product safety
- Easy Cabinet or Panel mount
- Wires for connection-termination
- Mechanically Sturdy, use 'lock nuts'
- Easy replace on service.
- Panel-Cabinet Mount.
- Clamp Serves as Shield.
- Split Bobbin Insulation.
- Mount on PCB and Solder.
- More Reliability, no-wires.
- Winding slip not possible.
- Make Modular supply card.
- High Efficiency
- Low Heat inside box
- Low Profile and space
- Long Life and low EMI
Transformers Made by Hammond
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