Mains Voltage Power Transformers


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Mains Voltage Power Transformers

Series and Parallel Connections in transformers. 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 may occur.

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 free.

Series and Parallel transformers

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 magnetized.

Center Tap Transformer

A more accurate reference on transformers is below ...