# Transformer with Multiple Primary Windings

Discussion in 'General Electronics Chat' started by whitbuzben, Apr 8, 2014.

1. ### whitbuzben Thread Starter New Member

Apr 8, 2014
2
0
Dear Sirs,

I was wondering if it would be possible to have a transformer with multiple primary windings that would allow two different voltages (lets say 11kV and 6.6kV) to be connected on the primary side. There would then be a single output on the secondary side of 33kV.

Presumably you would have two unconnected primary windings (one with 6.6kV across it and the other with 11kV across it). You would then series connect the two secondary windings with the turns ratio selected such that the voltages add to give 33kV. Does this sound logical.

Any advice would be much appreciated.

Many Thanks

2. ### #12 Expert

Nov 30, 2010
16,690
7,330
There are ways to do this. It's a design problem. Adding windings to the core and putting them in series with each other, in various combinations is done all the time. I don't believe YOU are going to do this, but it's possible, except for the part about connecting an 11kv winding to a 6.6kv winding and having them add up to 33kv. The method is well known. You just need to know the math.

3. ### PRS Well-Known Member

Aug 24, 2008
989
35
I'm not sure what you propose to do with this, but there is a way to get 33kV from either primary winding. You have to use two independent secondary windings. One to work with the 11kV winding and the other to work with the 6.6kV winding. Each primary would be associated with a particular secondary winding and only one circuit could be used at a time. The unused primary would have to be disconnected from its source.

4. ### whitbuzben Thread Starter New Member

Apr 8, 2014
2
0
Hi guys

Thank you for your responses. I believe that this is done in combined cycle thermal power plants where the gas turbine and steam turbine generators feed one transformer with two primaries having different voltages and different MVA ratings. The secondary then produces a single voltage for transmission. #12 perhaps you could elaborate for me on how this would actually be achieved (possibly a diagram might help).

Many Thanks