Can Transformers Create a 90 Degree Phase Shift?

[eng90]

I am learning about transformers and from everything I've read I can see how its possible to create a 180 degree phase shift by winding the primary and the secondary in opposite directions. What I wanted to know was if it's possible to make a 90 degree phase shift with a transformer.

 

[berkeman]

I am learning about transformers and from everything I've read I can see how its possible to create a 180 degree phase shift by winding the primary and the secondary in opposite directions. What I wanted to know was if it's possible to make a 90 degree phase shift with a transformer.

Welcome to the PF.

Not really. With a basic transformer you get either in-phase or opposite-phase in the transformation from primary to secondary.

That said, you can do some things with reactive impedances to give other phase shifts at selected frequencies, but you can do that without the transformer as well.

 

[gsal]

Another typical shift is that 30 degrees that occurs with 3-phase transformers when the primary is Y-connected and the secondary is delta-connected.

 

[SSWheels]

This isn't quite what you're referring to, but you may be interested in this anyway...

Look up Scott-T transformers to see how standard 3-phase power (where each of 3 AC waveforms lags another by 120 degrees) can be transformed into 2-phase power consisting of 2 AC waveforms that are separated by 90 degees.

Here's one site:
http://electricalnotes.wordpress.com/2012/05/06/scott-t-connection-of-transformer/

 

[eng90]

Thanks, I couldn't see how it was possible to get anything other than a 180 degree phase shift.

I'll definitely look into those Scott-T transformers.

 

[Scott McKie]

Thanks, I couldn't see how it was possible to get anything other than a 180 degree phase shift.

I'll definitely look into those Scott-T transformers.

There is a way to create your required 90 degree phase shift; and that is to first connect a capacitor in parallel with the primary input winding of the transformer. This will create a resonant tank circuit with a specific resonant frequency. Now connect a second capacitor (or capacitors) in parallel to the secondary transformer output winding. This creates a second resonant tank circuit. The second capacitor (or capacitors) has to be sized so that the second resonant frequency matches the first resonant frequency. The closer the frequency match, the closer to 90 degrees the resultant phase shift will be.