Notes on Transformers

by Gary - K4FMX


I ran across a handy formula for finding transformer low frequency cutoff with different impedance matches. This can be handy when using a mod transformer that is rated at a certain primary and secondary impedance, on different impedances (same ratio of course). This will tell you how far you can go before you start to lose the low frequency response.


f low = (rg x Rl)/[2pi x Lp(n squared x rg + Rl)]

Where: f low = -3db point
rg = generator source resistance
Rl = secondary load resistance
Lp = primary inductance in henries
n = the turns ratio Ns/Np
x means multiply (times)


Another thing in the same book:

Transformer saturation is observed on an oscilloscope as gross distortion of the secondary wave form from the applied source. A transformer that saturates at 15 volts at 6 Hz will saturate at 150 volts at 60 Hz.





8 June 2003