I'm a TA trying to convert a physical transformer circuit design that uses a transformer kit to an LT Spice simulation for some students who need practice but cannot attend my physical lab due to health concerns.
The physical lab uses a Function Generator set to 20 Vpp and 60 Hz with a 2 to 1 step down transformer. The idea is to use oscilloscope probes to measure voltages at points to determine their transformer kit's parameters. The students have to use Vb to determine the primary side current I1.
I tried implementing this in LT Spice following guides posted in the documentation for LT Spice and was getting the same voltage at point A as I was getting at point B, which I know shouldn't be the case due to the voltage drop across the DC resistance and windings of the primary. I'm getting 20 Volts for the measured voltages at points A and B. I'd really appreciate any advice on how to properly implement this in LT Spice.
Best Answer
Your source has a frequency of 60 Hz and your primary inductance is 2 mH which has an impedance of 0.75 ohms at 60 Hz hence, more than 99.9 per cent of the applied voltage appears across the 100 ohm series resistor R2. Try making the primary inductance more like 2 henry if you want to model an AC power transformer. 2 mH is waaaayyyy too small and it gives the impression (although not absolutely true) that A and B voltages are identical.