PSPICE & Transformers

Discussion in 'General Electronics Chat' started by Management, Oct 5, 2009.

  1. Management

    Thread Starter Active Member

    Sep 18, 2007
    Why is it that I have to always put huge resistors to ground when I am simulating a circuit that has transformers in it?

    When I say transformers I mean the XFRM_LINEAR in the ANALOG library.

    I feel like this may not be giving me the proper results.

    Can anyone comment on why this happens? Is it a glitch or am I not using transformers correctly? My source and loads are properly terminated to ground. Plus I'm not making up circuits but simulating an already proven schematic.

  2. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    It provides a reference to the software so that the calculations can be done.

    If you have a transformer secondary coil with a resistor across it, the current flowing through the transformer from driving the primary coil creates a voltage across the resistor on the secondary side, say Vr. However, because of the isolation of the transformer from the primary side, Vr is floating or not referenced to ground. So, although Vr is defined, Vfloat is not. This leads to an infinite number of solutions...

    I hope I explained it well enough, let me know...
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    It must be peculiar to the spice program. TINA doesn't require the loading.

    I've connected a voltage without referencing ground to the primary and measured across the secondary with the voltmeter ...

    TINA-TI is the free version at Texas Instruments.
  4. Management

    Thread Starter Active Member

    Sep 18, 2007
    Ah I see now. Thanks.