MULTISIM - timestep too small ??

Discussion in 'General Electronics Chat' started by Huby, Aug 13, 2012.

  1. Huby

    Thread Starter New Member

    Jul 5, 2012

    If you are reading this please take a look at the file that i have attached.

    If anyone else knows solution please be so kind and share it on the forum.

    When i click simulate i get error:

    Would you like to run convergence assistent to attempt to automaticly solve the problem ?.
    I click yes and then i get - doAnalasys --> timestemp to small --> tran simulation canceled.

    What can be the problem and how to define right timestep ?

  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    I don't have a solution for this, sorry. You might be better off at the NI forums. :

    There are surely more people there to help you with MS
  3. crutschow


    Mar 14, 2008
    Timestep errors usually mean the simulator can't get all the nodes to converge to a stable point.

    This can be tedious to solve. Here are some things to try:

    1. For a complex circuit, try simulating portions at a time until you identify the problem area. Sometimes a particular part model will be the problem.

    2. In the Analysis Options, change the simulation mode from Trapezoidal to Gear.

    3. In the Analysis Options, reduce the values of all the tolerance limits by a factor of ten or so. This will reduce the simulation accuracy somewhat but may allow the circuit to converge.

    Good Luck.
    spark8217 likes this.
  4. Huby

    Thread Starter New Member

    Jul 5, 2012
    I get solution from multisim forum and it worked:

    For your simulation, try changing the interactive simulation settings under the Simulate tab. Go to analysis options>>use custom settings and in Customize..., change the RSHUNT value to 1e+006 ohms, The RELTOL to 0.01, and the ABSTOL to 1e-006 amps. This should aid in the simulation of your circuit.

    A note:
    Try not to have unconnected instruments, components, etc. They are all taken into account in the simulation setting and can 'sometimes' cause issues with SPICE. If it's not needed, simply remove it form your design, it might not make a difference right now and it might not affect anything, but it is a chance you would probably like to minimize.
    Now, the question is why i dont get output on my IGBT's?. Any idea ?
    spark8217 likes this.