Help finding Mesh current with LTspice

Discussion in 'Homework Help' started by loneclock, Oct 16, 2012.

  1. loneclock

    Thread Starter New Member

    Oct 2, 2012
    4
    0
    I am confused on how to get the mesh current i1, i2, i3 in the picture from the branch currents generated by LTspice.

    Here is the circuit:
    Note the top resistor is 10kohms.
    http://imgur.com/KvoHf&MKr0y&dGfzl

    Here is my results:
    --- Operating Point ---

    V(1): 16.4166 voltage
    V(n001): 20 voltage
    V(2): 10.0987 voltage
    V(3): 12.1718 voltage
    V(n002): 10 voltage
    I(R6): -0.000217177 device_current
    I(R5): -0.00336624 device_current
    I(R4): 0.000207305 device_current
    I(R3): -0.000424482 device_current
    I(R2): -0.00315893 device_current
    I(R1): -0.00358342 device_current
    I(V2): 0.000217177 device_current
    I(V1): -0.00358342 device_current
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,716
    4,788
    Write the relationships between the mesh currents and the device currents and then solve for the mesh currents in terms of the device currents.
     
    loneclock likes this.
  3. loneclock

    Thread Starter New Member

    Oct 2, 2012
    4
    0
    Thanks, Is there no way to specify for the mesh currents on LTspice?
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    See the attachment.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,716
    4,788
    Not really, because simulators work with device currents and mesh currents are fictional abstractions to convert what would otherwise be a rather ad-hoc set of system equations into a very regimented set.

    For exterior meshes, you may be able to identify devices that only have a single mesh current in them. In this case, they are equal in magnitude but may have the opposite sign. For interior meshes, each device will normally have two (but can have many more) mesh currents flowing through it.
     
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