Common Mode Current
To calculate common mode current produced by the , click the Calculate Common Mode Current
button in the lower-left corner of the Source form. The Voltage
option button must be selected for the Calculate Common Mode Current
button to be visible, and the Voltage spectrum must have been calculated for the
Calculate Common Mode Current button to be enabled.
The time domain common mode current waveform is displayed
in the upper graph on the Source form and its frequency domain spectrum is
displayed in the lower graph.
Common mode current amplitude equals the Voltage amplitude
divided by the impedance of the capacitance entered in the Capacitance-to-Ground
text box on the Source form.
The common mode current amplitude shown on the Source form
graphs is the amplitude that is produced if the common mode impedance of the
circuit to which the Source is connected is zero, i.e. the amplitude shown on
the Source form graphs is the worst-case maximum. To the extent the common
mode impedance of the circuit to which the Source is connected (, , and
) is non-zero, the common mode
current from the Source will be lower than the amplitude shown on the Source
form graphs. The common mode impedance of the connected circuit appears in
series with the Source capacitance-to-ground, so common mode current for the
complete circuit may be less than the common mode current the Source is capable
of generating. For example, if the common mode impedance of the connected
circuit is equal to the impedance of the capacitance-to-ground, the common mode
current for the complete circuit will be one-half the amplitude shown on the
Source form.
EMI Analyst automatically corrects common mode
current to take into account the impedance of the circuit (Filter, Conductors, and Load) connected to the Source.
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