# Simulation step size dt

The simulation step size dt is defined in the dialog box Simulation Parameters in the menu Simulation.
As a rule of thumb, set dt 10 to 100 times smaller than the fastest transient you want to simulate.

Low frequency applications
For a 3-phase controlled rectifier operating at 50Hz you can choose the step size to be 40 times smaller than the period of the voltage.
Tperiod equals 20ms, so select as a rule of thumb dt=100µs.

High frequency applications
SMPS with a switch frequency of 100kHz and a time response of 1ms. Tperiod equals 1/100kHz = 10µs. No initial condition has to be used. 50µs < 1ms, so select as a rule of thumb dt=100ns:

Highest switching frequency | FS = |  | kHz
Calculate dt |  |
Simulation step size 10 steps per period | dt = |  | µs = |  | ns
Simulation step size 20 steps per period | dt = |  | µs = |  | ns
Simulation step size 50 steps per period | dt = |  | µs = |  | ns
Simulation step size 100 steps per period | dt = |  | µs = |  | ns
Reset form |  |  |  |