The firing angle progresses smoothly through intermediate values rather than jumping abruptly between the target speeds. This gradual transition is achieved by the UPDATE_RATE and UPDATE_STEP parameters, which incrementally adjust the firing delay every two AC cycles by 50μs. The smooth ramping prevents mechanical shock to the motor and driven load, reduces audible clicking or thumping noises, and minimizes current transients that can otherwise trip overcurrent protection or cause voltage flicker.

Figure 6-8 shows the output current behavior when changing speed from off to low mode. The motor current is increased smoothly as the motor accelerates.