typically in a circuit with an inductive load, the current must rise to full value before the volts across the device turning on can fall - so turn on losses are Vbus x 0.5 Iload x time to turn ON x freq = losses, assuming the current ramps up linearly. For resistive load losses = 0.5 times prev example as we assume the volts fall linearly at turn on.
Very similar for turn off losses for turning off an inductive load the volts go up quickly & stay high as the current goes from full to zero -> same formula losses = 0.5 x Vbus x Iload x time to turn off x freq.
ditto for resistive load turn off as turn on, for losses, as the V & I cross over linearly, 0.25 x V x I x Toff time x freq.
hope this helps