Interactive simulation
DC motor start-up simulation
Switch it on with the shaft stopped and nothing but the winding resistance limits the current.
Power is applied at t = 0 with the shaft stopped; the run plays once and then holds on its final operating point — move any control or press Restart to run it again. With ω = 0 there is no back-EMF, so the only thing standing between the supply and the winding is R: the current climbs toward V/R with the electrical time constant τ = L/R. Torque follows the current, the rotor accelerates, and the back-EMF Ke·ω it generates eats the supply voltage from the inside — the current collapses to whatever the friction and the load actually need, over the mechanical time constant τ = J·R/(Kt·Ke + R·B). That first peak is why a motor blows a fuse that its running current would never trouble. Raise the load torque past the stall torque Kt·V/R and the shaft never moves: the inrush simply never ends. Ke = Kt = 5 V/1000 rpm = 0.0477 V·s/rad here, viscous friction is fixed at 20 µN·m·s/rad.
