RL CIRCUIT Step and Pulse Response
Cuthbert Nyack
The RL circuit is shown schematically above with the alternating source replaced by a
fixed source.
If a unit step voltage is applied to the RL circuit, then the voltage as a
function of time is given by V(R) = 1 - e-Rt/L. and
V(L) = e-Rt/L.
The inductor voltage is shown in green and the resistor voltage in red.
If the voltage is reduced to zero after time T, (switch moved from
a to b) then the response is shown below.
For 0 £ t £
T the response is Vr = 1 - e-Rt/L
For T < t £
¥ the response is
Vr = e-Rt/L ´
(eRT/L - 1 )
For t < T , Vl + Vr = 1 and
fot t > T , Vl + Vr = 0.
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COPYRIGHT © 1996 Cuthbert A. Nyack.