Figure 28. Effect of short RL time constant

(3) The waveshapes illustrated in Figure 29 are those produced

when a square wave is applied to an RL circuit having a longtime

constant in respect to its duration time. The time constant used in

this circuit is 10 times the period of one complete input cycle, or

20 times the duration time. Since each halfcycle represents only 5

percent of 1 time constant, the current, resistor voltage (Figure

29D), and the inductor voltage (Figure 29C) changes are practically

linear. The resistor voltage starts each cycle at a slightly higher

value, and the inductor voltage starts at a slightly lower value,

until a point is reached where ER varies equally above and below the

average value of the applied voltage, and EL varies equally above and

below zero. These waveforms are illustrated by the dotted lines in

Figure 29.

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