RF = 150 Q R = 0.2055 N I= 48.65 A + + V. = 120 V V. = LF EA 240 V nm = 1500 rpm Field Armature Pout = 15 HP Fig. P6. Full-load specifications for a separately excited DC motor. Recall the basic machine equations EA = Kowm, Tdev (Also, wm KOIA, and P = Twm. 2nnm/60 and 1 HP = 746 W.) %3D + I
Consider the separately excited DC motor shown in Fig. P6, with
the steady-state full-load specifications as indicated. You may assume that the rotational losses for this machine are negligable
(a) Suppose that the motor is operating at rated capacity to help propel a
hybrid electric vehicle up a hill. Under full-load conditions, find the output
torque Tout, the induced voltage EA, field power loss PF , armature power
loss PA, and efficiency η.
(b) Now imagine that the vehicle is descending rapidly on the other side
of the hill, and that physical torque reverses on the motor shaft. The new
value is Tout= -30 Nm (i.e., negative 30 Nm). Determine the power in the
240 V source, and indicate if the source is absorbing or delivering power.
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