14-2. As a student project, a Dodge Charger is being converted into a hybrid veh
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Question
14-2. As a student project, a Dodge Charger is being converted into a hybrid vehicle which will use a 12kW (-16HP) induction motor in cruise mode. It requires 90VDC for efficient operation. It is intended that it be powered by a bank of 12-V automobile batteries in parallel, each of which has an internal resistance of 36 m (a) For a battery bank of 20 batteries in parallel find Ih, I, Vi, and shunt duty cycle Dp (b) Find the size inductances and capacitances necessary to keep the current ripple at the input and output to less than 5% if the converter is operated at Jc = 60 k (c) If each battery is rated at 100 A-hr, how long may the car run in cruise mode until battery depletion?Explanation / Answer
We shall have to design a boost converter.
P = 12 kW and Vout = 90 V
Therefore, I2 = Iout = P/Vout =12000/90 = 133 A
The motor will be powered by a 12V batteries in parallel.
Req = Equivalent resistance of batteries in parallel = 0.036/20 = 0.0018 Ohms. We can neglect this value, since it is quite small.
V1 = Input Voltage = 12 V for 20 batteries in parallel.
Vout = 90V and R = V2out /P = 0.675 Ohms.
For a boost converter, Vout = V1/D' . Hence, D' = 0.133
Therefore, duty cycle D = 0.8667.
I1= Vout/D'R = 90/(0.133 * 0.675) = 1002.5 A.
iL = Ripple current through inductor = 5% of I1= 5/100*1000=50A.
iL=(V1/2L)*DTS
50 =(12*0.8667)/(2*L*60000)
L = 1.7334 micro Henry.
w2 = 1/LC and w=2f = 376991 rad./s
Substituting the value of L , we get C as 4.059 micro Farad
The car needs 133 A. Each battery can supply 100 A in 1 hr. For 20 batteries,
20 * 100 A-h = 133 * t
t = 15 hours.
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