Explain why old and new batteries should not be connected in parallel. [4] Tests

Question

Explain why old and new batteries should not be connected in parallel. [4] Tests were conducted to determine the internal resistance of an old battery. It delivers a current of 1 A when a resistance of 10 Ohm is connected across its terminals. It delivers a current of 0.505 A when a resistance of 20 Ohm is connected across its terminals. Determine the internal resistance of the battery and its open circuit voltage. [6] The unipolar stator windings of a stepper motor are supplied power from a 12V DC source. Each winding has a resistance of 0.8 Ohm and an inductance of 20 mH. Draw the drive circuit using a BJT and explain the function of the freewheeling diode. [5] Calculate the winding time constant [1] Calculate the external resistance to be connected in series with each winding to reduce the time constant by 50%. Explain the drawback of this method of minimizing the time constant. [3] Sketch the wave shape of the winding current before and after adding the external resistance. [4] If 180 pulses/s are to be applied to complete one revolution, determine the angle of advance per step. [2]

Explanation / Answer

a)

You know the Batteries change their parameters according to age/cycling/temperature/brand/model ect (example lead acid batteries)

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