Calculate the field current, terminal current and torque corresponding to operation at an armature terminal of 250 V and a load of 250 hp.
A 250-V, 75-kW separately-excited dc motor is used as an adjustable-speed
drive over the range from 0 to 2400 r/min. It has an armature resistance of
42 m. When operated at a speed of 2400 r/min, the motor achieves its
rated terminal voltage at a field current of 4.5 A. Speeds from 0 to 1450 r/min
are obtained by adjusting the armature terminal voltage (up to 250 V at
1450 r/min) with the field current kept constant. Speeds from 1450 r/min to
2400 r/min are obtained by decreasing the field current with the armature
terminal voltage remaining at 250 V. For the purposes of this problem, you
may neglect armature-reaction effects.
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Jorleanderson Maia
JAIME GERARDO CAZAREZ BRICE�O
A biotechnologist wanted to compare the effects of different concentrations of a bacterial inhibitor in a fermentation process carried out by Saccharomyces cerevisiae. For this, 60 tests were carried out and they were divided into 5 treatments of 12 tests each. The first treatment (control) did not add an inhibitor, but the remaining ones were given the inhibitor in increasing doses (up to the maximum possible). After 48 hours of the process, the existing bacterial colony-forming units were counted in each treatment, obtaining the results of the table. Determine the following ... a) Value of Fcal. b) The null hypothesis is accepted or rejected. c) What is the best treatment option, considering the greatest reduction in CFU and the lowest possible concentration of the inhibitor? *
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