Can Anyone Help with These Electrical Engineering Exam Questions?

[Sam Newmo]

Hello all,

A 4th year apprentice here studying like mad for his final exams, have a few questions that have me stumped.

If anybody could please help it would be much obliged!

I have done most of the questions, though it would be good to check against some answers.

Here goes:

1) A 3 wire, star connected generator is supplying a balanced star connected oven. The phase voltage of the generator is 400v. Each phase of the generator is supplying 10A.

a) Phase voltage of the load?
b) Value of line current?
c)Total power consumed by the load?
d) Resistance of each phase of the load?2) A 3 phase,11kv/415v 250kVa transformer operates at .88PF LAG at full load.

a) Determine the full load secondary current?
b) Output power?3) You do a max demand for a 3phase, 400v installation, and determine the MD is 375A per phase. For this load, what is the minimum kVa transformer that may be used?4) A voltage divider network consisting of a 12kΩ and a 1.5kΩ resistor connected across 24v. The output is taken across the 6.8kΩ. (Doesnt make any sense to me? Maybe a spelling mistake in the question?)
Calculate the voltage across the 1.5kΩ resistor under no load?

b) If the value of the 1.5.kΩ resistor rises, what does the voltage across the 6.8kΩ resistor do?Please help!

Thanks in advance!

Sam

 

[berkeman]

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