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# 7. A factory has an average demand of 520 000 units per week.

### Resolved Question:

7. A factory has an average demand of 520 000 units per week. The
maximum demand is 25 MVA at 0.8 power factor and the minimum
power factor of 0.6 occurs when the demand is 11 MVA.
The factory is charged at 2.5 pence per unit with a surcharge of 0.2 pence
per unit for each 500 kW by which the maximum demand exceeds
18 MW and a further surcharge of 3% (of charge, plus surcharge) for
every increment of 0.05 by which the minimum power factor falls
below 0.8.
There is a large drive which operates continuously and is powered by an
induction motor with draws 2 MW at a power factor of 0.8 lagging.
This motor is replaced by a synchronous motor which draws the same
power but runs at a power factor of 0.8 leading.
Assuming the maximum demand penalty does not change
(i) Show that the maximum demand power is 20 MW.
(ii) Show that the total weekly charge for the factory is £19 219.20.
(iii) Calculate the new power factor and reactive penalty charge when
demand is 11 MVA.
(iv) Show that the new total weekly cost is £17 644.50.
(v) If the synchronous motor costs £250 000, calculate the time required
to recover the cost of the motor.
Submitted: 5 years ago.
Category: Homework
Expert:  akch2002 replied 5 years ago.
Thanks for request. Kindly indicate dead line for replying this question.
Expert:  akch2002 replied 5 years ago.
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Expert:  akch2002 replied 5 years ago.
I have seen that you floated some questions on DC motors, alternators etc but these questions remained unreplied. If you want answers to these questions, kindly raise separate thread to each question and I will try to reply as these are electrical engineering questions.I can help you with electrical engineering questions. Thanks.