Question

Electrical Circuit

A) A factory (with frequency 60 HZ) has the following electrical loads:

Induction motors    of 16 kW at a lagging power factor of 0.8.

Induction motors    of 20 kW at a lagging power factor of 0.7.

Load of 12 KVA at a lagging factor of 0.9. Load of 10 KVAR at a leading factor of 0.8

a-what is the overall power factor of the factory.

b- Assume that the voltage at the input to the factory is 440 V (rms). What is the rms magnitude of the current into the factory.

The factory is fed from a voltage source that is 50 m from the loads. If the source voltage must be

440 ± 3% V what is the minimum wire size (gauge) that you can use? What is the voltage at the source and the power loss on the wires?

b) Now, it is necessary to improve overall power factor of the factory be 0.95 (lagging), so a capacitor load is use. What is the capacitor reactive power and the capacitor value (Farads). What is the rms magnitude of the current into the factory and the minimum wire size(gauge) that you can use (source voltage 440 ± 3% V ) ? What is the voltage at the source and the power loss on the wires?

Assume an energy charge of 2¢ per kWh and a demand charge of $3.50 per kW per month if the power factor is between 0.9 lagging and unity and $5 per kVA per month if the power factor is less than 0.9 lagging. The demand curve (KW) is presented in the graph.

What is the monthly demand cost before and after the power factor improve?

Motor 16 KW

Motor 20 KW

Load of 12 KVA

Load of 10 KVAR

Answer 1