Lecture19 Examples

Presented by

Robert Trajkovski

Ex 19.1 For the circuit below, a) determine power delivered to the resistor at time t1 through t6 b) Plot the results c) Find the average value of the curve d) Find the energy dissipated by the resistor over a one full period

Ex 19.2 For the circuit below, a) determine power delivered to the inductor at time t1 through t6 b) Plot the results c) Find the average value of the curve d) Find the energy stored or released for any one pulse

Ex 19.3 For the circuit below, determine watts, VAR, VA, and power factor.

Ex 19.4 For the circuit below, a) determine watts, VAR, VA, and power factor. b) sketch the power triangle

c) Find the energy dissipated by the resistor d) Find the energy stored or released fby the inductor and capacitor

Ex 19.5 For the circuit below, a) determine average power, apparent powerr, reactive power, and pf b) total watts, VAR, VA and pf for the system

c) find I

Ex 19.6 For an electrical device rated 10kVA, 208V, and 0.7 power-factor lag. What is te impedance of the device in rectangular coordinates?

Ex 19.7 A 3 HP motor with 0.7 lagging pf and 95% efficiency that is connected to a 480V, 60 HZ supply a) determine the power triangle for the loadb) pf that must be placed in parallel with the load to raise the pf to unityc) determine the change in suppy current from the uncompensated to the compensated systemd) find the network equivalent of the above

Ex 19.8 a) A plant has a 20 kW heating load and 50 kVA inductive load due to a bank of induction motors. The heating elements are considered purely resistive (Fp=1), and the induction motors have a lagging power factor of 0.8. If the supply is 480V, 6-Hz determine the capacitive element required to raise the pf to 0.95 b) compare the levels of I drawn from the supply.

Ex 19.9 a) An air core is connected to a 120V,60Hz souce. The current is 6A, and a wattmeter reads 50W. Find the effective resistance and inductance of the coil. b) A brass core is then inserted n the coil. The ammeter reads 5A and the wattmeter reads 60W. Calculate the effective resistance of the core c) If a solid iron core is inserted in the coil, the current is 3A and the wattmeter is 45W. Calculate the effective resistance and inductance of the coil.

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