Hi guys anyone knows how to solve the below 3 problems, at least the idea. thanks in the advance.
Delta Load and Current-limiting Resistor with a short-Circuit
4- A 600 V (line-to-line) 3- phase source powers up a balanced delta connected inductive load that has per phase impedance of 0.75+ j6 Ω. If the maximum current through any line must not exceed 450 A:
a. What would be the resistance and the power handling capacity of the resistors that can be used as the current-limiting resistors?
b. Assume the load is a black box with only three terminals available (A, B, and C). How would you connect the current limiting resistors to the load? Explain your answer with a circuit diagram.
c. If the impedance of phase B of the load is short-circuited after the current limiting resistors are connected. Compute the line and phase currents as well as phase voltages. Also compute line to neutral voltages at the load terminals.
d. Use delta-V transformation to change delta connected load to a V-connected load and repeat part ©.
5. For the circuit in Fig. 3 use ZR1 =ZR2 = ZR3 = 75 Ω, ZL1 = ZL2 = ZL3 = 50 Ω, ZC1 = ZC2 = ZC3 = 42.65 Ω, and 30 Ω for each of the three line impedances (Z-line).
a. Compute the line and phase currents (11, Ip1, 12, Ip2, 13, and Ip3) as well as phase voltages (V//, V//, and V//) at the load.
b. Compute the apparent, real, and reactive power at the source as well as at the load.
Explain your results.
c. Use ZC1 = ZC2 = ZC3 = 60 Ω and repeat steps (a) and (B) above.
6. A 30 + j 40 Ω load (Z-load) is connected in parallel with a current limiting device of 750 A with rating of 9.375 MW. A relay controls a switch that connects the source to the load during normal operation. Only if the load impedance is short-circuited the switch disconnects the load from the source and connects the current limiting device to the source. The load carries 250 A of current (1Ioad). If base power PB = 200 KW and base voltage VB = 5000 V, calculate per-unit load voltage, current, power, and load impedance. What would happen to the base values in the following cases?
1-If the load inductance is short-circuited?
2-If Z-load is short-circuited and the relay did not work.
3-If Z-load is short-circuited and a 750 A current limiting device is triggered?
3Phase Problems.doc
Delta Load and Current-limiting Resistor with a short-Circuit
4- A 600 V (line-to-line) 3- phase source powers up a balanced delta connected inductive load that has per phase impedance of 0.75+ j6 Ω. If the maximum current through any line must not exceed 450 A:
a. What would be the resistance and the power handling capacity of the resistors that can be used as the current-limiting resistors?
b. Assume the load is a black box with only three terminals available (A, B, and C). How would you connect the current limiting resistors to the load? Explain your answer with a circuit diagram.
c. If the impedance of phase B of the load is short-circuited after the current limiting resistors are connected. Compute the line and phase currents as well as phase voltages. Also compute line to neutral voltages at the load terminals.
d. Use delta-V transformation to change delta connected load to a V-connected load and repeat part ©.
5. For the circuit in Fig. 3 use ZR1 =ZR2 = ZR3 = 75 Ω, ZL1 = ZL2 = ZL3 = 50 Ω, ZC1 = ZC2 = ZC3 = 42.65 Ω, and 30 Ω for each of the three line impedances (Z-line).
a. Compute the line and phase currents (11, Ip1, 12, Ip2, 13, and Ip3) as well as phase voltages (V//, V//, and V//) at the load.
b. Compute the apparent, real, and reactive power at the source as well as at the load.
Explain your results.
c. Use ZC1 = ZC2 = ZC3 = 60 Ω and repeat steps (a) and (B) above.
6. A 30 + j 40 Ω load (Z-load) is connected in parallel with a current limiting device of 750 A with rating of 9.375 MW. A relay controls a switch that connects the source to the load during normal operation. Only if the load impedance is short-circuited the switch disconnects the load from the source and connects the current limiting device to the source. The load carries 250 A of current (1Ioad). If base power PB = 200 KW and base voltage VB = 5000 V, calculate per-unit load voltage, current, power, and load impedance. What would happen to the base values in the following cases?
1-If the load inductance is short-circuited?
2-If Z-load is short-circuited and the relay did not work.
3-If Z-load is short-circuited and a 750 A current limiting device is triggered?
3Phase Problems.doc
