t is desired to assemble an overhead crane powered by a 20 HP motor (n= 0.84 / cos = 0.86). The transformer is operating at approximately 98% of its nominal power, so it would not be able to feed this additional motor. a) Calculate the total reactive power and the p.f. approximate. b) Calculate the power of the capacitors to be installed in order to reduce the reactive power in such a way that the new motor can be installed without replacing the transformer operating equal to 98% of its capacity.
A coarse crushing plant is powered by a 250 KVA 13.2/0.4 KV three-phase transformer. The plant has the machine chart that is detailed:
|
|
Mech power (HP) |
Mech power (kW) |
n Or power yield/perf. |
Apparent Power (kW) |
cos
|
Apparent Power (kVA) |
|
compressor |
25 |
18.75 |
0.84 |
22.32 |
0.88 |
25.37 |
|
crusher |
150 |
112.5 |
0.89 |
126.40 |
0.92 |
137.40 |
|
sieve |
45 |
33.75 |
0.88 |
38.35 |
0.89 |
43.09 |
|
conveyer belt |
40 |
30 |
0.87 |
34.48 |
0.87 |
39.64 |
|
Totals |
260 |
195 |
-- |
221.56 |
-- |
245.49 |
It is desired to assemble an overhead crane powered by a 20 HP motor (n= 0.84 / cos = 0.86). The transformer is operating at approximately 98% of its nominal power, so it would not be able to feed this additional motor.
a) Calculate the total reactive power and the p.f. approximate.
b) Calculate the power of the capacitors to be installed in order to reduce the reactive power in such a way that the new motor can be installed without replacing the transformer operating equal to 98% of its capacity.
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