|
"Power
Factor
Improvement:"
When using
power factor correction capacitors, the total KVAR on the load side of
the motor controller should not exceed the value required to raise the
no-load power factor to unity.
Over
correctiveness of this value may cause
high transient voltages, currents, and torques that can increase
safety hazards to personnel and possibly damage motor driven
equipment.
Never connect
power factor correction capictors at motor
terminals on elecvator motors, plugging or
jogging applications, multi-speed motors or open transition,
wye-delta, auto-transformer starting and
some part-winding start motors.
If possible,
capacitors should be located at position 2 (Table 1.1). This does
not change the current flowing through motor overload protectors.
Connection of capacitors at position 3 requires a change of overload
protectors. Capacitors should be located at position 1 for
applications listed in paragraph 2 above. Be sure bus power factor is
not increased above 95% under all loading conditions to avoid over
excitation.
Table 1.1
|
Original
Power
Factor
Percent |
Desired Power Factor Percent |
|
|
100% |
95% |
90% |
85% |
80% |
|
60% |
1.333 |
1.004 |
0.849 |
0.713 |
0.583 |
|
62% |
1.266 |
0.937 |
0.782 |
0.646 |
0.516 |
|
64% |
1.201 |
0.872 |
0.717 |
0.581 |
0.451 |
|
66% |
1.138 |
0.809 |
0.654 |
0.518 |
0.388 |
|
68% |
1.078 |
0.749 |
0.594 |
0.458 |
0.328 |
|
70% |
1.020 |
0.691 |
0.536 |
0.400 |
0.270 |
|
72% |
0.964 |
0.635 |
0.480 |
0.344 |
0.214 |
|
74% |
0.909 |
0.580 |
0.425 |
0.289 |
0.159 |
|
76% |
0.855 |
0.526 |
0.371 |
0.235 |
0.105 |
|
78% |
0.802 |
0.473 |
0.318 |
0.182 |
0.052 |
|
79% |
0.776 |
0.447 |
0.292 |
0.156 |
0.026 |
|
80% |
0.750 |
0.421 |
0.266 |
0.130 |
|
|
81% |
0.724 |
0.395 |
0.240 |
0.104 |
|
|
82% |
0.698 |
0.369 |
0.214 |
0.078 |
|
|
83% |
0.672 |
0.343 |
0.188 |
0.052 |
|
|
84% |
0.646 |
0.317 |
0.162 |
0.206 |
|
|
85% |
0.620 |
0.291 |
0.136 |
|
|
|
86% |
0.593 |
0.264 |
0.109 |
|
|
|
87% |
0.567 |
0.238 |
0.083 |
|
|
|
89% |
0.512 |
0.183 |
0.028 |
|
|
|
90% |
0.484 |
0.155 |
|
|
|
|
91% |
0.456 |
0.127 |
|
|
|
|
92% |
0.426 |
0.097 |
|
|
|
|
93% |
0.395 |
0.066 |
|
|
|
|
94% |
0.363 |
0.034 |
|
|
|
|
95% |
0.329 |
|
|
|
96% |
0.292 |
|
|
97% |
0.251 |
|
|
99% |
0.143 |
|
Assume Total plant load is 100 KW at 60% power factor. Capacitor KVAR rating
necessary to improve power factor to 80% is found by multiplying KW (100) by the
multiplier in table (0.583) which gives KVAR (58.3), nearest standard rating (60
KVAR) should be used. |
