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 (see diagram). 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.
Diagram
8
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
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.
96%
0.292
97%
0.251
99%
0.143
8
