Page 91 - Power Quality in Electrical Systems

74 Chapter Five

70
Mpr : 313.517
Mr : 171.304
50
Current (A) 30 Acr : 315.907
Avg : 33.5352
RVS : 54.3862
Of : 4.87557
10
FF : 1.52507
−10
−30
−50
40 50 60 70 80
Time (ms)
20
Freq : 50
Fwrd : 19.4713
Current (A) 10 5 ASD input current RMS : 31.0448
15
THD : 41.0054
RMSA : 315.907
ASUM : 37.3558
TIF : 427.213
IT :8990.51
0
0 600 1200 1800
Frequency (Hz)
Figure 5.13 The input line current and spectrum for an adjustable speed drive [5.2].
[© 1995, IEEE, reprinted with permission]
Summary
In this chapter, we’ve covered equipment that generates harmonics, such
as rectifiers, transformers, and switching power supplies. Harmonics
can cause many detrimental effects, including resonances with power
factor correction capacitors, the heating of neutral conductors, the false
tripping of relaying equipment, and the heating of capacitors. In the
next chapter, we’ll discuss power harmonic filters.

References

[5.1] R. W. Erickson and D. Maksimovic, Fundamentals of Power Electronics, second edi-
tion, Springer, 2001.
[5.2] IEEE, “IEEE Recommended Practice for Monitoring Electric Power Quality,” IEEE
Std. 1159-1995.