Technical data
June 2008
40-212
For more information visit: www.eaton.com CA08102001E
Adjustable Frequency Drives
40
CFX9000
Enclosed Drives
Figure 40-115. 6-Diode Rectifier Design
The 6-Pulse VFD drive creates harmonic current distortion.
The harmonic current that is created is energy that can not
be used by customers and causes external heat and losses
to all components including other drives that are on the
same power distribution. Figure 40-116 is a 100 hp drive
with 45A of damaging harmonic current.
Figure 40-116. 6-Pulse Nonproductive Harmonic Current
Table 40-313. 6-Pulse Nonproductive Harmonic Current
Guidelines of Meeting IEEE Std. 519-1992 Harmonic
Distortion Limits
The IEEE 519-1992 Specification is a standard that provides
guidelines for commercial and industrial users that are
implementing medium and low voltage equipment.
Table 40-314. Maximum Harmonic Current Distortion in % of the
Fundamental (120V through 69,000V)
The ratio ISC/IL is the ratio of the short-circuit current available at
the point of common coupling (PCC), to the maximum fundamental
load current. Consequently, as the size of the user load decreases
with respect to the size of the system, the percentage of harmonic
current that the user is allowed to inject into the utility system
increases.
Notes:
TDD = Total demand distortion is the harmonic current distortion in
percent of the maximum demand load current (15 or 30 minute
demand).
I
SC
= Maximum short circuit current at the PCC not counting motor
contribution.
I
L
= Maximum demand load current for all of the connected loads
(fundamental frequency component) at the PCC.
All of the limits are measured at a point of common coupling.
L2A
L1A
L3A
Output Transistors
IGBT Section
Dynamic Braking
Transistor
6-Pulse Diode
Bridge Rectifier
Converter Section
Inverter Section
(
–
) DC
(
+
) DC
Bus
Capacitors
AC
Motor
6-Pulse Circuit
Current Harmonics
I
1
= 100% I
11
= 6.10% I
19
= 1.77%
I
5
= 22.5% I
13
= 4.06% I
23
= 1.12%
I
7
= 9.38% I
17
= 2.26% I
25
= 0.86%
Power = 100 hp
Harmonic Current = 45 Amps
200
Current
Amps
100
0
-100
-200
Time
Isc/I
L
Harmonic Order (Odd Harmonics) TDD
h<11 11≤h<17 17≤h<23 23≤h<35 35≤h
<20 4.0 2.0 1.5 0.6 0.3 5.0
20<50 7.0 3.5 2.5 1.0 0.5 8.0
50<100 10.0 4.5 4.0 1.5 0.7 12.0
100<1000 12.0 5.5 5.0 2.0 1.0 15.0
>1000 15.0 7.0 6.0 2.5 1.4 20.0