Technical data
June 2008
CA08102001E For more information visit: www.eaton.com
40-245
Adjustable Frequency Drives
40
CPX9000
Enclosed Drives
3. Clean Power Drives
When the total load is of non-linear, the greatest harmonic
mitigation is required. Under these conditions, the currents
drawn from the supply need to be sinusoidal and “clean”
such that system interference and additional losses are neg-
ligible. The Cutler-Hammer CPX9000 Clean Power Drive uses
a phase-shifting auto transformer with delta-connected
winding. Three of the output phases are advanced and three
are retarded. The remaining three phases of this nine-phase
supply are in phase with the incoming line. This results in
nine separate phases. In this type of configuration, the total
required KVA rating of the transformer is only 48% of a drive
rate isolation transformer. A traditional isolated transformer
system, with multipulse windings, would require the full
KVA rating to be supported, which is more common in an
MV step-down transformer.
The integrated 18-pulse clean power drive, with near sine
wave input current and low harmonics will meet the require-
ments of IEEE 519-1992 under all practical operating condi-
tions. The comparisons with 6-pulse and 12-pulse systems
are shown in Figures 40-139, 40-143 and 40-145.
Figure 40-144. Basic 18-Pulse Rectifier with “Differential Delta” Transformer
Figure 40-145. 500 hp 480V Drive with 18-Pulse Rectifiers
Table 40-357. 500 hp 480V Drive with 18-Pulse Rectifiers
Advantages
■ Virtually guarantees compliance with IEEE 519-1992
■ Provides increased input protection for AFD and its semi-
conductors from line transients
■ Up to 4 times the harmonic reduction of 12-pulse methods
■ Smaller transformer than isolation transformer used in
12-pulse converter
Disadvantages
■ Larger and heavier magnetics than some other methods
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
A
C
N
Output Transistors
IGBT Section
Dynamic Braking
Tra nsistor
Pre-charge
Circuit
18-Pulse SCR
Bridge Rectifier
Converter Section
18-Pulse
Phase-Shifting
Auto-Transformer
Inverter Section
(
–
) DC
(
+
) DC
Diode Rectifiers
Bus
Capacitors
3-Phase
AC Input
1
2
3
AC
Motor
18-Pulse Clean Power
Current Harmonics
I
1
= 100% I
11
= 0.24% I
19
= 1.00%
I
5
= 0.16% I
13
= 0.10% I
23
= 0.01%
I
7
= 0.03% I
17
= 0.86% I
25
= 0.01%
Power = 500 hp
H
c
= 24 Amps
1000
Current
Amps
500
0
-500
-1000
0.100 0.10625 0.1125
Time in Seconds
0.11875 0.125