Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control - Manual (Page 16)

16 Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014
Chapter 1 Overview of Drive
Figure 4 - 3300/4160 AFE Rectifier with integral isolation transformer
Motor Compatibility The PowerFlex 7000 achieves near sinusoidal current and voltage waveforms to
the motor, resulting in no significant additional heating or insulation stress.
Temperature rise in the motor connected to the VFD is typically 3 °C (5.4 °F)
higher compared to across-the-line operation. Voltage waveform has dv/dt of less
than 50V/μs. Reflected wave and dv/dt issues often associated with VSI (voltage
source inverter) drives do not exist with the PowerFlex 7000. Typical motor
waveforms are shown in
Figure 5 . These motor friendly waveforms are achieved
by utilizing a selective harmonic elimination (SHE) pattern in the inverter to
eliminate major order harmonics, in conjunction with a small output capacitor
(integral to the drive) to eliminate harmonics at higher speeds.
Standard motors are compatible without de-rating, even on retrofit applications.
Motor cable distance is virtually unlimited. This technology is capable of
controlling motors up to 15 km (9.3 mi) away from the drive.
Figure 5 - Motor waveforms @ full load, full speed
2U (X1)
2V (X2)
2W (X3)
1U
1V
1W
SGCTs
LINE CONVERTER DC LINK
L+ M+
SGCTs
MACHINE CONVERTER
U (T1)
V (T2)
W (T3)
L- M-
INTEGRAL
ISTX
300.00
200.00
100.00
0.00
-100.00
-200.00
-300.00
10.00K
7.50K
5.00K
2.50K
0.00K
-2.50K
-5.00K
-7.50K
-10.00K
100.00 110.00 120.00 130.00
TIME (ms)
140.00 150.00
Arms
Vrms
Motor
Current
Motor
Voltage