Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C Frame) - Classic Control - Manual (Page 26)

1-8 Overview of Drive
7000L-UM300I-EN-P – June 2013 7000 “C” Frame
Motor Compatibility
The PowerFlex 7000L “C” Frame drive 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 (37 °F) higher
compared to across the line operation. Dv/dt in the voltage waveform
is less than 10 volts / microsecond. The peak voltage that the motor
insulation will see is the rated motor RMS voltage divided by 0.707.
Reflected wave and dv/dt issues often associated with VSI (voltage
source inverter) drives do not exist in the PowerFlex 7000L “C”
Frame drive. Typical motor waveforms are shown in Figure 1.4 .
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 miles) away from the
drive.
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
Figure 1.4 – Motor waveforms @ full load, full speed
Motor current
Motor voltage