Rockwell Automation 7000A PowerFlex Medium Voltage Drive (A-Frame) - Classic Control - Manual (Page 25)

Overview of Drive 1-7
7000 “A” Frame 7000A-UM150F-EN-P – June 2013
Motor Compatibility
The PowerFlex 7000 “A” Frame 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 with the PowerFlex 7000 “A” Frame. Typical
motor waveforms are shown in Figure 1.5. 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 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 1.5 – Motor waveforms @ full load, full speed
Motor current
Motor voltage