Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 24)

Overview of Drive 1-7
7000 “B” Frame 7000-UM150I-EN-P – June 2013
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 (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 are a non-issue with the PowerFlex 7000. 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 has been
tested, 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
4160V, 933 kW, 60 Hz
Motor current
Motor voltage