Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control - Manual (Page 17)

Rockwell Automation Publication 7000-UM202B-EN-P - June 2014 17
PowerFlex 7000 Overview Chapter 2
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 (5.5 °F)
higher compared to across-the-line operation. Voltage waveform has dv/dt of less
than 50 V/
μs . The peak voltage across the motor insulation is the rated motor
RMS voltage divided by 0.707.
Reflected wave and dv/dt issues often associated with voltage source inverter
(VSI) drives are a non-issue with the PowerFlex 7000.
Figure 5 shows typical
motor waveforms. The drive uses a selective harmonic elimination (SHE) pattern
in the inverter to eliminate major order harmonics, plus 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. Rockwell Automation has tested this
technology for controlling motors up to 15 km (9.3 mi) away from the drive.
Figure 5 - Motor waveforms @ full load, full speed
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
CURRENT
VOLTAGE