16 Rockwell Automation Publication 7000-UM202D-EN-P - May 2018
Chapter 1 PowerFlex 7000 Drive Overview
The PowerFlex 7000 drive provides a selectable option for enhanced torque
control capabilities and increased dynamic control performance. This high-
performance torque control (HPTC) feature delivers 100% torque at zero
speed and provides torque control through zero speed with smooth direction
transition.
Rectifier Designs
Configurations
The PowerFlex 7000 drive offers three rectifier configurations for “B” Frame
drives:
• Direct-to-Drive™ (AFE rectifier with integral line reactor and CMC)
• AFE rectifier with separate isolation transformer
• 18-pulse rectifier with separate isolation transformer
Direct-to-Drive
Direct-to-Drive technology does not require an isolation transformer or
multiple rectifier bridges as in voltage source inverter (VSI) topologies offered
by others. The approach is completely different. Instead of multiple
uncontrolled rectifiers, a single AFE rectifier bridge is supplied. The rectifier
semiconductors that are used are SGCTs. Unlike the diodes that are used in
VSI rectifier bridges, SGCTs are turned on and off by a gating signal. A PWM
gating algorithm controls the firing of the rectifier devices, similar to the
control philosophy of the inverter. The gating algorithm uses a specific
42-pulse switching pattern called selective harmonic elimination (SHE) to
mitigate the 5th, 7th, and 11th harmonic orders.
Figure 1 - Typical PWM Switching Pattern, Line Voltage Waveform
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