Power modules – Rockwell Automation 6012DB PowerFlex Medium Voltage Variable Frequency Drive User Manual
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Rockwell Automation Publication 6000-UM001B-EN-P - October 2014
Chapter 2
Drive System Layout
Power Modules
Power Modules are available in a wide variety of amperage ratings relating to the
required motor current. Power Modules rated up to and including 200 A are
fixed-mounted in the drive and ship already installed.
Drawout power modules are supplied for a drive current rating of >200 A. The
power modules are shipped separately and must be installed in the cabinet. A
Power Module lift cart is included and shipped together with the other
components.
Basic Principle of Power Module
The Power Module combines a three phase rectifier and an “H” bridge inverter,
powered from the secondary side windings of the Isolation Transformer. After
rectifying and filtering, it outputs AC current with variable frequency and
variable voltage under the control of four IGBTs using a PWM switching pattern.
Several Power Modules, after being connected in series and superposed, can
output three-phase AC current with adjustable frequency and voltage to control
an AC motor.
Figure 18 - Low Voltage Power Module
Control signals to the Power Module and the feedback signals from the Power
Module are transmitted by fiber optic cables which provide electrical isolation
between the medium voltage and low voltage sections of the drive, and protects
against electromagnetic interference.
Although the voltage produced by each power unit is typically less than 690V, the
voltage-to-ground can reach the VFD rated output voltage, if operating at rated
frequency.
The control signals from the main control unit, through the optical-electrical
converter, are sent to the Power Module control board for further processing and
to the corresponding gate drive circuits to turn the IGBTs on or off.
Input U
Input V
Input W
Fuse 1
Fuse 2
Three-phase Diode
Rectifier Bridge
DC Bus
Capacitor Network
Single Phase IGBT
Inverter Network
IGBT 1
IGBT 2
Output A
Output B
D1
D2
D3
D4
D5
D6
C1
R1
C2
R2
C3
R3