Cooling technology – Rockwell Automation 7000 PowerFlex Medium Voltage Air-Cooled (B Frame) Installation - ForGe Control User Manual
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Rockwell Automation Publication 7000-IN007E-EN-P - June 2014
Chapter 2
PowerFlex 7000 Overview
18 Pulse Rectifier with Separate Isolation Transformer
For high power, constant torque applications and/or when the line voltage is
higher than the motor voltage, a transformer is required for voltage matching.
The 18 Pulse rectifier uses SCRs instead of the SGCTs used for an AFE rectifier.
When used for high power and constant torque applications, the 18 Pulse
rectifier has lower losses than the AFE rectifier, making it ideal for the highest
power requirements. The 18 Pulse isolation transformer provides the required
input impedance and addresses common mode voltage just like the separate
isolation transformer used with the AFE rectifier. However, instead of a PWM
switching pattern and a single rectifier bridge, the 18 Pulse configuration
mitigates line side harmonics through harmonic current cancellation in the
isolation transformer phase shifted secondary windings. The inverter is the same
configuration for all available rectifier options.
Figure 4 - 3300/4160V 18 Pulse rectifier
Cooling Technology
These VFDs are supplied with heat sinks for low and mid-power configurations
and heat pipes for high-power configurations. While both configurations draw
heat away from the semiconductors, heat pipes are bigger, more efficient, and
require larger fans and airflow.
Information and graphics in this manual show both configurations.
LINE CONVERTER
L-
M-
DC LINK
L+
M+
MACHINE CONVERTER
U (T1)
V (T2)
W (T3)
4U (Z1)
4V (Z2)
4W (Z3)
ISTX
SCRs
3U (Y1)
3V (Y2)
3W (Y3)
2U (X1)
2V (X2)
2W (X3)
SGCTs
LINE CONVERTER
L-
M-
DC LINK
L+
M+
MACHINE CONVERTER
U (T1)
V (T2)
W (T3)
4U (Z1)
4V (Z2)
4W (Z3)
ISTX
SCRs
3U (Y1)
3V (Y2)
3W (Y3)
2U (X1)
2V (X2)
2W (X3)
SGCTs