Cooling technology – Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control User Manual

Page 16

Rockwell Automation Publication 7000-UM202B-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
(indoor and outdoor transformer options are available). The 18 Pulse rectifier
uses SCRs instead of the SGCTs used for an AFE rectifier. When used for high
power 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 rectifier 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 with Separate Isolation Transformer

Cooling Technology

These VFDs are supplied with heat sinks for most configurations and heat pipes
for the highest-power AFE 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