Rockwell Automation 7000L PowerFlex Medium Voltage AC Drive (C-Frame) - ForGe Control - Manual (Page 22)

22 Rockwell Automation Publication 7000L-UM301D-EN-P - June 2014
Chapter 1 Overview of Drive
SGCT Features and Benefits An SGCT is a Symmetrical Gate Commutated Thyristor with an integrated gate
drive. Positioning the gate drive close to the SGCT as shown in
Figure 5 , creates a
low inductance path that provides more efficient and uniform gating of the
device. As a result, the device is better suited than a conventional GTO to handle
the fluctuating levels of voltage and current while it is switching on and off during
gating.
An SGCT has similar characteristics to an IGCT (used on some VSI drives),
including low conduction and switching losses, low failure rate, and double sided
cooling for low thermal stress. However, the SGCT achieves voltage blocking
capability in both forward and reverse directions up to 6500 volts by a NPT
(Non-Punch-Through) structure and nearly symmetrical pnp transistor in the
wafer, while the current is unidirectional. Unlike many VSI topologies that use
IGBTs, the semiconductors used in the PowerFlex 7000L feature a non-rupture,
non-arc failure mode. In the unlikely event of a device failure, the fault would be
contained within the device.
Implementing SGCTs in the PowerFlex 7000L “B” Frame results in significant
advantages including:
1. Simplification of the snubber design and a reduction in the size of the
snubber capacitor by a factor of 10.
2. Operation at a higher switching frequency (420-540 Hz), hence reducing
the size of passive components (DC link inductor and motor filter cap) by
50%.
3. Improving performance of the drive.
4. Reduction of component count, hence improving reliability, cost, and size
of the drive.
5. Fail safe failure mode (non-rupture).
Figure 5 - SGCT with integrated gate drive (left) and unit cell structure (right)