Rockwell Automation MV SMC Flex Motor Controller (for Series K or later) - Manual (Page 31)

Rockwell Automation Publication 1560E-UM051F-EN-P - June 2013 21
Product Overview Chapter 1
Braking Control Options
The Braking Control options (Smart Motor Braking, Accu-Stop and Slow Speed
with Braking) are not offered for standard use in MV applications. Please consult
factory for further assistance.
Hardware Description The following sections contain descriptions of system components and system
operation. Each section will be described to give the user an understanding of the
MV SMC Flex to facilitate operation and maintenance of the system. Refer to
Figure 18 and Figure 19 , Typical MV SMC Flex Power System.
Power Module
The controller consists of three power modules, one for each phase. Each power
module consists of incoming and outgoing terminals for cables, SCRs, heatsink
and clamp assembly. The SCRs are connected in inverse parallel (and in series for
12- or 18-SCR assemblies) to form a three-phase, AC line controller
configuration.
Each power module includes a snubber circuit to limit the rate of rise in voltage
across each SCR pair. The module also includes patented current loop gate driver
circuits which derive their power primarily from the snubber circuit.
Voltage sharing resistors are connected across each SCR pair to provide static
voltage balance for series-connected SCRs. These resistors are tapped to provide
a reference for overvoltage protection circuitry on the gate driver board.
A voltage sensing board is used to reduce the line-side and load-side voltages to
lower levels that can be measured by the SMC Flex control module.
Current Loop Gate Driver (CLGD) Board
This board provides the turn-on capability for SCR devices. The board also
provides optical fiber isolation between itself and the gating source logic. It is
primarily powered by recovering energy from the snubber circuit, so it is fully
isolated from the control and logic circuits. The board also receives short-term
power from the current loop power supply.
The MV SMC Flex has three heatsinks fitted with a thermistor to monitor
temperature rise. The circuitry on the gate driver board accepts the thermistor,
and drives a fiber-optic cable if the temperature is below the setpoint (85°C). If
the temperature rises above the setpoint, the driver is turned off, and the MV
SMC Flex is signaled to stop gating and initiate a temperature fault.