Allen-Bradley 1391B Series, Instruction Manual

Page: 22 / 82

Description of Operation
Chapter 4
4-20
The shunt regulator behavior is further modified by an adjustable duty
cycle timer. The timer is used to model the shunt resistor temperature.
SW1, a selector switch located on the top of the controller (see Figure 1.1)
determines the temperature level and therefore the average power level at
which the controller will trip out. When this level is reached, the controller
will be forced to trip out on an Overvoltage Fault. This action would be
equivalent to turning the shunt regulator off. Refer to Chapter 9 for further
shunt regulator information.
Logic Power Supply The 1391B-ES control logic voltage is
±
12V DC and +5V DC. The
voltages are generated on the Power Driver Board, which receives its 36V
AC center-tapped input from a tertiary winding on the isolation
transformer.
Logic Control Boards The Logic Control Boards are the printed circuit boards that are readily
accessible behind the front cover of the controller. They contain all circuits
necessary to control the 1391B-ES. These circuits include: the velocity and
current loop, fault detection and annunciation circuits, power-up/power-
down logic, PWM generation and forward/reverse controlling circuits.
Figure 4.3
1391B-ES Block Diagram