Rockwell Automation 1391ES AC Servo Controller - Manual (Page 20)

4 Chapter
4-18
Description of Operation
Chapter Objectives Chapter 4 is intended to familiarize the reader with the circuitry of the
1391B-ES in terms of function and operation.
General The 1391B-ES PWM Servo Controller is made up of the following: 300V
DC power supply, power transistor output modules, shunt regulator circuit,
logic power supply, Logic Control Boards, isolated current sensing, circuit
breaker and line contactor.
The intended use of the 1391 ES is to control the speed and torque of an
AC servomotor in a closed loop position system. A complete servo system
can be configured with a 1391B-ES Servo Controller, 1326 AC
Servomotor and 1391 Isolation Transformer. Refer to the 1391B-ES Block
Diagram presented in Figure 4.3.
300V DC Power Bus Supply The controller contains an integral, unregulated, 300V DC nominal, full
load power supply. It consists of the power transformer input (230V AC,
three-phase, 50 or 60 Hz), a three-phase input bridge rectifier and one
power supply filter capacitor (C1).
PWM Operation The 1391B-ES incorporates a fixed timing wave (V
T
) of 2500 Hz. The
controller also generates a three-phase sine wave whose frequency
corresponds to the velocity command. An output voltage signal (V
O
) is
generated by the intersection of these two curves as shown in Figure 4.1.
Figure 4.1
PWM Waveform
V
T
E
T
V
O
E
d
T