Control Techniques FXM5, User Manual

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FXM5 User Guide
15
Issue Number: 5 www.controltechniques.com
4 Setting Up
4.1 Control-system description
Figure 4-1 Control of armature voltage and field current with varying motor speed
Refer to Figure 4-1. The FXM5 controller maintains the field current IF at a fixed value
until base speed n is reached (detected by the armature voltage V
A
reaching a
maximum value). Attempts by the Drive to increase the speed by further increasing the
armature voltage causes the controller to reduce the field current. Because the Drive,
FXM5 controller and motor operate in a closed loop, the armature voltage remains
constant when the speed is varied above base-speed, but the field current is reduced in
inverse proportion to increases in speed. For example, to allow the motor speed to
reach double the base-speed, the field current must be halved.