Elmo SERVO AMPLIFIER DBP SERIES - Manual (Page 19)

18
DBP - Rev 6/93
4.2.1 Current feedback, Current feedback multiplier (CFM) and
Current loop
Three current feedbacks are obtained by measuring the voltage drop across
current sensing resistors or by current transformers (when using the isolation
option). These three signals are synthesized and multiplexed which result in a
single voltage signal proportional to phases currents. It is then compared to
the current command. The error is processed by the current amplifier to provide
a voltage command to the PWM section.
Current loop control is obtained by op amp U21/A (current amplifier) and R4,
C1 which form a lag-lead network for current loop. The standard amp is equipped
with R4 and C1 to get optimum current response for an average motor in this
power range. These components are mounted in solderless terminals.
Error amplifier Current amplifier
Current feedback
CFM
x2
The amplifier is equipped with a Current Feedback Multiplier (CFM). By
turning DIP switch 2 (on the upper board of the power stage) to ON, the signal
of the current feedback is multiplied by 2 and consequently the following
changes occur:
- Current gains are multiplied by 2.
- Current monitor is divided by 2.
- Current limits are divided by 2.
- Dynamic range is improved.
- Commutation ripple is reduced.