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Okuma America Corporation
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Rev. 8-21-01
SERVO SYSTEMS
This section will cover the different types of servo systems used on Okuma’s 5000/5020 series
CNC machines. A servo system can be defined as a system for the automatic control of motion
by means of feedback. The controlled motion can be for positioning and/or velocity (RPM).
Okuma uses servo systems to control axis positioning and spindle revolution. Most of the servo
systems on machines with the 5000/5020 series control system use AC drive technology. Some
of the early models use DC drive technology with DC brush type motors. The following is a
description of the servo systems used on Okuma machines.
AXIS DRIVES
LDU 600
Some of the older lathes that use the early 5000L CNC control have the LDU 600 axis drive
servo system. LDU stands for Linear Drive Unit. This is a thyristor control system which
controls the rotational speed of a DC motor by regulating the firing angle of the thyristors. This
system utilizes PPS technology where the input voltage is converted into a series of gate pulses
with phase angles. PPS stands for Pulse Phase Shifting. A block diagram of the LDU 600 can
be seen below.
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