c 1.Closed
loop drives
There
are two system structures
o
direct current limit structure
o
inner current –loop structure
current limit (Ip) is set by the user and its specified upper limit for transient power current limit action grantees that armature current Ia will not exceed (Ip)
In this structure
limits over current indirectly by limiting current demand (Ia) within (Ip) is chosen
limit current
This structure gives
the fast response higher bandwidth and also inherent safety
2. Open loop drive
Open loop drive do not
other servo gate performance but adjustable speed facility this drives use simple
system structure
This system does not
use and explicit current limit action (as in closed loop system) but a simile
action is dive through a similar action “slow up /down” unit.
Slow up down unit convert stem demand of
‘Wr’ to slow rising of falling vibration of armature voltage demand.
Slowly varying Va will
not case over current. ramping time “T” is set by the user according to the
moment of inertia and torque of the motor load system for higher moment of
inertia we set “T” at on appropriate higher value .
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