Mark-vie TMR SERVO Control Issue (Valve Fluctuating)

we are using mark-vie for combined steam turbine control.
and after commission, we have some problem in TMR Servo Valve control
Three lvdt are installed in one valve and Three Servo Regulators control the servo valve
there are cv#1,#2 which have same parameters in our control system
only cv#1 have been fluctuated with 7% range(ex> demand: 40% , feedback: 33%~47%).
does not only just feed back also actual valve fluctuating. so when unstable condtion Electrical Hydrauric Control Line are vibrated criticaly.

FIRST: we already changed servo valve to new one, but problem still exist.
SERVO VALVE: REXROTH HYDRAULICS: 4WS2EM, nominal current per coil 30ma, resistance per coil 85ohm)

second : Althought we don't think there are some problem in our lvdts. we changed a one lvdt to new one because of both low probability in lvdt malfuction and our system with tmr control
but problem still exist

third: that is very interesting.
after we disconnected the R core from TMR servo control, Valve status back to normal
so we tested other core S,T one by one. Results are same above.

R(X)S(0)T(0)--> VALVE STATUS IS GOOD
R(0)S(X)T(0)--> VALVE STATUS IS GOOD
R(0)S(0)T(X)--> VALVE STATUS IS GOOD

fourth: in normal operation our cv#1#2 are full open status.
at that time, Valve is not moving any more(demand over 100%) but in other positions(20%,30%,50%70%..) during start up , we suffer the problem.

could you let me know how to solve this problem.
now i consider the pvso regualtor gain adjust but i want more imformation about this
i am so sorry grammar mistake due to not frendly with english in our country
 
Good afternoon Jakky,

Well, long time no see ToolboxST, I'm trying just to help, tell me please: You've changed one LVDT? you didn't tell us if calibration were done or not?. Also, did you checked Vrms (7 Vrms) feeding of LVDT with fluctuation?
Please check wires in PSVO terminals be sure that is well tighten, and be sure also LVDTs wires and shield wire are sain.

I'm a bit confused, could you explain please the test you've done, which consistes of disconnecting one servo each time?, This test has been done in normal operation (with steam passes through valve) or in shutdown conditions?.

When reaching mechanical 100% of position, demand it was about 110%. tell us please what was indicating LVDT with problem of fluctuation.

Best regards.





we are using mark-vie for combined steam turbine control.
and after commission, we have some problem in TMR Servo Valve control
Three lvdt are installed in one valve and Three Servo Regulators control the servo valve
there are cv#1,#2 which have same parameters in our control system
only cv#1 have been fluctuated with 7% range(ex> demand: 40% , feedback: 33%~47%).
does not only just feed back also actual valve fluctuating. so when unstable condtion Electrical Hydrauric Control Line are vibrated criticaly.

FIRST: we already changed servo valve to new one, but problem still exist.
SERVO VALVE: REXROTH HYDRAULICS: 4WS2EM, nominal current per coil 30ma, resistance per coil 85ohm)

second : Althought we don't think there are some problem in our lvdts. we changed a one lvdt to new one because of both low probability in lvdt malfuction and our system with tmr control
but problem still exist

third: that is very interesting.
after we disconnected the R core from TMR servo control, Valve status back to normal
so we tested other core S,T one by one. Results are same above.

R(X)S(0)T(0)--> VALVE STATUS IS GOOD
R(0)S(X)T(0)--> VALVE STATUS IS GOOD
R(0)S(0)T(X)--> VALVE STATUS IS GOOD

fourth: in normal operation our cv#1#2 are full open status.
at that time, Valve is not moving any more(demand over 100%) but in other positions(20%,30%,50%70%..) during start up , we suffer the problem.

could you let me know how to solve this problem.
now i consider the pvso regualtor gain adjust but i want more imformation about this
i am so sorry grammar mistake due to not frendly with english in our country
 
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