EVCO S.p.A.
EVDRIVE04 | User manual ver. 1.1 | Code 144EPD4I114
Page 21 of 78
The driving mode can be selected through parameter Driving mode selection (Pi01). If value 0 is selected (Pi01=0) the
driving mode is automatically calculated to ensure the maximum speed according to the step rate of the selected valve.
It means if the nominal step rate of the valve is higher than 625 steps/s, 8 microsteps/s will be used; while if the
nominal step rate is lower than 625 steps/s, 16 microsteps/s will be used.
It is recommended to use the driving type according to the valve features.
The Valve duty cycle (parameter Pr45) represent the limit of continuous operating of the valve: limiting the continuous
activity of the valve reduces the heating of same.
For example: setting Pr45 = 70% means for every 70 ms in which operational current is used, there will be 30 ms in
which maintenance current will be applied on the valve.
If the parameter is set to 100%, this algorithm is deactivated.
Furthermore, this procedure applies only to the normal operation of the valve: all forced movements (for example
synchronisation closure, positioning caused by probe errors or communication errors) are continuous until the target
position is reached.
6.1.3
Operation
During the re-synchronization phase (
Synchro wait
(1)) the valve is completely closed. When the instrument is
switched on, to ensure complete closure, the valve is closed by
Overdrive steps
steps. Instead, during normal
operation, to ensure complete closure, the valve is closed at 0 steps and then is closed another 10%*
Maximum
regulation steps
steps.
The valve is automatically resynchronized at every switch-on.
During normal operation of the valve, it assumes the 0% position corresponds to the physical position defined by
Minimum regulation steps, and that the 100% position corresponds to the physical position defined by Maximum
regulation steps.
A resynchronization request can be signalled using various methods:
-
rising edge on digital input DI2 (if DI2 is configured as “resynchronization command” and Enabling mode
(parameter Pr06) is configured as “standalone”
-
rising edge on Resynchro request (ResR) if Enabling mode (parameter Pr06) is configured as “network”
-
internal request from the algorithm
-
upon reaching the maximum limit of operational hours (Working hours, parameter Pr40), Resynchronization
interval (parameter Pr41), if configured.
A resynchronization request is performed only when it is safe to do, so when the state is Stand-by: this means that a
resynchronization request made when the valve is enabled is performed automatically only when it is disabled.
It is not currently possible to cancel a request.
The valve moves with a maximum velocity defined by the Stepping rate parameter.
The positioning speed depends on the operation mode:
-
during resynchronization is used the maximum speed, but towards the end of the positioning is made a
deceleration ramp
-
in debug mode is used the speed of the Debug step rate (parameter Prd0)
-
in manual mode and for all other positioning is used the maximum speed.
Using Limit valve opening (parameter Pr30) it is possible to adapt the valve to the application.
For example, for a valve with a maximum rating of 10 kW fitted to a machine with 7.5 kW, Pr30 would be set to 75%.
So, if the request position target is 90%, the final real position of the valve may be 67.5% = 90 x 75% of the
Maximum regulation steps.
The displayable variables for the current position and set-point in % are all referenced to the actual range of use of the
valve (0 - Pr30%), while the position in steps is the real position.
If an invalid selection (Max steps = 0) is performed a Configuration error 23 is displayed.
