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Valve outputs | Valve output - General
Image 14: Example of command value evaluation with limiting value
9.4.3 PWM cycle time
The "PWM cycle time" parameter specifies the period length of the pulse-width-mod-
ulated output signal of a valve output. It allows adaptation to the adjusting cycle times
(the adjusting time it takes the drive to bring the valve from its completely closed to its
completely opened position) of the valve drives used. In addition to the adjusting
cycle time, take account of the dead time (the time in which the valve drives do not
show any response when being switched on or off). If different actuators with differ-
ent adjusting cycle times are used at an output, take account of the longest of the
times.
The "PWM cycle time" parameter is also available for valve drives whose com-
mand value data format is configured to "Switching (1-bit)" or
"Constant (1-byte) with command value limiting value". For such valve outputs,
pulse width modulation can also be executed during an active forced position,
emergency operation, manual operation, after bus voltage return or after an
ETS programming operation, for which, as a result, the presetting of a cycle
time is required.
Generally, two different options of how to set the cycle time can be identified:
Case 1
Cycle time > 2 x Adjusting cycle time of the drives used (ETA)
In this case, the switch-on and switch-off times of the actuator are long enough for
the actuators to have sufficient time to fully open and fully close within a given period
(see figure 15).
–
Advantage:
The desired mean value for the command value and thus for the required
room temperature will be set relatively precisely, even for several actuators
triggered at the same time.
Heating actuator 6-gang with controller | Order no. 2139 00 | 21393100
Page 70 of 257
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