gefran GFX4-IR Configuration And Programming Manual page 63

HEURISTIC Control power
It is useful to be able to limit the delivery of total power to the loads in order to avoid input peaks from the single-phase
power line.
This condition occurs during switch-on phases when the machine is cold; the demand for heating power is 100%
until temperatures near the setpoint are reached. It is also useful to avoid simultaneity of conduction when there is ON-OFF
modulation for temperature maintenance.
The cycle time must be identical for all zones; the power percentage for each zone is limited to that necessary to
maintain current within set limits.
This function acts by enabling the control to search for the most appropriate input combinations.
Example 1:
4 loads 380V- 32A (zone 1), 16A (zone 2), 25A (zone 3), 40A
(zone 4)
(maximum current is 113A in case of simultaneity of conduc-
tion).
Current limit I.HEU=50A.
The following combinations of conduction are possible:
(to define the number of combinations, remember that the
combinations without repetitions are = n! / (k!*(n-k)!) )
I1+I2 = 48A
I1+I3 = 57A
I1+I4 = 72A
I2+I3 = 41A
I2+I4 = 56A
I3+I4 = 65A
I1+I2+I3 = 73A
I1+I2+I4 = 88A
I2+I3+I4 = 81A
I1+I3+I4 = 97A
I1+I2+I3+I4 = 113A
If P1= 100%, P2= 100%, P3= 100%, P4= 100%
Ptot=300%; since Ptot>100%, the conduction time of the zone x is obtained by Px * (100/Ptot)
P1,2,3,4 delivered = 100%*0.33 = 33%
If P1= 100%, P2= 50%, P3= 0%, P4= 25%
Ptot=175%; since Ptot>100%, the conduction time of the zone x is obtained by Px * (100/Ptot)
P1 delivered = 100%*0.57 = 57%
P2 delivered = 50%*0.57 = 28.5%
P3 delivered = 0%*0.57
P4 delivered = 25%*0.57 = 14.2%
80415F_MSW_GFX4-IR_05-2019_ENG
= 0%
The combination corresponding to current values below the
limit value are:
I1+I2 = 48A
I2+I3 = 41A
The one with lower current is given by zone 2 and zone 3.
In the single cycle time for the enabled zones, the delivery
of power may be reduced to respect the maximum current
limit.
The time distribution for activation of the zones is calculated
at the start of each cycle:
Ptot = P1+ P2 (if P2>P3) + P3 (if P3>P2) + P4
Simultaneity is allowed for zones 2 and 3.
ON Zone 1 ON Zone 2 / 3
Cycle time
ON Zone 1
Cycle time
ON Zone 4
ON Zone 2 ON Zone 4
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