Flc = first load current, Slc = second load current, Three-phase unbalanced loads – Precision Control Systems PanelIR 4555 User Manual
Page 32
Model 4555 PanelIR
TM
User Manual
Appendix A
Three-Phase Unbalanced
Loads
Often it is not possible to connect the lamps in the Model 4555 to make a balanced
load. In this case, the three line currents supplying the heater lamps can be calculated
as follows:
1. Determine the number of lamps in each load.
2. Determine the current per lamp.
3. Calculate the load current for each of the three loads based on the number of
lamps in each load and the current per lamp.
Line current = Lamp Current x Number of Lamps in Load.
4. Calculate the line current based on the current of the two loads connected to the
line:
Line Current = √(FLC
2
+ (FLC x SLC) + SLC
2
)
NOTE:
FLC = First Load Current
SLC = Second Load Current
Example: Assume quantity 2 Model 4555-25-12 and quantity 1 Model 4555 25-06
using 2500T3 lamps connected to a 480 volt source (see Figure A-4).
1. Number of lamps in each load
Load 1 = 12 lamps
Load 2 = 12 lamps
Load 3 = 6 lamps
2. The current per 2500T3 lamp connected to a 480 volt source is 5.2 amperes.
3. Load Current 1 – 5.2 Amperes x 12 Lamps = 62.4 Amperes
Load Current 2 – 5.2 Amperes x 12 Lamps = 62.4 Amperes
Load Current 3 – 5.2 Amperes x 6 Lamps = 31.2 Amperes
4. Line Current 1 = √(LC1
2
+ (LC1 x LC3) + LC3
2
) = √(62.4
2
+ (62.4 x 31.2) + 31.2
2
)
Line Current 2 = √(LC2
2
+ (LC2 x LC3) + LC3
2
) = √(62.4
2
+ (62.4 x 31.2) + 31.2
2
)
Line Current 3 = √(LC1
2
+ (LC1 x LC2) + LC2
2
) = √(62.4
2
+ (62.4 x 62.4) + 62.4
2
)
Research, Inc.
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