Omron 3G8F7-CRM21, User Manual

Page: 227 / 238

207
Wiring for Power Supply
Section E-5
Voltage Drop
Cable Voltage Drop
If the voltage drop is too large and the power supplied to the farthest Slave
Unit exceeds the allowable range, a Repeater Unit must be added and the
power must be supplied from the Repeater Unit.
•
Calculation Example
The allowable power supply voltage range for Slave Units is 14.0 to 26.4 VDC.
If a 24-VDC power supply is used, the allowable voltage drop is 10 V.
The following formula expresses the relation between the available cables and
the permissible cable extension length:
Use the following approximation formula if you want to add some margin in the
cable selection.
Where R is the cable conductor resistance, 0.025
Ω
/m, for a Flat Cable.
When a Flat Cable is used, the extendable length is:
L (m) <= 200 / (I1 + I2 + I3 + ... + In)
Voltage drop (V) = Current flow (A)
×
Cable conductor resistance (
Ω
/m)
×
Cable length
(m)
×
2
Ln L3 L1 L2
3 m max.
24-VDC
Power
Supply
Master
Board
Terminating
Resistor
Slave Unit
current
consumption I
n
Slave Unit
current
consumption I
3
Slave Unit
current
consumption I
2
Slave Unit
current
consumption I
1
10 (V) >= {(I
1
+ I
2
+ I
3
+...+ I
n
)
×
R
1
×
L
1
×
2} + {(I
2
+ I
3
+...+ I
n
)
×
R
2
×
L
2
×
2}
+ {(I
3
+...+ I
n
) × R
3
×
L
3
×
2} +... + {I
n
×
R
n
×
L
n
×
2}
10 (V) >= {(I
1
+ I
2
+ I
3
+ ... + I
n
)
×
R
×
L
×
2}
L (m) <= 200
÷
(I
1
+ I
2
+ I
3
+ ... + I
n
)