Omron CRT1 - 10-2009, Operation Manual

Page: 121 / 675

97
Power Supply Wiring
Section 3-5
The allowable currents for cables and connectors are given below.
Allowable Currents for
Cables Select the communications cable so that the total current consumption of all
Slave Units does not exceed the allowable current of the cable.
Allowable Currents for
Connectors There are limits to the allowable current for the communications power supply
connectors on the Master Unit and Repeater Units, Flat Connector Sockets,
and Flat Connector Plugs. Do not allow the current flow where these connec-
tors are used to exceed the allowable current.
Voltage Drop
Cable Voltage Drop The voltage drop must be considered so that the power supply voltage at the
Slave Unit that is the farthest from the power supply will still be within the
allowable power supply range.
The voltage drop is expressed by the following formula.
If the voltage drop is too large and power cannot be supplied to the farthest
Slave Unit within the allowable range, add a Repeater Unit and supply power
from the Repeater Unit.
Master
Unit
Power
supply,
24 VDC
Slave Unit
current con-
sumption I
1
Terminating
Resistor
Slave Unit
current con-
sumption I
2
Slave Unit
current con-
sumption I
3
Flat Connector Plug: 5 A max. (UL: 4 A)
Flat Connector Socket: 5 A max. (UL: 4A)
Cable
Slave Unit
current con-
sumption I
n
(a)
Cable allowable current
≥
I
1
+ I
2
+ I
3
+ · · · · I
n
(For the allowable cable current for “a” in the above diagram)
Name Model Allowable
current
Communications power supply connectors on CS/
CJ-Master Units CS1W-CRM21 5 A
(UL: 4 A)
CJ1W-CRM21
Communications power supply connector on
Repeater Unit CRS1-RPT01
Flat Connector Sockets DCN4-TR4
DCN5-TR4
Flat Connector Plugs DCN4-BR4
DCN5-BR4
Multidrop Connector DCN4-MD4
Flat Multidrop Connector Plug DCN4-MR4
Voltage drop (V) = Current (A)
×
Cable conductor resistance (
Ω
/m)
×
Cable length
(m)
×
2