Calculating Power Consumption - Omron CJ2 User Manual

2 Basic System Configuration and Devices
2-1-6

Calculating Power Consumption

The ambient operating temperature at the control panel for mounting a CJ-series PLC must be no
higher than 55°C. This section describes how to calculate the power consumption of a CPU Rack for
use in the thermal design of the control panel.

Calculating Power Consumption

Use the following equation to calculate the average power consumption (W) of a CJ-series CPU Rack.
W = W_PLC + W_IO_ONOFF
Basic PLC Power Consumption (W_PLC)
The basic PLC power consumption is calculated based on the overall power consumption of the
PLC and the power conversion rate of the Power Supply Unit.
W_PLC = W_unit ÷ η
• W_unit:
Total power consumption of Units mounted to the CPU Rack. For details on the current consump-
tion and voltage of individual Units, refer to ???.
• η:
Power Supply Unit power conversion rate.
The rate is 70% for the CJ Series, so use "0.7" in the calculation.
Basic I/O Unit Power Consumption (W_IO_ONOFF)
The Basic I/O Unit power consumption is the total consumption for the Input Units and the Output
Units.
• Input Units
Rated input voltage × Input current × Number of input points
• Output Units
Residual voltage × Maximum load current × Number of output points
Note For the CJ Series, calculate the residual voltage at 0.1 V.
2-20
Basic I/O Unit power consumption
Basic PLC power consumption
CJ2 CPU Unit Hardware User's Manual