F-2 Series 90-30 PLC Installation and Hardware Manual
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August 2002 GFK-0356Q
F
Procedure
Step 1: Basic Method to Calculate Module Dissipation
Note that this step does not apply to Power Supply Modules, which are covered in Step 2. The
values needed for this calculation are found in the “Load Requirements” table in Chapter 12.
Use the following electrical power formula in these calculations
Power (in watts) = Voltage (in volts) x Current (in Amps).
Assume that all input power to these modules is eventually dissipated as heat. The procedure is:
■ Look up the module in the “Load Requirements for Hardware Components” table (Chapter 12)
and obtain the current values for each of the three power supply voltages listed. The voltage is
printed at the head of each column. All modules use the 5VDC supply, and a relatively few
modules also use one or both of the two 24VDC supplies.
■ For a given module, calculate the power dissipation for each column in the table that contains a
current value by multiplying the current value (in Amps) times the voltage for that column. For
modules using more than one voltage, add the calculated power values to arrive at the total for
the module.
Example 1:
The “Load Requirements” table shows that the IC693CPU352 module draws:
■ 910 mA from the +5VDC supply.
■ No current from either of the two 12VDC supplies
To calculate power dissipation, multiply 0.910 Amps times 5 volts. The answer is:
■ 4.55 watts (of heat dissipated by this module)
Example 2:
The “Load Requirements” table shows that the IC693MDL241 module draws:
■ 80 mA from the +5VDC supply
■ 125 mA from the +24VDC Isolated supply
To calculate power dissipation from the +5VDC supply:
Multiply 0.08 Amps times 5 volts to arrive at a value of 0.40 watts.
To calculate power dissipation from the +24VDC supply:
Multiply 0.125 Amps times 24 volts to arrive at a value of 3.0 watts.
Adding the two together yields a total heat dissipation by this module of 3.4 watts.
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