Rockwell Automation 1791-XXXX Discrete I/O AC and DC Block I/O Input and Output Modules User Manual

Page 16

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I/O Interface and System Design

Chapter 2

2-6

Figure 2.6

Simplified Schematic of ac Output Circuit

Opto

Isolation

Indication

LED

(logic)

System

Circuitry

L1

L2

20-132V ac

10

0.033

µ

F

178

75

R

L

Output

Common

Out

When sizing output loads, check the documentation supplied with the
output device for the surge and continuous current needed to operate the
device. Refer to Table 2.A to determine which Allen-Bradley products
will directly interface to the outputs.

Example: The output device is an ac solenoid operated air valve with an
inrush current (surge) of 1.995A for 10ms and a holding current
(continuous) of 275mA. Figure 2.7 shows that the load of the output
device is within the operating specifications of the ac output.

Figure 2.7

ac Output Drive Current Load for ac Air Valve

10A

300mA

0

10ms

Time

Current

0

Surge

Continuous

2A

1.995A

275mA

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