35.2 PRACTICE PROBLEMS

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1. The best location for the PLC enclosure is:

a) close to the incoming power

b) in the control room

c) close to the machine or process

d) far away from the machine or process

(ans. c)

2. Typically, programmable controller systems installed inside an enclosure can withstand a maximum of:

a) 60°C outside the enclosure

b) 50°C outside the enclosure

c) 60°C inside the enclosure

d) 50°C inside the enclosure

(ans. c)

3. Input/Output racks are not typically placed:

a) adjacent to the CPU

b) beside the power supply

c) directly above the CPU

d) in a remote enclosure

(ans. c)

4. The I/O placement and wiring documents should be updated:

a) during maintenance

b) every time there is a change

c) at the end of the project

d) during the documentation

(ans. b)

5. What steps are required to replace a defective PLC?

(ans. in a rack the defective card is removed and replaced. If the card has wiring terminals these are removed first, and connected to the replacement card.)

6. Draw the electrical schematic and panel layout for the relay logic below. The system will be connected to 3 phase power. Be sure to include a master power disconnect.