Rockwell Automation 1747-L40 SLC 500 Fixed Hardware Style - Manual (Page 32)

Chapter 1
Selecting Your Hardware Components
1–13
The recommendations given previously provide favorable operating
conditions for most controller installations. Your application may involve
one or more of the following adverse conditions. Additional measures can
be taken to minimize the effect of these conditions.
Excessive Line Voltage Variations
The best solution for excessive line voltage variation is to correct any feeder
problems in your distribution system. Where this does not solve the line
variation problem, or in certain critical applications, use a constant voltage
transformer. If you require a constant voltage transformer, connect it to the
power supply and all input devices connected to the SLC 500 controller.
Connect output devices on the same power line, but their connection along
the power line is normally made before the constant voltage transformer. A
constant voltage transformer must have a sufficient power rating for its load.
Excessive Noise
When you operate the SLC 500 controller in a “noise polluted” industrial
environment, special consideration should be given to possible electrical
interference.
The following reduces the effect of electrical interference:
•
SLC 500 controller design features
•
proper mounting of controller within an enclosure
•
proper equipment grounding
•
proper routing of wiring
•
proper suppression added to noise generating devices
Potential noise generators include inductive loads, such as relays, solenoids,
and motor starters when operated by “hard contacts” like push buttons or
selector switches. Suppression may be necessary when such loads are
connected as output devices or when connected to the same supply line that
powers the controller.
Lack of surge suppression on inductive loads may attribute to processor
faults and sporadic operation, RAM memory can be corrupted (lost) and I/O
modules may appear to be faulty or reset themselves.
For extremely noisy environments, use a memory module and program it for
auto loading on processor fault or power cycle for quick recovery.
Special Considerations