Xycom 9457, Руководство пользователя

Страница: 39 / 80

Chapter 3 – Installation
3-17
•
All electrical racks or chassis and machine elements should be grounded to a central
ground bus, normally located near the point of entry for the plant power supply of
the enclosure. Paint and other nonconductive material should be scraped away from
the area where a chassis makes contact with the enclosure. In addition to the ground
connection made through the mounting bolt or stud, a one-inch metal braid or size #8
AWG wire can be used to connect between each chassis and the enclosure at the
mounting bolt or stud.
•
The enclosure should be properly grounded to the ground bus. Make sure a good
electrical connection is made at the point of contact with the enclosure.
•
The machine ground should be connected to the enclosure and to earth ground.
Excessive Heat
The 9457 is designed to withstand temperatures from 0º to 50º C (32º to 122º F) and is cooled
by two fans which draw a vertical column of air upward over the surface of the components.
To keep the temperature within this range, the cooling air at the base of the system must not
exceed 50º C. Proper spacing must also be allocated between internal components installed in
the enclosure.
When the air temperature is higher than 50º C in the enclosure, use of a fan or air conditioner
is required to maintain the operating temperature below the maximum rated limit.
Excessive Noise
Electrical noise can cause temporary malfunctions due to operating errors, which can result in
hazardous machine operation in certain applications. Noise may be present only at certain
times, may appear at widely-spread intervals, or in some cases may exist continuously.
Noise usually enters through input, output, and power supply lines and may be coupled into
lines electrostatically through the capacitance between these lines and the noise signal carrier
lines. This usually results from the presence of high voltage or long, closed-spaced conduc-
tors. When control lines are closely spaced with lines carrying large currents, the coupling of
magnetic fields can also occur. Use shielded cables to help minimize noise. Potential noise
generators include relays, solenoids, motors, and motor starters, especially when operated by
hand contacts like push buttons or selector switches. In accordance with National Electric
Code specifications, it is recommended that the high voltage and low voltage cabling be sepa-
rated and dressed apart. In particular, the AC cables and switch wiring should not be in the
same conduit with PLC communication cables.
Excessive Line Voltage
The power supply of the 9457 is built to sustain line fluctuations within ranges from 90-131
VAC or 182-264 VAC and still allow the system to function within its operating margin. As
long as the incoming voltage is adequate, the power supply provides all the logic voltages
necessary to support the processor, memory, and I/O.
In cases in which the installation is subject to unusual AC line variations, a constant voltage
transformer can be used to prevent the system from shutting down too often. However, a first