Specifications

3–1 1System Installation Recommendations
Publication 1747-6.2
Safety considerations are an important element of proper system
installation. Actively thinking about the safety of yourself and
others, as well as the condition of your equipment, is of primary
importance. Several safety areas are discussed below.
Disconnecting Main Power
The main power disconnect switch should be located where
operators and maintenance personnel have quick and easy access to
it. Ideally, the disconnect switch is mounted on the outside of the
enclosure, so that it can be accessed without opening the enclosure.
In addition to disconnecting electrical power, all other sources of
power (pneumatic and hydraulic) should be de-energized before
working on a machine or process controlled by an SLC controller.
Safety Circuits
Circuits installed on the machine for safety reasons, like overtravel
limit switches, stop push buttons, and interlocks, should always be
hard-wired directly to the master control relay. These devices must
be wired in series so that when any one device opens, the master
control relay is de-energized thereby removing power to the
machine. Never alter these circuits to defeat their function. Serious
injury or machine damage could result.
Power Distribution
There are some points about power distribution that you should be
aware of. First, the master control relay must be able to inhibit all
machine motion by removing power to the machine I/O devices
when the relay is de-energized.
Second, if you are using a DC power supply, interrupt the load side
rather than the AC line power. This avoids the additional delay of
power supply turn-on and turn-off. The DC power supply should be
powered directly from the fused secondary of the transformer.
Power to the DC input and output circuits is connected through a set
of master control relay contacts.
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afety
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onsiderations