Riken Keiki GD-84D-EX Series, Руководство по эксплуатации

Страница: 23 / 194

4. Installation 4-2 System design precautions
23 / 191
Lightning strikes may damage devices connected to the cable. Additionally, note that inductive lightning
surges due to lightning strikes cannot be entirely prevented, even if cables are installed in metal ducts or
buried underground. While it is not possible to completely protect against disasters caused by lightning,
the following protective measures are available:
<Protection against lightning>
Take appropriate measures based on environmental conditions and the importance of the facility.

Passing the signal transmission path through optical fiber, etc.

Protection using a lightning arrester (cable safety retainer)
A lightning arrester (cable safety retainer) can be installed before the field devices and central processing
equipment to safeguard against inductive lightning surges transmitted through the cable. For information
on how to use lightning arresters, please contact the manufacturer.
<Grounding>
Surge noise is caused by lightning strikes and other factors. This product must be grounded to protect
against these factors.
NOTE
 Lightning arresters include circuits to remove surge voltages that may damage field devices. For
this reason, installing a lightning arrester can attenuate signals.
Perform an operation check before installing lightning arresters. Additionally, lightning arresters
cannot remove all surge voltages.
<Using alarm contacts correctly>
The alarm contacts on this product are designed to transmit signals to activate external buzzers, alarm
indicators, revolving lights, etc.
Do not use for control purposes (e.g., controlling shutoff valves).
CAUTION

When relay contacts are to be left in a constantly closed state, burning may occur at the contacts
with minimal vibration.

A de-energized b contact (break contact) may cause a momentary open operation due to external
forces or other physical impact.

If a b contact is used as an alarm contact, implement measures to account for such momentary
operations—for example, add a delay operation (of approximately 1 second) to the signal on the b
contact receiving side.
The alarm contact specifications of the product assume resistance loads. If the alarm contacts use
inductive loads, a counter
‐
electromotive force will occur at the contacts, leading to the following potential
problems:

Relay contact welding, insulation failure, contact failure

Damage to electrical components due to high voltages occurring inside the product

Malfunctions due to CPU runaway
CAUTION

As a rule, do not use the alarm contacts of the product to operate inductive loads. In particular,
never use to operate devices like fluorescent lamps and motors.

If operating inductive loads, link using an external relay (contact amplification). However, since the
external relay coil also constitutes an inductive load, use a relay that runs on low voltage (within
100 V AC) and a suitable surge protector (CR circuit, etc.) to protect the contacts of this product.