Riken Keiki GD-3EC, Technical Manual

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4. Installation 4-2 System design precautions
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4-2 System design precautions
Consider the following precautions when designing a system in which the product is used:
CAUTION

An unstable power supply or noise may result in malfunctions or false alarms.

Consider the details described in this section before designing a system that uses the product.
4-2-1 Using a stable power supply
The product’s external output and alarm contacts may activate as the system stabilizes when the power is
turned on or right after an instantaneous power failure. If external output and alarm contacts activate due to
power failures or other reason, use a UPS (uninterruptible power system) or take other appropriate measures.
The product should be powered using a power supply specified below.
Power supply voltage 24 V DC (18 V - 30 V DC): Main unit terminal voltage
Time allowed for
instantaneous
power failures Up to approx. 20 ms
*1
Typical action:
Use an external uninterruptible power
supply or similar system to guarantee
continuous operation and functionality.
Miscellaneous Do not use with power supplies
subject to very high power loads or
high frequency noise. Typical action:
Where necessary, use a line filter or other
device. Keep the product away from
sources of noise.
*1: Restart the product when recovering after instantaneous power failures of 20 ms or more.
4-2-2 Lightning strike protective measures
In factories or plants where cabling is configured as follows, damage may result in the event of lightning strikes
due to the cables connected to the devices acting as a receiving antenna for the lightning:

When cables are installed outdoors

When cables are installed in the same duct as cables supplied from outside
In the event of lightning strikes, devices connected to the cables may be damaged by lightning energy.
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
lightning disasters, the following protective measures are useful:
<Lightning strike protective measures>
Implement appropriate measures based on environmental conditions and the importance of the facility.
A lightning arrester (cable protector) can be installed before the field devices and central processing equipment
as a safeguard against inductive lightning surges transmitted through the cables.
For information on how to use lightning arresters, please contact the manufacturer.
<Grounding>
Surge noise is caused by lightning strikes and other factors. Devices must be grounded to protect against these
noise sources.
NOTE
 Lightning arresters contain circuitry to remove voltage surges that could damage field devices. Installing
lightning arresters may therefore cause signal attenuation.
Perform an operation check before installing a lightning arrester. Also note that lightning arresters cannot
remove all voltage surges.