For Your Safety; Safety Circuit; Momentary Power Failures - Panasonic ELC500 User Manual

3.4

For your Safety

3.4.1

Safety Circuit

■Precautions regarding system design
In certain applications, malfunction may occur for the following reasons:
- Power on timing differences between ELC500 and input/output or mechanical power apparatus.
- Response time lag when a momentary power drop occurs.
- Abnormality in ELC500, external power supply, or other devices.
In order to prevent a malfunction resulting in system shutdown take the following measures as adequate:
● Install the interlock circuit outside PLC
- When a motor clockwise/counter-clockwise operation is controlled, provide an interlock circuit
externally.
● Install the emergency stop circuit outside ELC500
- Install an emergency stop circuit outside ELC500 to turn off power supply to the output device.
● Startup other devices before ELC500
- ELC500 should be started after booting the I/O device and mechanical power apparatus.
- When stopping the operation of ELC500, have the input/output devices turned off after ELC500 has
stopped operating.
● Install safety measures in case of alarm outside the PLC body
- When an alarm is released, PLC output is turned off and its operation is stopped. In order to prevent a
malfunction resulting in system shutdown under the above conditions, install safety measures outside
ELC500.
● Perform secure grounding
- When installing PLC next to devices that generate high voltages from switching, such as inverters, do
not ground them together. Use an exclusive ground for each device which should be grounded at a
grounding resistance of 100 Ω or less.
3.4.2

Momentary Power Failures

■Working when momentary power failure
The working when momentary power failure is differed depending on the combination of units, power
supply voltage and other conditions. It may work in the same way as power reset.
If the period of power failure is less than 10ms, ELC500 continues to the working.
When using by suppling 24V DC
The working at momentary power failure time less than 4 ms when 24 V DC is supplied to the ELC500
will continue. In case of that ELC500 restart due to power failure, demand calculation will be reset and
control for devices will be cancelled.
■When connecting ECOnect Remote I/O unit
When ELC500 restart after power failure for 10ms or more, ELC500 send setup data for ECOnect
Remote I/O unit and initialize the output status.
Note
We recommend using UPS.
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ELC500 Control unit