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8. SPECIFICATIONS AND WIRING OF THE I/O BLOCKS
8.4 Handling of the Relay Output Circuit
8.4.1 Relay output circuit
(1) Output terminals
The relay output type is a 4-, 8- or 16-point/1-common output type and the
common terminals are numbered [COM1] to [COM9].
Different common blocks (1 point increments for the separated common type)
can drive loads in different circuit voltage systems (for example, 200VAC,
100VAC, 24VDC).
(2) Circuit isolation
The PLC internal circuit and external load circuit are electrically isolated between
the coils and contacts of the output relays. The common blocks are also
separated each other.
(3) Operation indication
When the coil of the output relay is energized, the LED is lit and the output
contact switches on.
(4) Response time
Response time from when the coil of the output relay is energized or deenergized
to when the output contact switches on or off is approx. 10ms.
(5) Output current
At the circuit voltage of 250VAC or less, a purely resistive load of 2A/point, an
inductive load of 80VA or less (100VAC or 200VAC), or a lamp load of 100W or
less (100VAC or 200VAC) can be driven.
Refer to Table 8.4.1 for the contact life at switching of an inductive load. When a
DC inductive load is switched by the output contact, a commutating diode should
be connected in parallel with this load and the current voltage 30VDC or less.
(6) Open-circuit leakage current
As there are no leakage currents when the output contact turns off, a neon bulb
or the like can be driven.
(7) Relay output contact life
The standard life of the contact for an inductive AC load such as a contactor or
electromagnetic valve is 500,000,000 times at 35VA. Table 8.4.1 indicates the
guidelines for relay lives in accordance with our life tests.
Testing condition: 1 second ON/1 second OFF
8 - 7
MELSEC-A
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