Toshiba SX 2000 - Manual (Page 137)

Chapt.3 Precautions for I/O Modules
3.4 Precautions for AC Output Modules
( 1 )
( 2 )
Over-Current Protection Coordination
One 2A fuse per 4 output points is mounted in the triac output module.
Although, taking account of protecting elements by the fuse blowing even
in load short circuits, when the fuse blows the semiconductors are
subjected to considerable damage. Therefore, take care in handling and
wiring so that short circuits will not occur.
If an inductive load is connected, transient overvoltage will be generated at
the output is changed to OFF. To prevent malfunction caused by this surge
voltage, a CR snubber circuit is installed in the AC output module.
Flowever, to prevent the problem for other signal systems, install a surge
absorption element in parallel with the inductive load (install a surge
absorption element as near as possible to the inductive load).
Surge absorption element:
' Varistor (for the voltage clamp)
''-j
Bi-directional overvoltage absorption element with
a rated voltage of approx. 1.2 times of the max.
voltage (peak voltage)
Snubber (CR) circuit (for high-frequency attenuation)
R(£5) =
C(pF)
H hCIM
DC resistance value of the load
Jf____ ¡1 (I: peak value of load
10 20 current in ordinary time)
(3) Because the AC output module does not have a zero-cross function, the
OFF^ON occurs regardless of the load voltage phases. Flowever, the
ON-OFF change occurs when load current is near zero. Check this point
in load response.
1 2 0 Sequence Controller S2T