Toshiba Vm Series Instruction Manual page 146

(5) If the input module and inductive load are connected in parallel, with
the input contact, the controller may malfunction due to the surge
voltage generated between the two ends of the load at contact OFF
time. In this case, install a surge absorbing element in parallel to the
load to suppress the surge voltage.

L
Figure.C.2-3
(6) For inputting AC input module, use sinusoidal wave in the specified
voltage and frequency.
Waveform distortion or frequency hunting in the fundamental wave of
the AC input voltage may result in incorrect input (e.g. reading ON state
as OFF).
Following cases illustrate main causes of incorrect input:

Application of rectangular wave power supply output by
uninterruptible power supply (UPS)

Waveform distortion due to harmonic, such as inverter

Frequency hunting while applying low voltage transformer (CVT)
When applying AC input module, make sure the input waveform
distortion ratio of AC the voltage waveform is under 5%. To read OFF
instantaneously in ON state, writing a user program (Application of
OFF delay timer) is effective. The figure below shows an example of
program applying OFF delay timer to AC input "X0003."
X0003
R1003
Figure.C.2-4
Inductive load
Surge absorbing element
(e.g., snubber circuit)
Measure against Serge
100ms
Program timing example
Unified Controller Vm Series Controller typeS Instruction Manual
Input module
100ms
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