Mitsubishi Electric QX10-TS User Manual page 29

1 GENERAL SPECIFICATIONS AND PRECAUTIONS FOR USE
Circuit example
Varistor method
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POINT
(1) Avoid providing contact protection circuits shown below.
These circuits are effective for preventing an arc at shut-off. However, the
contact welding may occur because the charge current flows to capacitor when
the contact turns on or off.
A DC inductive load is usually harder for switching than a resistor load, but if a
proper protection circuit is configured, the performance will be similar to the
resistor load.
(2) A protection circuit must be provided closely to a load or contact (module). If
their distance is far, the protection circuit may not be effective. Appropriate
distance is within 50cm.
Method for selecting elements
Select a cut voltage (Vc) for
the varistor to meet the
following condition. Multiply
the value by root two for use
of AC power.
Vc Power supply voltage
1.5 (V)
Note that when selecting an
element whose Vc is too high,
its effect will weaken.
MELSEC-Q
Remarks
The recovery time delays
slightly.
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