
3.ACTION AGAINST NOISE TROUBLESHOOTING B-65395EN/01
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3.2 NOTES ON SELECTING THE SPARK KILLER
• Use a spark killer consisting of a resistor and capacitor in series.
This type of spark killer is called a CR spark killer.(Use it under
AC)
(A varistor is useful in clamping the peak voltage of the pulse
voltage, but cannot suppress the sudden rise of the pulse voltage.
FANUC therefore recommends a CR spark killer.)
• The reference capacitance and resistance of the spark killer shall
conform to the following based on the current (I (A)) and DC
resistance of the stationary coil:
❏ Resistance (R) : Equivalent DC resistance of the coil
❏ Capacitance (C) :
I
2
10
I
2
20
to
(µF)
where I : Current at stationary state of the coil
Equivalent circuit of the spark killer
R C
Spark killer
Spark killer
Motor
C relay
Mount the noise eliminator near a motor or a relay coil.
NOTE
Use a CR-type noise eliminator. Varistor-type noise
eliminators clamp the peak pulse voltage but cannot
suppress a sharp rising edge.
• Diode is used for direct-current circuits
Use a diode which can withstand a voltage
up to two times the applied voltage and a
current up to two times the applied current.
Diode
DC relay
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