
3. ACTION AGAINST NOISE
B--65245EN/02
TROUBLESHOOTING AND
COUNTERMEASURES
148
The AC/DC solenoid and relay are used in the power magnetics cabinet.
A high pulse voltage is caused by coil inductance when these devices are
turned on or off.
This pulse voltage induced through the cable causes the electronic circuits
to be disturbed.
D 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 ris e of the pulse voltage. FANUC
therefore recommends a CR spark killer.)
D The reference capacitance and resistance of the spark killer shall
conform to the following based on t he current (I (A)) and DC
resistance of the stationary coil:
1) Resistance (R) : Equivalent DC resistance of the coil
2) Capacitance (C) :
20
I
2
(←F)
to
I
2
10
I : C urrent at stationary state of the coil
Equivalent circuit of the spark killer
RC
Spark killer
Spark killer
Motor
AC
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.
D 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
--
+
D Noise Suppressor
Notes on selecti ng the
spark killer