
3. INSTALLATION
B–63323EN/03
22
AC/DC solenoids and relays 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.
Generally, to reduce this pulse voltage, use a spark killer when an AC
power source is used, and a diode when a DC power source is used.
Notes on selecting the spark killer
D Use a CR spark killer.
(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.)
D 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:
1) Resistance (R): Equivalent DC resistance of the coil
2) Capacitance (C): I
2
/10 to I
2
/20 (µF)
CR
Equivalent circuit of the spark killer
AC relay
Spark killer
Spark killer
Motor
3.6.4
Noise Suppresser