
5. MATTERS COMMON TO BOTH LCD–MOUNTED TYPE
AND STAND–ALONE TYPE i SERIES (HARDWARE)
B–63525EN/02
382
With a power magnetics cabinet, components such as an AC/DC solenoid
and AC/DC relay are used. When turned on and off, these components
generate a high–energy pulse voltage due to coil inductance.
Such a pulse voltage is induced into cables, for example, and can interfere
with electric circuitry.
D Select a CR–type spark killer (for use with AC circuitry) (A varistor
has a function for clamping the peak voltage of a pulse voltage, but
cannot suppress a spike–like voltage. For this reason, the use of a
CR–type spark killer is recommended.)
D As the CR values of a spark killer, use the following with the
steady–state coil current (I (A)) and DC resistance used as references:
1) Resistance (R): Coil DC resistance
2) Electrostatic capacitance (C):
20
I
2
(mF)
to
I
2
10
I: Coil steady–state current (A)
Equivalent circuit of spark killer
RC
AC relay
Spark killer
Motor
Install a spark killer near a motor, relay, and coil.
Spark killer
NOTE
Use a CR–type noise suppressor. A varistor has a function
for clamping the peak voltage of a pulse voltage, but cannot
suppress a spike–like voltage.
Diode (used for DC circuitry)
Diode
DC relay
As a guideline, select a diode which has
a breakdown voltage about two times
greater than an applied voltage, and al-
lows the flow of a current about two
times higher.
5.8.4
Noise Suppressor
Notes on spark killer
selection