
B-63945EN/02 5.MATTERS COMMON TO BOTH LCD-MOUNTED TYPE AND STAND-ALONE TYPE (HARDWARE)
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5.11.4 Noise Suppressor
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.
Notes on spark killer selection
• 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.)
• 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):
I
2
10
I
2
20
to
(F)
I : Coil steady-state current (A)
Equivalent circuit of spark killer
RC
Spark killer
Spark killer
Motor
C relay
Install a spark killer near a motor, relay, and coil.
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
DC relay
s a guideline, select a diode which has a
breakdown voltage about two times greate
than an applied voltage, and allows the flow o
a current about two times higher.
Diode (used for DC circuitry)