CAPZero
If lower dissipation or lower voltage across each resistor is required
during fault tests, the total external resistance can be divided into
more discrete resistors, however the total resistance must be equal to
that specified in Table 1.
Safety
X Capacitor
CAPZero meets safety requirements even if placed before the system
input fuse. If a short-circuit is placed between D1 and D2 terminals
of CAPZero, the system is identical to existing systems where
CAPZero is not used.
R1
With regard to open circuit tests, it is not possible to create a fault
condition through a single pin fault (for example lifted pin test) since
there are two pins connected to each of D1 and D2. If several pins
are lifted to create an open circuit, the condition is identical to an
open circuit X capacitor discharge resistor in existing systems where
CAPZero is not used. If redundancy against open circuit faults is
required, two CAPZero and R1 / R2 configurations can be placed in
parallel.
R2
≥4 mm
Discharge Operation
To meet the safety regulations, when the AC supply is disconnected,
CAPZero will discharge the X capacitor to the safety extra low voltage
(SELV) levels according to the above functional description. Although
there are no specific safety requirements below SELV, CAPZero still
continues the discharge until the X capacitor is fully discharged. As
such CAPZero can be safely used at low input voltages such as the
common industrial 18 VAC and 24 VAC supply rails while retaining X
capacitor discharge when the AC source is disconnected.
PI-5610-041310
Figure 4. Typical PCB Layout.
3
Rev. H 03/18
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