Rev. C 03/22

12

PFS5173-5178/5274

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Safety of X Capacitor Discharge

X capacitor discharge function can be implemented by connecting D1

to one AC line input through an external series resistor and D2 to the

other AC input line input through a separate external resistor.

X capacitor discharge function meets safety requirements even if

connection is placed before the system input fuse. If a short-circuit is

placed between D1 and D2 terminals, the system is identical to

existing systems where X capacitor discharge function is not used.

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 both 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 X

capacitor discharge function is not disabled.

Total X Capacitance

Total Series Resistance

100 nF to 6 µF

7.5 MΩ to 142 kΩ

Table 3.

X Capacitance and Discharge Resistance.

Test

Test With Existing System

CAPZero Equivalent

Comments

Open Circuit:

Disconnect one

pin of any

device to see

effect on

system

Open Circuit:

Lifting any one pin of D1 and

D2 pins has no effect as 2

pins are connected to each

drain terminal. The only way

to create an open circuit is by

lifting the leads of one of the

discharge resistors. This is

equivalent to an existing

system without the active

capacitor discharge function.

Short-Circuit:

Short any two

adjacent pins to

see effect on

system

Short-Circuit:

Shorting D1 and D2 pins

creates a condition equivalent

to an existing system not

using an active X capacitor

discharge function.

X Capacitor

AC

PI-6605a-110811

D1

R1

R2

D2

AC

PI-6604a-110811

D1

R2

D2

X Capacitor

CX

R2

AC

PI-5907-041310

CX

R2

R1

AC

PI-5908-041310

Table 4.

Single Point of Failure (SPOF) Tests as Pertaining to Failure Modes of the X Capacitor Discharge. HiperPFS-5 Device Passes Both Tests.